After more than 20 years of delays, the U.S. Environmental Protection Agency (EPA) has released its non-cancer science assessment for dioxins. The assessment establishes the first reference dose for dioxin exposure, and concludes that current exposures do not pose a significant health risk.
Dioxins are chemical byproducts that are released into the air from burning wastes and manufacturing processes that involve chlorine, including some plastics. The EPA data shows that industry releases have dropped over the past two decades, however, the chemicals still get into the air — and eventually meat, poultry, and dairy products — from backyard trash fires.
Cheryl Hogue at Chemical & Engineering News explains the reference dose:
The agency’s report… sets a safe daily dose of 0.0007 nanograms of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) per kilogram of body weight. This limit is based on a study finding adverse reproductive effects in men exposed to the chemical as boys and a study finding hormonal effects in infants born to mothers who were exposed to the substance. TCDD is the most potent form of a family of chemicals commonly called dioxins. It includes other chlorinated dioxins and furans and [polychlorinated biphenyls].
Reactions to the assessment were mixed. Bill Tomson at The Wall Street Journal reports that “the food and chemical industries have argued the EPA is using flawed science and will scare Americans about the food they eat, but federal officials said there will likely be no new regulations to restrict dioxin in food.”
Rebecca Trager reports on reaction to the assessment in Chemistry World:
Even supporters of the dioxin reassessment… express concern that the agency has failed to address the increased vulnerability to dioxin exposure of the unborn, as well as breast-feeding infants and adults with immune system problems.
They emphasise that sensitivity varies across the population, and fetuses and nursing children are at greater risk because their organs are still forming. Breastfed infants in particular receive a very large dose of dioxins in the fatty part of the mother’s milk, they argue.
“Although the agency concluded that most Americans have low-level exposure to dioxins,” Trager adds, “it noted that non-cancer effects of exposure to large amounts of dioxin include developmental and reproductive effects, immune system damage, hormone interference, skin disorders and possibly mild liver damage.”
So, do Americans need to change their eating habits? Tomson quoted the FDA’s response to the assessment: “Consumers should eat a balanced diet and follow the Dietary Guidelines for Americans, 2010, and should not avoid any particular foods because of dioxin.”
But Arnold Schecter, a professor of environmental and occupational health sciences at the University of Texas and a science advisory board member of a 2011 EPA dioxin review panel, told Tomson that this advice is irresponsible. Schecter advised that dioxin is a deadly toxin linked to cancer, and to lower their daily intake of dioxin, people need to reduce their consumption of animal fats.
The EPA is expected to release a separate report on cancer threat related to dioxins in the future.
Source: “EPA sets safe dioxin level,” Chemistry World, 2/23/12
Source: “EPA Updates Health Risks of Dioxins,” The Wall Street Journal, 2/17/12
Source: “Dioxins, Assessed At Last,” Chemical & Engineering News, 2/17/12
Image by Will Paddle, used under its Creative Commons license.
Rachel Petkewich is a freelance science writer and editor. She has worked as a research scientist in the chemical industry and spent eight years as a staff writer and editor at various science journals and magazines, including Chemical & Engineering News.