Inflammatory Bowel Disease

Subject Category: Inflammatory Bowel Disease

Am J Gastroenterol 2010; 105:2412–2419; doi:10.1038/ajg.2010.252; published online 29 June 2010

The Inflammatory Bowel Diseases and Ambient Air Pollution: A Novel Association

Gilaad G Kaplan MD, MPH1,2, James Hubbard MSc1, Joshua Korzenik MD3, Bruce E Sands MD, MSc3, Remo Panaccione MD1, Subrata Ghosh MD1, Amanda J Wheeler PhD4 and Paul J Villeneuve PhD5,6

  1. 1Division of Gastroenterology, Department of Medicine, University of Calgary, Calgary, Alberta, Canada
  2. 2Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada
  3. 3MGH Crohn's and Colitis Center and Gastrointestinal Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
  4. 4Air Health Science Division, Ottawa, Ontario, Canada
  5. 5Population Studies Division, Health Canada, Ottawa, Ontario, Canada
  6. 6Dalla Lana School of Public Health, University of Toronto, Ontario, Canada

Correspondence: Gilaad G. Kaplan, MD, MPH, Division of Gastroenterology, Departments of Medicine and Community Health Sciences, University of Calgary, Teaching Research and Wellness Center, 3280 Hospital Drive NW, 6th Floor, Room 6D17, Calgary, AB, Canada, T2N 4N1. E-mail:

Received 6 February 2010; Accepted 10 May 2010; Published online 29 June 2010.





The inflammatory bowel diseases (IBDs) emerged after industrialization. We studied whether ambient air pollution levels were associated with the incidence of IBD.



The health improvement network (THIN) database in the United Kingdom was used to identify incident cases of Crohn's disease (n=367) or ulcerative colitis (n=591), and age- and sex-matched controls. Conditional logistic regression analyses assessed whether IBD patients were more likely to live in areas of higher ambient concentrations of nitrogen dioxide (NO2), sulfur dioxide (SO2), and particulate matter <10μm (PM10), as determined by using quintiles of concentrations, after adjusting for smoking, socioeconomic status, non-steroidal anti-inflammatory drugs (NSAIDs), and appendectomy. Stratified analyses investigated effects by age.



Overall, NO2, SO2, and PM10 were not associated with the risk of IBD. However, individuals ≤23 years were more likely to be diagnosed with Crohn's disease if they lived in regions with NO2 concentrations within the upper three quintiles (odds ratio (OR)=2.31; 95% confidence interval (CI)=1.25–4.28), after adjusting for confounders. Among these Crohn's disease patients, the adjusted OR increased linearly across quintile levels for NO2 (P=0.02). Crohn's disease patients aged 44–57 years were less likely to live in regions of higher NO2 (OR=0.56; 95% CI=0.33–0.95) and PM10 (OR=0.48; 95% CI=0.29–0.80). Ulcerative colitis patients ≤25 years (OR=2.00; 95% CI=1.08–3.72) were more likely to live in regions of higher SO2; however, a dose–response effect was not observed.



On the whole, air pollution exposure was not associated with the incidence of IBD. However, residential exposures to SO2 and NO2 may increase the risk of early-onset ulcerative colitis and Crohn's disease, respectively. Future studies are needed to explore the age-specific effects of air pollution exposure on IBD risk.