Pollutant-sex specific differences in respiratory hospitalization and mortality risk attributable to short-term exposure to ambient air pollution

Background: Many studies have reported associations of individual pollutants with respiratory hospitalization and mortality based on different populations, which makes it difficult to directly compare adverse health effects among multiple air pollutants. Objectives: The study goal is to compare acute respiratory-related hospitalization and mortality associated with short-term exposure to three ambient air pollutants and analyze differences in health risks by season, age and sex. Methods: Hourly measurements of air pollutants (ozone, NO2, PM2.5) and temperature were collected from ground-monitors for 24 cities along with daily hospitalization (1996-2012) and mortality (1984-2012) data. National associations between air pollutant and health outcome were estimated for season (warm, cold vs. year-round), age (base >= 1, seniors > 65), and sex (females >= 1 and males >= 1) using Bayesian hierarchical models. Results: Overall, the three air pollutants were significantly associated with acute respiratory health outcomes at different lag-days. For respiratory hospitalization, the increased risks in percent changes with 95% posterior intervals for a 10-unit increase in each pollutant were: ozone (lag1, 0.7% (0.4, 0.9)), NO2 (lag0, 0.7% (0.1, 1.4)), and PM2.5 (lag1, 1.3% (0.7, 1.9)). For respiratory mortality: ozone (lag2, 1.2% (0.4, 1.9)), NO2 (lag1, 2.1% (0.6, 3.5)), and PM2.5 (lag1, 0.6% (-1.0, 2.2)). While some differences in risk were observed by season and age group, sex-specific differences were more pronounced. Compared with males, females had a higher respiratory mortality risk (1.8% (0.6, 2.9) vs 0.5% (-0.3, 1.3)) from ozone, a higher respiratory hospitalization risk (0.9% (0.0, 1.8) vs 0.6% (-0.3, 1.4)) but lower mortality risk (1.4% (-1.0, 3.7) vs 2.2% (0.4, 4.0)) from NO2, and a lower hospitalization risk (0.7% (-0.2, 1.7) vs 1.8% (1.0, 2.6)) from PM2.5. Conclusion: This study reports significant health effects of short-term exposure to three ambient air pollutants on respiratory hospitalization (ozone approximate to NO2 < PM2.5 per-10 unit; ozone>NO2 approximate to PM2.5 per-IQR) and mortality (ozone approximate to NO2 > PM2.5) in Canada. Pollutant-sex-specific differences were found, but inconclusive due to limited biological and physiological explanations. Further studies are warranted to understand the pollutant-sex specific differences. Crown Copyright (C) 2020 Published by Elsevier B.V.

Automated summary

This study compared the acute respiratory-related hospitalization and mortality associated with short-term exposure to three ambient air pollutants in different lag-days. The results showed significant associations between the pollutants and respiratory health outcomes, with sex-specific differences being more pronounced. Further studies are needed to understand the pollutant-sex specific disparities.