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      Does the Effect of PM 10 on Mortality Depend on PM Nickel and Vanadium Content? A Reanalysis of the NMMAPS Data

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          Abstract

          Background

          Lack of knowledge regarding particulate matter (PM) characteristics associated with toxicity is a crucial research gap. Short-term effects of PM can vary by location, possibly reflecting regional differences in mixtures. A report by Lippmann et al. [Lippmann et al., Environ Health Perspect 114:1662–1669 (2006)] analyzed mortality effect estimates from the National Morbidity, Mortality, and Air Pollution Study (NMMAPS) for 1987–1994. They found that average concentrations of nickel or vanadium in PM 2.5 (PM with aerodynamic diameter < 2.5 μm) positively modified the lag-1 day association between PM 10 and all-cause mortality.

          Objective

          We reestimated the relationship between county-specific lag-1 PM 10 (PM with aerodynamic diameter < 10 μm) effects on mortality and county-specific nickel or vanadium PM 2.5 average concentrations using 1987–2000 effect estimates. We explored whether such modification is sensitive to outliers.

          Methods

          We estimated long-term average county-level nickel and vanadium PM 2.5 concentrations for 2000–2005 for 72 U.S. counties representing 69 communities. We fitted Bayesian hierarchical regression models to investigate whether county-specific short-term effects of PM 10 on mortality are modified by long-term county-specific nickel or vanadium PM 2.5 concentrations. We conducted sensitivity analyses by excluding individual communities and considering log-transformed data.

          Results

          Our results were consistent with those of Lippmann et al. However, we found that when counties included in the NMMAPS New York community were excluded from the sensitivity analysis, the evidence of effect modification of nickel or vanadium on the short-term effects of PM 10 mortality was much weaker and no longer statistically significant.

          Conclusions

          Our analysis does not contradict the hypothesis that nickel or vanadium may increase the risk of PM to human health, but it highlights the sensitivity of findings to particularly influential observations.

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          Most cited references 34

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          Health effects of fine particulate air pollution: lines that connect.

           D W Dockery,  C Pope (2006)
          Efforts to understand and mitigate thehealth effects of particulate matter (PM) air pollutionhave a rich and interesting history. This review focuseson six substantial lines of research that have been pursued since 1997 that have helped elucidate our understanding about the effects of PM on human health. There hasbeen substantial progress in the evaluation of PM health effects at different time-scales of exposure and in the exploration of the shape of the concentration-response function. There has also been emerging evidence of PM-related cardiovascular health effects and growing knowledge regarding interconnected general pathophysiological pathways that link PM exposure with cardiopulmonary morbidiity and mortality. Despite important gaps in scientific knowledge and continued reasons for some skepticism, a comprehensive evaluation of the research findings provides persuasive evidence that exposure to fine particulate air pollution has adverse effects on cardiopulmonaryhealth. Although much of this research has been motivated by environmental public health policy, these results have important scientific, medical, and public health implications that are broader than debates over legally mandated air quality standards.
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            Spatial and Temporal Variation in PM2.5 Chemical Composition in the United States for Health Effects Studies

            Background Although numerous studies have demonstrated links between particulate matter (PM) and adverse health effects, the chemical components of the PM mixture that cause injury are unknown. Objectives This work characterizes spatial and temporal variability of PM2.5 (PM with aerodynamic diameter < 2.5 μm) components in the United States; our objective is to identify components for assessment in epidemiologic studies. Methods We constructed a database of 52 PM2.5 component concentrations for 187 U.S. counties for 2000–2005. First, we describe the challenges inherent to analysis of a national PM2.5 chemical composition database. Second, we identify components that contribute substantially to and/or co-vary with PM2.5 total mass. Third, we characterize the seasonal and regional variability of targeted components. Results Strong seasonal and geographic variations in PM2.5 chemical composition are identified. Only seven of the 52 components contributed ≥ 1% to total mass for yearly or seasonal averages [ammonium (NH4 +), elemental carbon (EC), organic carbon matter (OCM), nitrate (NO3 −), silicon, sodium (Na+), and sulfate (SO4 2−)]. Strongest correlations with PM2.5 total mass were with NH4 + (yearly), OCM (especially winter), NO3 − (winter), and SO4 2− (yearly, spring, autumn, and summer), with particularly strong correlations for NH4 + and SO4 2− in summer. Components that co-varied with PM2.5 total mass, based on daily detrended data, were NH4 +, SO4 2− , OCM, NO3 2−, bromine, and EC. Conclusions The subset of identified PM2.5 components should be investigated further to determine whether their daily variation is associated with daily variation of health indicators, and whether their seasonal and regional patterns can explain the seasonal and regional heterogeneity in PM10 (PM with aerodynamic diameter < 10 μm) and PM2.5 health risks.
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              Seasonal analyses of air pollution and mortality in 100 US cities.

              Time series models relating short-term changes in air pollution levels to daily mortality counts typically assume that the effects of air pollution on the log relative rate of mortality do not vary with time. However, these short-term effects might plausibly vary by season. Changes in the sources of air pollution and meteorology can result in changes in characteristics of the air pollution mixture across seasons. The authors developed Bayesian semiparametric hierarchical models for estimating time-varying effects of pollution on mortality in multisite time series studies. The methods were applied to the database of the National Morbidity and Mortality Air Pollution Study, which includes data for 100 US cities, for the period 1987-2000. At the national level, a 10-microg/m(3) increase in particulate matter less than 10 microm in aerodynamic diameter at a 1-day lag was associated with 0.15% (95% posterior interval (PI): -0.08, 0.39), 0.14% (95% PI: -0.14, 0.42), 0.36% (95% PI: 0.11, 0.61), and 0.14% (95% PI: -0.06, 0.34) increases in mortality for winter, spring, summer, and fall, respectively. An analysis by geographic region found a strong seasonal pattern in the Northeast (with a peak in summer) and little seasonal variation in the southern regions of the country. These results provide useful information for understanding particle toxicity and guiding future analyses of particle constituent data.
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                Author and article information

                Journal
                Environ Health Perspect
                Environmental Health Perspectives
                National Institute of Environmental Health Sciences
                0091-6765
                December 2007
                25 September 2007
                : 115
                : 12
                : 1701-1703
                Affiliations
                [1 ] Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
                [2 ] School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut, USA
                [3 ] Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
                Author notes
                Address correspondence to F. Dominici, 615 N. Wolfe St., Rm. E3634, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21215 USA. Telephone: (410) 614-5107. Fax: (410) 955-0958. E-mail: fdominic@ 123456jhsph.edu

                The authors declare they have no competing financial interests.

                Article
                ehp0115-001701
                10.1289/ehp.10737
                2137127
                18087586
                This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original DOI.
                Categories
                Research

                Public health

                v, particulate matter, ni, pm10, pm2.5, effect modification, mortality

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