WASHINGTON, Jan. 5 (UPI) -- A preliminary study has found Americans who live near toxic waste sites are hospitalized more for diabetes than those who live in clean communities.
The observational study, which tracked hospitalization rates for patients in New York between 1993 and 2000, found an increase in diabetes-related hospital admissions for people who live in ZIP codes containing toxic waste sites.
Although just an initial effort, the study does narrow the search for an answer to the U.S. diabetes boom, said study author Lawrence Lessner, an associate professor of epidemiology and biostatistics at the University at Albany in New York.
The study appeared in the January issue of Environmental Health Perspectives.
The researchers compared hospitalization rates by ZIP code for three types of communities: clean, without hazardous sites; contaminated by persistent organic pollutants, or POPs; and containing other types of waste or pollutants.
The authors examined whites and blacks between the ages of 25 to 74, correcting for potential factors that could skew the data, such as age, race, sex and average household income.
A major type of POPs are polychlorinated biphenyls, or PCBs, a former industrial ingredient of pesticides, paints, paper and other products. Although banned from U.S. industry in the 1970s, PCBs still exist in the environment. People are mainly exposed through eating animal fats, although they can also breathe in the pollutants.
Possible mechanisms for the association with diabetes are unknown, although some speculate that PCBs may influence the retention of fat in the body; more body fat is a risk factor for diabetes.
Likewise, PCBs may impair genes from working properly, said David Carpenter, director of the Institute for Health and the Environment at the University at Albany. The compounds cannot be broken down by the liver, and so they may alter the gene that regulates insulin sensitivity. Type 2 diabetes occurs when cells become less responsive to insulin. In addition, the pollutants may be especially potent in a person who already has a genetic predisposition to diabetes.
Carpenter was also surprised to find that people who inhabited areas rife with other waste or pollutants -- such as metals, radiation and volatile organic compounds -- also had higher rates of hospitalizations; he only expected to find this association with POPs.
Such results suggest environmental triggers of diabetes, a fairly new research area, are worthy of more investigation, Carpenter said. As type 2 diabetes has exploded -- a two-fold increase from 5.8 million to 13.3 million Americans from 1980 to 2002 -- scientists have scrambled to find explanations for the rise. Although experts often point to the obesity epidemic, that alone can't account for it, Carpenter said.
Indeed, the "evidence is accumulating rapidly that environmental exposures are very important factors," he said.
Dr. Larry Deeb, president of medicine and science at the American Diabetes Association, also stressed obesity can't be the only culprit for the dizzying increase in diabetes.
He noted the associations in the study between toxic waste exposures and hospitalizations were small, but were there nonetheless, and the idea of environmental factors is intriguing.
The study has limitations, as with any observational research. The results are too preliminary to assume any causation between toxic pollutants and diabetes. Likewise, PCBs likely require an unknown amount of time to incubate before a disease occurs.
The authors could not gather behavioral information on the patients or find out long they'd lived in their neighborhoods. It's possible some patients did not live in their homes long enough to see the effects of PCBs.
Although it's too early to draw conclusions about pollutants and diabetes, Carpenter points out one public-health message is clear: "We should do whatever we can to reduce exposure to these compounds coming from waste sites."
