A new study out of Stanford reinforces the link between type 2 diabetes and organochlorine (OC) pesticide exposure by pioneering a new method for assessing the contribution of environmental factors to disease formation more generally. More than 23 million people in the U.S. suffer from the disease, which is on the rise, and genetics have thus far offered little insight. The study’s specific findings were that the development of type 2 diabetes correlates strongly with the presence of the OC pesticide-derivative heptachlor in blood or urine, with environmental contaminant polychlorinated biphenyls (PCBs) also showing a significant association. Beta-carotenes had a protective effect against the development of type 2 diabetes. At least as significant as the study’s findings were its methodological advances in documenting environmental contributions to health outcomes.
Disease formation is enormously complex, requiring analysis of myriad causal factors over long time frames. Accordingly, the demonstration of causality for increased incidence of chronic diseases like cancer, type 2 diabetes and other autoimmune and metabolic disorders has been difficult. Over the last few decades, much more money has been devoted to the study of genetic and lifestyle causal factors than to environmental ones — one effect of which has been the "gross underestimation" of environmental contributions to disease-formation. The Stanford authors piloted an Environment-Wide Association Study (EWAS) in which epidemiological data are comprehensively and systematically interpreted in a way that builds upon Genome Wide Association Studies (GWAS). Using National Health and Nutrition Examination Survey data, scientists performed multiple cross-sectional analyses associating 266 environmental factors with the occurrence of type 2 diabetes. Of those 266 environmental factors, OC pesticide-derivative heptachlor showed the strongest correlation. According to Scientific American, the idea for conducting what amounts to a "mass-screening" of environmental risk factors came from a Stanford graduate student, Chirag Patel, the study’s lead author. Patel wanted to find a way to "use bioinformatics for the environment," in part to address widespread dissatisfaction with what genetics have been able to explain about disease risk factors. "The time is ripe, to usher in ‘enviromics’," claim the study’s authors.