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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 [...]

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.sub.2.5] (PM with aerodynamic diameter < 2.5 [mu]m) positively modified the lag-1 day association between [PM.sub.10] and all-cause mortality. OBJECTIVE: We reestimated the relationship between county-specific lag-1 [PM.sub.10] (PM with aerodynamic diameter < 10 [mu]m) effects on mortality and county-specific nickel or vanadium [PM.sub.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.sub.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.sub.10] on mortality are modified by long-term county-specific nickel or vanadium [PM.sub.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.sub.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. KEY WORDS: effect modification, mortality, Ni, particulate matter, [PM.sub.2.5], [PM.sub.10], V.Environ Health Perspect 115:1701-1703 (2007). doi:10.1289/ehp.10737 available via http://dx.doi.org/ [Online 25 September 2007], Associations between particulate matter (PM) total mass for [PM.sub.10] (PM with an aerodynamic diameter < 10 [mu]m) and [PM.sub.2.5] (PM with an aerodynamic diameter < 2.5 [mu]m) have been demonstrated [...]

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 (SO42-)]. Strongest correlations with PM2.5 total mass were with NH4+ (yearly), OCM (especially winter), NO3- (winter), and SO42- (yearly, spring, autumn, and summer), with particularly strong correlations for NH4+ and SO42- in summer. Components that co-varied with PM2.5 total mass, based on daily detrended data, were NH4+, SO42- , OCM, NO3-, 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. [ABSTRACT FROM AUTHOR]

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 PM2.5 (PM with aerodynamic diameter < 2.5 μm) positively modified the lag-1 day association between PM10 and all-cause mortality. OBJECTIVE: We reestimated the relationship between county-specific lag-1 PM10 (PM with aerodynamic diameter < 10 μm) effects on mortality and county-specific nickel or vanadium PM2.5 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 PM2.5 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 PM10 on mortality are modified by long-term county-specific nickel or vanadium PM2.5 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 PM10 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. [ABSTRACT FROM AUTHOR]

Presents letters to the editor, published in the November 2001 issue of the journal 'Environmental Health Perspectives,' on issues dealing with health. Confirmation of uterotrophic activity for 4-methylbenzylidine camphor in the immature rat; Impact of repeated exposure to fungi in a water-damaged building on the health of workers; Need of further research on markers of exposure to bioaerosols in case of patients with microbial exposure-related lung damage.