AUTHOR=Olstrup Henrik , Mohamed Hani A. S. , Honoré Julie , Schullehner Jörg , Sigsgaard Torben , Forsberg Bertil , Oudin Anna TITLE=Air pollution exposure and inflammatory bowel disease: a systematic literature review of epidemiological and mechanistic studies JOURNAL=Frontiers in Environmental Health VOLUME=3 YEAR=2024 URL=https://www.frontiersin.org/journals/environmental-health/articles/10.3389/fenvh.2024.1463016 DOI=10.3389/fenvh.2024.1463016 ISSN=2813-558X ABSTRACT=
This systematic literature review investigates the relationship between air pollution exposure and inflammatory bowel disease (IBD), encompassing Crohn's disease (CD) and ulcerative colitis (UC). Despite the growing concern over air pollution's impact on various health outcomes, studies specifically addressing effects on the digestive system, particularly IBD, are relatively rare. This review aims to synthesize the current knowledge on this topic, focusing on the mechanisms underlying these associations and the role of different air pollutants. Following PRISMA guidelines, a systematic literature search of PubMed and Web of Science databases was conducted, yielding 13 epidemiological studies and six mechanistic (toxicological) studies meeting the inclusion criteria. The epidemiological studies examined associations between IBD and various air pollutants, including PM2.5 (particles with an aerodynamic diameter smaller than, or equal to, 2.5 µm), PM10 (particles with an aerodynamic diameter smaller than, or equal to, 10 µm), PM2.5–10 (coarse particles with an aerodynamic diameter in the range of 2.5–10 µm), BC (black carbon), NO2 (nitrogen dioxide), NO (nitrogen monoxide), NOx (nitrogen oxides), N2O (nitrous oxide), CO (carbon monoxide), SO2 (sulfur dioxide), VOC (volatile organic compounds), O3 (ozone), Ox (oxidant capacity), and traffic load. Study methodologies varied among these 13 epidemiological studies, including four cohort studies, two ecological studies, three case-control studies, two studies using two-sample Mendelian randomization, and two longitudinal time-series studies. Eight studies investigated associations with Crohn's disease and ulcerative colitis separately, while five studies analyzed IBD as a whole without distinguishing between CD and UC. Eleven studies found statistically significant associations between air pollution exposure and IBD, although inconsistent results were found in several of these studies. A total number of six mechanistic (toxicological) studies were retrieved. Among these six studies, five were using particulate matter as exposure metric, and one was based on NO2 and O3 as exposure metrics. With a combination of animal, human, and