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Semen Quality and Reproductive Health of Young Czech Men Exposed to Seasonal Air Pollution.



This study of male reproductive health Within the framework of WHO's definition of health[1] as a state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity, reproductive health, or sexual health/hygiene  in the Czech Republic Czech Republic, Czech Česká Republika (2005 est. pop. 10,241,000), republic, 29,677 sq mi (78,864 sq km), central Europe. It is bordered by Slovakia on the east, Austria on the south, Germany on the west, and Poland on the north.  resulted from community concern about potential adverse effects of air pollution. We compared young men (18 years of age) living in Teplice, a highly industrialized in·dus·tri·al·ize  
v. in·dus·tri·al·ized, in·dus·tri·al·iz·ing, in·dus·tri·al·iz·es

v.tr.
1. To develop industry in (a country or society, for example).

2.
 district with seasonally elevated levels of air pollution, to those from Prachatice, a rural district with relatively clean air. Surveys were scheduled for either late winter, after the season of higher air pollution, or at the end of summer, when pollution was low. Participation included a physical examination, donation of a semen semen
 or seminal fluid

Whitish viscous fluid emitted from the male reproductive tract that contains sperm and liquids (seminal plasma) that help keep them viable.
 sample, and completion of a questionnaire on health, personal habits, and exposure to solvents and metals through work or hobby. Analysis of data from 408 volunteers showed that the men from Teplice and Prachatice were similar in physical characteristics, personal habits, and work- or hobby-related exposures. Sixty-six percent (272) of these men donated a single semen sample for routine semen analysis Semen Analysis Definition

Semen analysis evaluates a man's sperm and semen. It is done to discover cause for infertility and to confirm success of vasectomy.
, computer-aided sperm sperm or spermatozoon (spûr'mətəzō`ən, –zō`ŏn), in biology, the male gamete (sex cell), corresponding to the female ovum in organisms that reproduce sexually.  motion analysis, and sperm chromatin chromatin: see chromosome.  structure assay. The mean (median) sperm concentration and sperm count sperm count Urology A measure of the concentration of sperm in semen Normal ±100 million/mL. See Post-vasectomy sperm count, Semen analysis.  were 61.2 (44.0) million/mL semen and 113.3 (81.5) million, respectively, and were not associated with district of residence or period of elevated air pollution. However, periods of elevated air pollution in Teplice were significantly associated with decrements in other semen measures including proportionately pro·por·tion·ate  
adj.
Being in due proportion; proportional.

tr.v. pro·por·tion·at·ed, pro·por·tion·at·ing, pro·por·tion·ates
To make proportionate.
 fewer motile mo·tile
adj.
1. Moving or having the power to move spontaneously.

2. Of or relating to mental imagery that arises primarily from sensations of bodily movement and position rather than from visual or auditory sensations.
 sperm, proportionately fewer sperm with normal morphology morphology

In biology, the study of the size, shape, and structure of organisms in relation to some principle or generalization. Whereas anatomy describes the structure of organisms, morphology explains the shapes and arrangement of parts of organisms in terms of such
 or normal head shape, and proportionately more sperm with abnormal chromatin. These results suggest that young men may experience alterations in sperm quality after exposure to periods of elevated air pollution, without changes in sperm numbers. Key words, air pollution, epidemiology, human, semen, sperm chromatin, sperm count, sperm morphology, sperm motility Sperm motility describes the ability of sperm to move properly towards an egg. This can also be thought of as the 'quality' of the sperm, which is a factor in successful pregnancies, as opposed to the 'quantity'. . Environ Health Perspect 108:887-894 (2000). [Online 2 August 2000]

http://ehpnet1.niehs.nih.gov/docs/2000/108p887-894selevan/abstract.html

Air pollution in the Czech Republic increased dramatically with the advent of industrialization industrialization

Process of converting to a socioeconomic order in which industry is dominant. The changes that took place in Britain during the Industrial Revolution of the late 18th and 19th century led the way for the early industrializing nations of western Europe and
 in the 1950s, primarily the result of increasing use of brown coal (with high sulfur content) for both home heating and industry. Sulfur dioxide sulfur dioxide, chemical compound, SO2, a colorless gas with a pungent, suffocating odor. It is readily soluble in cold water, sparingly soluble in hot water, and soluble in alcohol, acetic acid, and sulfuric acid.  emissions in Czechoslovakia amounted to 0.9 million tons in the 1950s and increased to 3.5 million tons by 1985 (1). This increase was particularly pronounced in the mountainous moun·tain·ous  
adj.
1. Having many mountains.

2. Resembling a mountain in size; huge: mountainous waves.


mountainous
Adjective

1.
 region of Northern Bohemia Bohemia, Czech Čechy, historic region (20,368 sq mi/52,753 sq km) and former kingdom, in W and central Czech Republic. Bohemia is bounded by Austria in the southeast, by Germany in the west and northwest, by Poland in the north and northeast, and by , where coal comes from mammoth mammoth, name for several large prehistoric elephants of the extinct genus Mammuthus, which ranged over Eurasia and North America in the Pleistocene epoch.  open-pit mines and is used to heat homes and generate power for local industry. During the 1980s, ambient Surrounding. For example, ambient temperature and humidity are atmospheric conditions that exist at the moment. See ambient lighting.  [SO.sub.2] levels associated with high levels of particulate matter particulate matter
n. Abbr. PM
Material suspended in the air in the form of minute solid particles or liquid droplets, especially when considered as an atmospheric pollutant.

Noun 1.
 (PM) in the Teplice district The Teplice District (Czech: Okres Teplice) is a district in the Czech Republic and is part of the Ústí nad Labem Region along with the districts of Most, Louny, Chomutov, Litoměřice, Děčín and Ustí nad Labem.  of Northern Bohemia frequently exceeded U.S. and Czech air pollution standards (2,3) in winter, when the use of coal increases and thermal inversions favor retention of the air pollution in the valley (4).

The Teplice Program, an international research program, was initiated in 1991 in response to concerns over potential health effects of this pollution. This program sponsored cooperative research among the Czech Institute of Hygiene, the Czech Ministry of the Environment, and the U.S. Environmental Protection Agency Environmental Protection Agency (EPA), independent agency of the U.S. government, with headquarters in Washington, D.C. It was established in 1970 to reduce and control air and water pollution, noise pollution, and radiation and to ensure the safe handling and  to compare health status in Teplice district to that in Prachatice district Prachatice District (Czech: Okres Prachatice) is a district (okres) within South Bohemian Region of the Czech Republic. Its capital is Prachatice.  (5). We chose Prachatice because of its relatively cleaner air. A critical component of this program was the establishment of air monitoring in both districts to measure aerosol aerosol (âr`əsōl,–sŏl): see colloid.
aerosol

System of tiny liquid or solid particles evenly distributed in a finely divided state through a gas, usually air.
 and gas-phase air pollutants pollutants

see environmental pollution.
 [PM, including volatile and semivolatile polycyclic aromatic hydrocarbons polycyclic aromatic hydrocarbon
n.
Any of a class of carcinogenic organic molecules that consist of three or more rings containing carbon and hydrogen and that are commonly produced by fossil fuel combustion.
 (PAHs) and toxic metals toxic metal Environment Any metal known to be toxic to humans–eg, antimony, arsenic, beryllium, bismuth, cadmium, lead, mercury, nickel. Cf Nontoxic metal. ] as well as [SO.sub.2], nitrous oxides nitrous oxide or nitrogen (I) oxide, chemical compound, N2O, a colorless gas with a sweetish taste and odor. Its density is 1.977 grams per liter at STP. It is soluble in water, alcohol, ether, and other solvents.  ([NO.sub.x]), and carbon monoxide carbon monoxide, chemical compound, CO, a colorless, odorless, tasteless, extremely poisonous gas that is less dense than air under ordinary conditions. It is very slightly soluble in water and burns in air with a characteristic blue flame, producing carbon dioxide;  on an ongoing basis. Monitoring confirmed that levels of these air pollutants were considerably higher in Teplice than in Prachatice, and were higher in the winter than during the rest of the year in both districts (5,6). The Teplice Program includes studies of a number of health outcomes, including respiratory and neurologic neurologic /neu·ro·log·ic/ (-loj´ik) pertaining to neurology or to the nervous system.
Neurologic
Having to do with the nervous system.
 effects in children, biomonitoring of mutagens in adults, and reproductive health in pregnant women and young men (5).

Reproductive health studies were prompted by reports that rates of conception and incidence of congenital anomalies congenital anomaly
n.
See birth defect.
 were affected by seasonal increases in air pollution (7). To examine the potential relationship between the season of elevated air pollution and male reproductive health, we surveyed young (18-year-old) men and evaluated their semen quality semen quality Urology The measurable parameters of semen–eg, sperm concentration, total sperm count per ejaculate, % of motile sperm, number of abnormal and immature sperm . Metabolites Metabolites
Substances produced by metabolism or by a metabolic process.

Mentioned in: Interactions
 of the PAHs present in this industrial air pollution can form protein or DNA adducts A DNA adduct is an abnormal piece of DNA covalently-bonded to a cancer-causing chemical. This has shown to be the start of a cancerous cell, or carcinogenesis. DNA adducts in scientific experiments are used as bio-markers and as such are themselves measured to reflect  in body tissues (8) and thus have the potential to damage germ cell germ cell
n.
An ovum or a sperm cell or one of their developmental precursors. Also called sex cell.


Germ cell
One of the cells that ordinarily develop into eggs or sperm (also sperm and eggs).
 DNA DNA: see nucleic acid.
DNA
 or deoxyribonucleic acid

One of two types of nucleic acid (the other is RNA); a complex organic compound found in all living cells and many viruses. It is the chemical substance of genes.
. PAHs also reportedly alter male reproductive function in test species (9,10), providing additional rationale for this study. Furthermore, metals such as lead and cadmium cadmium (kăd`mēəm) [from cadmia, Lat. for calamine, with which cadmium is found associated], metallic chemical element; symbol Cd; at. no. 48; at. wt. 112.41; m.p. 321°C;; b.p. 765°C;; sp. gr. 8.  that are present in the particulate par·tic·u·late
adj.
Of or occurring in the form of fine particles.

n.
A particulate substance.



particulate

composed of separate particles.
 fraction of air pollution have been associated with decrements in human semen quality (11).

Methods

This project was a collaborative effort between Czech and U.S. scientists. The study protocol was reviewed and approved by the Institutional Review Board of the Regional Institute of Hygiene of Central Bohemia, Prague, Czech Republic.

Subject recruitment. All young men turning 18 in the two districts over the 6 months before sampling were sent a letter from their district Hygiene Station with an appointment for a physical examination. Appointments were scheduled within 1 week's time in either early fall (1993) or late winter (1993 and 1994) to allow comparisons between recent exposures to periods of either high (winter) or low (summer) pollution. When each man presented for his physical examination, the reproductive study was explained to him, including his right to decline to participate and/or donate a semen sample, and written informed consent was obtained from each participant. No financial incentive was provided for participation. A pilot study was conducted in fall 1992 to estimate participation levels, establish field methods for the laboratory measures, and field test the questionnaire. Because methods for recruiting the participants in the pilot study differed from those used in the main study, data from the pilot study are not included in this report. However, a preliminary summary report of the study findings included the pilot data (5).

Questionnaire, physical examination, and semen sampling. The Czech study team traveled to the Teplice and Prachatice District Institutes of Hygiene for each sampling cycle (5 days) with the necessary supplies and equipment. Data were collected by questionnaire, physical examination, and semen sampling. A structured questionnaire, customized for use in the Czech Republic, was given by two trained interviewers. The purpose of the questionnaire was to obtain information on health status; other exposures such as metals, solvents, or pesticides encountered through hobbies or work (for those men undertaking apprenticeships); lifestyle data; and reproductive history reproductive history Obstetrics A set of 4 numbers that may be used to define a woman's obstetric Hx–eg, 4-3-2-1, would mean 4 term infants delivered, 3 preterm infants, 2 abortions, 1 child currently living  including the date of last semen emission. Questions on other factors that could affect semen quality (such as fever, medications, exposure to X rays, cigarette use, consumption of alcohol and caffeinated beverages, and use of briefs) covered the previous 3 months. The physical examination included a urogenital urogenital /uro·gen·i·tal/ (-jen´i-tal) genitourinary.

u·ro·gen·i·tal or u·ri·no·gen·i·tal
adj.
Genitourinary.
 evaluation and determination of testis testis (tĕs`tĭs) or testicle (tĕs`tĭkəl), one of a pair of glands that produce the male reproductive cells, or sperm.  volume based on caliper caliper

Instrument that consists of two adjustable legs or jaws for measuring the dimensions of material parts. Spring calipers have an adjusting screw and nut; firm-joint calipers use friction at the joint to hold the legs unmoving.
 measures of testis length and width.

A single semen sample was collected on site by masturbation masturbation

Erotic stimulation of one's own genital organs, usually to achieve orgasm. Masturbatory behavior is common in infants and adolescents, and is indulged in by many adults as well. Studies indicate that over 90% of U.S. males and 60–80% of U.S.
 and sperm were videotaped within 1 hr of collection for subsequent motility motility /mo·til·i·ty/ (mo-til´ite) the ability to move spontaneously.mo´tile
Motility
Motility is spontaneous movement.
 analysis. Routine semen analysis included semen volume, sperm concentration [determined by hemocytometer hemocytometer /he·mo·cy·tom·e·ter/ (-si-tom´e-ter) hemacytometer.

he·mo·cy·tom·e·ter
n.
An instrument for counting the blood cells in a measured volume of blood.
 according to according to
prep.
1. As stated or indicated by; on the authority of: according to historians.

2. In keeping with: according to instructions.

3.
 World Health Organization guidelines guidelines,
n.pl a set of standards, criteria, or specifications to be used or followed in the performance of certain tasks.
; WHO (12)], total number of sperm per sample, percentage of motile sperm, percentage of sperm with normal morphology (entire cell considered), and percentage with normal head morphology. For the morphology assessment, we evaluated 300 sperm per sample from air-dried Papanicolaou-stained preparations and classified as either normal or abnormal according to strict criteria (12). The remaining semen was aliquoted into small tubes or straws, snap frozen on dry ice, and archived at -70 [degrees] C.

Computer-aided sperm analysis sperm analysis See Semen analysis.  (CASA Ca´sa

n. 1. A house or mansion.
I saw that Enriquez had made no attempt to modernize the old casa, and that even the garden was left in its lawless native luxuriance.
- Bret Harte.
). Within 1 hr of collection, an aliquot aliquot (al-ee-kwoh) adj. a definite fractional share, usually applied when dividing and distributing a dead person's estate or trust assets. (See: share)  of semen was diluted di·lute  
tr.v. di·lut·ed, di·lut·ing, di·lutes
1. To make thinner or less concentrated by adding a liquid such as water.

2. To lessen the force, strength, purity, or brilliance of, especially by admixture.
 at least 1:1 with Dulbecco's phosphate buffered saline Phosphate buffer saline (abbreviated PBS) is a buffer solution commonly used in biochemistry. It is a salty solution containing sodium chloride, sodium phosphate and potassium phosphate. The buffer helps to maintain a constant pH.  to obtain a concentration suitable for CASA analysis (13), loaded into a 20-micron-deep chamber (Microcell, Fertility Technologies, Inc., Natick, MA), placed on a stage warmer set to 37 [degrees] C, and videotaped (10x negative phase contrast with green filter). Video images were evaluated using a Hamilton-Thorne Integrated visual optical system (HTM-IVOS) semen analyzer (version 10.6; Hamilton-Thorne Research, Inc., Beverly, MA). We analyzed each field for 30 frames at 60 frames/second with minimum track length set at 20 points and examined enough fields to obtain velocity measures on at least 100 motile sperm. For oligospermic samples with [is less than] 100 motile sperm on the tape, mean velocities are included only when [is greater than or equal] 25 motile sperm were analyzed. We visually determined the percentage of motile sperm from the videotapes after scoring at least 100 sperm per sample. Because of technical difficulties, videotapes were unavailable for 10 men evaluated on 1 day in the Teplice (the late winter 1993 group).

CASA outcomes include indicators of a) sperm progression: straight-line velocity (VSL VSL Vessel (shipping)
VSL Value of Statistical Life
VSL Virtual Software Library
VSL Variable Speed of Light (theoretical cosmology/physics)
VSL Vector Statistical Library
VSL Straight Line Velocity
), straightness (STR STR
abbr.
synchronous transmitter receiver
 = VSL/VAP x 100, where VAP (Value Added Process) An executable program in a NetWare 2.x server. Starting with NetWare 3.x, VAPs were replaced by NLMs. See NetWare.  is the average velocity along a mathematically smoothed sperm path), and linearity (LIN = VSL/VCL x 100, where VCL VCL - Visual Component Library  is the curvilinear curvilinear

a line appearing as a curve; nonlinear.


curvilinear regression
see curvilinear regression.
 velocity); and b) vigor VIGOR Internal medicine A clinical study–Vioxx GI Outcomes Report comparing a proprietary COX-2 inhibitor to standard NSAIDs : curvilinear velocity (VCL), amplitude amplitude (ăm`plĭtd'), in physics, maximum displacement from a zero value or rest position.  of lateral head displacement (ALH ALH Advanced Light Helicopter
ALH Amplitude of Lateral Head (Displacement)
ALH Alpha Hospitality Corporation (former stock symbol; now ALHY)
ALH Advanced Liquid Hydrogen
), and beat cross frequency (BCF BCF Billion Cubic Feet
BCF Bioconcentration Factor
BCF British Chess Federation
BCF British Coatings Federation
BCF Breast Cancer Fund
BCF Bank Credit Facility
BCF Bulked Continuous Filament
BCF British Cycling Federation
BCF Boeing Converted Freighter
), as described in detail elsewhere (14). Some of these outcomes have been associated with fertility status (15-18) and have been affected by occupational exposures (19,20). We also calculated two composite outcomes: the total number of motile sperm per sample (sperm count x %motile) and the total number of progressive sperm per sample (total motile x an index of progressive motility defined as percent of motile sperm with VSL 25 microns/second or greater).

Sperm chromatin structure assay (SCSA (Signal Computing System Architecture) An open architecture for transmitting voice and video signals. Its backbone is the SCbus, a 131 Mbps data path that provides up to 2,048 time slots, the equivalent of 1,024 two-way voice conversations at 64 Kbps. ). Archived semen was shipped to South Dakota State University South Dakota State University, at Brookings; land-grant support; coeducational; chartered 1883 as Dakota Agricultural College, opened 1884. In 1907 it became South Dakota State College of Agriculture and Mechanic Arts, and in 1964 its present name was adopted.  (Brookings, SD) for analysis using the SCSA, a measure of sperm nuclear integrity (21-23). Briefly, thawed thaw  
v. thawed, thaw·ing, thaws

v.intr.
1. To change from a frozen solid to a liquid by gradual warming.

2.
 and diluted semen was incubated for 30 sec in acid (pH 1.2) to potentially denature de·na·ture
v.
1. To change the nature or natural qualities of.

2. To render unfit to eat or drink without destroying usefulness in other applications, especially adding methyl alcohol to ethyl alcohol.

3.
 nuclear DNA Nuclear DNA , nuclear deoxyribonucleic acid (nDNA), is DNA contained within a nucleus of eukaryotic organisms. In most cases it encodes more of the genome than the mitochondrial DNA and is passed sexually rather than matrilineally. , then immediately stained with the metachromatic metachromatic /meta·chro·mat·ic/ (-kro-mat´ik) staining differently with the same dye; said of tissues in which a dye gives different colors to different elements.

met·a·chro·mat·ic
adj.
1.
 dye, acridine orange acridine orange
n.
A basic fluorescent dye used as a metachromatic stain for nucleic acids and in screening cervical smears for abnormal cells.
 (AO). AO intercalated in·ter·ca·lat·ed
adj.
Inserted between two others; interposed.



in·terca·late
 into native double stranded DNA fluoresces green; AO complexed with single stranded DNA fluoresces red. We used flow cytometry flow cytometry (flōˑ sī·tˑ·m  to detect green (515-530 nm band pass filter See bandpass filter. ) and red (630 nm long pass filter) fluorescence fluorescence (flrĕs`əns), luminescence in which light of a visible color is emitted from a substance under stimulation or excitation by light or other forms of electromagnetic  in 5,000 individual sperm per sample. The presence of DNA denaturation denaturation, term used to describe the loss of native, higher-order structure of protein molecules in solution. Most globular proteins exhibit complicated three-dimensional folding described as secondary, tertiary, and quarternary structures.  in each cell was observed as a shift from green to red fluorescence and was quantitated by the expression "[[Alpha].sub.t]," defined as the ratio of red/(red + green) fluorescence. We used the "cells outside the main population" (COMP [[Alpha].sub.t]) variable, which represents the percentage of cells containing denatured de·na·ture  
tr.v. de·na·tured, de·na·tur·ing, de·na·tures
1. To change the nature or natural qualities of.

2.
 DNA. Normal sperm chromatin is resistant to acid induced DNA denaturation and fluoresces green. Increased red fluorescence indicates abnormal chromatin packaging and/or DNA damage. High COMP [[Alpha].sub.t] values have been associated with spermatogenic spermatogenic /sper·ma·to·gen·ic/ (-jen´ik) producing semen or spermatozoa.

spermatogenic

giving rise to spermatozoa.
 disorders and infertility infertility, inability to conceive or carry a child to delivery. The term is usually limited to situations where the couple has had intercourse regularly for one year without using birth control.  (21-28).

Air pollution data and exposure categories. Air pollution data were provided by I. Benes and R. Stevens from the air monitoring program of the Teplice Project (5,6). These data include particulate matter [is less than] 10 [micro]m in aerodynamic diameter Drug particles for pulmonary delivery are typically characterized by aerodynamic diameter rather than geometric diameter. The velocity at which the drug settles is proportional to the aerodynamic diameter, da.  ([PM.sub.10]) obtained using the versatile air pollution sampler sampler, sample piece of needlework or embroidery, of silk, cotton, or worsted, for the preservation of some pattern or as an example of the ability of a child or a beginner. In museums and private collections there are samplers dating from as early as 1643.  [VAPS VAPS Video Arcade Preservation Society
VAPS Variable Assist Power Steering
VAPS Virtual Avionics Prototyping System
VAPS Virtual Applications Prototyping System
VAPS Virginia Power Shift (student conference on global climate change) 
 (5,6)], PM-total suspended particulates (TSP TSP - travelling salesman problem ), [SO.sub.2], CO, and [NO.sub.x]. Because VAPS data were incomplete for earlier phases of the study, we present both VAPS and TSP data. The correlation between TSP and [PM.sub.10] was very high (r = 0.96, p = [is less than] 0.01, n = 171) for those days where both were available. [SO.sub.2] data (an indicator of coal-derived pollution) were more complete than PM data. [PM.sub.10] levels were significantly correlated with [SO.sub.2] (r = 0.81, p [is less than] 0.01, n = 274), with [NO.sub.x] (r = 0.58, p [is less than] 0.01, n = 274), and CO (r = 0.49, p [is less than] 0.01, n = 252).

The process of spermatogenesis involves a series of complex steps (stem cell stem cell

In living organisms, an undifferentiated cell that can produce other cells that eventually make up specialized tissues and organs. There are two major types of stem cells, embryonic and adult.
 replication, meiosis, and spermiogenesis spermiogenesis /sper·mio·gen·e·sis/ (sper?me-o-jen´e-sis) the second stage in the formation of spermatozoa, when spermatids transform into spermatozoa.

sper·mi·o·gen·e·sis
n.
) over approximately 74 days in humans (29,30). Epididymal epididymal

emanating from or pertaining to the epididymis.


epididymal inflammation
see epididymitis.

epididymal segmental aplasia
a defect in mesonephric development in which part of the epididymis is missing.
 transit time transit time

the time required for ingesta to pass through the gastrointestinal tract; a shorter transit time is seen in conditions associated with gut hypermotility, such as diarrhea. Delayed passage from any cause results in a longer transit time.
 [estimated at 3-12 days (31)] and abstinence abstinence: see fasting; temperance movements.  interval (controlled in the analysis) can add several weeks to the time before mature sperm are ejaculated. Thus an exposure period of approximately 90 days is generally accepted as being of sufficient duration for detecting effects on any stage of spermatogeneis when using semen measures as the biologic end points. Therefore, for purposes of estimating and categorizing exposures relevant to seasonal changes in air pollution, the air pollution data for the 90-day period preceding sampling were considered relevant. Examination of the mean levels of pollutants (Table 1) shows that they were uniformly low in the 90 days preceding the fall sampling periods in both districts and in the late winter sampling period in Prachatice in 1994, and somewhat higher preceding the late winter sampling in Prachatice in 1993. Because all mean values were well below both U.S. (3) and Czech standards (2), and individual values rarely, if ever, exceeded air quality standards, we considered these to be periods of low air pollution for the purposes of this study. In contrast, the mean levels of air pollutants were considerably higher in Teplice during the 90 days preceding the late winter samplings (Table 1), with 1993 levels considerably higher than 1994 levels. Furthermore, individual daily values frequently exceeded air quality standards. For descriptive purposes, we therefore considered winter 1993 in Teplice as a period of high air pollution and the winter of 1994 in Teplice as a period of medium air pollution. Air pollution peaks were episodic episodic

sporadic; occurring in episodes. e. falling a paroxymal disorder described in Cavalier King Charles spaniels in which affected dogs, starting at an early age, experience episodes of extensor rigidity, possibly brought on by stress. e.
; severe episodes lasted a few days to a week (6). If such an episode were to affect a particular cell type in the testes testes
 or testicles

Male reproductive organs (see reproductive system). Humans have two oval-shaped testes 1.5–2 in. (4–5 cm) long that produce sperm and androgens (mainly testosterone), contained in a sac (scrotum) behind the penis.
, the time between exposure and sampling would be important in detecting that effect. Because the time between severe episodes and sampling was different in the winters of 1993 and 1994, the exposure/effect relationship could also be different. Consequently, a clear cut exposure--response relationship would not necessarily be expected. Therefore, the high and medium exposure periods were analyzed as dummy variables This article is not about "dummy variables" as that term is usually understood in mathematics. See free variables and bound variables.

In regression analysis, a dummy variable
 so as not to impose a linear exposure--response relationship. Furthermore, season of semen collection Semen collection refers to the process of obtaining semen from domestic animals or humans with the use of various methods, for the purposes of insemination, or medical study (usually in fertility clinics).  has also been associated with sperm concentration (32) and some measures of sperm motility and morphology (33), and needs to be considered when interpreting any associations between periods of elevated air pollution and semen outcomes.

Table 1. Air pollution levels in the two communities for 90 days preceding collection of semen samples.
Location,                                                  Winter
pollutant              Characteristic                        1993


Teplice

[PM.sub.10]            Average [+ or -] SD    184.7 [+ or -] 211.9
  [micro]g/[m.sup.3]   Median                                125.3
  (VAPS)               Range                            10.6-832.0
                       No. days w/ data                         38
                       No. days > 150                   16 (42.1%)
                         (%days)

PM-TSP                 Average [+ or -] SD    195.2 [+ or -] 241.0
  [micro]g/[m.sup.3]   Median                                 86.2
                       Range                                 8-960
                       No. days w/ data                         44
                       No. days > 150                   15 (34.1%)
                         (%days)

[SO.sub.2]             Average [+ or -] SD    164.0 [+ or -] 161.0
  [micro]g/[m.sup.3]   Median                                106.9
                       Range                            14.4-697.9
                       No. days w/ data                         90
                       No. days > 150                   26 (28.9%)
                         (%days)

[NO.sub.x]             Average [+ or -] SD   109.12 [+ or -] 72.06
  [micro]g/[m.sup.3]   Median                                 83.9
                       Range                           7.20-367.20
                       No. days w/ data                         90
                       No. days > 100                   37 (41.1%)
                         (%days)

CO                     Average [+ or -] SD      1.72 [+ or -] 0.95
  mg/[m.sup.3]         Median                                 1.60
                       Range                              0.0-5.50
                       No. days w/ data                         90
                       No. days > 10                        0 (0%)
                         (%days)

Prachatice

[PM.sub.10]            Average [+ or -] SD      65.9 [+ or -] 47.6
  [micro]g/[m.sup.3]   Median                                 49.8
  (VAPS)               Range                             7.5-174.3
                       No. days w/ data                         25
                       No. days > 150                       1 (4%)
                         (%days)

PM-TSP                 Average [+ or -] SD      45.5 [+ or -] 30.9
  [micro]g/[m.sup.3]   Median                                   32
                       Range                                13-158
                       No. days w/ data                         90
                       No. days > 150                     1 (1.1%)
                         (%days)

[SO.sub.2]             Average [+ or -] SD      41.5 [+ or -] 35.3
  [micro]g/[m.sup.3]   Median                                 33.5
                       Range                                 7-192
                       No. days w/ data                         90
                       No. days > 150                     1 (1.1%)
                         (%days)

[NO.sub.x]             Average [+ or -] SD      25.1 [+ or -] 29.6
  [micro]g/[m.sup.3]   Median                                   16
                       Range                                 0-140
                       No. days w/ data                         90
                       No. days > 100                     5 (5.6%)
                         (%days)

CO                     Average [+ or -] SD      0.75 [+ or -] 0.52
        mg/[m.sup.3]   Median                                  0.6
                       Range                             0.20-2.60
                       No. days w/ data                         90
                       No. days > 10                        0 (0%)
                         (%days)

Location,                                                Summer
pollutant              Characteristic                      1993

Teplice

[PM.sub.10]            Average [+ or -] SD   35.5 [+ or -] 19.7
  [micro]g/[m.sup.3]   Median                              28.5
  (VAPS)               Range                          13.6-95.6
                       No. days w/ data                      22
                       No. days > 150                    0 (0%)
                         (%days)

PM-TSP                 Average [+ or -] SD   41.5 [+ or -] 17.2
  [micro]g/[m.sup.3]   Median                              37.0
                       Range                              15-80
                       No. days w/ data                      62
                       No. days > 150                         0
                         (%days)

[SO.sub.2]             Average [+ or -] SD   30.6 [+ or -] 14.9
  [micro]g/[m.sup.3]   Median                              25.1
                       Range                          10.6-70.0
                       No. days w/ data                      90
                       No. days > 150                    0 (0%)
                         (%days)

[NO.sub.x]             Average [+ or -] SD   42.1 [+ or -] 20.1
  [micro]g/[m.sup.3]   Median                              38.6
                       Range                            0-103.4
                       No. days w/ data                      90
                       No. days > 100                  1 (1.1%)
                         (%days)

CO                     Average [+ or -] SD                 0.19(d)
  mg/[m.sup.3]         Median                              0.19
                       Range
                       No. days w/ data                       1
                       No. days > 10                     0 (0%)
                         (%days)

Prachatice

[PM.sub.10]            Average [+ or -] SD    18.2 [+ or -] 8.2
  [micro]g/[m.sup.3]   Median                              14.6
  (VAPS)               Range                           6.8-31.2
                       No. days w/ data                      13
                       No. days > 150                    0 (0%)
                         (%days)

PM-TSP                 Average [+ or -] SD    24.1 [+ or -] 9.2
  [micro]g/[m.sup.3]   Median                                21
                       Range                              12-55
                       No. days w/ data                      88
                       No. days > 150                    0 (0%)
                         (%days)

[SO.sub.2]             Average [+ or -] SD     6.1 [+ or -] 3.2
  [micro]g/[m.sup.3]   Median                                 6
                       Range                               1-14
                       No. days w/ data                      74
                       No. days > 150                    0 (0%)
                         (%days)

[NO.sub.x]             Average [+ or -] SD   19.9 [+ or -] 14.0
  [micro]g/[m.sup.3]   Median                                17
                       Range                               3-70
                       No. days w/ data                      88
                       No. days > 100                    0 (0%)
                         (%days)

CO                     Average [+ or -] SD   0.30 [+ or -] 0.11
        mg/[m.sup.3]   Median                              0.27
                       Range                          0.12-0.73
                       No. days w/ data                      88
                       No. days > 10                     0 (0%)
                         (%days)

Location,                                                Winter
pollutant              Characteristic                      1994

Teplice

[PM.sub.10]            Average [+ or -] SD   61.3 [+ or -] 41.9
  [micro]g/[m.sup.3]   Median                              46.0
  (VAPS)               Range                          8.0-183.5
                       No. days w/ data                      90
                       No. days > 150                  4 (4.4%)
                         (%days)

PM-TSP                 Average [+ or -] SD                   --
  [micro]g/[m.sup.3]   Median                                --
                       Range                                 --
                       No. days w/ data                       0
                       No. days > 150                        --
                         (%days)

[SO.sub.2]             Average [+ or -] SD   79.8 [+ or -] 39.9
  [micro]g/[m.sup.3]   Median                              81.4
                       Range                         11.2-230.7
                       No. days w/ data                      90
                       No. days > 150                  4 (4.4%)
                         (%days)

[NO.sub.x]             Average [+ or -] SD   77.6 [+ or -] 40.9
  [micro]g/[m.sup.3]   Median                              70.3
                       Range                         12.8-193.3
                       No. days w/ data                      90
                       No. days > 100                24 (26.7%)
                         (%days)

CO                     Average [+ or -] SD   2.76 [+ or -] 0.86
  mg/[m.sup.3]         Median                              2.66
                       Range                             0-4.62
                       No. days w/ data                      90
                       No. days > 10                     0 (0%)
                         (%days)

Prachatice

[PM.sub.10]            Average [+ or -] SD   29.4 [+ or -] 20.3
  [micro]g/[m.sup.3]   Median                              23.0
  (VAPS)               Range                          3.1-106.5
                       No. days w/ data                      86
                       No. days > 150                    0 (0%)
                         (%days)

PM-TSP                 Average [+ or -] SD   28.5 [+ or -] 13.4
  [micro]g/[m.sup.3]   Median                                24
                       Range                              13-80
                       No. days w/ data                      90
                       No. days > 150                    0 (0%)
                         (%days)

[SO.sub.2]             Average [+ or -] SD   17.4 [+ or -] 12.6
  [micro]g/[m.sup.3]   Median                                13
                       Range                               1-63
                       No. days w/ data                      90
                       No. days > 150                    0 (0%)
                         (%days)

[NO.sub.x]             Average [+ or -] SD   18.2 [+ or -] 17.9
  [micro]g/[m.sup.3]   Median                                13
                       Range                               0-87
                       No. days w/ data                      90
                       No. days > 100                    0 (0%)
                         (%days)

CO                     Average [+ or -] SD   0.53 [+ or -] 0.25
        mg/[m.sup.3]   Median                              0.49
                       Range                             0-1.32
                       No. days w/ data                      90
                       No. days > 10                     0 (0%)
                         (%days)

Location,                                        Standards
pollutant              Characteristic          U.S.    Czech

Teplice

[PM.sub.10]            Average [+ or -] SD    50(a)   150(c)
  [micro]g/[m.sup.3]   Median                150(b)
  (VAPS)               Range
                       No. days w/ data
                       No. days > 150
                         (%days)

PM-TSP                 Average [+ or -] SD
  [micro]g/[m.sup.3]   Median
                       Range
                       No. days w/ data
                       No. days > 150
                         (%days)

[SO.sub.2]             Average [+ or -] SD    80(a)   150(b)
  [micro]g/[m.sup.3]   Median                365(b)
                       Range
                       No. days w/ data
                       No. days > 150
                         (%days)

[NO.sub.x]             Average [+ or -] SD   100(a)   100(b)
  [micro]g/[m.sup.3]   Median
                       Range
                       No. days w/ data
                       No. days > 100
                         (%days)

CO                     Average [+ or -] SD    10(e)     1(a)
  mg/[m.sup.3]         Median
                       Range
                       No. days w/ data
                       No. days > 10
                         (%days)

Prachatice

[PM.sub.10]            Average [+ or -] SD    50(a)   150(c)
  [micro]g/[m.sup.3]   Median                150(b)
  (VAPS)               Range
                       No. days w/ data
                       No. days > 150
                         (%days)

PM-TSP                 Average [+ or -] SD
  [micro]g/[m.sup.3]   Median
                       Range
                       No. days w/ data
                       No. days > 150
                         (%days)

[SO.sub.2]             Average [+ or -] SD    80(a)   150(b)
  [micro]g/[m.sup.3]   Median                365(b)
                       Range
                       No. days w/ data
                       No. days > 150
                         (%days)

[NO.sub.x]             Average [+ or -] SD   100(a)   100(b)
  [micro]g/[m.sup.3]   Median
                       Range
                       No. days w/ data
                       No. days > 100
                         (%days)

CO                     Average [+ or -] SD    10(e)     1(a)
        mg/[m.sup.3]   Median
                       Range
                       No. days w/ data
                       No. days > 10
                         (%days)


(a) Annual arithmetic mean (mathematics) arithmetic mean - The mean of a list of N numbers calculated by dividing their sum by N. The arithmetic mean is appropriate for sets of numbers that are added together or that form an arithmetic series. .

(b) 24-hr average (in the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. ; not to be exceeded more than once a year) (3).

(c) A limit is not officially determined for [PM.sub.10] in the Czech Republic, but 150 is generally accepted (2).

(d) Only one sample was available.

(e) 8-hr average not to be exceeded more than once a year.

Statistical analyses. We entered all data into SAS (1) (SAS Institute Inc., Cary, NC, www.sas.com) A software company that specializes in data warehousing and decision support software based on the SAS System. Founded in 1976, SAS is one of the world's largest privately held software companies. See SAS System.  (SAS Institute SAS Institute Inc., headquartered in Cary, North Carolina, USA, has been a major producer of software since it was founded in 1976 by Anthony Barr, James Goodnight, John Sall and Jane Helwig. , Cary, NC) and calculated summary statistics. Initially we used the Wilcoxon and Kruskal-Wallis tests for unadjusted comparisons between the two districts and the three exposures. We conducted multivariable regression in tiers: first, differences for each outcome were examined by district, then by season, and finally by exposure categories. In addition, season was considered a potential confounder con·found  
tr.v. con·found·ed, con·found·ing, con·founds
1. To cause to become confused or perplexed. See Synonyms at puzzle.

2.
, because it is related to exposure in these communities, for those outcomes with a priori a priori

In epistemology, knowledge that is independent of all particular experiences, as opposed to a posteriori (or empirical) knowledge, which derives from experience.
 data suggesting an association with season (32,33).

Outcome data were analyzed as continuous variables after transformation as needed as needed prn. See prn order.  to correct for nonnormal distribution: Log (count, concentration, number of progressive sperm, and SCSA COMP[[Alpha].sub.t]); square root [percent sperm with normal morphology, percent sperm with morphologically mor·phol·o·gy  
n. pl. mor·phol·o·gies
1.
a. The branch of biology that deals with the form and structure of organisms without consideration of function.

b.
 normal heads, semen volume, and curvilinear velocity (CASA)].

In all analyses we assessed risk factors known or suspected to be associated with poor semen quality (34) for inclusion in the models. Factors considered included sexual abstinence Sexual abstinence is the practice of voluntarily refraining from some or all aspects of sexual activity. Common reasons to deliberately abstain from the physical expression of sexual desire include religious or philosophical reasons (e.g.  [[is less than] 2 days vs. longer (35,36)], high fever ([is greater than] 38 [degrees] C) within the last 3 months, wearing briefs vs. loose-fitting underwear, alcohol consumption (0-25 mL ethanol/ week, 25-199 mL/week, or [is greater than or equal to] 200 mL/week), cigarette smoking [none, [is less than] one pack/day, or [is greater than or equal to] 1 pack/day (37)], caffeine caffeine (kăfēn`), odorless, slightly bitter alkaloid found in coffee, tea, kola nuts (see cola), ilex plants (the source of the Latin American drink maté), and, in small amounts, in cocoa (see cacao).  consumption [[is less than or equal to] 1/2 coffee cup equivalents, 1/2-3 cups, or [is greater than or equal to] 3 cup/day (38)], and hobby or work with solvents ([is greater than or equal] 10 hr/week vs. less) or with metals ([is greater than or equal] 10 hr/week vs. less). The volume of ethanol was estimated based on the self-reported numbers of servings of beer, wine, or liquor consumed per week and the serving size (which is regulated precisely in the Czech Republic and determines the amount of alcohol per drink). We considered other factors such as the use of medications or the presence of genital tract genital tract
n.
The genital passages of the urogenital system.


Genital tract
The organs involved in reproduction.
 conditions found by physical examination or by questionnaire, but the number of men affected was too small to be informative, and all of the men presented semen within the range of normal values normal values
pl.n.
A set of laboratory test values used to characterize apparently healthy individuals, now replaced by reference values.
 as specified by the WHO (12).

Results

Participation and description of the study group. Sixty-one percent of those men who were sent appointment notices came to the study center for their physical examination and completed the questionnaire portion of the study (408 of 670). Reasons for missing the appointment were not ascertained but are unlikely to affect response to the request for semen samples because the appointment notice did not specifically mention a reproductive health assessment. Of the men who completed the physical-and questionnaire, 67% (273) agreed to provide a semen sample. One specimen container leaked, which left a total of 272 semen samples available for analysis.

Based on physical examination and questionnaire data, men from Teplice and Prachatice were similar with respect to descriptive factors (height, total testicular testicular /tes·tic·u·lar/ (tes-tik´u-lar) pertaining to a testis.

tes·tic·u·lar
adj.
Of or relating to a testicle or testis.



testicular

pertaining to the testis.
 volume, age at first semen appearance, cigarette, and alcohol and caffeine consumption) (Table 2). The only differences by district were that on average, men in Prachatice weighed more than men in Teplice and were more likely to consume alcohol. None of the men were judged to be sexually immature immature /im·ma·ture/ (im?ah-chldbomacr´) unripe or not fully developed.

im·ma·ture
adj.
Not fully grown or developed.



immature

unripe or not fully developed.
 on the basis of testis size or physical development. No differences were observed in any of these factors between those who were only interviewed and those who provided semen samples (Table 2). Table 3 shows other potential risk factors and confounders examined for inclusion in the regression models by exposure category. Of these, differences in distribution were noted for amount of alcohol and caffeine consumed per day and for the number of men with [is greater than] 10 hr/week exposure to solvents or metals through work or hobbies. Several potential risk factors were present in the medical histories of only a few men (mumps, one case; injury to testes, one case; hydrocele hydrocele /hy·dro·cele/ (hi´dro-sel) a circumscribed collection of fluid, especially in the tunica vaginalis of the testis or along the spermatic cord.

hy·dro·cele
n.
, one case; and varicocele varicocele /var·i·co·cele/ (var´i-ko-sel)
1. varicosity of the pampiniform plexus of the spermatic cord, forming a scrotal swelling that feels like a “bag of worms.”

2.
, six cases in men from Prachatice and two cases in men from Teplice). These cases were reviewed individually and because each had semen measures above the WHO reference values ref·er·ence values
pl.n.
A set of laboratory test values obtained from an individual or from a group in a defined state of health.
 (39), none were excluded from the database.

Table 2. Characteristics of 18-year-old males in the study (mean [+ or -] SD).
                             All men interviewed

                                   Teplice
Characteristic                    (n = 215)

Height (cm)                  177.6 [+ or -] 6.8

Weight (kg)                   71.5 [+ or -] 13.2

Total testicular              44.0 [+ or -] 19.4
volume ([cm.sup.3])

Age semen appeared            14.1 [+ or -] 1.1
(years)

Smoker? (% yes)               37.7%
  Cigarettes/day              11.6 [+ or -] 8.4

Drinker? (% yes)              70.2%
  Alcohol/week (mL)          102.1 [+ or -] 105.9

Coffee equivalent/day(a)       1.3 [+ or -] 1.3

Work/hobbies with solvents    15.8%
  > 10 hr/week? (% yes)

Work/hobbies with metals      13.0%
  > 10 hr/wk? (% yes)

                             All men interviewed

                                  Prachatice
Characteristic                    (n = 193)

Height (cm)                  178.7 [+ or -] 7.4

Weight (kg)                   73.9 [+ or -] 11.5(*)

Total testicular              44.6 [+ or -] 19.7
volume ([cm.sup.3])

Age semen appeared            14.1 [+ or -] 1.1
(years)

Smoker? (% yes)               43.0%
  Cigarettes/day              10.3 [+ or -] 7.0

Drinker? (% yes)              80.8%(*)
  Alcohol/week (mL)          111.7 [+ or -] 132.1

Coffee equivalent/day(a)       1.3 [+ or -] 1.5

Work/hobbies with solvents    16.2%
  > 10 hr/week? (% yes)

Work/hobbies with metals      11.9%
  > 10 hr/wk? (% yes)

                                 Semen donors

                                   Teplice
Characteristic                    (n = 154)

Height (cm)                  177.9 [+ or -] 6.8

Weight (kg)                   71.0 [+ or -] 11.4

Total testicular              43.2 [+ or -] 16.7
volume ([cm.sup.3])

Age semen appeared            14.0 [+ or -] 1.1
(years)

Smoker? (% yes)               40.9%
  Cigarettes/day              11.4 [+ or -] 8.0

Drinker? (% yes)              67.5%
  Alcohol/week (mL)          109.4 [+ or -] 117.1

Coffee equivalent/day(a)       1.3 [+ or -] 1.3

Work/hobbies with solvents    14.9%
  > 10 hr/week? (% yes)

Work/hobbies with metals      14.9%
  > 10 hr/wk? (% yes)

                                 Semen donors

                                  Prachatice
Characteristic                    (n = 118)

Height (cm)                  178.9 [+ or -] 7.3

Weight (kg)                   74.0 [+ or -] 11.4(*)

Total testicular              43.1 [+ or -] 17.2
volume ([cm.sup.3])

Age semen appeared            14.0 [+ or -] 1.1
(years)

Smoker? (% yes)               43.2%
  Cigarettes/day              10.7 [+ or -] 6.9

Drinker? (% yes)              78.8%(*)
  Alcohol/week (mL)          134.5 [+ or -] 156.2

Coffee equivalent/day(a)       1.4 [+ or -] 1.4

Work/hobbies with solvents    16.1%
  > 10 hr/week? (% yes)

Work/hobbies with metals      12.7%(*)
  > 10 hr/wk? (% yes)


(a) Calculated as in Pastore and Savitz (38).

(*) p < 0.05 by Wilcoxon or Chi Square chi square (kī),
n a nonparametric statistic used with discrete data in the form of frequency count (nominal data) or percentages or proportions that can be reduced to frequencies.
 test comparing Teplice to Prachatice; no differences were found in the comparison of all men interviewed to semen donors.

Table 3. Distribution of factors (%) by exposure category(a) in men with semen samples.
                            Low       Medium      High
Factor                   (n = 162)   (n = 63)   (n = 47)

District(*)
  Teplice                   27.2       100.0      100.0
  Prachatice                72.8         0.0        0.0

Smokes cigarettes
  None                      59.3        50.8       63.8
  1-19/day                  32.7        31.8       31.9
  20+/day                    8.0        17.5        4.36

Drinks alcohol(*)
  < 25 mL/day               33.3        47.6       48.9
  25-199 mL/day             51.9        42.9       38.3
  200+ mL/day               14.8         9.5       12.8

Caffeine(*)(b)
  None (< 0.5)              34.2        39.7       10.6
  0.5- < 3 cups/day         55.9        44.4       74.5
  3+ cup/day                 9.9        15.9       14.9

Abstinence
  2+ days                   83.1        74.6       89.4
  < 2 days                  16.9        25.4       10.6

Fever > 38 [degrees] C
  No                        88.9        88.9       87.2
  Yes                       11.1        11.1       12.8

Wears briefs
  No                        19.9        14.3       17.4
  Yes                       80.1        85.7       82.6

Work/hobbies
with metals(*)
  < 10 hr/week              90.1        84.1       74.5
  10+ hr/week                9.9        15.9       25.5

Work/hobbies
with solvents
  < 10 hr/week              85.2        90.5       74.5
  10+ hr/week               14.8         9.5       25.5


(a) Low: Prachatice, all samples; Teplice, fall 1993; medium: Teplice, winter 1994; high: Teplice, winter 1993 (see Table 1).

(b) Calculated as in Pasture pasture, land used for grazing livestock. Land unsuited for cultivation, e.g., hilly or stony land, may be used as pasture. Tilled land and meadow may be pastured after the crops are removed.  and Savitz (38).

(*) p < 0.05 by Mantel-Haenszel chi square.

Semen quality. Semen volume and sperm numbers. The mean (median) semen volume for the entire group was 1.96 (1.80) mL and did not differ by district (Table 4). Two men were azospermic (0.5%) (one from each district) but neither was sampled after periods of medium or high pollution. There was no apriori reason to exclude them from the analysis; however, excluding them did not alter the sample median (data not shown). The mean (median) sperm concentration for all sampled men was 61.2 (44.0) million/mL semen (Table 4). The current WHO reference value for sperm concentration is [is greater than or equal to] 20 million/mL (39). In this group of men, 21% had sperm concentrations [is less than] 20 million/mL (21% in Teplice and 22% in Prachatice). No significant difference was observed by exposure category (Table 5).
Table 4. Semen outcomes: summary and by district.

                                            Summary

Outcome                           No.     Mean [+ or -] SD

Production of viable sperm
  Semen volume (mL)               272    1.96 [+ or -] 1.06
  Concentration (millions/mL)     272    61.2 [+ or -] 60.9
  Total count (millions/sample)   272   113.3 [+ or -] 119.2
  Percent motile(*)               256    33.6 [+ or -] 17.2
  Total motile (in millions)      256    44.2 [+ or -] 68.4
  Total progressive               228    33.3 [+ or -] 45.2
    (in millions)(a,b)

Sperm structure
  Percent normal morphology(*)    262    17.8 [+ or -] 8.0
  Percent morphologically         262    36.5 [+ or -] 10.1
    normal heads(*)
  SCSA COMP[[Alpha].sub.t]        266    20.2 [+ or -] 14.0

Quality of sperm
motion--CASA(b)
  VSL                             228    44.3 [+ or -] 9.6
  VCL                             228    91.8 [+ or -] 20.8
  Linearity                       228    48.6 [+ or -] 8.0

                                        Summary

Outcome                           Median     Range

Production of viable sperm
  Semen volume (mL)                1.80     0.5-6.0
  Concentration (millions/mL)      44.0       0-456
  Total count (millions/sample)    81.5       0-780
  Percent motile(*)                32.9       0-84
  Total motile (in millions)       24.3       0-579.7
  Total progressive                19.8     0.6-354.8
    (in millions)(a,b)

Sperm structure
  Percent normal morphology(*)     16.7       1-53.5
  Percent morphologically          35.5    10.7-76.0
    normal heads(*)
  SCSA COMP[[Alpha].sub.t]         15.9     2.0-81.0

Quality of sperm
motion--CASA(b)
  VSL                              45.0    20.1-72.0
  VCL                              90.9    48.6-139.3
  Linearity                        49.0    28.0-69.0

                                          Prachatice

Outcome                           No.    Mean  [+ or -] SD

Production of viable sperm
  Semen volume (mL)               118    2.09 [+ or -] 1.09
  Concentration (millions/mL)     118    60.6 [+ or -] 66.3
  Total count (millions/sample)   118   119.3 [+ or -] 137.0
  Percent motile(*)               113    36.1 [+ or -] 17.9
  Total motile (in millions)      113    52.5 [+ or -] 82.5
  Total progressive               105    38.6 [+ or -] 54.2
    (in millions)(a,b)

Sperm structure
  Percent normal morphology(*)    111    19.3 [+ or -] 8.6
  Percent morphologically         111    39.3 [+ or -] 11.0
    normal heads(*)
  SCSA COMP[[Alpha].sub.t]        116    19.8 [+ or -] 12.1

Quality of sperm
motion--CASA(b)
  VSL                             105    44.1 [+ or -] 9.6
  VCL                             105    93.0 [+ or -] 21.9
  Linearity                       105    48.0 [+ or -] 8.5

                                       Prachatice

Outcome                           Median     Range

Production of viable sperm
  Semen volume (mL)                2.00     0.5-6.0
  Concentration (millions/mL)      39.0       0-456
  Total count (millions/sample)    79.0       0-780
  Percent motile(*)                36.0       0-75
  Total motile (in millions)       27.6       0-579.7
  Total progressive                22.2     0.6-354.8
    (in millions)(a,b)

Sperm structure
  Percent normal morphology(*)     17.7     1.0-53.5
  Percent morphologically          39.0    10.7-76.0
    normal heads(*)
  SCSA COMP[[Alpha].sub.t]         15.9     2.7-57.6

Quality of sperm
motion--CASA(b)
  VSL                              45.2    21.5-65.7
  VCL                              91.9    51.7-139.3
  Linearity                        48.0    31.0-68.0

                                            Teplice

Outcome                           No.    Mean  [+ or -] SD

Production of viable sperm
  Semen volume (mL)               154    1.86 [+ or -] 1.03
  Concentration (millions/mL)     154    61.7 [+ or -] 56.6
  Total count (millions/sample)   154   108.6 [+ or -] 103.7
  Percent motile(*)               143    31.6 [+ or -] 16.3
  Total motile (in millions)      143    37.5 [+ or -] 54.2
  Total progressive               123    28.9 [+ or -] 35.4
    (in millions)(a,b)

Sperm structure
  Percent normal morphology(*)    151    16.6 [+ or -] 7.3
  Percent morphologically         151    34.4 [+ or -] 8.7
    normal heads(*)
  SCSA COMP[[Alpha].sub.t]        150    20.5 [+ or -] 15.4

Quality of sperm
motion--CASA(b)
  VSL                             123   44.5 [+ or -] 9.6
  VCL                             123   90.7 [+ or -] 19.9
  Linearity                       123   49.2 [+ or -] 7.5

                                        Teplice

Outcome                           Median     Range

Production of viable sperm
  Semen volume (mL)                1.70     0.5-5.5
  Concentration (millions/mL)      49.5       0-421
  Total count (millions/sample)    82.1       0-624
  Percent motile(*)                31.1       0-84
  Total motile (in millions)       22.5       0-398.1
  Total progressive                18.0     0.6-261.7
    (in millions)(a,b)

Sperm structure
  Percent normal morphology(*)     16.0     1.0-36.3
  Percent morphologically          33.7    15.0-60.7
    normal heads(*)
  SCSA COMP[[Alpha].sub.t]         15.8     2.0-81.0

Quality of sperm
motion--CASA(b)
  VSL                              44.0    20.1-72.0
  VCL                              90.1    48.6-132.3
  Linearity                        49.0    28.0-69.0


(a) Total progressive = Total motile x percent sperm with VSL > 25 [micro]m/sec.

(b) Only for samples with at least 25 sperm tracks; VSL and VCL are in [micro]m/sec.

(*) Different by district, p < 0.05 by Wilcoxon test Wilcoxon test

a test used in statistics to compare paired data. Has the advantage of incorporating the size of the difference between the two sets of data in the comparison.
.
Table 5. Semen outcomes by exposure.

                                             Low

Outcome                           No.     Mean [+ or -] SD

Production of viable sperm
  Semen volume(*) (mL)            162    2.00 [+ or -] 1.07
  Concentration (millions/mL)     162    59.9 [+ or -] 64.3
  Total count (millions/sample)   162   113.5 [+ or -] 130.7
  Percent motile(*)               156    36.2 [+ or -] 17.1
  Total motile (in millions)      156    50.6 [+ or -] 79.6
  Total progressive               139    36.6 [+ or -] 50.5
    (in millions)(*)(a,b)

Sperm structure
  Percent normal morphology(*)    154    19.8 [+ or -] 8.5
  Percent morphologically         154    39.3 [+ or -] 10.9
    normal heads(*)
  SCSA COMP[[Alpha].sub.t](*)     158    19.2 [+ or -] 12.2

Quality of sperm
motion--CASA(b)
  VSL(*)                          139    43.3 [+ or -] 10.0
  VCL(*)                          139    91.4 [+ or -] 21.7
  Linearity(*)                    139    47.6 [+ or -] 8.2

                                        Low

Outcome                           Median     Range

Production of viable sperm
  Semen volume(*) (mL)             1.90     0.5-6.0
  Concentration (millions/mL)      39.5       0-456
  Total count (millions/sample)    69.9     0.0-780
  Percent motile(*)                35.2       0-76
  Total motile (in millions)       25.0       0-580
  Total progressive                20.3     0.6-354.8
    (in millions)(*)(a,b)

Sperm structure
  Percent normal morphology(*)     18.3     1.0-53.5
  Percent morphologically          39.0    10.7-76.0
    normal heads(*)
  SCSA COMP[[Alpha].sub.t](*)      15.6     2.7-67.1

Quality of sperm
motion--CASA(b)
  VSL(*)                           44.1    21.5-66.2
  VCL(*)                           90.1    51.7-139.3
  Linearity(*)                     48.0    28.0-68.0

                                           Medium

Outcome                           No.    Mean [+ or -] SD

Production of viable sperm
  Semen volume(*) (mL)            63     1.65 [+ or -] 0.77
  Concentration (millions/mL)     63     65.4 [+ or -] 61.6
  Total count (millions/sample)   63    100.9 [+ or -] 97.6
  Percent motile(*)               63     27.9 [+ or -] 18.1
  Total motile (in millions)      63     29.8 [+ or -] 46.6
  Total progressive               58     23.5 [+ or -] 36.3
    (in millions)(*)(a,b)

Sperm structure
  Percent normal morphology(*)    62     15.9 [+ or -] 5.5
  Percent morphologically         62     30.3 [+ or -] 6.5
    normal heads(*)
  SCSA COMP[[Alpha].sub.t](*)     61     16.2 [+ or -] 9.3

Quality of sperm
motion--CASA(b)
  VSL(*)                          58     44.6 [+ or -] 9.5
  VCL(*)                          58     84.2 [+ or -] 17.6
  Linearity(*)                    58     53.2 [+ or -] 6.5

                                        Medium

Outcome                           Median     Range

Production of viable sperm
  Semen volume(*) (mL)              1.6     0.5-4.0
  Concentration (millions/mL)      56.0     0.1-421
  Total count (millions/sample)    82.6     0.1-560
  Percent motile(*)                25.0       0-84
  Total motile (in millions)       18.0       0-337
  Total progressive                17.2     0.6-61.7
    (in millions)(*)(a,b)

Sperm structure
  Percent normal morphology(*)     14.7     3.0-27.3
  Percent morphologically          29.4    16.7-45.7
    normal heads(*)
  SCSA COMP[[Alpha].sub.t](*)      14.5     2.0-45.6

Quality of sperm
motion--CASA(b)
  VSL(*)                           43.8    20.1-72.0
  VCL(*)                           79.8    48.6-129.0
  Linearity(*)                     53.0    39.0-69.0

                                             High

Outcome                           No.    Mean [+ or -] SD

Production of viable sperm
  Semen volume(*) (mL)            47     2.24 [+ or -] 1.28
  Concentration (millions/mL)     47     60.1 [+ or -] 46.7
  Total count (millions/sample)   47    129.1 [+ or -] 103.1
  Percent motile(*)               37     32.5 [+ or -] 13.2
  Total motile (in millions)      37     41.6 [+ or -] 40.4
  Total progressive               31     37.2 [+ or -] 31.4
    (in millions)(*)(a,b)

Sperm structure
  Percent normal morphology(*)    46     13.2 [+ or -] 6.5
  Percent morphologically         46     35.2 [+ or -] 6.8
    normal heads(*)
  SCSA COMP[[Alpha].sub.t](*)     47     28.8 [+ or -] 20.4

Quality of sperm
motion--CASA(b)
  VSL(*)                          31     48.3 [+ or -] 7.4
  VCL(*)                          31    107.8 [+ or -] 12.1
  Linearity(*)                    31     44.7 [+ or -] 5.6

                                        High

Outcome                           Median     Range

Production of viable sperm
  Semen volume(*) (mL)               2.0    0.5-5.5
  Concentration (millions/mL)       42.0      6-210
  Total count (millions/sample)    106.4    4.5-383
  Percent motile(*)                 33.8      0-51
  Total motile (in millions)        33.2      0-161
  Total progressive                 28.7    2.6-118.5
    (in millions)(*)(a,b)

Sperm structure
  Percent normal morphology(*)      13.5    1.0-28.5
  Percent morphologically           35.0   23.5-48.0
    normal heads(*)
  SCSA COMP[[Alpha].sub.t](*)       25.7    2.9-81.0

Quality of sperm
motion--CASA(b)
  VSL(*)                            50.4   27.9-59.9
  VCL(*)                           105.2   87.6-131.6
  Linearity(*)                      45.0   32.0-57.0


(a) Total progressive = Total motile x percent sperm with VSL > 25 [micro]m/sec.

(b) Only for samples with at least 25 sperm tracks; VSL and VCL are in [micro]m/sec.

(*) Different by Kruskal-Wallis test, p < 0.05.

The duration of sexual abstinence in these young men averaged 4.6 days ([+ or -] 4.4 days SD; range [is less than] 1-31 days), however, 18% were abstinent for [is less than] 2 days. Secondary analyses of abstinence data revealed that the best model to correct for short abstinence for this data set was [is less than] 2 days versus [is greater than or equal to] 2 days (40). After controlling for short abstinence, no relationship was found between sperm concentration or total sperm count and exposure to periods of medium or high air pollution (Table 6).
Table 6. Results of adjusted regression analyses, beta (95% CI).(a)

                                 Preliminary analyses

                        Teplice versus
Measure                   Prachatice               Season

Production of
viable sperm

Semen volume (mL)    -0.07 (-0.16-0.02)       0.04 (-0.06-0.14)
  Adjusted(a)                  A                      A
Concentration
(millions/mL)         0.08 (-0.03-0.18)       0.01 (-0.10-0.12)
  Adjusted(a)                A                       A
Total count
(millions/sample)     0.04 (-0.08-0.16)       0.04 (-0.08-0.16)
  Adjusted(a)                A, H                    A, H
Percent motile       -3.82 (-7.94-0.29)      -3.62 (-8.01-0.77)
  Adjusted(a)                B, H, S                 B, H, S
Total motile
(in millions)        -0.07 (-0.20-0.06)      -0.09 (-0.22-0.05)
  Adjusted(a)                A, H                    A, H
Total progressive
(b,c)(in millions)   -0.04 (-0.17-0.08)      -0.11 (-0.24-0.02)
  Adjusted(a)                A, H, S                 A, H, S

Sperm structure

Percent normal
morphology           -0.35 (-0.59-0.11)(*)   -0.21 (-0.47-0.04)
  Adjusted(a)                 --                     --
Percent
morphologically
normal heads         -0.38 (-0.58-0.18)(*)   -0.17 (-0.39-0.05)
  Adjusted(a)                 --                     --
SCSA COMP
[[Alpha].sub.t]      -0.02 (-0.09-0.05)       0.04 (-0.03-0.12)
  Adjusted(a)                 Smk                    Smk

Quality of sperm
motion--CASA(c)

VSL                   0.32 (-2.12-2.76)       5.80 (3.19-8.40)(*)
  Adjusted(a)                C, S                   C, S
VCL                  -0.01 (-0.03-0.02)       0.20 (-0.11-0.50)
  Adjusted(a)             B, C, S, Smk              C, S
LIN                   1.03 (-1.04-3.10)       5.46 (3.29-7.64)(*)
  Adjusted(a)                M                       --

                         Final analyses

                         Medium vs. low

Measure                    Adjusted(a)

Production of
viable sperm

Semen volume (mL)    -0.11 (-0.22-0.00)
  Adjusted(a)                A
Concentration
(millions/mL)         0.08 (-0.05-0.20)
  Adjusted(a)                A
Total count
(millions/sample)     0.02 (-0.125-0.17)
  Adjusted(a)                A, C
Percent motile       -8.12 (-12.95--3.30)(*)
  Adjusted(a)                B, H, S, Smk
Total motile
(in millions)        -0.16 (-0.32--0.01)(*)
  Adjusted(a)                A, H
Total progressive
(b,c)(in millions)   -0.15 (-0.30--0.01)(*)
  Adjusted(a)                A, H

Sperm structure

Percent normal
morphology           -0.42 (-0.69--0.14)(*)
  Adjusted(a)                  --
Percent
morphologically
normal heads         -0.73 (-0.96--0.50)(*)
  Adjusted(a)
SCSA COMP
[[Alpha].sub.t]      -0.14 (-0.34-0.06)
  Adjusted(a)                  Smk

Quality of sperm
motion--CASA(c)

VSL                   0.88 (-2.00-3.75)
  Adjusted(a)                C, Smk
VCL                  -0.04 (-0.06--0.01)(*)
  Adjusted(a)                B, C, S, Smk
LIN                   5.60 (3.25-7.95)(*)
  Adjusted(a)                A, M

                         Final analyses

                         Medium vs. low

Measure                    With Season

Production of
viable sperm

Semen volume (mL)     -0.16 (-0.29--0.03)
  Adjusted(a)                 A
Concentration
(millions/mL)          0.10 (-0.05-0.25)
  Adjusted(a)                 A
Total count
(millions/sample)    -0.003 (-0.17-0.16)
  Adjusted(a)                 A, C
Percent motile        -8.03 (-13.57--2.49)(*)
  Adjusted(a)                 B, H, S, Smk
Total motile
(in millions)         -0.14 (-0.32-0.03)
  Adjusted(a)                 A, H
Total progressive
(b,c)(in millions)    -0.11 (-0.27-0.05)
  Adjusted(a)                 A, H

Sperm structure

Percent normal
morphology            -0.54 (-0.86--0.22)(*)
  Adjusted(a)                  --
Percent
morphologically
normal heads          -0.87 (-1.13--0.60)(*)
  Adjusted(a)                  --
SCSA COMP
[[Alpha].sub.t]               NA(d)
  Adjusted(a)

Quality of sperm
motion--CASA(c)

VSL                   -2.10 (-5.24-1.03)
  Adjusted(a)                C, Smk
VCL                   -0.05 (-0.08--0.01)(*)
  Adjusted(a)                B, C, S, Smk
LIN                    3.28 (0.73-5.83)(*)
  Adjusted(a)                A, M

                        Final analyses

                         High vs. low

Measure                  Adjusted(a)

Production of
viable sperm

Semen volume (mL)     0.06 (-0.06-0.18)
  Adjusted(a)                A
Concentration
(millions/mL)         0.05 (-0.09-0.19)
  Adjusted(a)                A
Total count
(millions/sample)     0.11 (-0.05-0.27)
  Adjusted(a)                A, C
Percent motile       -3.02 (-8.99-2.95)
  Adjusted(a)                B, H, S, Smk
Total motile
(in millions)        -0.02 (-0.21-0.16)
  Adjusted(a)                A, H
Total progressive
(b,c)(in millions)    0.03 (-0.14-0.21)
  Adjusted(a)                A, H

Sperm structure

Percent normal
morphology           -0.84 (-1.15--0.53)(*)
  Adjusted(a)                  --
Percent
morphologically
normal heads         -0.30 (-0.56--0.04)(*)
  Adjusted(a)                  --
SCSA COMP
[[Alpha].sub.t]       0.30 (0.08-0.52)(*)
  Adjusted(a)                 Smk

Quality of sperm
motion--CASA(c)

VSL                   4.21 (0.56-7.86)(*)
  Adjusted(a)               C, Smk
VCL                   0.07 (0.03-0.11)(*)
  Adjusted(a)               B, C, S, Smk
LIN                  -3.67 (-6.61--0.74)(*)
  Adjusted(a)               A, M

                        Final analyses

                         High vs. low

Measure                  With season

Production of
viable sperm

Semen volume (mL)     0.01 (-0.12-0.15)
  Adjusted(a)                A
Concentration
(millions/mL)         0.07 (-0.08-0.23)
  Adjusted(a)                A
Total count
(millions/sample)     0.09 (-0.09-0.26)
  Adjusted(a)                A, C
Percent motile       -2.93 (-9.49-3.64)
  Adjusted(a)                B, H, S, Smk
Total motile
(in millions)        -0.01 (-0.21-0.20)
  Adjusted(a)                A, H
Total progressive
(b,c)(in millions)    0.07 (-0.12-0.27)
  Adjusted(a)                A, H

Sperm structure

Percent normal
morphology           -0.96 (-1.31--0.62)(*)
  Adjusted(a)
Percent
morphologically
normal heads         -0.44 (-0.73--0.14)(*)
  Adjusted(a)                  --
SCSA COMP
[[Alpha].sub.t]              NA(d)
  Adjusted(a)

Quality of sperm
motion--CASA(c)

VSL                   1.38 (-2.42-5.17)
  Adjusted(a)                C, Smk
VCL                   0.06 (0.02-0.10)(*)
  Adjusted(a)                B, C, S, Smk
LIN                  -5.88 (-8.93--2.82)(*)
  Adjusted(a)                A, M


Abbreviations:

A, abstinence;

B, wearing briefs;

C, caffeine;

H, high fever;

M, work/hobbies with metals;

S, work/hobbies with solvents;

Smk, packs of cigarettes.

(a) Factors considered for adjustment include those listed in Table 3.

(b) Total progressive = Total motile x percent sperm with VSL [is greater than or equal to] 25 [micro]m/sec.

(c) Only for samples with at least 25 sperm tracks; VSL and VCL are in [micro]m/sec.

(d) Not applicable; because SCSA was not associated with season in a longitudinal study longitudinal study

a chronological study in epidemiology which attempts to establish a relationship between an antecedent cause and a subsequent effect. See also cohort study.
 (25), this outcome was not tested for potential confounding confounding

when the effects of two, or more, processes on results cannot be separated, the results are said to be confounded, a cause of bias in disease studies.


confounding factor
 by season.

(*) p < 0.05.

Sperm motility and motion. In all samples, the average (mean) percentage of motile sperm was 33.6% (32.9%) and the mean for Prachatice donors was slightly, but significantly, higher than that for Teplice donors (Table 4). These mean values fall below the WHO reference value for percentage of motile sperm which is [is greater than] 50% (38). Percent motile was also different by exposure category (Table 5). After controlling for appropriate lifestyle factors, the multivariable analysis showed a significant relationship between the percentage of motile sperm and a period of medium, but not high, air pollution; this relationship remained after control of confounding by season (Table 6). This decrease in percent motile sperm translates into a significant exposure-related association with the total number of motile sperm per sample and the total number of progressive sperm (VSL [is greater than or equal to] 25 [micro]m/sec) for the medium exposure group (Table 6). However, after control for confounding by season, these associations were no longer significant.

CASA measures the quality of motion of the motile population of sperm. Although data were generated for seven CASA parameters for each sperm track, some of these measures were significantly correlated with each other and therefore are not independent. For example, VAP was highly correlated with VSL (r = 0.94), STR was highly correlated with LIN (r = 0.85), and three vigor terms were highly correlated: ALH and BCF were highly correlated with VCL (r = 0.89 and r = 0.31, respectively). We selected three measures that describe different aspects of sperm motion: VSL (the absolute distance traveled over time), a measure of progression, VCL (the average point to point velocity), a measure of vigor, and LIN (VSL/VCL x 100), a measure of swimming pattern, and considered them individually. These measures are also relatively independent of the type of CASA instrument used; therefore, results for these measures are more readily compared with those in other studies.

There were no associations between district of residence and any of these three measures (Tables 4 and 6). In contrast, there was a strong positive association between VSL and LIN, but not VCL, and season (Table 6), suggesting that sperm may swim faster and with straighter paths in the winter. Mean VSL was also higher in samples obtained after exposure to the season of high pollution (winter 1993) (Table 5), but the significance of this association disappeared after control for confounding by season (Table 6). Interestingly, VCL was also higher in this group of samples (Table 5), and this association remained significant (though relatively weak) after control for confounding by season (Tables 5 and 6). This apparent increase in sperm vigor (VCL), without an increase in progression (VSL), resulted in lower mean LIN (Table 5) and a significant negative association between exposure and LIN (Table 6), apparently because mean VCL increased relatively more than mean VSL. With increases in both VSL and VCL, the decrease in LIN would not be considered a sign of weakened-sperm motility. In the samples obtained after exposure to periods of medium air pollution (winter 1994), mean VSL was unchanged but mean VCL was decreased (Table 5) compared to the reference group (periods of low air pollution), resulting in an apparently contradictory positive association between exposure and LIN (Tables 5 and 6). These results may be biased by two factors that reduced the sample size for CASA analysis: a) 10 of 47 (31%) samples obtained in winter 1993 could not be analyzed by CASA because of technical problems; and b) samples with fewer than 25 motile sperm tracks were not included in the analyses because we did not consider means based on [is less than] 25 sperm to be representative of the sample. These samples without CASA data were distributed across exposure groups as follows: 21 of 160 or 13% in the low-exposure group, 3 of 63 or 5% in the medium-exposure group, and 6 of 47 or 13% in the high-exposure group.

Sperm structure. The mean ([+ or -] SD) percentage of normal sperm for all samples was 17.8 [+ or -] 8.0% (Table 4). The most recent WHO guidance (39) does not specify a reference value for this measure because multicenter population-based studies are underway to derive one using standardized standardized

pertaining to data that have been submitted to standardization procedures.


standardized morbidity rate
see morbidity rate.

standardized mortality rate
see mortality rate.
 strict criteria (as used in this study) for scoring each cell. Nevertheless, the guidance notes that as sperm morphology falls below 15% normal forms (using strict criteria for scoring sperm as normal), the fertilization fertilization, in biology, process in the reproduction of both plants and animals, involving the union of two unlike sex cells (gametes), the sperm and the ovum, followed by the joining of their nuclei.  rate in vitro in vitro /in vi·tro/ (in ve´tro) [L.] within a glass; observable in a test tube; in an artificial environment.

in vi·tro
adj.
In an artificial environment outside a living organism.
 decreases. We observed significant negative relationships between district of residence and/or exposure to periods of medium or high air pollution and the percent of sperm with overall normal morphology (considering head, midpiece, and tail) as well as the percent with normal head morphology (Tables 4-6). As demonstrated in Tables 4 and 5, we observed significant differences by district alone and by air pollution category alone, but these outcomes were unrelated to season. In the multivariable regression analyses, both the percentage of normal sperm and the percentage of normal sperm heads were significantly lower in men exposed to periods of medium or high pollution (Table 6). These differences remained after control of confounding by season. The decrement To subtract a number from another number. Decrementing a counter means to subtract 1 or some other number from its current value.  in percent normal sperm shows an increasing exposure-response relationship. However, the percent of normal sperm heads, albeit significantly decreased for both exposed periods, did not show an increasing exposure-response pattern, suggesting that alterations of sperm head shape may be a significant component of the sperm morphology effect but do not account for all of it.

Analysis of the SCSA data focused on the COMP[[Alpha].sub.t] variable, the percent of sperm with abnormal chromatin (i.e., demonstrating increased susceptibility susceptibility

the state of being susceptible. Refers usually to infectious disease but may be to physical factors such as wetting or to psychological factors such as harassment.
 to DNA denaturation in situ In place. When something is "in situ," it is in its original location. ). COMP[[Alpha].sub.t] was significantly higher in samples obtained after the period of high, but not medium, air pollution (Table 5) and this association remained significant in the multivariable analysis (Table 6). A longitudinal study with monthly semen samples for 45 men for a total of 8 sequential months suggests that SCSA measures do not vary by season (25); therefore, the analysis for COMP[[Alpha].sub.t] did not include control for potential confounding by season.

Discussion

This study was undertaken to obtain a preliminary characterization of reproductive health in 18-year-old men who live in either of two districts in the Czech Republic. It was initiated because of community concern that living in the Teplice district, an area with periods of elevated air pollution during the winter (compared with the Prachatice district, an area with considerably lower air pollution), may be associated with increased abnormal reproductive health and/or poor semen quality. The data obtained are unusual in that all the men were young and of the same age when sampled. In addition, during these young men's lifetimes, movement between communities was uncommon. These demographics The attributes of people in a particular geographic area. Used for marketing purposes, population, ethnic origins, religion, spoken language, income and age range are examples of demographic data.  are advantageous when looking for Looking for

In the context of general equities, this describing a buy interest in which a dealer is asked to offer stock, often involving a capital commitment. Antithesis of in touch with.
 effects related to environmental exposures because the young men in this study group would have had similar lifetime exposures to environmental pollution and would be less likely than older men to have experienced significant occupational exposures to reproductive toxicants. Furthermore, changes in semen quality known or suspected to occur with advancing age are not an issue in this study group. On the other hand, few comparison databases on semen quality exist for men of this age and they were too young to evaluate their fertility.

Data obtained from the physical examination and questionnaire indicated that the young men living in Teplice were similar to those living in Prachatice with respect to physical characteristics, lifestyle, and general health. The physical examination revealed no evidence of delayed puberty Puberty is described as delayed when a boy or girl has passed the usual age of onset of puberty with no physical or hormonal signs that it is beginning. Puberty may be delayed for several years and still occur normally, in which case it is considered constitutional delay, a ; all men were sexually mature based on secondary sex characteristics secondary sex characteristic
n.
Any of various characteristics specific to females or males but not directly concerned with reproduction.


secondary sex characteristic 
. Furthermore, there were no differences by district in testicular volume or self-reported age at first semen appearance.

We categorized cat·e·go·rize  
tr.v. cat·e·go·rized, cat·e·go·riz·ing, cat·e·go·riz·es
To put into a category or categories; classify.



cat
 exposure in this study based on mean levels of pollutants monitored during the 90 days preceding the sample collection. Monitoring methods have been described in detail elsewhere (6) along with more detailed analyses of source (industry vs. home heating) and components (specific PAHs and metals). These efforts documented that periods of elevated air pollution occurred in Teplice in the winters of 1993 and 1994, with conditions being worse in 1993. Analysis of representative samples of particulate matter for metal content indicated that ambient lead and cadmium levels were well below the existing standards for these metals. However, because internal measures of metal exposure were not available in the study participants and exposure to these metals has been associated with adverse effects on semen quality (11), a potential association between metals in the air pollution and adverse semen outcomes cannot be ruled out. However, the specific component(s) of the air pollution that may account for any adverse effects observed in this study were not identified.

Although air measurements were made in one central location in each community, each individual's precise exposure to any component of the air pollution during the time period would be expected to depend on his location within the community, his activity patterns, and the weather conditions. The magnitude of exposure in the different sampling periods varied widely and was used to define periods of high, medium, or low air pollution for the purpose of analysis. If the important exposures are the peak levels, error may be introduced given the timing of these peaks within the 90-day period. Both the number of peaks and the time between the peaks and semen sampling varied between the two winters in Teplice. Because the ability to detect an effect of an acute exposure on a susceptible germ cell stage depends on the time the semen is sampled, such effects can be missed in a study such as this one, with only one sampling time. Also, an effect detected on a particular semen measure might be stronger one winter than the other, based on differences in the duration of the pollution episodes and the time between exposure and sampling. Thus, strict exposure-response relationships might not be expected. With these problems inherent in the study design, we considered each winter exposure period separately when making comparisons with the samples obtained after periods of relatively low exposures.

Sperm concentrations and total sperm counts in these men, although not significantly associated with district, season, or exposure to periods of elevated air pollution, were at the low end of the ranges reported for populations of men worldwide (41). With respect to reference values for these measures provided by the WHO (39), 54% of these samples fell below 2.0 mL for semen volume, 21% fell below 20 million/mL for sperm concentration, and 28% fell below 40 million sperm/sample for total sperm count. Short abstinence intervals in young men could account for these observations. However, even after omitting samples from men reporting [is less than] 2 days sexual abstinence, the respective percentages are still relatively high: 51% below 2.0 mL, 19% below 20 million sperm/mL, and 21% below 40 million sperm/sample. This sperm concentration statistic statistic,
n a value or number that describes a series of quantitative observations or measures; a value calculated from a sample.


statistic

a numerical value calculated from a number of observations in order to summarize them.
 is similar to that reported recently for a cohort of men in the United States consisting of partners of women presenting for infertility evaluation: 18% of the men had sperm concentrations [is less than] 20 million/mL (42). However, the mean sperm concentration of the Czech men (61.2 million/mL) was lower than that determined for this group of American men (94.4 million/mL) (42). Nevertheless, the median sperm concentration for the Czech men in this study (44.0 million/mL) is comparable to that recently reported for a cohort of unselected young Danish men [41.0 million/mL (43,44)], and both cohorts have lower median sperm concentrations when compared to a cohort of Finnish men without proven fertility [126.8 million/mL (41)]. These reports strengthen the evidence for geographic (possibly genetic) differences in sperm concentrations in Europe, as have been reported in the United States (45).

Exposure to environmental pollution may contribute to a perceived decline in sperm counts world wide (41-47). One recent report showed progressive declines in sperm production in Greece during a time period when air pollution increased (48). However, our results do not support a relationship between either district of residence or exposure to periods of elevated air pollution and decreased sperm production (concentration or sperm per sample) in the Czech Republic.

Evidence from laboratory and wildlife populations indicates that exposure to endocrine-disrupting chemicals during fetal or neonatal neonatal /neo·na·tal/ (ne?o-nat´'l) pertaining to the first four weeks after birth.

ne·o·na·tal
adj.
Of or relating to the first 28 days of an infant's life.
 development may alter sexual differentiation sexual differentiation See Hermaphroditism, hirsutism, Müllerian ducts, Precocious puberty, Pseudoprecocious puberty, Tanner staging, Testis-determining factor, Virilization, Wolffian ducts, XXX, XXY, XXXY, XYY syndromes, Y Chromosome. , sperm production, and/or epididymal storage capability in adulthood (reviewed elsewhere by Toppari et al. (41) and Kavlock et al. (49). Air pollution since 1975-1996, when these men were born, has followed the same patterns by district and season observed during the years under study. Therefore, sperm counts might also differ by district if potential endocrine disruptors Endocrine disruptors are exogenous substances that act like hormones in the endocrine system and disrupt the physiologic function of endogenous hormones. Studies have linked endocrine disruptors to adverse biological effects in animals, giving rise to concerns that low-level  were present in the air pollution (49). Although our sample size is limited for detecting such effects, we found no evidence to support this hypothesis. However, this study does not address the possibility that other types of pollution present in the environment, or lifestyle factors such as consumption of alcohol and cigarettes from a relatively young age, might impact in general upon sperm production potential in young Czech men.

Nevertheless, when sampled at the end of winter after periods of elevated air pollution, men from Teplice showed evidence of lower sperm motility (1994 samples) and poorer morphology (both years) when compared with men sampled after periods of lower air pollution (Teplice in the fall and Prachatice the late winter or fall). These observations provide preliminary evidence that periods of elevated air pollution may be associated with decrements in sperm quality. While fertility data for this group of young men are not available, low values for sperm motility and normal morphology have been associated with infertility (50-53).

Decreases in the percentage of motile sperm (a measure of sperm viability) were observed in the men sampled late winter 1994 but not late winter 1993 despite the fact that levels of air pollutants were higher in 1993. The apparent lack of an exposure--response relationship for this measure could be due to differences in the dynamics of the exposure or, alternatively, to other factors not assessed in this study. Additional studies in which men are sampled at various times between exposure and sampling could further examine this association.

We used CASA to evaluate the quality of sperm motion, and these results, albeit somewhat difficult to interpret, did not demonstrate any consistent negative associations between the quality of sperm motion and periods of high air pollution. However, positive associations were observed between VSL and LIN and season (winter). CASA has not been applied widely in field studies, in part because the logistics of recording the sample promptly (to avoid degradation of sperm motility over time) and controlling the temperature precisely (13) are challenging in the field setting. Despite careful attention to these details, the recording equipment failed on 1 study day, and CASA data for 10 samples were unfortunately lost. Furthermore, the difficulty of recording a sufficient number of motile sperm in samples with very low percentages of motile sperm is widely recognized (13). The extent to which missing CASA data could have biased the results is difficult to determine. Nevertheless, based on the data available in this study, the quality of sperm motion did not appear to be negatively impacted in any consistent manner after periods of elevated air

pollution. Limited information is available suggesting seasonal variations in sperm velocity measures (33) and this topic merits further study.

We found highly significant associations between exposure to periods of medium (1994) and high (1993) air pollution and poor sperm morphology in this study. For both sperm morphology and sperm head morphology, no association was observed with season alone, and the negative associations with periods of pollution in both years remained strong after controlling for potential confounding by season. This finding may be important for public health because in clinical studies, sperm morphology is a relatively good predictor of fertility status (53).

The SCSA was included in this study to provide a measure of the genetic integrity of sperm. Periods of high air pollution encountered in winter 1993 were associated with increased percent sperm with abnormal chromatin structure (COMP[[Alpha].sub.t]). High COMP[[Alpha].sub.t] ([is greater than] 30) has been associated with infertility and spontaneous abortion spon·ta·ne·ous abortion
n.
A naturally occurring termination of a pregnancy. Also called miscarriage.


spontaneous abortion 
 (24) in clinical studies, but this measure has only recently been applied to epidemiology studies. One such study found an association between exposure to cigarette smoke (which, like air pollution, also contains genotoxic genotoxic /ge·no·tox·ic/ (je´no-tok?sik) damaging to DNA: pertaining to agents known to damage DNA, thereby causing mutations, which can result in cancer.

ge·no·tox·ic
adj.
 PAHs) and elevated COMP[[Alpha].sub.t] (54). It may be relevant, therefore, that smoking was retained in the COMP[[Alpha].sub.t] model in this report. In this regard, it is noteworthy that another measure of genetic integrity, namely sperm aneuploidy aneuploidy /an·eu·ploi·dy/ (an?u-ploi´de) any deviation from an exact multiple of the haploid number of chromosomes, whether fewer or more.

an·eu·ploi·dy
n.
, was significantly elevated in a subset of the same Czech men exposed to periods of high air pollution (nonsmokers from the Teplice winter 1993 group) compared to men exposed to periods of low air pollution (nonsmokers from the Teplice summer 1993 group) (54). Interestingly, a subset of active smokers (1 pack/day, selected from the Teplice winter 1994 group) also exhibited sperm with elevated levels of aneuploidy compared to nonsmokers in the same group (56). Taken together, these intriguing in·trigue  
n.
1.
a. A secret or underhand scheme; a plot.

b. The practice of or involvement in such schemes.

2. A clandestine love affair.

v.
 observations suggest further consideration of the potential impact of air pollution and/or smoking on the genetic integrity of human sperm.

REFERENCES AND NOTES

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Leigh Rubin began making and distributing his own greeting cards in 1979 through his company Rubes.
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(6.) Pinto pinto

Spotted horse, also called paint, piebald, skewbald, and other terms to describe variations in colour and markings. The American Indian ponies of the western U.S. were often pintos. Most pure-breed associations refuse to register horses with pinto colouring.
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New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of
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In the uterus.



in utero adv.
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en·do·crine
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adj.
Not capable of initiating, sustaining, or supporting reproduction.


infertile,
adj unable to produce offspring.
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(16.) Marshburn PB, McIntire D, Cart BR, Byrd W, Spermatozoal spermatozoal

pertaining to spermatozoa.


spermatozoal motility
a guide to viability and potency of a semen sample; a highly motile sample shows wave movement under low power and individual sperm movement under high power.
 characteristics from fresh and frozen donor semen and their correlation with fertility outcome after intrauterine insemination intrauterine insemination Turkey baster insemination Reproduction medicine The direct introduction of sperm in the uterus, a maneuver used in unexplained or ♂-factor infertility. See Artificial reproductive technology. . Fertil Steril 58(1):179-186 (1992).

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1. Of, relating to, or useful in prognosis.

2. Of or relating to prediction; predictive.

n.
1. A sign or symptom indicating the future course of a disease.

2.
 significance of computerized motility analysis for in vivo in vivo /in vi·vo/ (ve´vo) [L.] within the living body.

in vi·vo
adj.
Within a living organism.



in vivo adv.
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emanating from or pertaining to mammals.
 sperm chromatin heterogeneity het·er·o·ge·ne·i·ty
n.
The quality or state of being heterogeneous.



heterogeneity

the state of being heterogeneous.
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The study of the activities, functions, properties, and structures of cells. Cells were discovered in the middle of the seventeenth century after the microscope was invented.
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venous hum  a continuous blowing, singing, or humming murmur heard on auscultation over the right jugular vein in the sitting or erect position; it is
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(25.) Evenson DP, Jost LK, Baer RK, Turner TW, Schrader SM. Individuality individuality,
n collective characteristics or traits that distinguish one person or thing from all others.
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Kinetics (classical mechanics)

That part of classical mechanics which deals with the relation between the motions of material bodies and the forces acting upon them.
. Environ Mol Mutagen mutagen: see mutation.
mutagen

Any agent capable of altering a cell's genetic makeup by changing the structure of the hereditary material, DNA. Many forms of electromagnetic radiation (e.g.
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(27.) Evenson DP. Alterations and damage of sperm chromatin structure and early embryonic em·bry·on·ic or em·bry·on·al
adj.
Of, relating to, or being an embryo.


Embryonic
In the life cycle of the round worm, a very early life stage occurring within the uterus of the female round worm.
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(28.) Sailer Sail´er

n. 1. A sailor.
2. A ship or other vessel; - with qualifying words descriptive of speed or manner of sailing; as, a heavy sailer; a fast sailer s>.
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1. radiotherapy.

2. the dispersion of nervous impulse beyond the normal path of conduction.

3.
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see spermatozoon.
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1. To rent (property one holds by lease) to another.

2. To subcontract (work).

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(35.) Bonde JPE JPE Journal of Political Economy
JPE Jump If Parity Even
JPE Journal of Private Equity
JPE Joel Plaskett Emergency (Halifax, Nova Scotia band)
JPE Japanese Pharmaceutical Excipients
JPE Truncated JPEG file extension
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Tool (or bit) used with a carpenter's brace for drilling holes, usually in wood. It looks like a corkscrew and produces extremely clean holes, almost regardless of how large the bit is.
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Sherry G. Selevan,(1) Libor Borkovec,(2) Valerie L. Slott,(3) Zdena Zudova,(4) Jiri Rubes,(2) Donald P. Evenson,(5) and Sally D. Perreault(6)

(1) U.S. Environmental Protection Agency, Washington, DC, USA;(2) Veterinary Research Institute, Brno, Czech Republic;(3) Parexel, Durham, North Carolina Durham is a city in the U.S. state of North Carolina. It is the county seat of Durham CountyGR6 and is the fourth-largest city in the state by population. , USA; (4) Institute of Hygiene, Brno, Czech Republic;(5) South Dakota State University, Brookings, South Dakota Brookings is a city in Brookings County, South Dakota, USA. Brookings is the fifth largest city in South Dakota, with a population of 18,504 at the 2000 census. It is the county seat of Brookings County,GR6 , USA;(6) U.S. Environmental Protection Agency, Research Triangle Park Research Triangle Park, research, business, medical, and educational complex situated in central North Carolina. It has an area of 6,900 acres (2,795 hectares) and is 8 × 2 mi (13 × 3 km) in size. Named for the triangle formed by Duke Univ. , North Carolina North Carolina, state in the SE United States. It is bordered by the Atlantic Ocean (E), South Carolina and Georgia (S), Tennessee (W), and Virginia (N). Facts and Figures


Area, 52,586 sq mi (136,198 sq km). Pop.
, USA

Address correspondence to S.G. Selevan, U.S. Environmental Protection Agency (8623D), Washington, DC 20460, USA. Telephone:(202) 564-3312. Fax: (202) 565-0078. E-mail: selevan.sherry@ epa.gov

We thank the many people who contributed to the success of this project including F. Kotesovec, R. Sram, and J. Lewtas for programmatic pro·gram·mat·ic  
adj.
1. Of, relating to, or having a program.

2. Following an overall plan or schedule: a step-by-step, programmatic approach to problem solving.

3.
 support; I. Benes and R. Stevens for the air pollution data; R. Hajnova for medical examinations; the staff of the Teplice and Prachatice Hygiene Stations for subject recruitment; and U.S. EPA and Czech laboratory technicians. We also thank S. Schrader, D. Katz, E. Clegg, and J. Ratcliffe for their advice regarding study design and technical aspects of semen analysis; and M. Leixner for air pollution data management.

This study was supported by the Czech Ministry of the Environment (Teplice Program), the U.S. Environmental Protection Agency, the U.S. Agency for International Development, and grants from CEC (Central Electronic Complex) The set of hardware that defines a mainframe, which includes the CPU(s), memory, channels, controllers and power supplies included in the box. Some CECs, such as IBM's Multiprise 2000 and 3000, include data storage devices as well.  (PHARE II, EC/HEN18/CZ), and the U.S. EPA [R820968 (DPE DPE Digital Preservation Europe
DPE Designated Pilot Examiner (conducts FAA checkrides)
DPE Distributed Processing Environment
DPE Dual-Phase Extraction (DNAPL removal system) 
) and CR820076].

This manuscript has been reviewed in accordance with U.S. EPA policy, and approved for publication. Approval does not signify sig·ni·fy  
v. sig·ni·fied, sig·ni·fy·ing, sig·ni·fies

v.tr.
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 that the contents necessarily reflect the views and policies of the U.S. EPA.

Received 27 October 1999; accepted 22 January 2000.
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Author:Perreault, Sally D.
Publication:Environmental Health Perspectives
Date:Sep 1, 2000
Words:12583
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