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Diabetes Epidemic Linked to Toxic Chemicals in Food & Environment

ON 10 July 1976, a reactor at a chemical plant near the small town of Seveso in northern Italy exploded, sending a toxic cloud drifting into the summer sky. Around 18 square kilometres of land was contaminated with TCDD, a member of the notorious class of industrial chemicals known as dioxins.

The immediate after-effects were relatively mild: 15 children landed in hospital with skin inflammation and around 3300 small animals were killed. Today, however, the accident casts a long shadow over the people of Seveso, who are suffering increased numbers of premature deaths from cancer, cardiovascular disease and, perhaps surprisingly, diabetes (American Journal of Epidemiology, vol 167, p 847).

To some diabetes researchers, Seveso serves as a warning to us all. Ask why diabetes is epidemic in the 21st century and most people will point the finger at bad diet, laziness and obesity. According to a small but growing group of scientists, though, the real culprit is a family of toxic chemicals known as persistent organic pollutants, or POPs. If these researchers are right, POPs - which include some of the most reviled chemicals ever created, including dioxins, DDT and PCBs - may be key players in the web of events that lead people to develop the disease.

The claim has yet to attract widespread attention from mainstream diabetes research. Even its champions were initially surprised by it. "I had never even heard of POPs until 2005," says Duk-Hee Lee, an epidemiologist at Kyungpook National University in Daegu, Korea, who led the work. Lee and her co-workers are now convinced, albeit reluctantly, that they are onto something. "The hypothesis is one that I wish were not true," says her colleague David Jacobs of the University of Minnesota, Minneapolis.

Diabetes, and particularly its commonest form, type 2 (see "Diabetes basics"), is practically everyone's business. The World Health Organization estimates that it already affects 180 million people worldwide, with the number predicted to more than double by 2030. Last year the epidemic cost $174 billion in the US alone, according to the American Diabetes Association.

The standard explanation for type 2 diabetes is that it is a "lifestyle disease" caused by laziness and gluttony. For at least a decade, however, epidemiologists have known that people briefly exposed to high concentrations of POPs face a modest increase in their risk of developing diabetes later in life. Those affected include the people of Seveso and US veterans who were exposed to dioxin-contaminated Agent Orange during the Vietnam war.

Two years ago, Lee, Jacobs and others decided to see whether everyday exposure to POPs is also linked to diabetes. To their surprise and horror, they found that it is.

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