Effect modification by maximum temperature of the association between PM(2.5) and short-term cardiorespiratory mortality and emergency room visits in Lima, Peru, 2010-2016

BACKGROUND: The health effects of fine particulate matter (PM(2.5)) may be worse at higher temperatures. OBJECTIVE. To investigate temperature’s effect on PM(2.5)-mortality/morbidity associations in Lima, Peru. METHODS. Time-series regressions relating PM(2.5) and temperature to mortality and emergency room (ER) visits during 2010-2016. Daily PM(2.5) levels (assigned to 40 Lima districts) and daily maximum temperature (Lima-wide) were estimated based on ground monitors, remote sensing, and modeling. We analyzed all-cause, cardiovascular (ICD codes I00-I99), and respiratory (ICD codes J00-J99) mortality, and cardiovascular and respiratory causes for ER visits. RESULTS. The average PM(2.5) concentration was 20.9 ug/m(3) (IQR 17.5-23.5). The mean daily maximum temperature was 23.8 °C (IQR 20.8-26.9). PM(2.5)’s effect on all-cause, respiratory, and circulatory disease mortality was significantly (p<0.05) stronger at temperatures above the maximum temperature median. The rate ratios per increase of 10 ug/m(3) of PM(2.5) for all cause, respiratory, and circulatory mortality respectively were 1.03 (1.00-1.06), 1.04 (0.98-1.10), and 1.04 (0.98-1.10) at temperatures below the median, vs. 1.08 (1.04-1.12), 1.11 (1.03-1.19), and 1.14 (1.05-1.25) when temperatures were above the median. Results were analogous for ER visits for respiratory but not circulatory disease. SIGNIFICANCE. Results strengthen the evidence that air pollution may be more dangerous when temperatures are higher. IMPACT. Our data contribute to a growing body of literature which indicates that the damaging effects of PM(2.5) may be worse at higher temperature, adding new evidence from Lima, Peru.