Environmental exposure to dioxin-like compounds and the mortality risk in the U.S. population

Little is known about the mortality risk associated with chronic dioxin exposure in the general U.S. populations.

To explore the association between dioxin-like chemicals and mortality risk in a large population-based cohort study.

The analysis included 2361 subjects aged 40 years or older from the 1999-2004 National Health and Nutrition Examination Survey (NHANES). Exposure to a mixture of dioxin-like chemicals, including dibenzo-p-dioxins, dibenzofurans, and polychlorinated biphenyls was estimated using toxic equivalency values (TEQs) calculated with 2005 World Health Organization toxic equivalency factors. All-cause and cause-specific mortalities were obtained from the NHANES-linked follow-up data through December 31, 2006. Cox proportional-hazards models were applied to assess the associations of interest.

A total of 242 deaths occurred during the follow-up period, including 75 from cardiovascular disease and 72 from cancer. There was an increased mortality risk associated with logarithmically expressed dioxin TEQs for all-cause deaths (hazard ratio=1.19, 95% confidence interval=1.02-1.39, p=0.02). Similar graded dose-response trends were found for cardiovascular and cancer mortality which did not reach statistical significance.

In general, higher dioxin exposure is associated with an increased mortality risk among subjects aged 40 and above. The cause-specific analyses and responsible mechanisms will require further investigation.