South Asian Immigrants Exposed to Pesticides Have Increased Risk of Diabetes

South Asian immigrants exposed to higher levels of organochlorine (OC) pesticides also are at a higher risk of developing diabetes, meaning there could be a positive association between these pesticides and incidence of diabetes, according to a study recently published in the Journal of the Endocrine Society.

Researchers led by Martyn T. Smith, PhD, of the Division of Environmental Health Sciences, School of Public Health at the University of California in Berkeley, write that South Asians living in the United Kingdom are two or three times more likely to have type 2 diabetes than their white counterparts, and that South Asians develop type 2 diabetes at a lower body weight, blood lipid level, and age compared to other ethnic groups. “One possibility is that South Asians have a higher exposure to organochlorine (OC) pesticides, which have been associated with diabetes mellitus in European, American, and Korean populations,” the authors write.

They go on to note that South Asians have been exposed to higher levels at OC pesticides for longer periods of time, so the team hypothesized “1) baseline levels of OC pesticides are higher in South Asian immigrants than European whites in the London area; and, 2) diabetes mellitus is associated with OC pesticide exposure in South Asians.” One hundred twenty South Asians of Tamil or Telugu descent and 72 European whites were recruited into the London Life Sciences Population (LOLIPOP) Study cohort. Plasma levels of p,p’-dichlorodiphenyldichloroethylene (p,p’-DDE), p,p’– dichlorodiphenyltrichloroethane (DDT), β-hexachlorohexane (β-HCH), and polychlorinated biphenyl-118 (PCB-118) were analyzed by gas-chromatography mass spectrometry. South Asian cases and controls were categorized by binary exposure (above versus below the 50^th percentile) to perform logistic regression, the authors write.

“One possibility is that South Asians have a higher exposure to organochlorine (OC) pesticides, which have been associated with diabetes mellitus in European, American, and Korean populations,” the authors write.

Tamils had three to nine times higher levels of OC pesticides and Telugus has nine to 30 times higher levels of OC pesticides than European whites. “Odds of exposure to p,p’-DDE above the 50^th percentile was significantly greater in South Asian diabetes cases than controls, OR= 7.00 (2.22, 22.06 95%CI). Odds of exposure to β-HCH above the 50^th percentile were significantly greater in the Tamil cases than controls, OR= 9.35 (2.43, 35.97 95%CI),” the authors write.

The researchers acknowledge that there are limitations to their study, including the small sample size, the fact that OC pesticides might not contribute independently to diabetes risk but may act through similar mechanisms, and that diabetes risk may depend on timing and dose of cumulative OC pesticide levels as opposed to current measurements of single analytes or chemical classes. However, these findings add to the growing number of studies linking OC pesticides to diabetes and may implicate another endocrine-disrupting chemical which may be an underappreciated contributor to disparities in metabolic disease risk.

Based on their findings the authors conclude: “South Asian immigrants have a higher body burden of OC pesticides than European whites. Diabetes mellitus is associated with higher p,p’-DDE and β-HCH concentrations in this population. Additional longitudinal studies of South Asian populations should be performed.”