Association of short-term exposure to ambient air pollutants with liver function and mediation by fasting insulin: evidence from a rural cohort in China.

Abstract

Air pollution and the rising prevalence of liver diseases have become public health concerns. Nevertheless, the relationship and underlying mechanisms between ambient air pollution and liver function remain inadequately investigated. A total of 4096 rural residents living in the suburb of Xinxiang city, China, were recruited from the Henan Rural Cohort. The participants underwent two physical examinations conducted in 2017 and 2021, respectively. A linear mixed-effects model was utilized to evaluate the associations between individual ambient air pollutants and liver function biomarkers. To determine the main air pollutants that impact liver function biomarkers, weighted quantile sum (WQS) regression models were applied. Additionally, the mediating role of fasting insulin (FINS) in these associations was investigated using mediation analysis. For each increase in the interquartile range (IQR) of fine particulate matter (PM_2.5) (lag03, representing the average exposure over the current and previous 3 days) concentration (IQR 17.73 μg/m³), aspartate aminotransferase levels increased by 2.30% (95% confidence interval [CI]: 1.34%, 3.28%). Similar relationships were also detected between other air pollutants and biomarkers of liver function. WQS regression analysis confirmed that sulfur dioxide (weight: 0.64), nitrogen dioxide (NO₂) (0.13), and ozone (0.18) were the main contributing pollutants associated with total bilirubin (TBIL). FINS was significantly associated with NO₂ exposure and increases in indirect bilirubin (IBIL) (11.41%, 95% CI 9.78%, 16.58%), direct bilirubin (DBIL) (5.32%, 95% CI 5.02%, 8.47%), and TBIL (11.56%, 95% CI 9.97%, 16.58%). The mediating effect of FINS in the relationship between PM_2.5 and alanine aminotransferase levels was significant. It accounted for - 49.92% (95% CI - 96.56%, - 29.99%) of the total effect. There is a positive association between short-term exposure to ambient air pollutants and biomarkers of liver function. Moreover, FINS may play mediating roles in these associations.