US Immigrants From India At Higher Risk Of Diabetes Due To Previous Exposure Of Pesticide DDT In India
A study conducted by University of California, Davis found that previous exposure to the pollutant DDT
(dichlorodiphenyltrichloroethane) may contribute to the risk of diabetes
among Asian Indian
immigrants to the United States.
The recent study in the American Chemical Society's journal Environmental Science & Technology
, linked high levels of DDT
, or dichlorodiphenyltrichloroethane
, in Indian
immigrants with risk factors for metabolic disease
Dr Michele La Merrill, an associate professor in the UC Davis Department of Environmental Toxicology and lead author told Thailand Medical
News, "Our findings evoke a new interpretation of Rachel Carson's famous book Silent Spring, in that the high DDT
exposures of South Asian immigrants in the U.S. currently fall on deaf ears in the U.S. Although DDT
remains in use in other nations and migration globalizes these exposures, people in the U.S. often mistakenly regard DDT
exposure as no longer relevant to our society due to its ban in this country nearly 50 years ago."
Dr La Merrill said that high exposure levels in these immigrants may be causing their increased risk of obesity and other metabolic diseases
, but medical doctors are often not aware of that possible link.
Asians from India
have a higher risk of diabetes
than other populations, and this risk extends to Indian immigrants in the U.S., Europe and elsewhere.
The United Nations Stockholm Convention in 2004 banned the production and use of many persistent organic pollutants, or POPs, such as DDT
and polychlorinated biphenyls, or PCBs. However, POP production and use continue in some nations that did not ratify the treaty, including India
and other South Asian countries such as Cambodia, Vietnam, Thailand, Malaysia, Myanmar and also China. Past studies have found DDT
in samples taken from the environment, food and people of the Indian
subcontinent and also in other South East Asian countries. DDT was rampant in the whole system from foods, water supplies to even blood samples.
Dr La Merrill and colleagues wondered whether prior exposure to DDT
and other POPs could influence Asian Indian
risk, even after they had immigrated to the U.S. Based on results from animal studies, the researchers hypothesized that POPs could contribute to diabetes
by causing excess fat deposition in the liver, which in turn can lead to insulin resistance.
To confirm and test their hypothesis, the researchers examined the levels of 30 environmental pollutants in blood plasma samples from 147 Asian Indian
participants, 45 to 84 years old, living in the San Francisco Bay Area. The researchers detected levels of numerous POPs that were much higher than levels previously found in other U.S. populations.
The findings showed that people with higher levels of DDT
in their blood were more likely to be obese, store excess fat in their livers and show increased insulin resistance compared to people with lower levels.
Though more research is needed to establish a causal relationship, these findings could help explain the increased diabetes
risk for Indian
immigrants and have public health implications for the approximately 1.8 billion South Asians throughout the world, the researchers said.
The problem is not only unique to India
but also to many other countries in Asia that is still using DDT
as a pesticide in the agricultural and livestock industries.
Reference: Michele A. La Merrill et al. Exposure to Persistent Organic Pollutants (POPs) and Their Relationship to Hepatic Fat and Insulin Insensitivity among Asian Indian Immigrants in the United States, Environmental Science & Technology (2019). pubs.acs.org/doi/abs/10.1021/acs.est.9b03373