# Seasonally modulated nonlinear effects of PM2.5 on pediatric respiratory health: evidence from a time-series analysis in urban China

## TL;DR

This study shows that PM2.5 pollution increases the risk of respiratory diseases in children in Guangzhou, with stronger effects during summer and winter.

## Contribution

The study reveals seasonally modulated nonlinear effects of PM2.5 on pediatric respiratory health in a developing country context.

## Key findings

- PM2.5 exposure increases the risk of respiratory diseases in children with a zigzag-shaped association.
- The risk of respiratory diseases is notably higher during summer and winter seasons.
- Boys show a significantly increased risk of respiratory diseases due to PM2.5 exposure.

## Abstract

Although many studies have shown that fine particulate matter (PM2.5) is associated with respiratory diseases (RDs) in children, fewer studies have examined this association in developing countries. We aimed to use the latest PM2.5 standards to investigate the interaction between PM2.5 and RDs among children in Guangzhou.

We included 18,291 pediatric inpatients aged 0–14 years with a primary diagnosis of RDs admitted to hospitals in Guangzhou, China, from January 1, 2018, to December 31, 2021. The association between PM2.5 and RDs was analysed using a non-linear distributed lag model, and additional subgroup analyses were performed based on sex and season.

The association of PM2.5 with RDs showed a zigzag shape. Specifically, the cumulative effects of PM2.5 at the 25th, 50th, and 75th percentiles, with a lag of 0–14 days, were associated with increases in the relative risk (RR) of RDs by 0.4% (95% confidence interval (CI) [1.000–1.007]), 3.4% (95% CI [1.004–1.065]), and 7.7% (95% CI [1.010–1.149]), respectively. Additionally, for each 10 µg/m3 increase in PM2.5 concentration, the on-the-day lagged effect on lag day 4 and lag day 7 was associated with an elevated risk of RDs, with RR of 1.018 (95% CI [1.002–1.034]) and 1.016 (95% CI [1.000–1.032]), respectively. Additionally, PM2.5 exposure significantly increased the risk of RDs in boys and elevated that risk in children during both summer and winter seasons.

This study reveals a significant effect of PM2.5 exposure on RDs in children, with notably elevated risks during summer and winter seasons. These findings underscore the critical importance of implementing air quality improvement measures to safeguard children’s health, particularly in developing countries.