Abstract
Abstract Background Crohn's Disease (CD) is a chronic intestinal disease with an unclear etiology and suspected environmental risk factors. The CROPS (CROhn’s disease and Pollution of Soils) project was initiated in Northern France to investigate links between the high incidence of CD and environmental pollutants. In this context, we combined data of a population-based registry of Inflammatory Bowel Disease (IBD) with environmental sampling data to identify the environmental profile of multi-contamination associated with high incidence. Methods This ecological study was conducted at the municipal level within the coverage area of the registry in Northern France. All patients diagnosed between 2000 and 2017 were included (n=9,019). Spatial clusters of significantly high (n=4) and low (n=4) CD incidence, adjusted for age and sex, were identified based on patients' residence addresses at diagnosis. Within these clusters, environmental sampling was performed across 240 sites using a hexagonal grid to ensure 30 samples per cluster. A total of 490 parameters were analyzed: 306 in soil (including emerging pollutants such as hormones and antibiotics, polycyclic aromatic hydrocarbons [PAHs], heavy metals, and pesticides), 152 in tap water (examining heavy metals and PAHs), and 30 in lichens (assessing heavy metals as indicators of air quality). Multi-contamination indices, such as the Mean Impregnation Ratio (MIR) and Pollution Index, were applied. Data analysis included Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA), and Analysis of Variance (ANOVA) tests. Results High-incidence clusters, predominantly agricultural, had elevated heavy metal concentrations in soil (notably chromium, arsenic, zinc, and nickel), sulfadiazine in soils, high nitrate levels in water, and heavy metals in lichens. Low-incidence clusters, with greater urbanization, showed elevated PAHs in soil, heavy metals in water, and BPA in soils. Pollution profiles aligned with different land covers, with significant findings for agricultural lands (p<0.0001). A positive correlation between the relative risk and soil’s MIR for heavy metals in agricultural zones was noted (r=0.557, p=0.005). Conclusion These findings suggest a possible link between high CD incidence and heavy metal exposure in agricultural lands. Profiles of pollution were created for each cluster. Future studies should expand on pesticide and agricultural pollutant analysis to strengthen this hypothesis, and consider individual-level epidemiological approaches to further elucidate these potential environmental risk factors.
Published Version
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