Association between long-term ambient fine particulate matter exposure and risk of postneonatal infant mortality in Taiwan

Infants and children may be potentially susceptible to harm from ambient fine particulate matter (PM_2.5) pollution because of the following characteristics (1) immature immune systems (2) not yet fully developed respiratory systems (3) possess a higher absorption rate of pollutants, and (4) and daily activities may expose infants to varying levels. However, few studies have examined the possible correlation between exposure to PM_2.5 and mortality in infants. Therefore, the aim of this study was to investigate the association between long-term exposure to ambient PM_2.5 and post-neonatal mortality in 65 municipal areas across Taiwan. The mean annual PM_2.5 levels of each municipality were categorized from 2013 to 2022 and divided into tertiles. The natural logarithm of the annual post-neonatal mortality rates per 1000 live births was assessed with respect to PM_2.5 level, urbanization level, physician density, and mean annual average household income. Weighted-multiple linear regression was utilized to compute the adjusted RRs and their 95% confidence intervals (CIs). When data were not stratified by PM_2.5 levels, a significant positive association was observed between long-term lifetime exposure to ambient PM_2.5 and post-neonatal mortality rates after adjustment for physician density, urbanization level, and average household income. When PM_2.5 levels (in tertiles) were stratified, a positive but nonsignificant trend was found in post-neonatal mortality frequency from the lowest to the highest PM_2.5 category. These findings suggest that long-term exposure to PM_2.5 increases the risk of post-neonatal mortality rates in Taiwan.