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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



The health effects of fine particulate matter (PM2.5) may be worse at higher temperatures.


To investigate temperature’s effect on PM2.5-mortality/morbidity associations in Lima, Peru.


Time-series regressions relating PM2.5 and temperature to mortality and emergency room (ER) visits during 2010–2016. Daily PM2.5 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.


The average PM2.5 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). PM2.5’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 PM2.5 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.


Results strengthen the evidence that air pollution may be more dangerous when temperatures are higher.


Our data contribute to a growing body of literature which indicates that the damaging effects of PM2.5 may be worse at higher temperature, adding new evidence from Lima, Peru.

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Fig. 1: Lima districts and the hospitals in the study.
Fig. 2: Rate ratios for 10 μg/m3 increase in PM2.5 exposure for mortality and morbidity.
Fig. 3: Spline curve for the association of PM2.5 with respiratory (ER) visits, Lima 2010-2016.
Fig. 4: Spline curve for the association of PM2.5 with circulatory hospital (ER) visits, Lima 2010-2016.


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Vilma Tapia and Vanessa Vasquez kindly provided the hospital data on emergency room visits, and the mortality data, as part of our collaborative work on the GeoHealth Hub in Peru. Temperature data came from public information available from SENAMHI (National Meteorology and Hydrology Service of Peru), a Peruvian government agency, while hospital data came from MINSA (Ministry of Health), and we thank both these agencies for their help.


The present study was founded by the National Institutes of Health (Fogarty Program) [Grant U01TW010107, 1/2 Regional GEOHealth Hub centered in Peru]. NS is supported by the NIEHS-funded HERCULES Center (P30ES019776).

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KS, BV and NS contributed to the writing of the paper. KS conducted the analyses. BV helped with data management.

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Correspondence to Kyle Steenland.

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Steenland, K., Vu, B. & Scovronick, N. 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. J Expo Sci Environ Epidemiol (2021).

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  • Temperature
  • PM2.5
  • Effect modification
  • Mortality
  • Emergency room visits


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