Prenatal exposure to arsenic in drinking water and type 1 diabetes in a nationwide population-based cohort of Danish children

Background: Exposure to inorganic arsenic during pregnancy has been associated with immune dysregulation and shifts in leukocyte subpopulations critically involved in the pathogenesis of type 1 diabetes (T1D). Objectives: This study explores the association between prenatal drinking water arsenic exposure and the autoimmune disease T1D in Danish children. Methods: Prenatal arsenic exposure from household drinking water was linked with information on T1D diagnoses from The Danish National Patient- and Prescription Registries. All singleton births from 2002 to 2012, located from The Danish Medical Birth Registry, and living in a household using a public water supply, were included. Cox proportional hazards models were used with age as underlying time scale and adjusted for calendar year, sex at birth, maternal age, smoking status, BMI, parental T1D status, education and income. Results: In a total of 563,871 births, a positive association between prenatal arsenic drinking water exposure and T1D was observed. In fully adjusted models using <1 µg/L as reference, a monotonically increasing association was observed, HR (95 % CI): 1.10 (0.98–1.24), 1.29 (0.88–1.87) and 2.04 (1.15–3.60) for 1–5, 5–10, and ≥10 µg/L, respectively. A higher risk was observed among children born above median compared with below median birth weight across all exposure categories. Discussion: To our knowledge, this is the first study to investigate the association between prenatal arsenic exposure from drinking water and T1D. We found that low levels of arsenic during pregnancy increased risk of T1D in public supply users, highlighting arsenic as a potential modifiable risk factor for T1D.