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09-08-2011 | Cardiology | Article

Plasma dioxin levels not linked to increased cancer risk


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MedWire News: Plasma dioxin levels are associated with risk for all-cause mortality and ischemic heart disease in individuals exposed to herbicides, research shows.

Dioxin levels were not linked to an increased risk for cancer, however, with the exception of non-Hodgkin's lymphoma, report investigators.

The study failed to confirm previously reported risks for mortality from all cancers, including respiratory and urinary cancers, Roel Vermeulen (Utrecht University, the Netherlands) and colleagues report in the journal Occupational and Environmental Medicine.

The researchers explain that chlorophenoxy herbicides are used widely in agriculture, with chlorophenols used as a raw material for the production of herbicides and for wood preservation. Chlorophenoxy herbicides and chlorophenols can become contaminated with dioxins, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), during production, they add.

A previous study showed that Dutch workers exposed to chlorophenoxy herbicides had an increased risk for all cancers. However, this and other studies failed to link the risks with available qualitative exposure markers.

In the present study, plasma TCDD levels of 187 men working in herbicide factories between 1955 and 1985 were used to develop a predictive model for TCDD exposure. The researchers then used this model to estimate associations between time-varying TCDD exposure and cause-specific mortality in 2056 male workers from the same factories, 1410 of whom were still alive at the end of follow-up in 2006.

For each unit increase in TCDD exposure there was a 9% increased risk for death from non-cancer causes among the factory workers. Additionally, there was a 36% increased risk for non-Hodgkin's lymphoma for each unit increase in TCDD exposure.

There was no relationship observed between TCDD exposure and death from all cancers, including respiratory and urinary cancers.

The researchers also observed a significantly increased risk for accidents, poisoning, and violence among individuals with increased TCDD exposure. This suggests that the results might be "partly confounded by differences in risk profiles between exposed and non-exposed workers," they say.

A 19% increased risk for death from ischemic heart disease for each unit increase in TCDD exposure is consistent with previous data, according to the investigators.

They speculate that alterations in lipid metabolism occur after exposure to TCDD, and subsequently lead to cardiovascular disease. Other mechanisms, including pro-inflammatory effects of chlorophenoxy herbicides and chlorophenols might also be responsible, they conclude.

By MedWire Reporters

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