Particle Concentrations in Urban Microenvironments.Although ambient Surrounding. For example, ambient temperature and humidity are atmospheric conditions that exist at the moment. See ambient lighting. 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. has been associated with a range of health outcomes, the health risks for individuals depend in part on their daily activities. Information about particle mass concentrations and size distributions in indoor and outdoor microenvironments can help identify high-risk individuals and the significant contributors to personal exposure. To address these issues in an urban setting, we measured particle count concentrations in four size ranges and particulate matter [is less than or equal to] 10 [micro]m ([PM.sub.10]) concentrations outdoors and in seven indoor microenvironments in Boston, Massachusetts “Boston” redirects here. For other uses, see Boston (disambiguation). Boston is the capital and most populous city of Massachusetts.[3] The largest city in New England, Boston is considered the unofficial economic and cultural center of the entire New . Particle counts and [PM.sub.10] concentrations were continuously)measured with two light-scattering devices. Because of the autocorrelation Autocorrelation The correlation of a variable with itself over successive time intervals. Sometimes called serial correlation. between sequential measurements, we used linear mixed effects models with an AR-1 autoregressive correlation structure to evaluate whether differences between microenvironments were statistically significant. In general, larger particles were elevated in the vicinity of significant human activity, and smaller particles were elevated in the vicinity of combustion sources, with indoor [PM.sub.10] concentrations significantly higher than the outdoors on buses and trolleys. Statistical models demonstrated significant variability among some indoor microenvironments, with greater variability for smaller particles. These findings imply that personal exposures can depend on activity patterns and that microenvironmental concentration information can improve the accuracy of personal exposure estimation. Key words. air pollution, exposure assessment, indoor air, microenvironments, particulate matter. Environ en·vi·ron tr.v. en·vi·roned, en·vi·ron·ing, en·vi·rons To encircle; surround. See Synonyms at surround. [Middle English envirounen, from Old French environner Health Perspect 108:1051-1057 (2000). [Online 16 October 2000] http://ehpnet1.niehs.nih.gov/docs/2000/108p1051-1057levy/abstract.html Recent epidemiologic studies epidemiologic study A study that compares 2 groups of people who are alike except for one factor, such as exposure to a chemical or the presence of a health effect; the investigators try to determine if any factor is associated with the health effect have established relationships between particulate matter and both morbidity morbidity /mor·bid·i·ty/ (mor-bid´it-e) 1. a diseased condition or state. 2. the incidence or prevalence of a disease or of all diseases in a population. mor·bid·i·ty n. and premature mortality and presented evidence that fine particulate matter (the fraction of particulate matter [is less than] 2.5 [micro]m in diameter) may be responsible for these adverse outcomes (1-6). Although some physiologic and toxicologic evidence exists (7-9), most of the evidence for particulate matter health effects is taken from epidemiologic studies that use fixed-site ambient measurements as estimates of exposure. Critics of the positive epidemiologic ep·i·de·mi·ol·o·gy n. The branch of medicine that deals with the study of the causes, distribution, and control of disease in populations. [Medieval Latin epid findings consider the disconnect disconnect - SCSI reconnect between ambient monitors and actual exposure to be a potential source of error (10,11). However, although some studies have found poor correlations between personal exposure and ambient concentrations (12-14), the correlations have been stronger when evaluated within individuals across time (15,16). Furthermore, any errors induced by using fixed-site monitors to represent personal exposure would likely be "Berkson errors," which would not induce bias if the dose-response relationship The Dose-response relationship describes the change in effect on an organism caused by differing levels of exposure (or doses) to a stressor (usually a chemical). This may apply to individuals (eg: a small amount has no observable effect, a large amount is fatal), or to populations were linear (17). Despite these facts, knowledge about personal exposure to particulate matter is crucial in a risk assessment and public policy context. Estimates of the distribution of exposures can help identify high-risk individuals and risks to susceptible subpopulations, and understanding the primary contributors to personal exposure can lead to well-designed control policies. Because individuals spend a significant fraction of the day indoors, with variable ventilation rates and differing indoor sources, the differences in personal exposures between individuals represented by the same fixed monitor could be substantial. Because it would be implausible im·plau·si·ble adj. Difficult to believe; not plausible. im·plau  si·bil to measure the personal exposures
of a significant number of people, a theoretically sound alternative is
to measure concentrations in a number of microenvironments and determine
the time spent by individuals in these microenvironments. A
microenvironment microenvironment /mi·cro·en·vi·ron·ment/ (-en-vi´ron-ment) the environment at the microscopic or cellular level. can be defined as a physical compartment compartmenta part of the body as a whole and divided from the rest by a physical partition. fluid compartment that liquid part of the body excluded by cell membranes. Includes intravascular and intercellular compartments. or defined space with relatively homogeneous The same. Contrast with heterogeneous. homogeneous - (Or "homogenous") Of uniform nature, similar in kind. 1. In the context of distributed systems, middleware makes heterogeneous systems appear as a homogeneous entity. For example see: interoperable network. air pollution concentrations (18). Simple microenvironmental models could involve estimates of indoor and outdoor concentrations and the amount of time spent in each of these two settings. For more complex models, such as the Probabilistic (probability) probabilistic - Relating to, or governed by, probability. The behaviour of a probabilistic system cannot be predicted exactly but the probability of certain behaviours is known. Such systems may be simulated using pseudorandom numbers. National Ambient Air Quality Standards The National Ambient Air Quality Standards (NAAQS) are standards established by the United States Environmental Protection Agency that apply for outdoor air throughout the country. Exposure Model (pNEM) (19) or the Simulation of Human Air Pollutant pol·lut·ant n. Something that pollutes, especially a waste material that contaminates air, soil, or water. Exposure (SHAPE) for 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; (20), there is a need to understand concentration patterns across a number of different microenvironments that have not been well characterized to date. Along with particulate matter mass concentrations, there are compelling reasons to estimate the particle counts and the size distributions of those particles. From a health effects standpoint, it has been argued that particle surface area or number could be more important than particle mass, due to the potential impairment Impairment 1. A reduction in a company's stated capital. 2. The total capital that is less than the par value of the company's capital stock. Notes: 1. This is usually reduced because of poorly estimated losses or gains. 2. of macrophage macrophage /mac·ro·phage/ (mak´ro-faj) any of the large, mononuclear, highly phagocytic cells derived from monocytes that occur in the walls of blood vessels (adventitial cells) and in loose connective tissue (histiocytes, phagocytic functions associated with clearance (21). In addition, because different source types provide different particle sizes Particle size, also called grain size, refers to the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials. and chemical compositions, understanding the sizes of particles present in different microenvironments can establish a framework for source attribution at·tri·bu·tion n. 1. The act of attributing, especially the act of establishing a particular person as the creator of a work of art. 2. . Recent evidence that particulate matter from combustion sources may have greater effects than crustal crust·al adj. Of or relating to a crust, especially that of the earth or the moon. Adj. 1. crustal - of or relating to or characteristic of the crust of the earth or moon particulate matter (22) gives source attribution added significance. Continuous real-time monitoring can provide the information necessary to detect the influence of a local source or changes in local circumstances on particulate matter counts or mass concentrations. In addition, continuous monitoring allows us to evaluate short-term particle exposures, a topic for which very little exposure or health information has been collected (2.3). To address these issues, we continuously monitored particulate matter mass concentrations and particle counts in a number of indoor microenvironments in an urban area over a period of 4 days, with outdoor measurements taken outside each microenvironment. We considered building or source factors as well as temporal trends in pollution concentrations to determine the significance of differences among indoor microenvironments. By determining microenvironments that might contribute significantly to personal exposure and by capturing the degree of microenvironmental variability in an urban area, we provide a template to better estimate personal exposures to particulate matter. Methods We measured particle counts and mass concentrations in seven indoor microenvironments as well as outdoors over a 4-day period in June 1998. To measure particle counts, we used an APC-1000 Airborne Particle Counter A particle counter is an instrument that detects and counts particles. Applications of particle counters are separated into two primary categories:
prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. the manufacturer, the theoretical upper bound for the largest particle size category is on the order of 1,000 [micro]m, although particle counts are generally minimal above 5 [micro]m because particles much larger would not be suspended in ambient air. The APC-1000 also provided measurements of temperature and relative humidity relative humidity n. The ratio of the amount of water vapor in the air at a specific temperature to the maximum amount that the air could hold at that temperature, expressed as a percentage. and was factory-calibrated using isotropic Refers to properties that do not differ no matter which direction is measured. For example, an isotropic antenna radiates almost the same power in all directions. In practice, antennas cannot be 100% isotropic. polystyrene polystyrene (pŏl'ēstī`rēn), widely used plastic; it is a polymer of styrene. Polystyrene is a colorless, transparent thermoplastic that softens slightly above 100°C; (212°F;) and becomes a viscous liquid at around 185°C; spheres within the year before use. Past exposure assessment studies have found the APC-1,000 to be useful for evaluating short-term concentration peaks and making preliminary source attributions (23). We measured particulate matter mass concentrations using a DustTrak 8520 (TSI TSI Total Solar Irradiance (sum solar light in energy per unit of time) TSI Trading Standards Institute (UK) TSI Transportation Safety Institute (US DOT) , Minneapolis, MN), a laser photometer Photometer An instrument used for making measurements of light, or electromagnetic radiation, in the visible range. In general, photometers may be divided into two classifications: laboratory photometers, which are usually fixed in position and yield results designed to measure particles between 0.1 and 10 [micro]m. The DustTrak was factory-calibrated using A1 test dust (Arizona Test Dust, ISO (1) See ISO speed. (2) (International Organization for Standardization, Geneva, Switzerland, www.iso.ch) An organization that sets international standards, founded in 1946. The U.S. member body is ANSI. 12103-1) within the year before use and was calibrated cal·i·brate tr.v. cal·i·brat·ed, cal·i·brat·ing, cal·i·brates 1. To check, adjust, or determine by comparison with a standard (the graduations of a quantitative measuring instrument): to a zero filter during the sampling period. Nine students from the Harvard School of Public Health The Harvard School of Public Health is (colloquially, HSPH) is one of the professional graduate schools of Harvard University. Located in Longwood Area of the Boston, Massachusetts neighborhood of Mission Hill, next to Harvard Medical School and Cambridge, Massachusetts, Summer Program in Biostatistics biostatistics /bio·sta·tis·tics/ (-stah-tis´tiks) biometry. bi·o·sta·tis·tics n. The science of statistics applied to the analysis of biological or medical data. were trained in the operation of all equipment and divided into three sampling groups. The Summer Program in Biostatistics is a short-term program funded by the National Institute of Environmental Health Sciences The National Institute of Environmental Health Sciences (NIEHS) is one of 27 Institutes and Centers of the National Institutes of Health (NIH),which is a component of the Department of Health and Human Services (DHHS). The Director of the NIEHS is Dr. David A. Schwartz. , which is intended to introduce undergraduate mathematics majors from underrepresented minority underrepresented minority Social medicine Any ethnic group–African American, Hispanic, Native American–whose representation among professionals in biomedical sciences is disproportionately less than their proportion in the general population. groups to biostatistics, environmental health, and public health research. On each of the 4 sampling days, each group sampled for up to three sessions in designated microenvironments in the Boston, Massachusetts, area. To normalize normalize to convert a set of data by, for example, converting them to logarithms or reciprocals so that their previous non-normal distribution is converted to a normal one. for temporal trends, measurements were taken between 1100 and 1700 hr on all 4 days. The students followed a detailed script that directed them to spend 20-40 min in each of several sampling locations. Along with the monitoring data, the groups recorded other information about site characteristics that might affect particulate matter concentrations, including the presence of smokers or air conditioning air conditioning, mechanical process for controlling the humidity, temperature, cleanliness, and circulation of air in buildings and rooms. Indoor air is conditioned and regulated to maintain the temperature-humidity ratio that is most comfortable and healthful. , whether windows were kept open or closed, and the distance from the street. The seven indoor microenvironments selected were 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 as bus, gymnasium gymnasium In Germany, a state-maintained secondary school that prepares pupils for higher academic education. This type of nine-year school originated in Strasbourg in 1537. , hospital, museum, restaurant, store, and subway subway: see rapid transit. subway Underground railway system used to transport passengers within urban and suburban areas. The first subway line, 3. (Table 1). In Boston, the buses are largely diesel fueled, and the subway line is electric and consists of both a street-level and an underground section. These microenvironments were chosen strategically to represent typical activities of urban residents that had not been previously incorporated into many microenvironmental models. The students mimicked the typical behaviors within microenvironments (i.e., walking in stores, sitting in restaurants), so that their personal influence on particle concentrations would not alter true exposure patterns. In addition, outdoor measurements were taken in the vicinity of all microenvironments, with additional measurements taken in parks and on sidewalks.
Table 1. Descriptions of indoor and outdoor microenvironments.
Microenvironment Description
Bus Diesel-fueled city buses and medical area shuttle
(all urban travel)
Subway Electric-powered subway traveling both above
ground (on-street trolley) and underground
Gymnasium Athletic facility located near medical area
Hospital Two hospitals located across the street from
one another, along bus route
Museum Art museum in urban area
Restaurant Small pizza place, fast-food restaurant, coffee
shop
Store Three large shopping malls downtown, shops
near medical area and other urban areas
Sidewalk High-traffic roads near medical area, other
urban areas
Park Park areas downtown, close to traffic
No. of sessions
Microenvironment (indoor, outdoor)
Bus 15
(7, 8)
Subway 21
(12, 9)
Gymnasium 2
(1, 1)
Hospital 6
(3, 3)
Museum 2
(1, 1)
Restaurant 10
(5, 5)
Store 15
(8, 7)
Sidewalk 8
(0, 8)
Park 6
(0, 6)
Because the APC-1000 requires a 15-sec standby period between measurements, we used a 2-min averaging time for the APC-1000 and a 135-sec averaging time for the DustTrak. This ensured that the two instruments were synchronized syn·chro·nize v. syn·chro·nized, syn·chro·niz·ing, syn·chro·niz·es v.intr. 1. To occur at the same time; be simultaneous. 2. To operate in unison. v.tr. 1. throughout the measurement period. The sampling interval was selected to provide a reasonable sample size within each microenvironment while dampening the effects of short-term spikes in concentrations. Statistics Aside from estimating particle mass and count concentrations and size profiles within different microenvironments, the primary goal of this study was to understand the degree of variability between microenvironments, controlling for common factors. However, standard statistical comparisons between microenvironments are impeded im·pede tr.v. im·ped·ed, im·ped·ing, im·pedes To retard or obstruct the progress of. See Synonyms at hinder1. [Latin imped by two aspects of our study design. First, environmental measurements were taken with short averaging times, making it unlikely that the measurements are independent of one another within microenvironments (a required assumption for many standard statistical methods). Second, when comparing a number of microenvironments, random variability could be the cause of significant deviations, and adjustments for multiple comparisons are needed. The anticipated autocorrelation between sequential measurements was confirmed by exploratory analysis using the variogram technique (24). Given this, we sought a statistical model that could account for the autocorrelation. We considered using generalized gen·er·al·ized adj. 1. Involving an entire organ, as when an epileptic seizure involves all parts of the brain. 2. Not specifically adapted to a particular environment or function; not specialized. 3. estimating equations (GEEs) within our regression analysis In statistics, a mathematical method of modeling the relationships among three or more variables. It is used to predict the value of one variable given the values of the others. For example, a model might estimate sales based on age and gender. , but preliminary simulations suggested that a linear mixed effects (LME See London Metal Exchange. LME See London Metal Exchange (LME). ) model (25) had better properties, particularly in terms of Type I error. Consequently, we applied LMEs within our regression analysis, assuming an AR-1 autoregressive correlation structure within each session. Thus, for each session i and replicate rep·li·cate v. 1. To duplicate, copy, reproduce, or repeat. 2. To reproduce or make an exact copy or copies of genetic material, a cell, or an organism. n. A repetition of an experiment or a procedure. j, we statistically modeled each measurement [y.sub.ij] as [y.sub.ij] = [x.sub.i][Beta] + [b.sub.i] + [u.sub.ij], where [x.sub.i] is a row-vector consisting of the covariates of interest, [Beta] is a corresponding set of regression coefficients Regression coefficient Term yielded by regression analysis that indicates the sensitivity of the dependent variable to a particular independent variable. See: Parameter. regression coefficient to be estimated, [b.sub.i] is a normally distributed random effect intercept intercept in mathematical terms the points at which a curve cuts the two axes of a graph. , and [u.sub.ij] is a normally distributed error with AR-1 structure [u.sub.ij] = [Rho][u.sub.ij-1]+ [e.sub.ij], (each [e.sub.ij] being independent and normally distributed). We constructed separate models for indoors and outdoors, given differences in relevant factors as well as a desire to determine the degree of heterogeneity het·er·o·ge·ne·i·ty n. The quality or state of being heterogeneous. heterogeneity the state of being heterogeneous. among both types of microenvironments. All particle count and mass concentration parameters were log-transformed to more closely approximate normal distributions. For indoor microenvironments, the predictors considered for the model include indicator variables for microenvironment, open windows, and presence of central air conditioning, number of people nearby, and temperature and relative humidity. For outdoor microenvironments, we considered indicator variables for microenvironment, presence of smokers nearby, as well as number of people nearby and temperature and relative humidity. It should be noted that no smokers were present in any indoor microenvironments, explaining its exclusion from the indoor model. In addition, we incorporated a term for date of measurement into both models, to account for meteorological me·te·or·ol·o·gy n. The science that deals with the phenomena of the atmosphere, especially weather and weather conditions. [French météorologie, from Greek or other differences that could influence ambient concentrations. Once the LME models have established whether there are significant differences among microenvironments in indoor or outdoor settings, we need to determine which microenvironments differ significantly from one another. To make this comparison, we used Wald tests The Wald test is a statistical test, typically used to test whether an effect exists or not. In other words, it tests whether an independent variable has a statistically significant relationship with a dependent variable. on the estimated group means for different microenvironments. However, this technique can result in specious spe·cious adj. 1. Having the ring of truth or plausibility but actually fallacious: a specious argument. 2. Deceptively attractive. statistical findings if the effect of multiple comparisons is not properly accounted for. In ordinary least-squares regression, multiple comparison methods such as the Tukey and Scheffe tests have been developed to control the Type I error probability without significantly increasing the likelihood of a Type II error (26). However, these techniques are not applicable to LME. To address this issue, we conducted multiple comparisons using two procedures at opposite extremes. First, we effectively ignored the multiple comparisons issue, rejecting the null A character that is all 0 bits. Also written as "NUL," it is the first character in the ASCII and EBCDIC data codes. In hex, it displays and prints as 00; in decimal, it may appear as a single zero in a chart of codes, but displays and prints as a blank space. hypotheses if p [is less than] 0.05. This adequately controls for Type II errors but could yield extremely high Type I errors. On the other extreme, we used the Bonferroni probability of 0.05/n (where n is the number of comparisons) to yield an overall Type I error rate of 0.05 while increasing Type II errors. These two extreme methods should bracket In programming, brackets (the [ and ] characters) are used to enclose numbers and subscripts. For example, in the C statement int menustart [4] = ; the [4] indicates the number of elements in the array, and the contents are enclosed in curly braces. the correct statistical inferences Inferential statistics or statistical induction comprises the use of statistics to make inferences concerning some unknown aspect of a population. It is distinguished from descriptive statistics. . For all statistical assessments, we evaluated the particle counts within specified size ranges rather than the measured threshold values. In other words Adv. 1. in other words - otherwise stated; "in other words, we are broke" put differently , the APC-1000 measures the number of particles per unit volume that have diameters of at least 0.3 [micro]m, 0.5 [micro]m, 1.0 [micro]m, and 5.0 [micro]m. We analyzed an·a·lyze tr.v. an·a·lyzed, an·a·lyz·ing, an·a·lyz·es 1. To examine methodically by separating into parts and studying their interrelations. 2. Chemistry To make a chemical analysis of. 3. the differences between these categories, reflecting the particle size ranges of 0.3-0.5 [micro]m, 0.5-1.0 [micro]m, 1.0-5.0 [micro]m, and [is greater than] 5.0 [micro]m. Past studies have found that these ranges correspond to aerodynamic diameters 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. of 0.9-1.2 [micro]m, 1.2-1.7 [micro]m, 1.7-3.7 [micro]m, and [is greater than] 3.7 [micro]m (23). Results In total, the microenvironmental sampling yielded 578 measurements taken within 85 measurement sessions. Due to equipment issues, there were only 381 measurements for which all four particle size counts from the APC-1000 and the [PM.sub.10] concentration using the DustTrak were valid (66%). Because of our interest in evaluating variability in and predictors of particle counts within specified size ranges, we focused our analysis on these 381 measurements, even though this reduced the statistical power of our analysis. Descriptive statistics descriptive statistics see statistics. as well as statistical models did not differ significantly when applied to the full set of data when appropriate. For all descriptive statistics, we estimated the geometric mean (mathematics) geometric mean - The Nth root of the product of N numbers. If each number in a list of numbers was replaced with their geometric mean, then multiplying them all together would still give the same result. and geometric standard deviation In probability theory and statistics, the geometric standard deviation describes how spread out are a set of numbers whose preferred average is the geometric mean. If the geometric mean of a set of numbers is denoted as μg to account for the logarithmic distribution In probability and statistics, the logarithmic distribution (also known as the logarithmic series distribution) is a discrete probability distribution derived from the Maclaurin series expansion GSD Graduate School of Design GSD Glycogen Storage Disease GSD General Services Division GSD Gundam Seed Destiny (anime) GSD Ground Sample Distance GSD Geometric Standard Deviation ) of 1.9 (Table 2). Indoor [PM.sub.10] concentrations were generally higher and more variable, with a geometric mean concentration of 35 [micro]g/[m.sup.3] (range 0-380 [micro]g/[m.sup.3]) and a GSD of 3.0. The patterns are similar for the four particle size ranges, with higher geometric mean count concentrations as well as greater variability indoors.
Table 2. Particle count and mass concentrations aggregated
across urban microenvironments.
[PM.sub.0.3-0.5]
(particles/
Sample [cm.sup.3])
size GM GSD
Outdoors
All 147 1.1 2.0
RH [is less than or equal to] 30% 66 0.9 1.9
RH > 30% 81 1.4 1.9
Temperature [is less than or 79 1.0 1.9
equal to] 24 [degrees] C
Temperature > 24 [degrees] C 68 1.3 2.1
Nonsmoking 47 1.1 1.8
Smoking 100 1.2 2.1
Indoors
All 234 1.5 2.4
RH [is less than or equal to] 30% 62 1.5 2.2
RH > 30% 172 1.5 2.5
Temperature [is less than or 143 1.3 2.6
equal to] 24 [degrees] C
Temperature > 24 degrees] C 91 1.9 2.1
No AC 10 1.2 1.5
AC 224 1.5 2.5
[PM.sub.0.5-1.0]
(particles/[cm.sub.3])
GM GSD
Outdoors
All 0.4 2.4
RH [is less than or equal to] 30% 0.4 2.3
RH > 30% 0.3 2.5
Temperature [is less than or 0.3 2.4
equal to] 24 [degrees] C
Temperature > 24 [degrees] C 0.5 2.3
Nonsmoking 0.3 2.4
Smoking 0.4 2.4
Indoors
All 0.8 3.8
RH [is less than or equal to] 30% 1.2 3.3
RH > 30% 0.7 3.8
Temperature [is less than or 0.6 3.6
equal to] 24 [degrees] C
Temperature > 24 [degrees] C 1.4 3.3
No AC 0.4 1.5
AC 0.8 3.8
[PM.sub.1.0-5.0]
(particles/[cm.sub.3])
GM GM
Outdoors
All 0.08 1.8
RH [is less than or equal to] 30% 0.07 1.9
RH > 30% 0.09 1.8
Temperature [is less than or 0.08 1.9
equal to] 24 [degrees] C
Temperature > 24 [degrees] C 0.08 1.8
Nonsmoking 0.07 1.8
Smoking 0.08 1.9
Indoors
All 0.15 2.5
RH [is less than or equal to] 30% 0.17 2.6
RH > 30% 0.15 2.5
Temperature [is less than or 0.12 2.4
equal to] 24 [degrees] C
Temperature > 24 [degrees] C 0.23 2.4
No AC 0.10 1.5
AC 0.16 2.6
[PM.sub.5.0+]
(particles/[cm.sup.3]
GSD GM
Outdoors
All 0.004 2.0
RH [is less than or equal to] 30% 0.004 1.8
RH > 30% 0.003 2.2
Temperature [is less than or 0.004 2.0
equal to] 24 [degrees] C
Temperature > 24 [degrees] C 0.004 2.1
Nonsmoking 0.004 1.7
Smoking 0.004 2.2
Indoors
All 0.007 2.9
RH [is less than or equal to] 30% 0.008 2.5
RH > 30% 0.007 3.0
Temperature [is less than or 0.005 2.5
equal to] 24 [degrees] C
Temperature > 24 [degrees] C 0.012 2.8
No AC 0.003 1.4
AC 0.007 2.9
[PM.sub.10]
[micro]g/[m.sup.3]
GM GSD
Outdoors
All 19 1.9
RH [is less than or equal to] 30% 15 1.8
RH > 30% 24 1.9
Temperature [is less than or 18 1.7
equal to] 24 [degrees] C
Temperature > 24 [degrees] C 21 2.1
Nonsmoking 17 1.7
Smoking 20 2.0
Indoors
All 35 3.0
RH [is less than or equal to] 30% 33 2.8
RH > 30% 36 3.0
Temperature [is less than or 30 3.2
equal to] 24 [degrees] C
Temperature > 24 [degrees] C 46 2.4
No AC 21 1.4
AC 36 3.0
Abbreviations: AC, air conditioning; GM, geometric mean;
RH, relative humidity.
To compare the two instruments, we followed the methodology of Brauer and colleagues (23) and used an assumed particle density The particle density or true density of a particulate solid or powder, is the density of the particles that make up the powder, in contrast to the bulk density, which measures the average density of a large volume of the powder in a specific medium (usually air). of 2.8 g/[cm.sup.3] (7) to convert particle counts into particle mass. Assuming spherical spher·i·cal adj. Having the shape of or approximating a sphere; globular. shape and using the midpoint mid·point n. 1. Mathematics The point of a line segment or curvilinear arc that divides it into two parts of the same length. 2. A position midway between two extremes. of the particle diameter ranges (7.5 [micro]m assumed for the largest size range), the calculated particle mass from the APC-1000 is well correlated cor·re·late v. cor·re·lat·ed, cor·re·lat·ing, cor·re·lates v.tr. 1. To put or bring into causal, complementary, parallel, or reciprocal relation. 2. with the [PM.sub.10] mass concentration measures (r = 0.87). In addition, we can compare our measurements to concentrations from fixed monitors. Although [PM.sub.10] data are only available every 6 days from the nearest 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 (U.S. EPA EPA eicosapentaenoic acid. EPA abbr. eicosapentaenoic acid EPA, n.pr See acid, eicosapentaenoic. EPA, n. ) monitoring station (Kenmore Square, Boston), the ambient concentration was approximately 20 [micro]g/[m.sup.3], similar to our geometric mean outdoor value. When we consider some simple comparisons by site characteristic, we see some systematic differences (Table 2). Particle counts and mass concentrations tend to be greater with higher temperatures and higher relative humidity, both in indoor and outdoor microenvironments. Particle counts and mass concentrations are slightly higher in outdoor microenvironments with smokers and in indoor microenvironments with central air conditioning, although few measurements were taken indoors without air conditioning (n = 10). Stratifying by microenvironment, we can see some systematic differences between indoor and outdoor particle mass concentrations (Figure 1). Indoor [PM.sub.10] concentrations appear to be elevated over outdoor concentrations in the subway, bus, and museum microenvironments, with occasional peaks within restaurants. Indoor [PM.sub.10] concentrations also appear to vary more substantially across microenvironments than outdoor concentrations, an expected finding given the similarity among the urban outdoor settings. To determine whether the outdoor mass concentrations were homogeneous and could therefore be considered a single microenvironment, we applied a Wald test to the LME model for outdoor [PM.sub.10] measurements, controlling for temperature, relative humidity, and date of measurement. With this model, there was no evidence of outdoor microenvironment heterogeneity (p = 0.75), a finding that was not altered by the inclusion of additional covariates. [GRAPH OMITTED] Similarly, outdoor particle count concentrations and size distributions appear relatively similar across microenvironments (Figure 2). Wald tests on the outdoor particle count data (controlling for temperature, relative humidity, and date of measurement) found relatively little evidence of significant heterogeneity (p = 0.03 for 0.3-0.5 [micro]m; p = 0.005 for 0.5-1.0 [micro]m; p = 0.11 for 1.0-5.0 [micro] m; p = 0.97 for 5.0 [micro] m). Although we cannot reject heterogeneity for the smaller particles, multiple comparisons reveal that no differences are significant at the Bonferroni 5%. For pairwise 5% comparisons, only the park microenvironment differs significantly from other microenvironments for 0.3-0.5 [micro]m, with a small number of significant comparisons for 0.5-1.0 [micro]m. Thus, the overall evidence suggests that our outdoor count measurements are relatively homogeneous, and we therefore consider the outdoors as a single microenvironment in the multiple comparisons below. [GRAPH OMITTED] Within indoor microenvironments (Figure 3), both the total particle count concentrations and the size distributions appear to differ significantly. For example, the subway microenvironment has its highest median particle count concentration within the 0.5-1.0 [micro]m range, whereas the store microenvironment has relatively more coarse particles. In general, particle counts for larger particle sizes are greater in microenvironments with significant pedestrian traffic (i.e., museum and store), whereas particle counts for smaller particle sizes are highest near combustion sources (i.e., subway, bus, and restaurant). [GRAPH OMITTED] Considering indoor/outdoor ratios stratified stratified /strat·i·fied/ (strat´i-fid) formed or arranged in layers. strat·i·fied adj. Arranged in the form of layers or strata. by microenvironment (defined as the ratio between the geometric mean concentrations indoors and outdoors, measured sequentially) helps to emphasize the differences among microenvironments (Table 3). For the subway, bus, and restaurant microenvironments, indoor count concentrations were most significantly elevated over outdoor concentrations for [PM.sub.0.5-1.0], a particle-size range associated with fuel combustion (both from proximity to traffic and indoor combustion sources). In the remaining four microenvironments, the greatest elevation occurred for [PM.sub.5.0+], indicative of dust or other coarse particles generated by human activities. The information from particle size counts provides more extensive evidence of source contributions than [PM.sub.10] mass measures. For example, the [PM.sub.10] indoor/outdoor ratios are almost identical in the museum and subway microenvironments, despite the differences in the types of particles penetrating from the outdoors and generated indoors. In general, the fact that the indoor/outdoor ratio is [is less than] 1 only for the store microenvironment indicates that significant particle exposures occur in many indoor environments.
Table 3. Ratios between geometric mean indoor and
outdoor particle counts (particles/[cm.sup.3]) and [PM.sub.10]
concentrations ([micro]g/[m.sup.3]), stratified across
urban microenvironments.
[PM.sub.0.3-0.5] [PM.sub.0.5-1.0] [PM.sub.1.0-5.0]
Subway 2.0 4.5(a) 3.0
Bus 1.8 3.3(a) 2.2
Restaurant 1.0 1.4(a) 1.2
Hospital 0.8 1.4 1.7
Gymnasium 0.8 0.7 0.8
Museum 0.6 1.9 4.0
Store 0.5 0.6 1.1
[PM.sub.5.0+] [PM.sub.10]
Subway 2.2 2.3
Bus 1.6 2.1
Restaurant 0.9 1.2
Hospital 1.8(a) 1.0
Gymnasium 0.9(a) 1.1
Museum 4.1(a) 2.2
Store 2.5(a) 0.8
(a) The largest particle count concentration ratio within
each microenvironment.
To move from these qualitative descriptions to quantitative comparisons between microenvironments, we constructed LME models for the eight microenvironments (seven indoor microenvironments and the pooled outdoor microenvironment). For our primary model, we controlled for date of measurement, temperature, and relative humidity. The indoor microenvironments with hypothesized proximity to combustion sources (subway, bus, and restaurant) tended to have significantly greater particle counts and mass concentrations than other microenvironments, particularly for smaller particle sizes (Table 4). For particles [is greater than] 5.0 [micro]m, store and museum had the highest count concentrations, although none of the differences between indoor microenvironments were statistically significant. In general, greater microenvironmental variability was seen for [PM.sub.0.3-0.5] and [PM.sub.0.5-1.0] than for larger particles.
Table 4. Multiple comparisons among microenvironments
using LME model.(a)
Subway Bus
[PM.sub.0.3-0.5] (no./[cm.sup.3])
Subway = =
Bus = =
Restaurant < =
Outdoor << <
Gymnasium << <
Store << <<
Hospital << <<
Museum << <<
[PM.sub.0.5-1.0](no./[cm.sup.3]) Subway Bus
Subway = >
Bus < =
Restaurant << =
Outdoor << <
Store << <
Museum << =
Gymnasium << <
Hospital << <
[PM.sub.1.0-5.0](no./[cm.sup.3]) Subway Bus
Subway = =
Bus = =
Restaurant < =
Museum = =
Store << =
Outdoor << <
Gymnasium << <
Hospital << <
[PM.sub.5.0+](no./[cm.sup.3]) Store Museum
Store = =
Museum = =
Subway = =
Restaurant = =
Bus = =
Hospital = =
Outdoor < =
Gymnasium
[PM.sub.10]([micro]g/[m.sup.3]) Subway Bus
Subway = >
Bus < =
Museum = =
Restaurant << =
Outdoor << <
Store << <
Gymnasium << =
Hospital << <<
Restaurant Outdoor
[PM.sub.0.3-0.5] (no./[cm.sup.3])
Subway > >>
Bus = >
Restaurant = =
Outdoor = =
Gymnasium = =
Store < <<
Hospital << <<
Museum < <
[PM.sub.0.5-1.0](no./[cm.sup.3]) Restaurant Outdoor
Subway >> >>
Bus = >
Restaurant = =
Outdoor = =
Store = =
Museum = =
Gymnasium = =
Hospital < <
[PM.sub.1.0-5.0](no./[cm.sup.3]) Restaurant Museum
Subway > =
Bus = =
Restaurant = =
Museum = =
Store = =
Outdoor = =
Gymnasium = =
Hospital < =
[PM.sub.5.0+](no./[cm.sup.3]) Subway Restaurant
Store
Museum = =
Subway = =
Restaurant = =
Bus = =
Hospital = =
Outdoor < =
Gymnasium = =
[PM.sub.10]([micro]g/[m.sup.3]) Museum Restaurant
Subway = >>
Bus = =
Museum = =
Restaurant = =
Outdoor = =
Store = =
Gymnasium = =
Hospital = <
Gymnasium Store
[PM.sub.0.3-0.5] (no./[cm.sup.3])
Subway >> >>
Bus > >>
Restaurant = >
Outdoor = >>
Gymnasium = =
Store = =
Hospital = =
Museum = =
[PM.sub.0.5-1.0](no./[cm.sup.3]) Store Museum
Subway >> >>
Bus > =
Restaurant = =
Outdoor = =
Store = =
Museum = =
Gymnasium = =
Hospital = =
[PM.sub.1.0-5.0](no./[cm.sup.3]) Store Outdoor
Subway >> >>
Bus = >
Restaurant = =
Museum = =
Store = =
Outdoor = =
Gymnasium = =
Hospital = =
[PM.sub.5.0+](no./[cm.sup.3]) Bus Hospital
Store = =
Museum = =
Subway = =
Restaurant = =
Bus = =
Hospital = =
Outdoor = =
Gymnasium = =
[PM.sub.10]([micro]g/[m.sup.3]) Outdoor Store
Subway >> >>
Bus > >
Museum = =
Restaurant = =
Outdoor = =
Store = =
Gymnasium = =
Hospital < <
Hospital Museum
[PM.sub.0.3-0.5] (no./[cm.sup.3])
Subway >> >>
Bus >> >>
Restaurant >> >
Outdoor >> >
Gymnasium = =
Store = =
Hospital = =
Museum = =
[PM.sub.0.5-1.0](no./[cm.sup.3]) Gymnasium Hospital
Subway >> >>
Bus > >
Restaurant = >
Outdoor = >
Store = =
Museum = =
Gymnasium = =
Hospital = =
[PM.sub.1.0-5.0](no./[cm.sup.3]) Gymnasium Hospital
Subway >> >>
Bus > >
Restaurant = >
Museum = =
Store = =
Outdoor = =
Gymnasium = =
Hospital = =
[PM.sub.5.0+](no./[cm.sup.3]) Outdoor Gymnasium
Store > =
Museum = =
Subway > =
Restaurant = =
Bus = =
Hospital = =
Outdoor = =
Gymnasium = =
[PM.sub.10]([micro]g/[m.sup.3]) Gymnasium Hospital
Subway >> >>
Bus = >>
Museum = =
Restaurant = >
Outdoor = >
Store = >
Gymnasium = =
Hospital = =
(a) <<, significant difference at Bonferroni 5% = 0.139%;
<, significant difference at pairwise 5%, insignificant at Bonferroni
5%; =, no significant difference. The microenvironments with the
highest concentrations are listed at the top; therefore, >
indicates that the row element is greater than the column element;
< means that the row element is less than the column element.
To determine whether the differences among indoor microenvironments could be related to site characteristics, we constructed LME models including presence of open windows and central air conditioning. Using Wald tests, there was no evidence of significant heterogeneity associated with either of these parameters for [PM.sub.10] concentrations or particle counts (p [is greater than] 0.05 for all). Discussion In general, we found that mass concentrations of particulate matter as well as particle counts differed significantly among some indoor microenvironments, with higher levels found in close proximity to motor vehicles or other combustion sources. Our measurements of particle counts in different size ranges as well as particle mass concentrations allow for preliminary conclusions regarding the sources responsible for levels in different microenvironments. For example, the indoor subway microenvironment had significantly greater [PM.sub.10] concentrations than the indoor hospital microenvironment, with significantly greater particle count concentrations for particles [is less than] 5 [micro]m and no significant differences for particles [is greater than] 5 [micro]m, despite similar outdoor levels. This result could be explained by the closer proximity to traffic for the street-level trolley trolley: see streetcar. and the better air filtration system in the hospital. In addition, [PM.sub.10] concentrations and fine particle counts were significantly higher within the subway than outdoors, implying that particulate matter could be concentrating within this microenvironment. Along with the microenvironmental concentrations and patterns, our study applied a statistical model that accounted for autocorrelation between sequential measurements, an aspect that is often overlooked in continuous monitoring settings. Use of ordinary least squares for these data would have likely overstated o·ver·state tr.v. o·ver·stat·ed, o·ver·stat·ing, o·ver·states To state in exaggerated terms. See Synonyms at exaggerate. o the significance of our findings, given the significant autocorrelation. Simulations run under a variety of"true" correlation structures corroborate To support or enhance the believability of a fact or assertion by the presentation of additional information that confirms the truthfulness of the item. The testimony of a witness is corroborated if subsequent evidence, such as a coroner's report or the testimony of other this statement, with ordinary least squares underestimating standard errors by approximately a factor of three. Furthermore, the use of GEEs to account for autocorrelation yielded significant Type I error for simulated data, implying that GEE gee 1 n. The letter g. gee 2 interj. Used to command a horse or ox to turn to the right. intr.v. models would conclude that greater heterogeneity existed among microenvironments than actually was found. Along with the relevant information for personal exposure modeling, our study also provided useful benefits for the students participating in our Summer Program in Biostatistics. Students with good mathematics training but relatively little exposure to statistical analysis techniques were able to directly experience data collection and the issues inherent in field experiments. By participating in both the data collection and elementary statistical analyses, the students were able to gain a greater perspective on the interplay in·ter·play n. Reciprocal action and reaction; interaction. intr.v. in·ter·played, in·ter·play·ing, in·ter·plays To act or react on each other; interact. between these project elements. Although our study demonstrated microenvironmental variability and estimated relative particle mass concentrations and counts for the microenvironments studied, the study design and methods imply some limitations in the generalizability of our findings. First, the sampling was conducted over a relatively limited time period, and the exposure patterns during these four summer days may not be representative of general exposure patterns. In addition, measurements were taken within the Boston area, and the microenvironments evaluated in our study may not correspond directly to similar microenvironments elsewhere. In other words, subway systems may be configured con·fig·ure tr.v. con·fig·ured, con·fig·ur·ing, con·fig·ures To design, arrange, set up, or shape with a view to specific applications or uses: differently in different cities, restaurants may have different smoking laws, and stores may be located differently relative to busy streets. We attempted to include covariates that would control for some of these differences, but it is difficult to determine whether the lack of significance for many of the covariates implies that they have relatively small effects on particle mass concentrations or counts or whether this is simply a function of a relatively small sample size. Interpretation of our particle count concentration data is limited by the fact that the APC-1000 has a lower limit of 0.3 [micro]m, implying that ultrafine particles (including many combustion particles) were not measured in our analysis. It is also difficult to determine whether the "personal clouds" of the investigators contributed to the measured particulate par·tic·u·late adj. Of or occurring in the form of fine particles. n. A particulate substance. particulate composed of separate particles. concentrations, although their activities mimicked typical microenvironmental activities and the "persons nearby" term was statistically insignificant. Finally, although the categories of microenvironments were chosen to reflect common urban activities, the specific locations were not randomly selected according to systematic protocols. Thus, the concentrations that were allocated to a specific microenvironment may not be representative of the average concentrations in that microenvironment across the city of Boston. Nevertheless, the patterns in particle counts and mass concentrations are demonstrative of Adj. 1. demonstrative of - serving to prove or demonstrate; "the oath of office is...demonstrative of the legislative opinion on this subject"- John Marshall relationships that would be expected given source types and ventilation systems ventilation system Public health An air system designed to maintain negative pressure and exhaust air properly, to minimize the spread of TB and other respiratory pathogens in a health care facility , which indicates that the general findings would likely remain consistent in a broader investigation. Future studies should focus on a more systematic collection of predictive covariates to allow for more substantive conclusions about relevant sources. Quantification quan·ti·fy tr.v. quan·ti·fied, quan·ti·fy·ing, quan·ti·fies 1. To determine or express the quantity of. 2. of distance from combustion sources and information about air filtration systems would add substantially to the power of a microenvironmental exposure protocol. In addition, the lack of smokers in indoor microenvironments within our sample precluded us from drawing conclusions about the role of environmental tobacco smoke environmental tobacco smoke (ETS/passive smoke), n the gaseous by-product of burning tobacco products, including but not limited to commercially manufactured cigarettes and cigars; contains toxic elements harmful to the health of adults and children in indoor microenvironmental variability. Despite the omission omission n. 1) failure to perform an act agreed to, where there is a duty to an individual or the public to act (including omitting to take care) or is required by law. Such an omission may give rise to a lawsuit in the same way as a negligent or improper act. of these parameters, the findings regarding microenvironmental variability as well as the microenvironments with highest and lowest concentrations were relatively robust with respect to the parameters included in the LME regression. Particle size distributions The particle size distribution[1] ("PSD") of a powder, or granular material, or particles dispersed in fluid, is a list of values or a mathematical function that defines the relative amounts of particles present, sorted according to size. in different microenvironments should also be investigated at greater length. In a recent study by Brauer and colleagues using the APC-1000 (23), the geometric mean indoor particle count concentrations in microenvironments in Vancouver were found to be 1.5 particles/[cm.sup.3] between 0.3 and 0.5 [micro]m, 3.1 particles/[cm.sup.3] between 0.5 and 1.0 [micro]m, 0.5 particles/[cm.sup.3] between 1.0 and 5.0 [micro]m, and 0.04 particles/[cm.sup.3] [is greater than] 5.0 [micro]m. Thus, Brauer's study found a bulk of the particles to be in the 0.5-1.0 [micro]m range, whereas our study found relatively more particles in the 0.3-0.5 [micro]m range. This disparity dis·par·i·ty n. pl. dis·par·i·ties 1. The condition or fact of being unequal, as in age, rank, or degree; difference: "narrow the economic disparities among regions and industries" could indicate geographic differences between Vancouver and Boston, differences in selected microenvironments, or could potentially be an instrumentation issue. In our analysis, [PM.sub.0.5-1.0] was greater than [PM.sub.0.3-0.5] only within the indoor subway or restaurant microenvironments. Because Brauer and colleagues focused on both transit and indoor microenvironments with cooking, these two microenvironments may be more representative of the microenvironments evaluated in Vancouver than other microenvironments, provided that the instrument implementation was identical. The peak indoor/outdoor ratios for subway, bus, and restaurant in our study were found in the [PM.sub.0.5-1.0] size range, which would be supportive of combustion peaks in this size range. Finally, a logical extension of this research would involve collecting activity diaries and determining whether these microenvironmental concentration patterns improve the ability to predict personal exposures beyond simple models based on indoor and outdoor levels. In theory, many individuals may spend a significant fraction of their time either at home, at work, or within microenvironments measured within this study or similar to those measured. This would allow for an accurate prediction of personal exposures as well as a preliminary determination of which sources contribute greatly to the exposure of a given individual. Conclusions We have measured particle counts and mass concentrations within a range of indoor and outdoor microenvironments, finding significant variability among some indoor microenvironments and relative homogeneity Homogeneity The degree to which items are similar. among outdoor microenvironments. Higher [PM.sub.10] concentrations and fine particle counts were found in indoor microenvironments in dose proximity to significant combustion sources (including subway, bus, and restaurant), indicating that these sources could contribute to variability in particulate matter exposure. Our findings indicate that information about time spent in indoor microenvironments would be useful in estimating personal exposure and in understanding which segments of the population are more likely to be highly exposed to both indoor and outdoor particle sources. Further investigations should focus on expanding the microenvironments investigated and the predictive covariates collected to determine the degree of microenvironmental variability and improve the ability to predict personal exposures. REFERENCES AND NOTES (1.) Dockery DW, Pope CA III CA III Challenge Athena version III (Navy SATCOM link) . Acute respiratory effects of particulate air pollution. Annu Rev Public Health 15:107-132 (1994). (2.) Schwartz J. Air pollution and daily mortality: a review and meta-analysis. Environ Res 64:36-52 (1964). (3.) Lew JI, Hammitt JK, Spengler JD. Estimating the mortality impacts of particulate matter: what can be learned from between-study variability? Environ Health Perspect 108:109-117 (2000). (4.) Schwartz J, Dockery DW, Neas LM Is daily mortality associated specifically with fine particles Fine particles are an air pollutant mainly produced by cars running on diesel. Other sources are the combustion of fossil fuels in power plants and various industrial processes. ? J Air Waste Manag Assoc 46:927-939 (1996). (5.) Schwartz J, Neas LM. Fine particles are more strongly associated than coarse particles with acute respiratory health effects in schoolchildren schoolchildren school npl → écoliers mpl; (at secondary school) → collégiens mpl; lycéens mpl schoolchildren school . Epidemiology epidemiology, field of medicine concerned with the study of epidemics, outbreaks of disease that affect large numbers of people. Epidemiologists, using sophisticated statistical analyses, field investigations, and complex laboratory techniques, investigate the cause 11:6-10 (2000). (6.) Schwartz J, Norris G, Larson T, Sheppard L Claiborne C, Koenig J. Episodes of high coarse particle concentrations are not associated with increased mortality. Environ Health Perspect 107:339-342 (1999). (7.) Churg A, Brauer M. Human lung The human lungs are the human organs of respiration. Humans have two lungs, with the left being divided into two lobes and the right into three lobes. Together, the lungs contain approximately 1500 miles (2,400 km) of airways and 300 to 500 million alveoli, having a total parenchyma Parenchyma A ground tissue of plants chiefly concerned with the manufacture and storage of food. The primary functions of plants, such as photosynthesis, assimilation, respiration, storage, secretion, and excretion—those associated with living retains [PM.sub.2.5]. Am J Respir Crit Care Med 155:2109-2111 (1997). (8.) Dreher K, Jaskot R, Richards J, Lehmann J, Winsett D, Hoffman A, Costa D. Acute pulmonary pulmonary /pul·mo·nary/ (pool´mo-nar?e) 1. pertaining to the lungs. 2. pertaining to the pulmonary artery. pul·mo·nar·y adj. Of, relating to, or affecting the lungs. toxicity toxicity /tox·ic·i·ty/ (tok-sis´i-te) the quality of being poisonous, especially the degree of virulence of a toxic microbe or of a poison. of size fractionated ambient air particulate matter [Abstract]. Am J Respir Crit Care Med 153:A15 (1996). (9.) Godleski JJ, Verrier RL, Koutrakis P, Catalano P. Mechanisms of Morbidity and Mortality Morbidity and Mortality can refer to:
HEI Health Effects Institute HEI Hautes Études Internationales HEI House Ear Institute HEI Healthy Eating Index HEI Hautes Etudes d'Ingénieur HEI High-Explosive Incendiary , 2000. (10.) Gamble JF. [PM.sub.2.5] and long-term mortality in prospective cohort studies A cohort study is a form of longitudinal study used in medicine and social science. It is one type of study design. In medicine, it is usually undertaken to obtain evidence to try to refute the existence of a suspected association between cause and disease; failure to refute : cause-effect or statistical associations? Environ Health Perspect 106:535-549 (1998). (11.) Moolgavkar SH, Luebeck EG. A critical review of the evidence on particulate air pollution and mortality. Epidemiology 7:420-428 (1997). (12.) Dockery DW, Spengler JD. Personal exposure to respirable respirable /res·pir·a·ble/ (re-spir´ah-b'l) 1. suitable for respiration. 2. small enough to be inhaled. res·pi·ra·ble adj. 1. Fit for breathing, as air. particulates and sulfates. J Air Pollut Control Assoc 31:153-159 (1981). (13.) Sexton sex·ton n. An employee or officer of a church who is responsible for the care and upkeep of church property and sometimes for ringing bells and digging graves. K, Spengler JD, Treitman RD. Personal exposure to respirable particles: a case study in Waterbury, Vermont Waterbury is a town in Washington County in central Vermont. It is also the name of a village within that town. Economy Industry Waterbury is the location of Ben & Jerry's Ice Cream, whose factory tours have become Vermont's most popular tourist attraction. . Atmos Environ 18:1385-1398 (1984). (14.) Ozkaynak H, Xue J, Weker R, Butler D, Spengler d. The Particle TEAM (PTEAM PTEAM Particle Total Exposure Assessment Methodology ) Study: Analysis of the Data, Volume III [Draft Final Report]. EPA contract 68-02-4544. 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. , NC:U.S. Environmental Protection Agency, 1993. (15.) Janssen NAH, Hoek G, Harssema H, Brunekreef B. Personal exposure to fine particles in children correlates closely with ambient fine particles. Arch Environ Health 54:95-101 (1999). (16.) Wallace L. Indoor particles: a review. J Air Waste Manag Assoc 46:96-126 (1996). (17.) Carrothers TJ, Evans JS. Assessing the impact of differential measurement error on estimates of fine particle mortality. J Air Waste Manag Assoc 50:65-74 (2000). (18.) Ott WR, Mage DT, Thomas J. Comparison of microenvironmental CO concentrations in two cities for human exposure modeling. J Expo Anal anal (a´n'l) relating to the anus. a·nal adj. 1. Of, relating to, or near the anus. 2. Environ Epidemiol 2:249-267 (1992). (19.) Law PL, Lioy P J, Zelenka MP, Huber AH, McCurdy TR. Evaluation of a probabilistic exposure model applied to carbon monoxide (pNEM/CO) using Denver personal exposure monitoring data. J Air Waste Manag Assoc 47:491-500 (1997). (20.) Ott WR. Exposure estimates based on computer generated activity patterns. J Toxicol Clin Toxicol 21:97-128 (1984). (21.) MacNee W, Donaldson K. Particulate air pollution: injurious in·ju·ri·ous adj. 1. Causing or tending to cause injury; harmful: eating habits that are injurious to one's health. 2. and protective mechanisms in the lungs. In: Air Pollution and Health (Holgate ST, Samet JM, Koren HS, Maynard RL, eds). London:Academic Press, 1999;653-672. (22.) Laden F, Neas LM, Schwartz J. The association of crustal particles in the fine particulate fraction with daily mortality in six cities [Abstract]. Am J Respir Crit Care Med 159:A332 (1999). (23.) Brauer M, Hirtle RD, Hall AC, Yip TR. Monitoring personal fine particle exposure with a particle counter. J Expo Anal Environ Epidemiol 9:226-236 (1999). (24.) Diggle PJ, Liang KY, Zeger SL. Analysis of longitudinal lon·gi·tu·di·nal adj. Running in the direction of the long axis of the body or any of its parts. data. Oxford, UK:Clarendon Press, 1995. (25.) Davidian M, Giltinan DM. Nonlinear A system in which the output is not a uniform relationship to the input. nonlinear - (Scientific computation) A property of a system whose output is not proportional to its input. Mixed Effects Models for Repeated Measurement Data. London:Chapman and Hall Chapman and Hall was a British publishing house, founded in the first half of the 19th century by Edward Chapman and William Hall. Upon Hall's death in 1847, Chapman's cousin Frederic Chapman became partner in the company, of which he became sole manager upon the retirement of , 1995. (26.) Kleinbaum DG, Kupper LL, Muller Mul·ler , Hermann Joseph 1890-1967. American geneticist. He won a 1946 Nobel Prize for the study of the hereditary effect of x-rays on genes. Mül·ler , Johannes Peter 1801-1858. KE, Nizam A. Applied Regression Analysis and Other Multivariable Methods. 3rd ed. Pacific Grove Pacific Grove, residential and resort city (1990 pop. 16,117), Monterey co., W central Calif., on a point where Monterey Bay meets the Pacific Ocean; inc. 1889. , CA:Duxbury Press, 1998. Jonathan I. Levy,(1) E. Andres Houseman? Louise Ryan,(2) Dejuran Richardson,(2) Students from the 1998 Summer Program in Biostatistics,(*) and John D. Spengler(1) (1) Department of Environmental Health; (2) Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts, USA Address correspondence to J.I. Levy, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115 USA. Telephone: (617) 432-4845. Fax: (617) 432-4122. E-mail: jilevy@hsph.harvard.edu (*) B. Acosta-Garcia (University of Puerto Rico Founded in 1903, the University of Puerto Rico (Universidad de Puerto Rico in Spanish, UPR) is the oldest and largest university system in Puerto Rico. Though Puerto Rico is not a U.S. ), M. Cote (Harvard/Main Program for Children), T. Jones (LeMoyne-Owen College History LeMoyne-Owen College was formed through the 1968 merger of LeMoyne College and Owen College, both private, historically black church-related colleges.[1] ), R. Moore (Bennett College Oprah Winfrey and Maya Angelou have recently offered public support to Bennett College. History Bennett's founding and coeducational years Bennett College was founded by Albion Tourgee an activist in the second half of the 19th century who championed the cause of ), M. Price (Albany State University Historical Background Joseph Winthrop Holley founded the institution in 1903 as the Albany Bible and Manual Training Institute. Holley was born in 1874 to former slaves in Winnsboro, South Carolina. ), R. Sebro (Morehouse College Morehouse College: see Atlanta Univ. Center. Morehouse College Private, historically black, men's liberal arts college in Atlanta, Ga. It was founded as the Augusta Institute, a seminary, in 1867 and renamed in 1913 in honour of Henry L. ), K. Taylor (Hampton University Hampton University, at Hampton, Va.; coeducational; founded 1868, chartered 1870 as a normal and agricultural school; known as Hampton Institute 1930–84. ), and I. Williams (Howard University Howard University, at Washington, D.C.; coeducational; with federal support. It was founded in 1867 by Gen. Oliver O. Howard of the Freedmen's Bureau, to provide education for newly emancipated slaves. A normal and preparatory department was opened the same year. ). We thank H. Ozkaynak for providing valuable feedback, and we are indebted in·debt·ed adj. Morally, socially, or legally obligated to another; beholden. [Middle English endetted, from Old French endette, past participle of endetter, to oblige to all of the Summer Program students for their interest and assistance. Funding for this research was provided in part by the National Cancer Institute (CA48061), NIH (R25 GM55353), U.S. EPA Cooperative Agreement CR825267-01, and by a U.S. EPA EMPACT EMPACT Environmental Monitoring for Public Access and Community Tracking EMPACT Employees Motivated To Protect Assets and Curtail Theft grant. In addition, students in the Summer Program in Biostatistics were supported by NIEHS (5 T35 ES07293-05). This paper has not been subjected to review by the above agencies and does not necessarily reflect their views. Received 17 April 2000; accepted 5 July 2000. |
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