Association of Fine Particulate Matter from Different Sources with Daily Mortality in Six U.S. Cities.Previously we reported that fine particle mass (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. [is less than or equal to] 2.5 [micro]m; [PM.sub.2.5]), which is primarily from combustion sources, but not coarse particle mass, which is primarily from 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 sources, was associated with daily mortality in six eastern U.S. cities (1). In this study, we used the elemental elemental emanating from or pertaining to elements. elemental diet see elemental diet. composition of size-fractionated particles to identify several distinct source-related fractions of 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. and examined the association of these fractions with daily mortality in each of the six cities. Using specific rotation specific rotation n. Symbol  The arc of rotation, expressed in angular degrees, through which the plane of polarized light moves when it is in a light path one decimeter in factor analysis for each city, we identified a silicon factor classified as soil and crustal material, a lead factor classified as motor vehicle exhaust, a selenium selenium (səlē`nēəm), nonmetallic chemical element; symbol Se; at. no. 34; at. wt. 78.96; m.p. 217°C;; b.p. about 685°C;; sp. gr. 4.81 at 20°C;; valence −2, +4, or +6. factor representing coal combustion, and up to two additional factors. We extracted daily counts of deaths from National Center for Health Statistics National Center for Health Statistics (NCHS) is part of the Centers for Disease Control and Prevention (CDC), which is part of the United States Department of Health and Human Services. NCHS is the United States' principal health statistics agency. records and estimated city-specific associations of mortality with each source factor by Poisson regression In statistics, the Poisson regression model attributes to a response variable Y a Poisson distribution whose expected value depends on a predictor variable x, typically in the following way: n a statistical device used to determine the range within which an acceptable datum would fall. Confidence intervals are usually expressed in percentages, typically 95% or 99%. (CI), 1.7-5.2%], and the equivalent increase in fine particles from coal combustion sources accounted for a 1.1% increase [CI, 0.3-2.0%). [PM.sub.2.5] crustal particles were not associated with daily mortality. These results indicate that combustion particles in the fine fraction from mobile and coal combustion sources, but not fine crustal particles, are associated with increased mortality. Key words, air pollution, coal combustion, fine particles, mobile sources, mortality, [PM.sub.2.5], source apportionment The process by which legislative seats are distributed among units entitled to representation; determination of the number of representatives that a state, county, or other subdivision may send to a legislative body. The U.S. . Environ Health Perspect 108:941-947 (2000). [Online 29 August 2000] http://ehpnet1.niehs.nih.gov/docs/2000/108p941-947laden/abstract.html In a study of six U.S. cities, we previously demonstrated that daily mortality was associated with fine particulate matter (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. [is less than or equal to] 2.5 [micro]m; [PM.sub.2.5]) and not coarse particulate matter (aerodynamic diameter between 2.5 and 10 [micro]m [PM.sub.2.5-10]) (1). Each 10 [micro]g/[m.sup.3] increase in the 2-day mean concentration of [PM.sub.2.5] was associated with a 1.5% [95% confidence interval (CI), 1.1-1.9%) increase in daily mortality. An equivalent change in [PM.sub.2.5-10] was associated with only a 0.4% increase in total mortality (CI, 0.1-1.0%) and no increase after control for [PM.sub.2.5.] Particle size 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. is an important determinant determinant, a polynomial expression that is inherent in the entries of a square matrix. The size n of the square matrix, as determined from the number of entries in any row or column, is called the order of the determinant. of the site and efficiency of pulmonary deposition, but particle size is also a surrogate surrogate n. 1) a person acting on behalf of another or a substitute, including a woman who gives birth to a baby of a mother who is unable to carry the child. 2) a judge in some states (notably New York) responsible only for probates, estates, and adoptions. for particle source and composition. [PM.sub.2.5-10] consists mainly of crustal particles mechanically generated from agriculture, mining, construction, road traffic, and related sources, as well as particles of biological origin. [PM.sub.2.5] consists mainly of combustion particles from motor vehicles and the burning of coal, fuel oil, and wood, but also contains some crustal particles from finely pulverized pul·ver·ize v. pul·ver·ized, pul·ver·iz·ing, pul·ver·iz·es v.tr. 1. To pound, crush, or grind to a powder or dust. 2. To demolish. v.intr. road dust and soils. Although a convincing body of evidence has accumulated on the adverse effects of [PM.sub.2.5] (1-11), the specific sources and constituents responsible for these adverse effects have not been determined. In this study, we used the elemental composition of size-fractionated particles to identify several distinct source-related fractions of fine particles. We then examined the association of these fractions with daily mortality in each of the six cities and combined the city-specific results in a meta-analysis to derive overall relative risks for each fraction. Materials and Methods Air pollution data. As part of the Harvard Six Cities Studies (12), dichotomous di·chot·o·mous adj. 1. Divided or dividing into two parts or classifications. 2. Characterized by dichotomy. di·chot virtual impactor samples were placed at a central residential monitoring site in Watertown, Massachusetts The Town of Watertown is a city[1] in Middlesex County, Massachusetts, United States. The population was 32,986 at the 2000 census. History Watertown, first known as Saltonstall Plantation, was one of the earliest of the Massachusetts Bay settlements. ; Kingston-Harriman, Tennessee; St. Louis, Missouri; Steubenville, Ohio
Steubenville is a city located along the Ohio River in Jefferson County, Ohio, in the United States. ; Portage, Wisconsin Portage, Wisconsin is a city in Columbia County, Wisconsin, United States. The city uses the slogan "Where the North Begins". The population was 9,728 at the 2000 census. It is the county seat of Columbia CountyGR6. ; and Topeka, Kansas This article is about the state capital of Kansas. For other uses, see Topeka (disambiguation). Topeka is the capital of the U.S. state of Kansas and the county seat of Shawnee County, which is named after the Shawnee Indians. . Separate filter samples were collected of fine particles [PM.sub.2.5] and of the coarse mass [PM.sub.2.5-10] fraction. The 2.5 [micro]m cutpoint for dichotomous samplers represents the aerodynamic diameter at which 50% of the particles are sent to the fine particle filter This article is about the statistical method. For the pollution control device, see diesel particulate filter. Particle filters, also known as Sequential Monte Carlo methods (SMC), are sophisticated model estimation techniques based on simulation. and 50% to the coarse mass filter. The cutoff is relatively sharp, but some larger particles, including some crustal material, will still be deposited on the fine fraction filter. In addition, there is crustal material between 1 and 2.5 [micro]m, representing the low end of the coarse-mode particle size distribution 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. . Integrated 24-hr samples were collected at least every other day from 1979 until the late 1980s (1), with daily sampling during health survey periods. For fine and coarse particle samples, mass concentration was determined separately by beta-attenuation (13). With the exception of a period between October 1981 and January 1984 in all cities, elemental composition of fine and coarse mass was determined by X-ray fluorescence X-ray fluorescence (XRF) is the emission of characteristic "secondary" (or fluorescent) X-rays from a material that has been excited by bombarding with high-energy X-rays or gamma rays. (14). Elemental composition was available on 97% of these samples. In the fine fraction, 15 elements were routinely found above the limit of detection: silicon, sulfur, chlorine, potassium potassium (pətăs`ēəm), a metallic chemical element; symbol K [Lat. kalium=alkali]; at. no. 19; at. wt. 39.0983; m.p. 63.25°C;; b.p. 760°C;; sp. gr. .862 at 20°C;; valence +1. , calcium, vanadium vanadium (vənā`dēəm), metallic chemical element; symbol V; at. no. 23; at. wt. 50.9415; m.p. about 1,890°C;; b.p. 3,380°C;; sp. gr. about 6 at 20°C;; valence +2, +3, +4, or +5. Vanadium is a soft, ductile, silver-grey metal. , manganese manganese (măng`gənēs, măn`–) [Lat.,=magnet], metallic chemical element; symbol Mn; at. no. 25; at. wt. 54.938; m.p. about 1,244°C;; b.p. about 1,962°C;; sp. gr. 7.2 to 7. , aluminum, nickel, zinc, selenium, bromine bromine (brō`mēn, –mĭn) [Gr.,=stench], volatile, liquid chemical element; symbol Br; at. no. 35; at. wt. 79.904; m.p. –7.2°C;; b.p. 58.78°C;; sp. gr. of liquid 3.12 at 20°C;; density of vapor 7. , lead, copper, and iron. Source identification. In separate analyses for each city, we used specific rotation factor analysis to identify up to 5 common factors from the 15 specified elements. We specified a single element as the tracer for each factor and maximized the projection of these elements using the Procrustes rotation, a variant of the oblique o·blique adj. Situated in a slanting position; not transverse or longitudinal. oblique slanting; inclined. rotation method that is commonly used in psychometric testing psychometric test Any test used to quantify a particular aspect of a person's mental abilities or mindset–eg, aptitude, intelligence, mental abilities and personality. See IQ test, Personality testing, Psychological testing. (15,16). This method is similar to the factor analytic Adj. 1. factor analytic - of or relating to or the product of factor analysis factor analytical approach used by Koutrakis and Spengler (17), but it uses standard software (18). We selected tracer elements in three steps. First, we identified tracers Tracers Refers to investment trusts which are populated by corporate bonds. In October 2001, Morgan Stanley's Tradable Custodial Receipts (Tracers) was launched. Tracers contain a number of coporate bonds and credit default swaps which are selected for liquidity and diversity. on the basis of the chemical composition of fine particulate matter from known sources and the previous source apportionment research in Watertown by Thurston and Spengler (19) and in Steubenville by Koutrakis and Spengler (17). Second, we regressed total fine mass on the identified factors and rejected any factors that had negative 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 . Third, we attempted to identify additional, possibly local, sources by examining elements that did not load heavily on the positive factors from step 2 and created the additional factors that were both positive predictors of total fine mass and maximized the model [R.sup.2]. In steps 1 and 2, we defined three sources of fine particles in all six cities: a silicon factor classified as soil and crustal material, a lead factor classified as motor vehicle exhaust, and a selenium factor representing coal combustion sources. In city-specific analyses, we also considered vanadium (fuel oil combustion), chlorine (salt), and selected metals (nickel, zinc, or manganese) as possible targets and sources. We identified five source factors for each city, except for Topeka, where we were only able to identify three positive predictors of total [PM.sub.2.5]. Daily factor scores. For each metropolitan area, we calculated daily scores for each of the identified factors. Information on the relative concentration of each of the 15 elements in each factor is provided by the standardized standardized pertaining to data that have been submitted to standardization procedures. standardized morbidity rate see morbidity rate. standardized mortality rate see mortality rate. scoring coefficients. Therefore, the score for each factor for each day was calculated by multiplying the normalized concentration of each element by the respective standardized scoring coefficient for that element and factor and then summing across these 15 products. We recentered these daily factor scores by calculating a factor score for a hypothetical day on which all of the elemental concentrations were zero and then subtracting this minimum factor score from the daily factor score (19). To rescale Verb 1. rescale - establish on a new scale resize - change the size of; make the size more appropriate scale down - reduce proportionally; "The model is scaled down" scale up - increase proportionally; "scale up the model" the factor scores from the normalized scale to the mass scale (in [micro]g/[m.sup.3]), we regressed the total daily fine particle concentrations on the daily factor scores for all of the factors in separate regression models for each city and obtained the product of each factor score with its regression coefficient (19). Only sources that were significant predictors of total fine particle mass (p [is less than] 0.10) were considered in the mortality analyses. As in our earlier study (1), we assumed that mortality was associated with the 2-day mean of the non-missing particle concentrations on the same and on the previous day. Because much of the monitoring was conducted every other day during the study period, this technique imputed Attributed vicariously. In the legal sense, the term imputed is used to describe an action, fact, or quality, the knowledge of which is charged to an individual based upon the actions of another for whom the individual is responsible rather than on the individual's missing days using the non-missing values on the previous days, which increased the number of days included in the mortality analysis from 6,211 to 9,108. For this imputation IMPUTATION. The judgment by which we declare that an agent is the cause of his free action, or of the result of it, whether good or ill. Wolff, Sec. 3. , we assumed that the sampling schedule, and hence the missing values In statistics, missing values are a common occurrence. Several statistical methods have been developed to deal with this problem. Missing values mean that no data value is stored for the variable in the current observation. , were random with respect to daily mortality. Meteorological data Meteorological facts pertaining to the atmosphere, such as wind, temperature, air density, and other phenomena that affect military operations. . We obtained meteorological data from the National Center for Atmospheric Research The National Center for Atmospheric Research (NCAR) is a non-governmental U.S.-based institute whose stated mission is "exploring and understanding our atmosphere and its interactions with the Sun, the oceans, the biosphere, and human society. (Boulder, CO) including hourly measures of temperature, dew point dew point: see dew. temperature, and precipitation precipitation, in chemistry precipitation, in chemistry, a process in which a solid is separated from a suspension, sol, or solution. In a suspension such as sand in water the solid spontaneously precipitates (settles out) on standing. from the National Oceanographic and Atmospheric Administration (Washington, DC) weather station nearest to each city. We calculated 24-hr mean values for temperature and dew point temperature. Mortality data. We defined the six metropolitan areas in this study as the county containing the air pollution monitor and contiguous counties (1). For the mortality analysis, each study area is identified by the name of its largest city (e.g., Watertown as Boston; Kingston-Harriman as Knoxville; Portage Portage (1, 2 pôr`təj; 3 pôr`tĭj). 1 Town (1990 pop. 29,060), Porter co., NW Ind., a suburb of Gary, on Lake Michigan; inc. 1959. as Madison). We extracted daily deaths for people who lived and died in the selected counties from annual detail mortality tapes (from the National Center for Health Statistics, Hyattsville, MD) for the time periods with fine particulate par·tic·u·late adj. Of or occurring in the form of fine particles. n. A particulate substance. particulate composed of separate particles. measurements. After excluding all deaths due to accidents and other external causes [International Classification of Diseases, Ninth Revision (ICD-9), clinical modification codes 800-999)], we analyzed the remaining total daily deaths as well as daily deaths from ischemic heart disease Ischemic heart disease Insufficient blood supply to the heart muscle (myocardium). Mentioned in: Myocarditis ischemic heart disease (ICD-9 410-414), pneumonia (ICD-9 480-486), and chronic obstructive pulmonary disease chronic obstructive pulmonary disease n. Abbr. COPD A chronic lung disease, such as asthma or emphysema, in which breathing becomes slowed or forced. (ICD-9 490-496). Since the 1996 analysis, the mortality data were updated to restrict deaths of those individuals who both lived and died within the specified counties and to correct for administrative changes in the county codes for St. Louis in 1982. Poisson regression of mortality. We investigated the association of daily deaths with sources of fine particles separately for each city using Poisson regression in a generalized additive model In statistics, the generalized additive model (or GAM) is a statistical model developed by Trevor Hastie and Rob Tibshirani blending properties of multiple regression (a special case of general linear model) with additive models. (20,21). To control for trend and season, we used a locally weighted linear regression Linear regression A statistical technique for fitting a straight line to a set of data points. (Loess loess (lĕs, lō`əs, Ger. lös), unstratified soil deposit of varying thickness, usually yellowish and composed of fine-grained angular mineral particles mixed with clay. ) smooth function of date with a span of 0.05 (22). For the smooth functions of temperature and dew point temperature, we used Loess functions with spans of 0.80. Indicator variables for day of the week also were included in the models. The relative risks for each source were evaluated by including the absolute factor scores (in micrograms per cubic meter Noun 1. cubic meter - a metric unit of volume or capacity equal to 1000 liters cubic metre, kiloliter, kilolitre metric capacity unit - a capacity unit defined in metric terms ) simultaneously in the model. That is, the estimate of the mobile source factor is in a model controlling for coal derived particles, crustal particles, and the other source factors, and vice versa VICE VERSA. On the contrary; on opposite sides. . To obtain summary estimates of the association between the different sources of fine particles and daily mortality, we combined the city-specific regression coefficients using inverse variance weights. This method produces similar summary estimates as weighting by the number of deaths in each city and takes into account the precision of each individual estimate. As an alternative approach, we evaluated the association of daily deaths with individual elements. Based on previous toxicological research suggesting which elements might be important in ambient Surrounding. For example, ambient temperature and humidity are atmospheric conditions that exist at the moment. See ambient lighting. particle toxicity (23-26), we built city-specific models that included daily measurements of lead, iron, sulfur, nickel, vanadium, manganese, and zinc individually and in combination. Trend, season, and weather were controlled for as described above. Results Source apportionment. The mean and standard deviations In statistics, the average amount a number varies from the average number in a series of numbers. (statistics) standard deviation - (SD) A measure of the range of values in a set of numbers. for the 15 elements varied across the six metropolitan areas (Table 1). As the most common element in the fine fraction, the mean sulfur concentration varied by a factor of two across five areas (1.5-2.6 [micro]g/[m.sup.3]) and was much higher in Steubenville (4.2 [micro]g/[m.sup.3]). Because these measurements were conducted before the removal of lead from gasoline, the lead concentrations were relatively high ([is greater than] 0.1 [micro]g/[m.sup.3]) in every city except Portage and Topeka. Vanadium was much higher in Watertown and Steubenville than in the other metropolitan areas. Table 1. Means and standard deviations of total fine particulate matter < 2.5 [micro]m diameter (in [micro]g/[m.sup.3]) and selected elements (in ng/[m.sup.3]) by metropolitan area, six U.S. cities, 1979-1988.
Watertown
(Boston) St. Louis
Mean [+ or -] SD Mean [+ or -] SD
[PM.sub.2.5] 16.5 [+ or -] 9.2 19.2 [+ or -] 10.1
Silicon 114.2 [+ or -] 107.8 195.9 [+ or -] 256.9
Aluminum 65.5 [+ or -] 88.7 161.2 [+ or -] 211.7
Calcium 33.9 [+ or -] 31.6 78.8 [+ or -] 54.6
Iron 62.2 [+ or -] 53.5 143.7 [+ or -] 132.7
Manganese 3.7 [+ or -] 2.8 19.2 [+ or -] 27.3
Potassium 75.6 [+ or -] 56.5 118.0 [+ or -] 87.2
Lead 240.3 [+ or -] 212.1 212.7 [+ or -] 223.9
Bromine 58.7 [+ or -] 66.5 39.8 [+ or -] 59.3
Copper 11.0 [+ or -] 14.5 29.7 [+ or -] 46.6
Zinc 24.8 [+ or -] 18.7 57.0 [+ or -] 62.6
Sulfur 1921.6 [+ or -] 1,391.3 2350.3 [+ or -] 1,583.4
Selenium 0.7 [+ or -] 0.9 2.2 [+ or -] 1.9
Vanadium 23.2 [+ or -] 19.8 2.0 [+ or -] 4.4
Nickel 8.8 [+ or -] 7.0 2.2 [+ or -] 4.8
Chlorine 49.3 [+ or -] 148.6 20.5 [+ or -] 98.1
Kingston-Harriman Portage
(Knoxville) (Madison)
Mean [+ or -] SD Mean [+ or -] SD
[PM.sub.2.5] 21.1 [+ or -] 9.3 11.3 [+ or -] 7.5
Silicon 203.4 [+ or -] 188.4 109.1 [+ or -] 155.7
Aluminum 152.5 [+ or -] 150.2 70.5 [+ or -] 127.0
Calcium 98.7 [+ or -] 142.3 35.2 [+ or -] 33.7
Iron 116.9 [+ or -] 89.1 44.1 [+ or -] 45.7
Manganese 8.8 [+ or -] 21.8 3.2 [+ or -] 3.1
Potassium 109.4 [+ or -] 71.8 59.6 [+ or -] 36.4
Lead 108.7 [+ or -] 95.6 33.3 [+ or -] 33.7
Bromine 21.5 [+ or -] 22.4 6.1 [+ or -] 5.7
Copper 12.7 [+ or -] 16.4 6.4 [+ or -] 8.3
Zinc 33.8 [+ or -] 54.1 15.9 [+ or -] 13.2
Sulfur 2555.9 [+ or -] 1491.4 1481.5 [+ or -] 1327.2
Selenium 1.9 [+ or -] 1.5 0.9 [+ or -] 0.8
Vanadium 1.4 [+ or -] 3.3 0.1 [+ or -] 2.9
Nickel 1.0 [+ or -] 1.1 0.5 [+ or -] 0.7
Chlorine 6.7 [+ or -] 15.8 9.1 [+ or -] 101.3
Steubenville Topeka
Mean [+ or -] SD Mean [+ or -] SD
[PM.sub.2.5] 30.5 [+ or -] 22.4 12.2 [+ or -] 7.1
Silicon 283.3 [+ or -] 360.4 202.4 [+ or -] 281.2
Aluminum 186.8 [+ or -] 238.0 130.1 [+ or -] 205.2
Calcium 101.7 [+ or -] 155.3 134.0 [+ or -] 200.0
Iron 542.4 [+ or -] 738.3 72.0 [+ or -] 88.2
Manganese 30.4 [+ or -] 41.5 4.7 [+ or -] 3.5
Potassium 344.4 [+ or -] 411.1 84.5 [+ or -] 99.0
Lead 184.5 [+ or -] 195.3 71.5 [+ or -] 104.9
Bromine 30.2 [+ or -] 31.4 18.2 [+ or -] 32.1
Copper 11.9 [+ or -] 10.7 6.7 [+ or -] 9.7
Zinc 138.4 [+ or -] 214.6 13.8 [+ or -] 15.5
Sulfur 4,248.4 [+ or -] 3,185.3 1,368.3 [+ or -] 1,168.9
Selenium 5.2 [+ or -] 4.2 0.8 [+ or -] 0.7
Vanadium 10.5 [+ or -] 20.4 0.6 [+ or -] 2.8
Nickel 3.7 [+ or -] 4.7 0.6 [+ or -] 1.0
Chlorine 58.7 [+ or -] 263.0 10.6 [+ or -] 49.5
The identified sources and their contribution to total daily fine mass in each community are presented in Table 2. Using silicon, lead, and selenium as tracer elements, we identified crustal, mobile, and coal combustion factors, respectively, in all six metropolitan areas. Coal and mobile sources account for the majority of fine particles in each city; the proportion of fine particulate matter accounted for by these two factors combined ranged from 0.44 in St. Louis to 0.79 in Watertown. In Watertown the crustal factor accounted for [is less than] 1% of the fine particle mass and was not a significant predictor in the regression model. Therefore, in Boston, the larger metropolitan area represented by Watertown, this factor was not included in the mortality analyses. We identified a vanadium factor, representing fuel oil combustion in Watertown and Steubenville. A chlorine factor (salt) was identified in Watertown, Kingston-Harriman, and Portage. We identified a metal factor in St. Louis (zinc), Steubenville (zinc), and Kingston-Harriman (nickel), presumably pre·sum·a·ble adj. That can be presumed or taken for granted; reasonable as a supposition: presumable causes of the disaster. related to local manufacturing. Finally, we found a manganese factor in St. Louis and Portage. In Topeka, which had a low average [PM.sub.2.5] concentration, we were able to identify only the crustal, mobile, and coal combustion factors. The source of at least 18% of the total mass remained unexplained unexplained Adjective strange or unclear because the reason for it is not known Adj. 1. unexplained - not explained; "accomplished by some unexplained process" in all cities, except Steubenville (8% unexplained). Table 2. Proportional composition of fine particulate matter ([PM.sub.2.5]) by source and metropolitan area, six U.S. cities, 1979-1988.
Watertown
Source Target (Boston) St. Louis
Crustal Silicon < 0.01 0.14
Mobile Lead 0.29 0.15
Coal Selenium 0.50 0.29
Fuel oil Vanadium 0.03 --
Metals (a) -- 0.12
Salt Clorine 0.01 --
Manganese Manganese -- 0.03
Residual 0.18 0.28
Kingston-Harriman Portage
Source (Knoxville) (Madison)
Crustal 0.08 0.03
Mobile 0.21 0.27
Coal 0.32 0.45
Fuel oil -- --
Metals 0.14 --
Salt 0.04 0.01
Manganese -- 0.07
Residual 0.21 0.18
Source Steubenville Topeka
Crustal 0.14 0.08
Mobile 0.05 0.17
Coal 0.63 0.57
Fuel oil 0.03 --
Metals 0.08 --
Salt -- --
Manganese -- --
Residual 0.08 0.19
(a) The target element varied by metropolitan area: zinc in St. Louis and Steubenville and nickel in Knoxville. The crustal factor consisted predominantly of silicon (the tracer element), aluminum, iron, potassium, and calcium. The elemental composition of road dust identified by published chemical analyses was similar (27), and the relative contributions of each element (the standardized scoring coefficients) were fairly consistent across the six metropolitan areas (Table 3). The coefficient for silicon, the marker for sandy soils, varied only slightly from 0.25 to 0.36, whereas the coefficient for aluminum, a marker for clay soils, varied much more--from 0.17 in Watertown to 0.50 in Steubenville. Except for Kingston-Harriman, the contribution of calcium was relatively constant across the metropolitan areas. These differences in the standardized scoring coefficients for the crustal factor may reflect regional differences in the composition of soils. Table 3. Crustal factor with silicon as the target element: standardized scoring coefficients by element and metropolitan area, six U.S. cities, 1979-1988.
Watertown Kingston-Harriman
Element (Boston) St. Louis (Knoxville)
Silicon 0.28 0.33 0.25
Aluminum 0.17 0.29 0.29
Calcium 0.26 0.25 -0.04
Iron 0.26 0.20 0.11
Manganese 0.14 0.00 0.30
Potassium 0.08 0.18 0.26
Lead 0.00 0.00 0.00
Bromine 0.02 0.00 0.05
Copper 0.06 -0.01 -0.28
Zinc 0.00 0.00 0.19
Sulfur 0.00 -0.01 -0.14
Selenium 0.00 0.00 0.00
Vanadium 0.00 0.02 0.38
Nickel 0.02 -0.06 0.00
Chlorine 0.00 0.15 0.00
Portage
Element (Madison) Steubenville Topeka
Silicon 0.30 0.36 0.27
Aluminum 0.27 0.50 0.24
Calcium 0.26 0.29 0.17
Iron 0.24 -0.01 0.27
Manganese 0.00 0.11 0.17
Potassium 0.13 0.06 0.12
Lead 0.00 0.00 0.00
Bromine 0.01 -0.17 0.01
Copper -0.02 -0.04 0.00
Zinc -0.03 0.00 -0.01
Sulfur 0.05 0.02 -0.02
Selenium 0.00 0.00 0.00
Vanadium -0.14 0.00 0.04
Nickel -0.14 -0.25 0.03
Chlorine 0.00 -0.24 -0.01
Because these measurements were conducted while leaded gasoline was still in use, lead provided a good marker for mobile sources. To minimize the possibility of noise in the data in the later years when leaded gasoline was being phased out, we evaluated a measurement of lead adjusted by time. This correction did not substantially affect the results, so it was not used in the main analyses and is not presented here. For the mobile source factor, the standardized scoring coefficients were similar for lead and bromine (a constituent of commercial tetra-ethyl lead Tetra-ethyl lead, abbreviated TEL, is an organometallic compound with the formula (CH3CH2)4Pb. Once a common anti-knock additive in gasoline (petrol), TEL usage was largely discontinued because of the toxicity of lead and its disadvantageous mixtures), except in Steubenville and Kingston-Harriman, where the coefficients for bromine were low (Table 4). Copper had surprisingly high scoring coefficients for this source factor, especially in Steubenville and Kingston-Harriman. Furthermore, sulfur loaded particularly high on the lead factor in Kingston-Harriman. Thus, we must be careful in the interpretation of this factor as a mobile source in Kingston-Harriman and perhaps in Steubenville. Table 4. Mobile source factor with lead as the target element: standardized scoring coefficients by element and metropolitan area, six U.S. cities, 1979-1988.
Watertown Kingston-Harriman
Element (Boston) St. Louis (Knoxville)
Silicon 0.00 0.00 0.00
Aluminum -0.16 -0.09 -0.10
Calcium 0.09 0.19 0.34
Iron 0.11 0.11 0.05
Manganese 0.10 0.00 -0.37
Potassium 0.04 0.10 -0.17
Lead 0.28 0.33 0.11
Bromine 0.26 0.37 0.01
Copper 0.30 -0.03 0.42
Zinc 0.14 0.00 -0.23
Sulfur 0.06 -0.07 0.24
Selenium 0.00 0.00 0.00
Vanadium 0.00 -0.32 -0.50
Nickel 0.01 -0.11 0.00
Chlorine 0.00 0.16 0.00
Portage
Element (Madison) Steubenville Topeka
Silicon 0.00 0.00 0.00
Aluminum -0.06 0.26 -0.06
Calcium 0.15 0.04 0.16
Iron 0.09 -0.08 0.07
Manganese 0.00 0.05 0.10
Potassium 0.09 0.26 0.08
Lead 0.27 0.44 0.33
Bromine 0.25 0.03 0.31
Copper 0.21 0.40 0.20
Zinc 0.15 0.00 0.18
Sulfur 0.08 0.01 0.05
Selenium 0.00 0.00 0.00
Vanadium -0.30 0.00 -0.11
Nickel -0.13 -0.54 0.06
Chlorine 0.00 -0.50 0.11
For the selenium or coal combustion factor, the standardized scoring coefficients reflected the important contribution of sulfur from this source factor in every metropolitan area except Kingston-Harriman (Table 5). In Kingston-Harriman, this factor had high coefficients for vanadium, manganese, and potassium that were not seen in the other metropolitan areas. Again, as with the mobile factor, we should be cautious in interpreting this factor as a coal combustion source factor in Kingston-Harriman. Table 5. Coal combustion factor with selenium as the target element: standardized scoring coefficients by element and metropolitan area, six U.S. cities, 1979-1988.
Watertown Kingston-Harriman
Element (Boston) St. Louis (Knoxville)
Silicon 0.00 0.00 0.00
Aluminum 0.10 0.05 0.11
Calcium -0.12 -0.10 -0.29
Iron -0.04 -0.03 -0.11
Manganese 0.16 0.00 0.28
Potassium 0.07 -0.07 0.26
Lead 0.00 0.00 0.00
Bromine -0.06 -0.10 0.09
Copper -0.04 0.09 -0.42
Zinc 0.21 0.00 0.15
Sulfur 0.41 0.56 -0.08
Selenium 0.43 0.39 0.26
Vanadium 0.00 -0.12 0.50
Nickel -0.01 -0.25 0.00
Chlorine 0.00 -0.47 0.00
Portage
Element (Madison) Steubenville Topeka
Silicon 0.00 0.00 0.00
Aluminum 0.08 -0.26 0.04
Calcium -0.08 -0.26 -0.06
Iron -0.04 0.06 0.00
Manganese 0.00 -0.04 0.14
Potassium 0.09 -0.01 0.09
Lead 0.00 0.00 0.00
Bromine -0.12 0.14 -0.04
Copper -0.17 0.05 0.08
Zinc 0.12 0.00 0.22
Sulfur 0.57 0.40 0.39
Selenium 0.46 0.31 0.41
Vanadium -0.08 0.00 0.19
Nickel -0.24 0.41 0.14
Chlorine 0.00 -0.03 -0.04
For the three communities in which we identified metal source factors, the pattern of high coefficients was different for each. In St. Louis, the zinc factor also had high coefficients for nickel, copper, and vanadium as well as potassium and chlorine. In Steubenville, the zinc factor had high coefficients for nickel, iron, manganese, chlorine, bromine, and calcium. Finally, in Kingston-Harriman, the nickel factor had high coefficients for iron and copper, but not for zinc. In Watertown, vanadium and nickel were highly correlated, and both loaded high on the factor targeted by vanadium and defined as fuel oil combustion (19). In Steubenville, the vanadium factor had moderate scoring coefficients only for aluminum and calcium. The manganese factors in Portage and St. Louis had high factor scoring coefficients for nickel and vanadium. Therefore, manganese may serve to identify a fuel oil combustion factor in some midwestern communities. Association of mortality with specific source factors. Because elemental composition was not available on every day in which fine mass was measured, the current data set is a subset of the data described in the 1996 analysis (1). Results for the combined analysis of total fine mass were similar to the previously published results: total daily mortality increased by 1.6% (CI, 1.1-2.1%) with each 10 [micro]g/[m.sup.3] increase in the 2-day mean of [PM.sub.2.5], as compared to the previous report of a 1.5% increase (CI, 1.1-1.9%) using the full data set (1). The magnitude of the associations with ischemic heart disease and chronic obstructive pulmonary disease were similar to those for total mortality (approximately 2). These point estimates were slightly attenuated Attenuated Alive but weakened; an attenuated microorganism can no longer produce disease. Mentioned in: Tuberculin Skin Test attenuated having undergone a process of attenuation. and the confidence intervals wider in these data compared to the earlier analysis. For the three source factors identified in all six metropolitan areas, we found the strongest increase in daily mortality associated with the mobile source (lead) factor (Table 6). In the combined analysis across the six cities, daily mortality increased by 3.4% (CI, 1.7-5.2%) with each 10 [micro]g/[m.sup.3] increase in the 2-day mean of the mobile-source factor. The communities are presented in the table in order of decreasing population size, and consequently decreasing contribution to the summary measure. In St. Louis, Knoxville (Kingston-Harriman), and Madison (Portage), the estimated effects were 4.3, 5.2, and 6.3%, respectively. The associations in Steubenville and Topeka were inverse, but the standard errors were large and the contribution of mobile sources to total [PM.sub.2.5] was modest in Steubenville (Table 2). Similar to the association observed with total [PM.sub.2.5], there was evidence of a 2% increase in daily mortality from ischemic heart disease with each 10 [micro]g/[m.sup.3] increase in mobile sources; however, it was not statistically significant (CI, -1.1-5.2). We did not identify adverse effects for respiratory deaths (chronic obstructive pulmonary disease or pneumonia). Table 6. Percent increase in daily deaths and 95% CIs associated with a 10 [micro]g/[m.sup.3] increase in mass concentration from a specific major source of fine particles by metropolitan area, six U.S. cities, 1979-1988.(a)
Crustal (Si)
Mean
daily deaths Percent
City deaths increase 95% CI
Boston(b) 59 -- --
St. Louis 55 -3.0 -7.7-1.6
Knoxville 12 -1.7 -20.0-17.0
Madison 11 40.5 -26.8-112.5
Steubenville 3 -1.4 -7.1-4.2
Topeka 3 -7.9 -42.4-27.9
Summary(c) -2.3 -5.8-1.2
Motor (Pb) Coal (Se)
Percent Percent
City increase 95% CI increase 95% CI
Boston(b) 1.2 -1.9-4.3 2.8 1.2-4.4
St. Louis 4.3 1.6-7.0 0.3 -1.1-1.6
Knoxville 5.2 1.2-9.2 0.8 -2.7-4.3
Madison 6.3 -3.1-15.8 0.9 -2.5-4.2
Steubenville -0.2 -20.5-20.5 1.1 -1.2-3.5
Topeka -8.2 -29.0-13.1 -3.9 -11.2-3.5
Summary(c) 3.4 1.7-5.2 1.1 0.3-2.0
(a) Each multivariate The use of multiple variables in a forecasting model. model includes Loess smooth function of date with a span of 0.05, Loess functions of temperature and dew point temperature with spans of 0.80, indicator variables for day of the week, and all source factors simultaneously. (b) The crustal factor was not a statistically significant predictor of fine mass in Watertown (Boston); therefore, it was not included in the analysis. (c) Summary estimates obtained by combining the city-specific regression coefficients using inverse variance weights. The coal combustion (selenium) factor was positively associated with mortality in all metropolitan areas, with the exception of Topeka (Table 6). The summary relative risk indicated that a 10 [micro]g/[m.sup.3] increase in the 2-day mean mass concentration from coal combustion sources was associated with a 1.1% increase in daily mortality (CI, 0.3-2.0%). Deaths from chronic obstructive pulmonary disease and pneumonia increased by higher percentages than did deaths from all causes: 4.5% (CI, -0.4-9.3%) and 7.9% (CI, 3.1-12.7%), respectively. Unlike the motor source factor, there was no evidence of an increased effect of exposure to coal combustion sources for ischemic heart disease. As we mentioned before, the elemental profiles for the lead (mobile) and selenium (coal) factors in Knoxville differed from the profiles in the other cities. When Knoxville is omitted from the meta-analysis, the increase in daily mortality attributed to mobile sources and coal combustion changed only slightly. In all of the metropolitan areas combined, 46% of the total fine particle mass was attributed to coal combustion and 19% to mobile sources. Therefore, the difference between the 5th and 95th percentile percentile, n the number in a frequency distribution below which a certain percentage of fees will fall. E.g., the ninetieth percentile is the number that divides the distribution of fees into the lower 90% and the upper 10%, or that fee level is considerably different for coal combustion (28.7 [micro]g/[m.sup.3]) than for mobile sources (12.9 [micro]g/[m.sup.3]). However, the summary estimate of the change in daily mortality across this range of exposure still indicated a difference in magnitude; the increase was 4.5% (CI, 2.2-18.3) for mobile sources and 3.2% (CI, 0.7-5.8%) for coal combustion. The crustal factor in fine particulate matter was not associated with mortality. If anything, the summary relative risk suggested a protective association between crustal particles and mortality. However, the confidence intervals were wide and the association far from statistical significance. This factor was not included in the mortality analysis in Boston (Watertown) because, even though it was identified in that city, it was not a significant predictor of and accounted for [is less than] 1% of total fine particulate matter. There is a suggestion of a large positive association of fuel oil combustion with daily mortality in the cities in which the vanadium factor was identified; however, the confidence intervals were wide and included a 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. effect (Boston: 27.3% increase, CI, -2.0-57.5%; Steubenville: 13.6% increase, CI, -34.2-63.8%). If we consider the manganese factor as defining a fuel oil combustion source in Madison and St. Louis, then the summary effect estimate for the four cities is 5.6% (CI, -1.8- 13.2%) for a 10 [micro]g/[m.sup.3] increment To add a number to another number. Incrementing a counter means adding 1 to its current value. in [PM.sub.2.5] from this factor. Association of mortality with specific elements. In models with measurements for the individual elements included simultaneously, sulfur, nickel, and lead were significantly associated with total mortality (Table 7). An increase of sulfur across its range of exposure (5916 ng/[m.sup.3]: 5th-95th percentile for all cities combined) was associated with a 3.0% (CI, 0.9-5.2%) increase in total daily mortality. The equivalent increases in nickel (10.3 ng/[m.sup.3]) and lead (461.4 ng/[m.sup.3]) were associated with a 1.5% (CI, 0.5- 2.6%) and 1.6% (CI, 0.2-2.9%) increase in mortality, respectively. Vanadium and iron, although statistically significant predictors when evaluated separately, were not significant when included simultaneously with nickel, lead, and sulfur. Table 7. Percent increase in daily deaths and 95% CIs associated with an increase in mass of elements across the total range of exposure (5th to 95th percentile) by metropolitan area, six U.S. cities, 1979-1988.(a)
Nickel Lead
Percent Percent
increase 95% CI increase 95% CI
Boston 1.9 0.4-3.4 -0.5 -2.8-1.8
St. Louis 1.0 -0.4-2.5 2.2 0.5-3.9
Knoxville 12.2 -5.8-33.8 15.0 5.0-26.0
Madison -23.9 -38.1-6.5 35.7 -1.8-81.0
Steubenville 8.2 0.3-16.6 3.9 -4.7-13.3
Topeka -27.8 -50.9-6.2 -5.2 -19.3-11.3
Summary(b) 1.5 0.5-2.6 1.6 0.2-2.9
Sulfur
Percent
increase 95% CI
Boston 7.9 3.9-12.1
St. Louis 0.8 -2.4-4.2
Knoxville 1.0 -6.8-9.4
Madison 4.6 -3.0-12.7
Steubenville 0.5 -6.8-8.3
Topeka -10.3 -23.1-4.6
Summary(b) 3.0 0.9-5.2
The equivalent increases for nickel, lead, and sulfur were 10.3, 461.4, and 5,916, respectively. (a) Each multivariate model includes Loess smooth function of date with a span of 0.05, Loess functions of temperature and dew point temperature with spans of 0.80, indicator variables for day of the week, and nickel, lead and sulfur, (b) Summary estimates obtained by combining the city-specific regression coefficients using inverse variance weights. Discussion Using specific rotation factor analysis, we were able to identify crustal, mobile, and coal combustion source of fine particles in each of six cities and to estimate the percentage of daily deaths attributable to changes in the concentration of each factor. In the combined analysis across the six cities, controlling for the other sources, a 10 [micro]g/[m.sup.3] increase in [PM.sub.2.5] from mobile sources accounted for a 3.4% increase in daily mortality (CI, 1.7-5.2%) and from coal combustion sources a 1.1% increase (CI, 0.3-2.0%). [PM.sub.2.5] from crustal particles was not associated with increased daily mortality. A possible residual oil residual oil n. The low-grade oil products that remain after the distillation of petroleum, used in adhesives, roofing compounds, and asphalt manufacture. Noun 1. combustion source was identified in four of the six cities, and the summary effect estimate was positive but not statistically significant (5.6% increase, CI, -1.8-13.2%). Results from element-specific mortality analyses were consistent with the analysis of sources; lead and sulfur, markers for mobile and coal combustion sources, respectively, were independently associated with daily deaths. Additionally, nickel was positively associated with daily deaths. The association between particulate air pollutants pollutants see environmental pollution. , either measured as total suspended particulates (TSP TSP - travelling salesman problem ) or inhalable particles ([PM.sub.10]; aerodynamic diameter [is less than or equal to] 10 [micro]g/[m.sup.3]), has been extensively studied and is well established. The magnitude of association has been consistent across studies with the weighted mean percent change in daily mortality for each 10 [micro]g/[m.sup.3] increase in [PM.sub.10] concentration of approximately 0.8% (28). Most of the fine particles ([PM.sub.2.5]) are deposited in the alveolar alveolar /al·ve·o·lar/ (al-ve´o-lar) [L. alveolaris ] pertaining to an alveolus. al·ve·o·lar adj. Relating to an alveolus. region and are therefore not cleared efficiently. These particles include toxic sulfates, nitrates, and bioavailable transition metals (25,26). Prospective studies (6,10) and studies of daily deaths (1,2,5,9,11) have observed associations of [PM.sub.2.5] with mortality. Associations with morbidity also have been reported (3,4,7,8). Our previous analysis demonstrating that [PM.sub.2.5] was more strongly associated with all-cause mortality than was [PM.sub.2.5-10] has been criticized because the larger particles in the [PM.sub.2.5-10] filters were more likely to fall off the filter before being measured. Hence, it has been suggested that poorer predictive power The predictive power of a scientific theory refers to its ability to generate testable predictions. Theories with strong predictive power are highly valued, because the predictions can often encourage the falsification of the theory. was due to measurement error (29). In this study, we found that crustal material in the fine size range is not associated with daily deaths. Boston was not included in this analysis because the mass attributed to the crustal factor in that city was small and was not a significant predictor of total fine mass. The percent increase in mortality in the other cities associated with this factor were consistently null and in the same direction in all communities except Madison, Wisconsin Madison is the capital of the U.S. state of Wisconsin and the county seat of Dane County. It is also home to the University of Wisconsin–Madison. The 2006 population estimate of Madison was 223,389, making it the second largest city in Wisconsin, after Milwaukee, and . The crustal material on the [PM.sub.2.5] filters tends to be in particles that are [is greater than] 1 [micro]m in aerodynamic diameter. This suggests that a reduction in the size cutoff for the particles (e.g., to 1.5 [micro]m) would more specifically focus on the most toxic particles. In 1987, Ozkaynak and Thurston (2) concluded that particles from industrial sources (iron and steel emissions) and from coal combustion were more significant contributors to mortality than soil-derived particles based on analyses using 1980 U.S. Vital Statistics data and available ambient air pollution data. Recently, Schwartz and co-workers (30) examined dust storms in Spokane, Washington Spokane (pronounced [spoʊ̯ˈkæn]) is a city located in Eastern Washington. The seat of Spokane County, Spokane is the metropolitan center of the Inland Northwest, the second largest city in Washington state, and . In 17 episodes with very high concentrations of coarse but not fine particles, they found no evidence of excess mortality (30). In another recent study in Salt Lake City, Utah For ships of the United States Navy of the same name, see . Salt Lake City is the capital and the most populous city of the U.S. state of Utah. The name of the city is often shortened to Salt Lake, or its initials, S.L.C. , and the neighboring neigh·bor n. 1. One who lives near or next to another. 2. A person, place, or thing adjacent to or located near another. 3. A fellow human. 4. Used as a form of familiar address. v. Wasatch Front The Wasatch Front (Or Greater Wasatch) is an urban area in the U.S. state of Utah. It consists of a chain of cities and towns stretched along the Wasatch Range from approximately Santaquin in the south to Brigham City in the north. communities, the estimated association between [PM.sub.10] and mortality was stronger when pollution episode days that were obviously dominated by windblown-dust were excluded (31). Similarly, Schwartz and Neas (32) reported that coarse particles were not associated with lower respiratory symptoms or peak flow deficits in panel studies of children. We believe these results present a consistent pattern of less toxic reactions to crustal particles, even when in the fine range, and no association with daily deaths. The finding of a greater effect per microgram microgram /mi·cro·gram/ (µg) (mi´kro-gram) one millionth (10-6) of a gram. mi·cro·gram n. Abbr. per cubic meter for mobile source particles than for coal combustion source particles, which are predominantly sulfate sulfate, chemical compound containing the sulfate (SO4) radical. Sulfates are salts or esters of sulfuric acid, H2SO4, formed by replacing one or both of the hydrogens with a metal (e.g., sodium) or a radical (e.g., ammonium or ethyl). , is 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. . Sulfates have long been implicated im·pli·cate tr.v. im·pli·cat·ed, im·pli·cat·ing, im·pli·cates 1. To involve or connect intimately or incriminatingly: evidence that implicates others in the plot. 2. as the major toxicologic component in fine particulates (23) and have been shown to be associated with respiratory disease Noun 1. respiratory disease - a disease affecting the respiratory system respiratory disorder, respiratory illness adult respiratory distress syndrome, ARDS, wet lung, white lung - acute lung injury characterized by coughing and rales; inflammation of the and mortality (24). However, Peters et al. (33) reported a stronger association of some health endpoints with ultrafine particles than with sulfate particles. Ultrafine particles are primarily from mobile sources (34), and our mobile source factor may be standing for variations in ultrafine particles. Alternatively, the organic 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. associated with traffic pollution may be more toxic even if it is not in the ultrafine component, or an identical ambient concentration increase of mobile source particles may have a stronger relationship to personal exposure than do particles from power plant sources. Another important issue is possible 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 gaseous gas·e·ous adj. 1. Of, relating to, or existing as a gas. 2. Full of or containing gas; gassy. air pollutants. The traffic particles in particular may reflect 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; effects. CO is an important constituent of motor-vehicle emissions and has been shown to be correlated with adverse respiratory effects (35). However, a recent analysis found no confounding of the [PM.sub.10] mortality relationship by CO in 10 U.S. cities (36). A second recent study (37) found no evidence of confounding, and also no evidence of an effect of CO on daily deaths, when examining 20 cities. Hence, we think that confounding by CO is unlikely to explain our results. Particles from vehicle exhaust were more strongly associated with deaths due to ischemic heart disease but not with deaths due to chronic obstructive obstructive having the characteristic of obstruction. obstructive colic see equine colic. obstructive constipation constipation of sufficient severity as to obstruct the rectum. disease or pneumonia (diseases less common than ischemic heart disease). In contrast, the coal-derived particles were more strongly associated with respiratory deaths than with deaths due to ischemic heart disease. This suggests that these particles may affect health by different mechanisms. In a recent study, dogs exposed to concentrated air particles had more cardiovascular responses to the traffic-derived than to the sulfate/coalderived particles (38). Further examination of this issue is warranted. We also note that although the residual oil factor was not significant, it had a large slope. Residual oil is rich in metals that have been implicated in some of the toxicity studies (25,26). More investigation of oil burning seems warranted. The primary limitation in this study is the identification and interpretation of the factors. In the factor analysis, we chose 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. the elements to target to identify the first three sources: silicon (crustal), lead (mobile), and selenium (coal). These choices and their interpretation are supported by the published source apportionment and chemical composition literature. Silicon is a crustal element unlikely to be related to combustion sources. In other source apportionment studies, silicon has consistently been correlated with other crustal elements, that together have been determined to be derived from soil (19,39). Lead is considered a reliable marker of mobile source particles during the years when leaded gasoline was in widespread use (19,39). Coal combustion is responsible for between 62% (40) and 85% (41) of selenium emissions 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. . We do not have direct confirmation that these three major factors truly represent the sources we have attributed to them. However, we are confident that, in all cities, with the possible exception of Kingston-Harriman (Knoxville), the silicon, lead, and selenium factors are identifying crustal, mobile, and coal combustion sources, respectively. The elemental profile of the crustal factor was qualitatively similar to published chemical analyses of road dust (27). Bromine was correlated with lead in all cities except Steubenville and Knoxville, and in chemical analyses of emissions from noncatalyst automobiles, both lead and bromine accounted for high percentages of the total mass (42). In all cities except for Knoxville, sulfur, a major component of coal combustion, was found predominantly on the selenium factor. After these first three major source factors, the selection of additional factors was more problematic. We chose the targets for the remaining two factors for each city on an individual basis, guided primarily by statistical considerations. A previous source apportionment study in Watertown identified a residual oil fly-ash source with high loadings of nickel and vanadium and a salt or chlorine source (19). Therefore, nickel, vanadium, and chlorine were considered first as potential targets for the other factors in all cities. Manganese also would appear to be a good target for an oil source because the manganese factor identified in two cities had high loadings of nickel and vanadium. We did not tailor our factor analysis in each city to specific local sources, and this limitation could influence the appropriateness of our selection of factor targets. As a sensitivity analysis, we performed nontargeted oblique rotation factor analysis [the "promax" rotation option of 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. software (18)] for each city. Factors with high relative concentrations of silicon, lead, and selenium or sulfur were identified in each city by this method as well. The choice of targets for each of the factors influences the relative concentration of each element attributed to each factor, which in turn could affect the conclusions from the mortality analysis. We evaluated the association of factors identified by the nontargeted (promax) rotation described above with daily mortality and observed similar results for crustal, mobile and coal combustion sources. Results were also similar if, based on the source apportionment in Watertown, we selected vanadium and chlorine a priori as the targets for the fourth and fifth factors in the other cities. The elemental profiles of the sources in Kingston-Harriman were not consistent with those for the other cities. However, mortality results from the meta-analysis were similar when we omitted this city. Finally, we analyzed the elements thought to be of toxicological significance rather than focusing on sources. Two of the elements that appeared most important in this analysis were sulfates and lead. The difference in these results from the factor analysis results is the significant association with nickel. Nickel never emerged as its own factor, and it usually loaded on several factors in each city. Hence, the association of nickel with mortality may indicate a direct toxic effect of that metal. Alternatively, it may reflect the effect of particles from metal industries and residual oil combustion more broadly. It is also important to acknowledge that this is an analysis of six communities. The results for these six cities may not be generalizable gen·er·al·ize v. gen·er·al·ized, gen·er·al·iz·ing, gen·er·al·iz·es v.tr. 1. a. To reduce to a general form, class, or law. b. To render indefinite or unspecific. 2. to all urban areas in the United States; however, they are internally consistent. The cities did not have equal weights in the meta-analysis due to their size; Boston and St. Louis were the largest communities included. The use of inverse variance weights is similar to weighting by the number of deaths and accounts for the precision of the estimate. Therefore, the conclusions are more heavily influenced by the results observed in Boston and St. Louis. In conclusion, particulate matter from combustion sources was associated with increased mortality in these six U.S. cities. The relative potency of combustion-related particles were inversely related to their relative abundance, but particulate matter from mobile sources and coal combustion were associated with increased mortality. Conversely con·verse 1 intr.v. con·versed, con·vers·ing, con·vers·es 1. To engage in a spoken exchange of thoughts, ideas, or feelings; talk. See Synonyms at speak. 2. , particulate matter of crustal origin, even in the fine fraction ([PM.sub.2.5]) was not associated with increased mortality. Although a small portion of the particles containing silica silica or silicon dioxide, chemical compound, SiO2. It is insoluble in water, slightly soluble in alkalies, and soluble in dilute hydrofluoric acid. Pure silica is colorless to white. , aluminum, and iron may be produced from crustal inclusions in coal, most of the [PM.sub.2.5] mass associated with the crustal factor is from the lower tail of the coarse mode distribution [is less than] 2.5 [micro]m (43). Thus, lack of an association between mortality and our crustal factor in the fine fraction is consistent with our earlier finding that mortality was not associated with coarse particles between 2.5 and 10 [micro]m (2) REFERENCES AND NOTES (1.) Schwartz J, Dockery DW, Neas LM. Is daily mortality associated specifically with fine particles? J Air Waste Manag Assoc 46:927-939 (1996). (2.) Ozkaynak H, Thurston GD. Associations between 1980 U.S. mortality rates and alternative measures of airborne particle concentration. Risk Anal 7:449-461 (1987). (3.) 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Effects of sulfur oxides Noun 1. sulfur oxide - any of several oxides of sulphur sulphur oxide oxide - any compound of oxygen with another element or a radical and 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 on human health: methodology and demography demography (dĭmŏg`rəfē), science of human population. Demography represents a fundamental approach to the understanding of human society. of populations in study. Am Rev Respir Dis 120:767-779 (1979). (13.) Courtney WJ, Shaw RW, Dzubay TD. Precision and accuracy of a beta-gauge for aerosol mass determination. Environ Sci Technol 16:236 (1982). (14.) Spengler JD, Thurston G. Mass and elemental composition of fine and coarse particles in six U.S. cities. J Air Pollut Control Assoc 33:1162-1171 (1983). (15.) Browne MW. On oblique procrustes rotation. Psychometrika 32:125-132 (1967). (16.) Gower JC. Generalized procrustes analysis The Procrustes distance provides a metric to minimize in order to align a pair of shape instances annotated by Landmark points. The Generalized Procrustes Analysis (GPA) is a procedure applying the aforementioned Procrustes analysis method to align a population of shapes instead of only . Psychometrika 40:33-51 (1975). (17.) Koutrakis P, Spengler JD. Source apportionment of ambient particles in Steubenville, OH using specific rotation factor analysis. Atmos Environ 21:1511-1519 (1987). (18.) 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. Inc. SAS/STAT User's Guide, Version 6, 4th ed, Vol 1. Cary, NC:SAS Institute Inc., 1989. (19.) Thurston GD, Spengler JD. A quantitative assessment of source contributions to inhalable particulate matter pollution in metropolitan Boston. 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Environ Health Perspect 108:563-568 (2000). (37.) Samet J, Zeger SL, Domenici F, Schwartz J, Zanobetti A, Dockery DW. National Morbidity and Mortality Morbidity and Mortality can refer to:
(38.) Godleski JJ. Mechanisms of Morbidity and Mortality from Exposure to Ambient Air Particles, HEI HEI Higher Education Institution (UK) 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 Report No. 91. Cambridge, MA:Health Effects Institute, 2000. (39.) Glover Glov´er n. 1. One whose trade it is to make or sell gloves. Glover's suture a kind of stitch used in sewing up wounds, in which the thread is drawn alternately through each side from within outward. DM, Hopke PK, Vermette SJ, Landsberger S, D'Auben DR. Source apportionment with site specific source profiles. J Air Waste Manag Assoc 41:294-305 (1991). (40.) NAS (1) See network access server. (2) (Network Attached Storage) A specialized file server that connects to the network. A NAS device contains a slimmed-down operating system and a file system and processes only I/O requests by supporting the popular . Medical and Biological Effects of Environmental Pollutants-Selenium. Washington, DC:Committee on Medical and Biological Effects of Environmental Pollutants environmental pollutants, n.pl the substances and conditions, including noise, that adversely affect the health and well-being of the people within a community. , National Academy of Sciences, 1976. (41.) Eimutis EC, Quill quill: see pen. RP, Rinaldi GM. Source assessment: noncriteria pollutant emissions. 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:Monsanto Research Corp. for U.S.E.P.A. Industrial and Environmental Research Laboratory, 1978. (42.) Hildemann LM, Markowski GR, Cass GR. Chemical composition of emissions from urban sources of fine organic aerosol. Environ Sci Technol 25:744-759 (1991). (43.) U.S. EPA EPA eicosapentaenoic acid. EPA abbr. eicosapentaenoic acid EPA, n.pr See acid, eicosapentaenoic. EPA, n. . Air Quality Criteria for Particulate Matter, Vol 1, Chapter 3, 3-162-3-168. EPA/600/P-95/001AF. Washington DC: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 , Office of Research and Development, 1996. Francine Laden,(1) Lucas M. Neas,(2) Douglas W. Dockery,(1,3) and Joel Schwartz(1,3) (1) Channing Laboratory, Department of Medicine, Brigham and Women's Hospital Brigham and Women's Hospital (BWH) is a hospital in the Longwood Area of the Boston, Massachusetts neighborhood of Mission Hill. With Massachusetts General Hospital, it is one of the two founding members of Partners HealthCare. , Harvard Medical School Harvard Medical School (HMS) is one of the graduate schools of Harvard University. It is a prestigious American medical school located in the Longwood Medical Area of the Mission Hill neighborhood of Boston, Massachusetts. , Boston, Massachussetts, USA; (2) Epidemiology and Biomarkers Branch, Human Studies Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, 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; (3) Environmental Epidemiology Program, Department of Environmental Health, 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, , Boston, Massachussetts, USA Address correspondence to F. Laden, Channing Laboratory, 181 Longwood Avenue, Boston, MA 02115 USA. Telephone: (617) 525-2711. Fax: (617) 731-1541. E-mail: francine.laden@ channing.harvard.edu We thank D. Sredl and A. Heff for their expert assistance with the analysis. Supported by U.S. EPA grant R826245-01 and 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. grant ES-000002. F. Laden was supported in part by a National Institute of Health National Research Service Award T32HL07427. The views expressed in this article are those of the individual authors and do not necessarily reflect the views and policies of the U.S. EPA. The research described in this article has been subject to U.S. EPA peer and administrative review and it has been approved for publication. Received 6 January 2000; accepted 30 May 2000. |
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