Cause-specific mortality and the extended effects of particulate pollution and temperature exposure

Air pollution exposure studies in the past decade have focused on acute (days) or long-term (years) effects. We present an analysis of medium-term (weeks to months) exposure effects of particulate pollution and temperature. We assessed the associations of particulate pollution (black smoke) and temperature with age-standardized daily mortality rates over 17 years in Dublin, Ireland, using a polynomial distributed lag model of both temperature and particulate air pollution simultaneously through 40 days after exposure. When only acute effects (3-day mean) were considered, we found total mortality increased by 0.4% for each 10-microg/m3 increase in black smoke concentration. When deaths in the 40 days after exposure were considered, we found a 1.1% increase. For respiratory mortality, the estimated effect was 0.9% for acute exposures, but 3.6% for the extended follow-up. We found each increase in current-day temperature by 1 degree C was associated with a 0.4% increase in total mortality, whereas each decrease of 1 degree C was associated with a 2.6% increase in mortality in the following 40 days. For both temperature and pollution, the largest effects on cardiovascular mortality were observed immediately, whereas respiratory mortality was delayed and distributed over several weeks. These effects were two to three times greater than the acute effects reported in other studies, and approach the effects reported in longer-term survival studies. This analysis suggests that studies on the acute effects of air pollution have underestimated the total effects of temperature and particulate air pollution on mortality.