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Factors relating to windblown dust in associations between PM2.5 and mortality across the United States
Citation:
Rappazzo, K., B. Alman, J. Reyes, AND L. Neas. Factors relating to windblown dust in associations between PM2.5 and mortality across the United States. International Society for Environmental Epidemiology, Annual Conference, Rome, ITALY, September 01 - 04, 2016.
Impact/Purpose:
To investigate the contribution of windblown dust to heterogeneity in PM2.5-mortality associations.
Description:
Introduction: In effect estimates of city-specific PM2.5-mortality associations across United States (US), there exists a substantial amount of spatial heterogeneity. Some of this heterogeneity may be due to mass distribution of PM; areas where PM2.5 is likely to be dominated by large size fractions (above 1 micron; e.g., the contribution of windblown dust), may have a weaker association with mortality. Methods: Log rate ratios (betas) for the PM2.5-mortality association—derived from a model adjusting for time, an interaction with age-group, day of week, and natural splines of current temperature, current dew point, and unconstrained temperature at lags 1, 2, and 3, for 313 core-based statistical areas (CBSA) and their metropolitan divisions (MD) over 1999-2005—were used as the outcome. Using inverse variance weighted linear regression, we examined change in log rate ratios in association with PM10-PM2.5 correlation as a marker of windblown dust/higher PM size fraction; linearity of associations was assessed in models using splines with knots at quintile values. Results: Weighted mean PM2.5 association (0.96 percent increase in total non-accidental mortality for a 10 ug/m3 increment in PM2.5) increased by 0.34 (95% confidence interval: 0.20, 0.48) per interquartile change (0.25) in the PM10-PM2.5 correlation, and explained approximately 8% of the observed heterogeneity; the association was linear based on spline analysis. Conclusions: Preliminary results provide evidence that markers of areas where PM2.5 is composed of larger mass fractions explain some of the heterogeneity in city-specific PM2.5-mortality associations; cities in which windblown dust is a substantial source of PM2.5 may have weaker associations with mortality. This abstract does not necessarily reflect EPA policy.