Long-Term Exposure to Low-Level Arsenic in Drinking Water and Diabetes Incidence: A Prospective Study of the Diet, Cancer and Health Cohort Original paper

What was studied?

The study investigated the relationship between long-term low-level arsenic exposure in drinking water and the incidence of diabetes in Denmark. The research focused on determining whether low-level arsenic exposure, typically defined as less than 50 μg/L, is associated with an increased risk of diabetes in a large cohort over several years. This prospective cohort study utilized data from the Diet, Cancer, and Health (DCH) cohort and linked individual exposure to arsenic with diabetes incidence as tracked through the Danish National Diabetes Register.

Who was studied?

The study included 52,931 eligible participants from the DCH cohort, aged between 50 and 64 years, who were enrolled between 1993 and 1997. Participants were recruited from the Copenhagen and Aarhus areas in Denmark and followed for a mean period of 9.7 years. The study population was geographically diverse, with individuals living in areas with varying arsenic concentrations in their drinking water. The cohort’s health data, lifestyle factors, and residential history were extensively documented, and the National Diabetes Register (NDR) was used to identify cases of diabetes. The study excluded individuals with pre-existing diabetes or a cancer diagnosis at the time of enrollment.

Most important findings

The study found a weak but positive association between long-term exposure to low-level arsenic and the incidence of diabetes. Specifically, for every 1 μg/L increase in arsenic levels in drinking water, the incidence rate ratio (IRR) for all diabetes cases was 1.03 (95% CI: 1.01, 1.06), and for strict diabetes cases, it was 1.02 (95% CI: 0.99, 1.05). The study also observed no significant differences in diabetes risk based on sex, waist circumference, smoking status, or physical activity, suggesting that the effect of arsenic on diabetes risk may be consistent across different subgroups. Additionally, the study revealed a potential exposure threshold, as the association between arsenic levels and diabetes risk appeared to plateau at higher concentrations of arsenic.

Key implications

The study’s findings suggest that long-term exposure to low-level arsenic in drinking water may contribute, albeit modestly, to the development of diabetes. This highlights the need to further investigate the role of environmental chemicals, like arsenic, in the rising incidence of diabetes globally, especially in populations with chronic low-level arsenic exposure. The study also underscores the importance of prospective cohort designs that track environmental exposures and health outcomes over time. For public health, these findings suggest a need for monitoring and regulating arsenic levels in drinking water, even at concentrations well below the currently accepted safety thresholds set by organizations such as the WHO. Further research is needed to determine the biological mechanisms through which arsenic influences glucose metabolism and to confirm whether a threshold exists for its toxic effects.