PM2.5 constituents and hospitalizations for a wide spectrum of digestive diseases exacerbation: Insights from a nationwide case-crossover study with mixed-exposure model.

Increasing evidence suggests that fine particulate matter (PM2.5) affects digestive system, but the individual and joint effects of its constituents remain unclear. We collected hospitalization records for 10 major categories and 12 specific digestive diseases from 153 Chinese hospitals during 2005 -2020. Daily average concentrations of PM2.5 constituents including black carbon (BC), organic matter (OM), sulfate (SO42-), nitrate (NO3-), and ammonium (NH4+) were estimated using satellite-based models. A case-crossover design with conditional logistic regression models was applied to evaluate the independent effects of each constituent. We further developed a pair weighted quantile sum (pairWQS) model to investigate their joint effects and quantify individual contributions. A total of 1030,512 patients were hospitalized for digestive diseases. Short-term exposure (lag 0 -1 day) to PM2.5 constituents was significantly associated with higher hospitalization risks for four major disease categories. Per interquartile range increase in each constituent, effect estimates ranged from 1.43% to 2.03% for diseases of esophagus, stomach, and duodenum, 3.70-5.01% for noninfective enteritis and colitis, 0.99-1.79% for liver diseases, and 2.33-2.41% for other digestive diseases. Among the 12 specific diseases, six were significantly associated with PM2.5 constituents. The pairWQS models indicated that NO3- (39.99%) was the predominant contributor to gastric diseases, whereas BC (40.82%) and OM (50.86%) were dominant contributors to intestinal and liver diseases. This study demonstrates that acute exposure to PM2.5 constituents increases hospitalization risks for digestive diseases exacerbation, highlighting the need for a strategic shift from only reducing total PM2.5 mass to targeting its toxic constituents to achieve greater health benefits.