Exposure to air pollution and risk of gastrointestinal diseases: a systematic review and meta-analysis of epidemiological evidence.

Gastrointestinal (GI) diseases represent a significant global health burden, and emerging evidence suggests air pollution may be a risk factor. We reviewed relevant literature and performed a meta-analysis. We searched original studies investigated the associations between long- and short-term exposure to particulate matter (diameter ≤ 2.5 µm [PM2.5], ≤ 10 µm [PM10]) and gaseous pollutants (nitrogen dioxide, sulfur dioxide, carbon monoxide, and ozone [O3]) and GI diseases. DerSimonian and Laird random-effects meta-analyses were conducted when at least 2 studies were available for a given pollutant (per 10 μg m-3 increment) and a specific GI disease. A total of 70 studies were included. Long-term exposure to PM2.5 was significantly associated with increased mortality rate from all GI cancers (OR = 1.128; 95% CI, 1.019-1.248), with the strongest association observed for colorectal cancer (OR = 1.214; 95% CI, 1.061-1.389). For non-cancer GI diseases, long-term exposure to PM2.5 was significantly associated with increased risks of duodenal ulcer (OR = 1.073; 95% CI, 1.057-1.089) and irritable bowel syndrome (OR = 1.353; 95% CI, 1.222-1.497); PM10 was also linked to the latter (OR = 1.108; 95% CI, 1.012-1.213). Short-term exposure, particularly to PM2.5, PM10, and O3, was significantly associated with appendicitis hospitalization (OR = 1.003 [95% CI, 1.001-1.004]; OR = 1.017 [95% CI, 1.015-1.019]; and OR = 1.001 [95% CI, 1.000-1.003], respectively). PM2.5 was also associated with peptic ulcer bleeding (OR = 1.006; 95% CI, 1.001-1.011). Long- and short-term exposures to air pollution, especially PM2.5, are associated with increased risks of GI diseases.