Abstract
BackgroundAssociations of short-term exposure to fine particulate matter (PM2.5) with daily mortality may be due to specific PM2.5 chemical components. Daily concentrations of PM2.5 components were measured over five years in Denver to investigate whether specific PM2.5 components are associated with daily mortality.MethodsDaily counts of total and cause-specific deaths were obtained for the 5-county Denver metropolitan region from 2003 through 2007. Daily 24-hour concentrations of PM2.5, elemental carbon (EC), organic carbon (OC), sulfate and nitrate were measured at a central residential monitoring site. Using generalized additive models, we estimated relative risks (RRs) of daily death counts for daily PM2.5 and four PM2.5 component concentrations at single and distributed lags between the current and three previous days, while controlling for longer-term time trend and meteorology.ResultsRR of total non-accidental mortality for an inter-quartile increase of 4.55 μg/m3 in PM2.5 distributed over 4 days was 1.012 (95 % confidence interval: 0.999, 1.025); RRs for EC and OC were larger (1.024 [1.005, 1.043] and 1.020 [1.000, 1.040] for 0.33 and 1.67 μg/m3 increases, respectively) than those for sulfate and nitrate. We generally did not observe associations with cardiovascular and respiratory mortality except for associations with ischemic heart disease mortality at lags 3 and 0–3 depending on the component. In addition, there were associations with cancer mortality, particularly for EC and OC, possibly reflecting advanced deaths of a frail population.ConclusionsPM2.5 components possibly from combustion-related sources are more strongly associated with daily mortality than are secondary inorganic aerosols.Electronic supplementary materialThe online version of this article (doi:10.1186/s12940-015-0037-4) contains supplementary material, which is available to authorized users.
Highlights
Associations of short-term exposure to fine particulate matter (PM2.5) with daily mortality may be due to specific PM2.5 chemical components
The Denver Aerosol Sources and Health (DASH) study features daily PM2.5 speciation data measured over the five years that allow full use of daily mortality data, as well as the ability to estimate the total effect of a pollutant component over a range of days rather than an effect of one day in isolation
We found no evidence for associations between cardiovascular mortality and PM2.5 or the PM2.5 components, whereas total mortality was associated with elemental carbon (EC) and organic carbon (OC)
Summary
Associations of short-term exposure to fine particulate matter (PM2.5) with daily mortality may be due to specific PM2.5 chemical components. Recent observational epidemiologic studies have focused on the adverse health effects of outdoor fine particulate matter (PM2.5) chemical components in order to identify the most toxic components responsible for the association between PM2.5 and human health. Most of these studies investigated the short-term association of exposures to PM2.5 components on a given day and counts of deaths or hospital admissions. Most regulatory monitoring networks have sampled PM2.5 components on a regularly missing schedule such as every 3rd or 6th day [8, 9] These limitations may affect health effect analyses that aim to gain insight into features of PM2.5 that are more toxic [10, 11]. We report findings from the DASH study on associations of daily concentrations of PM2.5 and four PM2.5 components (EC, OC, sulfate and nitrate) with daily mortality attributed to the most common causes of death in the 5-county Denver metropolitan area over the 5 years of the study
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