Dr. David Carpenter is a Professor of Environmental Health and Toxicology at SUNY-Albany. (Courtesy of Institute for Health and the Environment/ SUNY-Albany)
A recent study suggests that high body levels of persistent organic pollutants, also known as POPs, may be linked to increased risk of diabetes. Host Bruce Gellerman talks to POPs expert Dr. David Carpenter of the State University of New York at Albany about the findings.
GELLERMAN: Among the most pernicious substances ever created is a group of chemicals known as POPs or Persistent Organic Pollutants. Among them: DDT, dioxins, PCBs and Chlordane. And even though twelve POPs – the so-called “dirty dozen” were restricted or banned by international convention in 2003, they continue to pose a threat to people and wildlife because POPs accumulate in the food we eat. Virtually every person on the planet has POPs in their body and the chemicals have been linked to cancers, birth defects and disabilities. Now a group of researchers in Korea have found strong evidence linking POPs and diabetes.
David Carpenter, Professor of Environmental Health and Toxicology at the State University of New York at Albany, reviewed the Korean study for Living on Earth. So, Dr. Carpenter just how strong a relationship did the Korean scientists find between diabetes and POPs?
CARPENTER: Well, one considers individual pollutants the magnitude was between three and five fold increased risk but the most striking observation was when they considered the sum of all six pollutants that they monitored and they selected pollutants that we all have in our bodies so that very few individuals had levels below the level of detection. Under those circumstances they were getting increased risk of the order of thirty-eight fold which is absolutely enormous.
GELLERMAN: Well what does that mean? Does that mean the higher your exposure to these kinds of chemicals the higher your likelihood of getting diabetes is?
CARPENTER: Well the authors are very careful to not say directly that the presence of diabetes is caused by exposure to these chemicals. Clearly the authors think that that is the case, but no single study is going to prove that. The most interesting observation in this paper is that there was no relationship between being obese and developing diabetes in those persons that did not have high levels of these organic pollutants in their bodies.
GELLERMAN: Well, how do you explain that? I always thought, well, the fatter you were the higher the likelihood that you’d get diabetes.
CARPENTER: Well that certainly is the general medical view because there is a strong association between obesity and diabetes, but it may well be that people that are obese eat much more animal fat than people that are not obese and these persistent organic pollutants are all found in animal fats. So the question really is whether it is the obesity that leads to the diabetes or rather the presence of these persistent organic pollutants. It may well be that it’s the pollutants that cause the diabetes, not the obesity.
GELLERMAN: Or it could be diabetes causes a higher buildup or retention of these POPs.
CARPENTER: That is correct and the, the authors make that statement and clearly don’t expect that that’s the explanation but their study does not disprove that that’s a possibility.
GELLERMAN: So what could be the mechanism by which these pollutants are related to diabetes?
CARPENTER: Well, certainly there is nothing in this paper that definitively identifies a mechanism. But we do know a number of actions of these compounds that suggest possible mechanisms. When these compounds bind to the liver they induce various genes. Some of those genes are involved in regulation of glucose uptake into cells and we think that it is that process that leads to this disruption of glucose regulation and causes diabetes.
GELLERMAN: Now, 20 million Americans have diabetes and we all have these POPs in us but how come not all of us get diabetes?
CARPENTER: Well, we don’t have these POPs in our bodies at the same concentration and that’s the strength of this particular study. The amount of persistent organic pollutants in each person’s body is a reflection of their diet, where they live, what the concentration of these substances is in the air they breathe, and probably related to how rapidly they metabolize these compounds.
GELLERMAN: Now, these compounds have been banned for many years by international convention.
CARPENTER: That’s correct, yes. The Stockholm Convention and, well in the US for example PCB manufacture was banned in 1977 and DDT and these other pesticides were banned even before that, however they are very persistent. They have been continued to be manufactured in some parts of the world until relatively recently and the dioxins are byproducts of combustion so they still are produced. And in the human body these compounds last about ten years before you get rid of half of them. In the environment they’re even more persistent.
GELLERMAN: So what can we do with this information?
CARPENTER: Well I think there are a number of things. We’ve got to get these compounds out of our environment and that requires political action and that’s not easy to do and it’s not inexpensive. We have many contaminated sites filled with things like PCB’s and dioxins that have not been cleaned up and remediated. I’ve already indicated that reducing our consumption of animal fats is an important thing that one could do.
GELLERMAN: You know Dr. Carpenter, as I hear you talk about this it seems this is the revenge of Silent Spring. That Rachel Carson had it absolutely correct 50 years ago.
CARPENTER: That’s absolutely right. This is the same issue from Silent Spring. We have not really appreciated how dangerous these substances are to human health. The diseases most people of, diabetes, heart disease, cancer, these are the chronic diseases of old age. All of these diseases are aggravated, increased, we’re more susceptible to them when we’re exposed to these compounds and now we’re reaping the grim harvest of the exposure that we all have to these compounds.
GELLERMAN: Dr. Carpenter, I want to thank you very much.
CARPENTER: My great pleasure.
GELLERMAN: Thank you very much.
GELLERMAN: Dr. David Carpenter is a Professor of Environmental Health and Toxicology at the State University of New York at Albany.
“A Strong Dose-Response Relation Between Serum Concentrations of Persistent Organic Pollutants and Diabetes. Results from the National Health Examination Survey 1999-2002” in Diabetes Care 29:1638-1644
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