Does Pollution Cause Diabetes? The Disease/Environmental Toxin ConnectionAlan R. Gaby, M.D. October 1, 2007
The prevalence of diabetes mellitus in the United States has been increasing over the past few decades. In 2005, an estimated 7% of the US population, approximately 21 million people, had diabetes, primarily type 2. Scientists have attributed this epidemic mainly to various lifestyle factors, such as obesity, lack of exercise, and excessive intake of high-fructose corn syrup and other refined carbohydrates.
However, recent evidence suggests that exposure to certain commonly encountered environmental pollutants is another important contributing factor to the high prevalence of diabetes. Chemicals that may be involved include some pesticides (or their metabolites) and metabolites of polychlorinated biphenyls (PCBs). Many of these compounds accumulate in human adipose tissue, where they persist for decades. Another compound that may play a role in the pathogenesis of diabetes is bisphenol A, which is widely used in the chemical industry to produce polycarbonates and other plastics. Bisphenol A is used in the manufacturing of coatings for the inner surfaces of food and beverage cans. It is known to leach from these containers into the foods and beverages, and it has been found in 95% of urine samples from people in the U.S.
In prospective cohort studies, people exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; the most potent dioxin congener of persistent organic pollutants) or other persistent organic pollutants had an increased risk of diabetes or insulin resistance. TCDD has also been found to decrease glucose transport in animals and in vitro. In mice, subcutaneous administration of a bisphenol A (100 mcg per kg of body weight per day for four days) appeared to cause insulin resistance, as demonstrated by the development of hyperinsulinemia and altered glucose tolerance.
Just how large a role environmental pollution plays in the pathogenesis of diabetes was suggested by a recent cross-sectional study that included 2,016 adults participating in the National Health and Nutrition Examination Survey, 1999-2002. The study examined the association between the prevalence of diabetes (types 1 and 2 combined) and serum concentrations of pollutants that persist in the environment and in adipose tissue. The six pollutants studied (2,2′,4,4′,5,5′-hexachlorobiphenyl, 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin, 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin, oxychlordane, p,p’-dichlorodiphenyltrichlo-roethane, and trans-nonachlor) were selected because they were detectable in at least 80% of the participants. Compared with subjects with serum concentrations below the limit of detection, the prevalence of diabetes (adjusted for age, sex, race, ethnicity, income, body mass index, and waist circumference) was strongly positively associated with lipid-adjusted serum concentrations of each of the six pollutants. Individuals in the highest category of exposure (> 90th percentile) of the six pollutants combined had a prevalence of diabetes 38 times higher than those in the lowest category of exposure (< 25th percentile) (p for trend < 0.001). Furthermore, obesity was found not to be a risk factor for diabetes among participants who had undetectable levels of these pollutants. Obesity was associated with diabetes only among individuals at or above the 25th percentile for the sum of the six exposures.
This study was reviewed in editorial in the Lancet. Commenting on the lack of association between obesity and diabetes among people with non-detectable levels of pollutants, the writer stated: “This finding might imply that virtually all the risk of diabetes conferred by obesity is attributable to persistent organic pollutants, and that obesity is only a vehicle for such chemicals. This possibility is shocking.”
MY OWN EXPERIENCE
Shocking, indeed! Makes you want to eat only organically grown foods and to exercise more and take infrared saunas to start sweating some of those poisons out of your body. I purchased an infrared sauna about a year ago, figuring it might be a good idea to try to remove some of the chemicals that have been accumulating for more than half a century. I did not think my body burden of such chemicals was high, since I have not lived in heavily polluted areas and have done regular aerobic exercise for most of my life. I was surprised, therefore, to find that after sitting for 20 minutes in an infrared sauna my sweat smelled like a combination of chlorine bleach and Exit 9 on the New Jersey Turnpike. After more than 20 sessions in the sauna during the past year, that same type of perspiration odour has persisted, suggesting that more poisons are still in my body.
There is a growing body of evidence that a number of environmental pollutants act as disruptors of the endocrine system. Most of the research to date has focused on the effects of these chemicals on the reproductive system and on cancer risk. The new studies suggest that toxic chemicals may be an important cause of another common endocrine disease, diabetes mellitus.
Reprinted with permission from Towsend Letter for Doctors and Patients, 911 Tyler Street, Pt. Towsend, Washington, tel: (360) 385-6021. For subscription information go to: www.townsendletter.com.
 Alonso-Magdalena P, et al. The estrogenic effect of bisphenol A disrupts pancreatic beta-cell function in vivo and induces insulin resistance. Environ Health Perspect. 2006;114:106-112.
 Lee DH, Lee et al. A strong dose-response relation between serum concentrations of persistent organic pollutants and diabetes: results from the National Health and Examination Survey 1999-2002. Diabetes Care. 2006;29:1638-1644.
 Porta M. Persistent organic pollutants and the burden of diabetes. Lancet. 2006;368:558-559.