The impact of components of fine particulate matter on cardiovascular mortality in susceptible subpopulations.

BACKGROUND: Several studies have demonstrated associations between daily mortality and ambient particulate matter less than 2.5 microns in diameter (fine particles or PM2.5). Few, however, have examined the relative toxicities of PM2.5 constituents, including elemental carbon and organic carbon (EC and OC, respectively), nitrates and transition metals. There is also little information about whether associations between PM2.5 constituents and mortality are modified by socioeconomic and demographic factors. AIM: To examine associations of daily cardiovascular mortality with PM2.5 and its constituents after stratification by gender, race/ethnicity and education, using data from six California counties during 2000 to 2003. METHODS: The association of daily counts of cardiovascular mortality with PM2.5 components was analysed using time-series regression analyses. Poisson models with natural splines were used to control for time-varying covariates such as season and weather. Separate models were run after stratification by gender, race/ethnicity (White, Hispanic, Black) and education (high school graduation or not). Models were run for each county and results were combined using random effects meta-analysis. RESULTS: Daily counts of cardiovascular mortality were associated with PM2.5 and several of its species including EC, OC, nitrates, sulphates, potassium, copper and iron. For many of these species, there were significantly higher effect estimates among those with lower educational attainment and Hispanic individuals. For example, while essentially no association was observed for individuals who graduated from high school, an interquartile change in several of the components of PM2.5 was associated with a 3-5% increase in daily mortality among non-high school graduates. CONCLUSION: There is evidence that several PM2.5 constituents may represent important contributors to cardiovascular mortality. Many of these constituents are generated by motor vehicles, especially those with diesel engines, and by residential wood combustion. In addition, factors associated with low educational attainment may increase susceptibility to PM2.5 and its components.

Coarse and fine particles and daily mortality in the Coachella Valley, California: a follow-up study.

Many epidemiological studies provide evidence of an association between ambient particles, measured as PM10, and daily mortality. Most of these studies have been conducted in urban areas where PM10 is highly correlated with and dominated by fine particles less than 2.5 microm in diameter (PM2.5). Fewer studies have investigated impacts associated with the fraction of coarse mode particles (between 2.5 and 10 microm in diameter). In a previous study using data from 1989 through 1992 in the Coachella Valley, a desert resort and retirement area east of Los Angeles, we reported associations between PM10 and several different measures of mortality [Ostro B.D., Hurley S., and Lipsett M.J. Air pollution and daily mortality in the Coachella Valley, California: a study of PM10 dominated by coarse particles. Environ. Res. 1999: 81: 231-238]. In this arid environment, coarse particles of geologic origin are highly correlated with and comprise approximately 60% of PM10, increasing to >90% during wind events. This study was intended to repeat the earlier investigation using 10 years (1989-1998) of daily data on mortality and PM10. The last 2.5 years of data also included daily measures of PM2.5, allowing examination of size-specific impacts. To ensure adequate statistical power, we attempted to develop predictive models for both fine and coarse particles to use in analyses of the full 10-year period. An acceptable fit was found only for coarse particles, which were found to be a cubic function of PM10 (R2 = 0.95). Outcome variables included several measures of daily mortality, including all-cause (minus accidents and homicides), cardiovascular and respiratory mortality. Multivariate Poisson regression analyses using generalized additive models were employed to explain the variation in these endpoints, controlling for temperature, humidity, day of the week, season, and time, using locally weighted smoothing techniques. Pollution lags of up to 4 days were examined. Several pollutants were associated with all-cause mortality, including PM2.5, carbon monoxide and nitrogen dioxide. More consistent results were found for cardiovascular-specific mortality, for which associations were found for coarse particles (RR = 1.02; 95% C.I., 1.01-1.04), PM10 (RR = 1.03; 95% C.I., 1.01-1.05). None of the pollutants was associated with respiratory-specific mortality. Ozone was not associated with any of the mortality outcomes. These findings are generally consistent with those we previously reported for the Coachella Valley for the period 1989-1992, demonstrating associations between several measures of particulate matter and daily mortality in an environment in which particulate concentrations are dominated by the coarse fraction.

Air pollution and daily mortality in the Coachella Valley, California: a study of PM10 dominated by coarse particles.

Many epidemiological studies provide evidence of an association between airborne particles, measured as PM10 (particulate matter less than 10 microm in diameter), and daily morbidity and mortality. Most of these studies have been conducted in urban areas where PM10 consists primarily of fine particles (<2.5 microm in diameter). Few studies have investigated impacts associated with coarse mode particles (>2.5 microm in diameter). We investigated associations between PM10 and daily mortality in the Coachella Valley, a desert resort and retirement area east of Los Angeles, where coarse particles of geologic origin typically comprise approximately 50-60% of PM10 and can exceed 90% during wind events. Our analysis utilized daily data on mortality from 1989 through 1992 as well as several pollutant and meteorological variables, including PM10, nitrates, sulfates, ozone, nitrogen dioxide, carbon monoxide, temperature, and relative humidity. Outcome variables included several measures of daily mortality, including all-cause, cardiovascular and respiratory mortality, and counts of deaths for those above age 50. Multivariate Poisson regression models were used to explain these health endpoints, controlling for temperature, humidity, day of the week, season, and time, using locally weighted smoothing techniques. The analysis indicated statistically significant associations between PM10 (2- or 3-day lags) and each measure of mortality. The results were robust to various model specifications, correction for autocorrelation and overdispersion, and analysis of influential observations. A 10 microg/m3 change in daily PM10 was associated with an approximately 1% increase in mortality, which is of similar magnitude to particle-associated impacts identified in urban areas. Thus, our findings provide evidence for a mortality effect of PM10 in an area where the particulate mass is dominated by coarse particles.

Indoor air pollution and asthma. Results from a panel study.

Although there is abundant clinical evidence of asthmatic responses to indoor aeroallergens, the symptomatic impacts of other common indoor air pollutants from gas stoves, fireplaces, and environmental tobacco smoke have been less well characterized. These combustion sources produce a complex mixture of pollutants, many of which are respiratory irritants. We report here results of an analysis of associations between indoor pollution and several outcomes of respiratory morbidity in a population of adult asthmatics residing in the Denver, Colorado, metropolitan area. A panel of 164 asthmatics recorded in a daily diary the occurrence of several respiratory symptoms, nocturnal asthma, medication use, and restrictions in activity, as well as the use of gas stoves, wood stoves, or fireplaces, and exposure to environmental tobacco smoke. Multiple logistic regression analysis suggests that the indoor sources of combustion have a statistically significant association with exacerbations of asthma. For example, after correcting for repeated measures and autocorrelation, the reported use of a gas stove was associated with moderate or worse shortness of breath (OR, 1.60; 95% CI, 1.11-2.32), moderate or worse cough (OR, 1.71; 95% CI, 0.97-3.01), nocturnal asthma (OR, 1.01; 95% CI, 0.91-1.13), and restrictions in activity (OR, 1.47; 95% CI, 1.0-2.16). Among this panel of relatively moderate to severe asthmatics, the respiratory irritants produced by several domestic combustion sources were associated with increased morbidity.

Air pollution and respiratory morbidity among adults in southern California.

This paper reports the results of an investigation of the acute effects of air pollution in 321 nonsmoking adults residing in Southern California. Previous epidemiologic investigations of effects of acute exposure to ozone have focused on groups who may not be representative of the general public, such as asthmatics or student nurses. For this study, participants recorded the daily incidence of several respiratory symptoms over a 6-month period between 1978 and 1979. The authors examined the impact of ambient concentrations of ozone, particulate sulfates, and other air pollutants on the incidence of respiratory morbidity, measured as either upper or lower respiratory tract symptoms. Using a logistic regression model, the authors found a significant association between the incidence of lower respiratory tract symptoms and 1-hour daily maximum ozone levels (odds ratio (OR) = 1.22, 95% confidence interval (Cl) 1.11-1.34, for a 10 parts per hundred million (pphm) change), 7-hour average ozone levels (OR = 1.32, 95% Cl 1.14-1.52), and ambient sulfates (OR = 1.30, 95% Cl 1.09-1.54, for a 10-micrograms/m3 change), but no association was found with coefficient of haze, a more general measure of particulates. The existence of a gas stove in the home was also associated with lower respiratory tract symptoms (OR = 1.23, 95% Cl 1.03-1.47). The effects of ozone were greater in the subpopulation without a residential air conditioner. In addition, ozone appears to have had a greater effect among individuals with a preexisting respiratory infection.

Asthmatic responses to airborne acid aerosols.

BACKGROUND: Controlled exposure studies suggest that asthmatics may be more sensitive to the respiratory effects of acidic aerosols than individuals without asthma. This study investigates whether acidic aerosols and other air pollutants are associated with respiratory symptoms in free-living asthmatics. METHODS: Daily concentrations of hydrogen ion (H+), nitric acid, fine particulates, sulfates and nitrates were obtained during an intensive air monitoring effort in Denver, Colorado, in the winter of 1987-88. A panel of 207 asthmatics recorded respiratory symptoms, frequency of medication use, and related information in daily diaries. We used a multiple regression time-series model to analyze which air pollutants, if any, were associated with health outcomes reported by study participants. RESULTS: Airborne H+ was found to be significantly associated with several indicators of asthma status, including moderate or severe cough and shortness of breath. Cough was also associated with fine particulates, and shortness of breath with sulfates. Incorporating the participants' time spent outside and exercise intensity into the daily measure of exposure strengthened the association between these pollutants and asthmatic symptoms. Nitric acid and nitrates were not significantly associated with any respiratory symptom analyzed. CONCLUSIONS: In this population of asthmatics, several outdoor air pollutants, particularly airborne acidity, were associated with daily respiratory symptoms.

Problems associated with the use of immediately dangerous to life and health (IDLH) values for estimating the hazard of accidental chemical releases.

The possibility of accidental industrial chemical releases has generated considerable recent attention. One area requiring research for emergency planning is the development of safe exposure concentrations for the public in the event of an inadvertent release. The United States Environmental Protection Agency (EPA) has established a list of extremely hazardous substances and suggested that the toxicity ranking for 92 hazardous materials could be based on the "immediately dangerous to life or health" (IDLH) values developed by the National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA). Eighty-four compounds with IDLH values for which published toxicologic data were available were reviewed to assess the appropriateness of applying such values to accidental release situations. When compared with 30-min animal median lethal concentrations (LC50s), 18 of the IDLHs reviewed were in the same range as lethal levels for animals. For 45 compounds the IDLH values were comparable to concentrations producing severe toxic effects (specifically, unconsciousness, incapacitation, or intolerable irritation). Where available, emergency planning guidelines for the military were compared to IDLHs, and in all 31 cases, the IDLHs exceeded the military exposure guidelines. Twenty compounds also were found to pose a potential cancer risk according to common regulatory guidelines, even under the assumption of a single, 30-min exposure at the IDLH concentration. In addition, the high degree of variability (four orders of magnitude) in the relationship of IDLH values to outcomes of lethality or severe toxicity suggests that the use of IDLH values as emergency planning guidelines for accidental releases is questionable.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute health effects of community exposure to cotton defoliants.

In September and October of 1987, the California Department of Health Services responded to community complaints by investigating the relationship between health symptoms and community exposure to cotton defoliants. Symptoms experienced during the 1987 cotton defoliation season by 232 residents of cotton-growing communities were compared with symptoms of 175 residents of non-cotton-growing agricultural communities. Fatigue, eye irritation, rhinitis, throat irritation, nausea, and diarrhea were statistically elevated in rates adjusted for age, sex, and race and were reported 60-100% more frequently by respondents living or working near sprayed cotton fields than by the comparison group. These symptom rate elevations were substantially unchanged even after adjustment by a model of potentially confounding factors that included cigarette smoking, chronic illness, and some additional demographic variables.

Predicting respiratory morbidity from pulmonary function tests: a reanalysis of ozone chamber studies.

Some consequences of acute exposure to ozone are best measured in studies of human respiratory responses in controlled exposure chambers. These studies typically examine relationships between exposures to alternative pollutant concentrations and indicators of lung function as measured by spirometry, such as forced expiratory volume in one second, FEV1. However, the association of respiratory morbidity with these changes in lung function is not well established. To gain a better understanding of the relationship between ozone-related changes in pulmonary function and respiratory symptoms, data from several clinical studies have been reanalyzed. Logistic regression models were used to determine the quantitative relationship between changes in FEV1 and the probability of a mild or moderate lower respiratory symptom. Models were developed that corrected for repeated sampling of individuals and both population-averaged and subject-specific effects were determined. The results indicate the existence of a strong and consistent quantitative relationship between changes in lung function and the probability of a respiratory symptom. Specifically, a 10 percent reduction in FEV1 is associated with a 15 percentage point increase in the probability of a mild, moderate or severe lower respiratory symptom and a 6 percentage point increase in the probability of a moderate or severe lower respiratory symptom.