Finding an association between an antioxidant like vitamin E and diabetes was unexpected and a bit puzzling, Butte says, but it's not particularly surprising that the chemicals showed up in the analsysis.
The specific pesticide and chemical identified by the study have a long history of toxicity and negative health effects.
Polychlorinated byphenyls, often referred to as PCBs, raised public health suspicions as early as the 1930s. Later research linked PCBS to a number of health risks, including liver cancer, and the production of PCBS was banned in the U.S. in 1979. In certain "closed" applications, PCBS are still used today, however.
Similarly, heptachlor epoxide, the pesticide identified by the study was one that was banned in the 1980s because of its toxic impact on humans, Butte says, but remnants of the chemical remain in the soil on locations where it was used heavily.
Though these two chemicals were not previously associated with diabetes, Dr. Philip Landrigan, professor and chairman of Community and Preventive Medicine at the Mount Sinai School of Medicine, says it may be in line with growing research to think that toxic chemicals like these could affect diabetes.
"The basic notion that certain chemicals can predispose people to obesity is becoming more and more believable as the research progresses," says Landrigan, adding taht given the tight connection between obesity and type II diabetes, these chemicals may be likely suspects for increasing environmental risk.
But Patel cautions that while EWAS is useful for research purposes, the environmental ingredients identified by EWAS do not prove a direct link between diabetes and these chemicals. "These are very strong associations, but they're still just associations," he says, not causal links.
It could be that those who already have type II diabetes are more likely to come into contact with the elements identified, either through medication, diet changes, or supplements (especially in the case of vitamin E), Butte points.
Also, the chemicals identified are all fat-soluble, "meaning that they tend to live in our bodies in fat tissue," Patel says, so it could be that because those with type II diabetes are more likely to be overweight, they are more likely to have stored greater concentrations of these chemicals in their fat.
Nonetheless, these EWAS is a powerful tool for pointing researchers towards possible environmental causes, says Dr. Marcel Casavant, chief of pharmacology and toxicology at Ohio State University.
"This is a whole new way to explore possible environmental factors," he says. "Now we know if we want to look into possible causes of type II diabetes, we need to look at these [three factors]."