Oct. 1, 2010 -- New research shows a strong link between diabetes rates and exposure to auto exhaust, industrial smoke, and other types of fine particulate air pollution.
People living in areas where air quality levels were near, but still below, the acceptable safety limits of the Environmental Protection Agency (EPA) had a more than 20% higher diabetes prevalence than people exposed to fewer air pollutants.
The link persisted even after researchers factored in the impact of known diabetes risk factors such as obesity, race, and sedentary lifestyle.
The study does not prove air pollution exposure contributes to diabetes risk, but it is the first large-scale, national study to explore a possible link.
“We know exposure to air pollution is a risk factor for cardiovascular disease,” says John Brownstein, PhD, of the Children’s Hospital Boston and Harvard Medical School. “This is just one more piece of evidence that pollution impacts health.”
Brownstein and colleagues combined county-by-county EPA data on fine particulate air pollution levels with nationwide diabetes figures from the CDC during 2004 and 2005. Obesity rates for specific areas, as well as population density, ethnicity, income, education, and health insurance coverage were measured using data from the CDC and the U.S. Census Bureau.
As expected, a strong relationship was seen between obesity rates in a given area and diabetes prevalence.
But the analysis also showed a strong and consistent association between diabetes rates and air pollution levels.
The study appears in the October issue of Diabetes Care.
“The most disturbing thing was that this was seen even in areas where pollution levels were considered acceptable by the EPA,” says study co-researcher Allison B. Goldfine, MD, of Harvard Medical School’s Joslin Diabetes Center.
In counties that did not exceed the EPA’s limits for fine particulate air pollution, those with the highest pollution levels had a more than 20% increase in diabetes prevalence after taking into account obesity rates and other known risk factors for the disease.
“The findings don’t prove air pollution is involved in the diabetes epidemic, but they suggest a role for environmental factors other than those related to what we typically think of as our Western lifestyle,” Goldfine tells WebMD.
The ‘Agent Orange’ Experience
In animal studies, chronic inflammation has been shown to promote insulin resistance, which leads to diabetes. Chemicals in air pollution have been linked to inflammation.
This link may be stronger in obese people, the researchers suggest, because many chemicals accumulate in fat.
“Obesity may play a critical permissive role in priming the body for pollution-induced inflammation and disordered metabolism,” they write.
American Diabetes Association Vice President of Medicine and Science Vivian Fonseca, MD, notes that there is precedent for the idea that chemical exposures increase diabetes risk.
Following the Vietnam War, many veterans exposed to the chemical dioxin through the widely used defoliant Agent Orange claimed the exposure caused their diabetes.
In 2000, the Veteran’s Administration added type 2 diabetes to the list of “presumptive” diseases associated with the herbicide exposure. The American Diabetes Association characterizes the evidence linking Agent Orange with diabetes as “modest.”
“This study is thought provoking, but it is certainly not definitive,” Fonseca tells WebMD. “It makes sense that exposure to air pollution might play a role in diabetes, but more research is needed to prove it.”
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