Abstract
The Stockholm Convention on Persistent Organic Pollutants eliminated the production, use, and/or emissions of persistent pollutants which include organochlorines. Banned organochlorines are resistant to biodegradation and are therefore still present in soil, air, and water. They are lipophilic and bioaccumulate up the food chain so the major source of human exposure comes from fatty food. More than 40 epidemiological studies have indicated a positive association of organochlorines with type 2 diabetes but the data are insufficient to establish causality since most studies are case-control and cross-sectional where temporal associations cannot be determined. Also, some epidemiological studies have reported negative associations where organochlorine concentrations were lower in diabetics than controls and others showed inconsistencies across different populations or geographic areas. Because cross-sectional studies are prone to such biases, prospective studies were indicated. Most of these cohort prospective studies were not population based and had such small numbers of diabetics that the odds ratios’ confidence intervals were large enough to engender uncertainty. It has also been suggested that obesity or diabetes may increase the level of organochlorines (reverse causation) rather than high levels leading to disease (causation). In addition, non-monotonic dose-response relationships have been reported between organochlorines and metabolic syndrome endpoints such as impaired insulin action, triglyceride levels, and type 2 diabetes prevalence. Concerns like these reinforce the need to move away from epidemiological studies and toward mechanistic research to determine whether the association between organochlorines and type 2 diabetes is causal. To this end, a literature review was conducted searching for publications suggesting mechanisms for the positive association. The most interesting mechanisms are described in detail. In addition to describing the evidence for possible mechanisms, various concerns and suggestions are discussed.