S1519 Heavy Metals in Surface and Ground Water Predict New-Onset Inflammatory Bowel Disease: A Geospatial Case-Control Study Using Open Environmental Data and Electronic Health Records

Introduction: Exposure to lead or mercury has been associated with developing inflammatory bowel disease (IBD), but the role of heavy metals (HM) more broadly has not been as well studied. The growth of public data on environmental exposures has enabled new epidemiological studies via linkage to health records at the level of residential zip codes. Methods: A total of 10,905 Crohn’s disease (CD, International Classification of Diseases-9: 555; International Classification of Diseases-10: K50) and 13,139 ulcerative colitis (UC, International Classification of Diseases-9: 556; International Classification of Diseases-10: K51) cases diagnosed between 1990 and 2023 were extracted from the UCSF data warehouse, which were matched by sex at a 1:10 ratio to 240,440 patients without any International Classification of Diseases code for IBD. Surface and ground water HM concentrations were queried from the California Department of Water Resources and mapped to patient data using the reciprocal of the great-circle distance between water stations and the centroids of patient residential zip codes. A saturated multivariable logistic regression model was used to examine the HM effects. Results: Only 0.35–3.35% of patients resided in zip codes where lead, mercury, arsenic, and cadmium concentration in surface and ground water exceeded the maximum contaminant level (MCL) defined for drinking water by the Environmental Protection Agency, while 95% resided in zip codes where aluminum was above National Secondary Drinking Water Regulations . Both ulcerative colitis and Crohn’s disease patients had higher odds of residing where lead (odds ratio [OR]: 1.30, 95% confidence interval [CI]: 1.20–1.41) or arsenic (OR: 3.23, 95% CI: 2.68–3.88) were above MCL but lower odds for aluminum (OR: 0.69, 95% CI: 0.66–0.73) or cadmium (OR: 0.63, 95% CI: 0.54–0.74) compared with controls. Conclusion: Lead and arsenic exposure predict IBD, whereas aluminum and cadmium exposure predict a reduced risk. Additional epidemiologic validation from other centers and countries, together with mechanistic studies, can further test the hypothesis that heavy metal exposures explain the rising global incidence of IBD.