Effect modification by maximum temperature of the association between PM2.5 and short-term cardiorespiratory mortality and emergency room visits in Lima, Peru, 2010–2016

Abstract

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 µg/m³ (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 µg/m³ 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.