Effect of ambient air pollution on the incidence of appendicitis

¹ Division of Gastroenterology, Department of Medicine, and the Department of Community Health Sciences, University of Calgary, Calgary, Alta.
² Division of Gastroenterology, Departments of Community Health Sciences and Surgery, University of Calgary, Calgary, Alta.
³ Division of Gastroenterology, Department of Medicine, University of Calgary, Calgary, Alta.
⁴ Alberta Health Services, Edmonton, Alta.
⁵ Population Studies Division, Health Canada, Ottawa, Ont.
⁶ Air Health Science Division, Health Canada, Ottawa, Ont.
⁷ Division of Gastroenterology, Department of Surgery, University of Calgary, Calgary, Alta.
⁸ Population Studies Division, Health Canada, Ottawa, Ont.; and the Dalla Lana School of Public Health, University of Toronto, Toronto, Ont.

	Abstract

Background: The pathogenesis of appendicitis is unclear. We evaluated whether exposure to air pollution was associated with an increased incidence of appendicitis.

Methods: We identified 5191 adults who had been admitted to hospital with appendicitis between Apr. 1, 1999, and Dec. 31, 2006. The air pollutants studied were ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide, and suspended particulate matter of less than 10 µ and less than 2.5 µ in diameter. We estimated the odds of appendicitis relative to short-term increases in concentrations of selected pollutants, alone and in combination, after controlling for temperature and relative humidity as well as the effects of age, sex and season.

Results: An increase in the interquartile range of the 5-day average of ozone was associated with appendicitis (odds ratio [OR] 1.14, 95% confidence interval [CI] 1.03–1.25). In summer (July–August), the effects were most pronounced for ozone (OR 1.32, 95% CI 1.10–1.57), sulfur dioxide (OR 1.30, 95% CI 1.03–1.63), nitrogen dioxide (OR 1.76, 95% CI 1.20–2.58), carbon monoxide (OR 1.35, 95% CI 1.01–1.80) and particulate matter less than 10 µ in diameter (OR 1.20, 95% CI 1.05–1.38). We observed a significant effect of the air pollutants in the summer months among men but not among women (e.g., OR for increase in the 5-day average of nitrogen dioxide 2.05, 95% CI 1.21–3.47, among men and 1.48, 95% CI 0.85–2.59, among women). The double-pollutant model of exposure to ozone and nitrogen dioxide in the summer months was associated with attenuation of the effects of ozone (OR 1.22, 95% CI 1.01–1.48) and nitrogen dioxide (OR 1.48, 95% CI 0.97–2.24).

Interpretation: Our findings suggest that some cases of appendicitis may be triggered by short-term exposure to air pollution. If these findings are confirmed, measures to improve air quality may help to decrease rates of appendicitis.