Age- and season-specific effects of ambient particles (PM, PM, and PM) on daily emergency department visits among two Chinese metropolitan populations.

Background: Ambient PM has been identified as the top leading cause of risk-attributable deaths worldwide, particularly in China. Evidence suggested that PM contributed the most majority of PM concentrations in Chinese cities. However, epidemiologic knowledge to date is of wide lack regarding PM-associated health effects.

Methods: We collected daily records of all-cause emergency department visits (EDVs) and ground measurements of ambient air pollutants and meteorological factors in Guangzhou and Shenzhen, China, 2015-2016. Case-crossover design and conditional logistic regression models were used to comparatively assess the short-term effects of ambient PM, PM, and PM on EDVs. Stratified analyses by gender, age and season were performed to identify vulnerable groups and periods.

Results: PM, PM and PM were all significantly associated with increased EDVs in both cities. Population risks for EDVs increased by 2.2% [95% confidence interval, 1.8 to 2.6] in Guangzhou and 1.7% [1.0 to 2.4] in Shenzhen, for a 10 μg/m rise in PM at lag 0-1 days and lag 0-4 days, respectively. Relatively lower risks were found to be associated with PM and PM. PM-EDVs associations exhibited no gender differences, but varied across age groups. Compared with adults and the elderly, children under 14 years-of-age suffered higher PM-induced risks. Results from both cities suggested greatly significant effect modification by season, with consistently stronger PM-EDVs associations during cold months.

Conclusions: Our study added comparative evidence for increased EDVs risks associated with short-term exposures to ambient PM, PM and PM. Besides, PM-associated effects were significantly stronger among children and during cold months.