Chemical Exposures May Explain Disparities in Diabetes Risk

Liam Davenport

December 01, 2017

The higher rates of diabetes seen in some ethnic groups, such as African American and Latino populations, may be due in part to increased exposure to endocrine-disrupting chemicals (EDCs) found in everyday items and left over from former industrial and pesticide use, suggest US researchers.

In a new review, Robert M Sargis, MD, PhD, division of endocrinology, diabetes, and metabolism, University of Illinois at Chicago, and colleagues found that chemicals used in household plastics and products such as hair sprays and deodorants not only increase diabetes risk but do so disproportionately in vulnerable populations.

The research was published online November 15 in Diabetes Care.

While it has "long been recognized" that African American, Latino, and other socioeconomically disadvantaged individuals "bear a higher burden of diabetes," the underlying reasons "are not completely understood," say the researchers.

They add: "We provide evidence that higher exposure to diabetogenic pollutants is an important contributor.

"Although further work is required to validate the EDC–diabetes link and better quantify exposure disparities, current evidence suggests that improvements in environmental health could reduce diabetes risk and disparities."

Those treating patients with unexpected type 2 diabetes or excessive medication use should therefore look at potential EDC exposure, say the authors, who then suggest ways in which clinicians can advise patients on how to reduce such exposures.

Evidence That EDCs Have a Bigger Impact on Diabetes in Certain Groups

To try to connect the dots between established evidence that diabetes disproportionately affects vulnerable members of society and emerging data that hint at a link between environmental EDC exposure and metabolic dysfunction, the researchers examined the US National Library of Medicine for articles examining the two issues  that were published between 1996 and 2016.

The team identified 27 prospective studies examining the associations between EDC exposure and diabetes risk, which together identified several types of chemicals that may play a role.

These include polychlorinated biphenyls (PCBs), a group of industrial chemicals that were banned in 1977 by the US Environmental Protection Agency but that persist in the environment, particularly in fish, meat, and dairy products. Numerous studies showed that exposure to PCBs is associated with an approximate doubling of the risk of developing diabetes.

Organochlorine (OC) pesticides were also, for the most part, banned in the 1970s but are still measurable in the US population, with exposure coming from consumption of some high-fat meats and dairy products as well as from fatty fish. Again, these pesticides have been linked to an approximate twofold increased risk of developing diabetes.

Other EDCs associated with diabetes risk in the studies were:

  • Traffic-related air pollution and particulate matter.

  • Bisphenol A, which is a synthetic chemical commonly used in the manufacturing of plastics found in consumer products.

  • Phthalates, which are a large group of chemicals used in food packaging, toys, building materials, pharmaceuticals, and personal-care products, such as perfume, hair spray, and deodorant.

Crucially, the researchers found that exposure to EDCs had a greater impact in nonwhite populations than in their white counterparts.

For example, one study showed that PCBs almost tripled the risk of diabetes in nonwhites vs a doubling in whites, while another showed almost identical findings for OC pesticide exposure.

How Can Doctors Help Their Patients Reduce Exposure to EDCs?

The team says their findings "suggest that African Americans and Latinos have heightened sensitivity to the diabetogenic effects of environmental contaminants because of potential synergy with other diabetes risk factors."

For example, vulnerable populations are more likely to live in neighborhoods with fewer green spaces, greater exposure to industrial air pollution, and reduced access to healthy foods compared with white populations, they note.

To being to tackle the problem, the team suggest that "astute clinicians" take "comprehensive occupational and environmental histories in patients without the classical clinical features of type 2 diabetes and without a genetic explanation," as well as in those who have "greater-than-anticipated" medication needs.

This could help identify background chemical exposures that might worsen metabolic dysfunction and allow clinicians to offer targeted interventions to reduce exposures and improve outcomes.

Doctors should advise patients to wash fruit and vegetables, trim fat from meat and skin from fish, and replace old fluorescent bulbs and deteriorating building materials to reduce PCB exposure. And in areas where OC pesticides were used, floors should be cleaned regularly and hands should be washed often, especially before eating or preparing food.

To minimize BPA exposure, they advise avoiding plastic containers with #7 on the bottom and opting for glass and porcelain containers instead and reducing the handling of thermal paper, such as that used in sales receipts. They also recommend that nonplastic alternatives be used for toys, shower curtains, flooring, and medical equipment wherever possible to reduce phthalate exposure, with plastics labeled #3 to be avoided

People should also be encouraged to read the labels of personal-care products to ensure that they are phthalate-free and avoid products containing synthetic fragrances.

 "As additional data accumulate and the field matures, the practicing diabetologist and endocrinologist will be uniquely positioned to address exposure to diabetogenic environmental toxicants as part of individualized diabetes care plans to reduce disease risk and to improve diabetes outcomes across the population," they conclude.

This work was supported by the National Institute of Child Health and Human Development and the National Institute of Diabetes and Digestive and Kidney Diseases through the Chicago Center for Diabetes Translational Research as well as by the American Diabetes Association. The authors report no relevant financial relationships.

Diabetes Care. Published online November 15, 2017. Article

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