Report Spotlights Low-Dose Effects of EDCs

April 19, 2012
Debate on the impact of endocrine-disrupting chemicals could prompt more testing.

The hazards of endocrine-disrupting chemicals (EDCs) have been well chronicled in recent years and are the focus of research on many fronts.


Much work has centered on bisphenol A (BPA), a chemical that's been present in many hard plastic bottles and metal-based food and beverage cans since the 1960s.

A chapter in the ongoing debate about this particular EDC seemed to close on March 30 when the U.S. Food and Drug Administration (FDA), Washington, D.C., rejected a petition from the Natural Resources Defense Council (NRDC), New York City, to ban BPA in food-contact materials.

The FDA's decision was promptly welcomed by the American Chemistry Council (ACC), a Washington, D.C.-based group to which most major American chemical makers belong. "FDA's decision … which has taken into consideration the best available science, again confirms that BPA is safe for use in food-contact materials, as it has been approved and used safely for four decades. FDA has closed the book on NRDC's 2008 petition and clearly resolved that there was no scientific evidence presented that would warrant any change in the food-contact applications of BPA," said Steven G. Hentges of the ACC's polycarbonate/BPA global group.

"Consumers should understand from this announcement that the position of the independent, scientific experts at FDA is that BPA continues to be safe for use in food-contact materials. FDA's scientific review is consistent with the consensus of major government agencies around the world, including the European Food Safety Authority, the Japanese National Institute of Advanced Industrial Science and Technology and the German Federal Institute for Risk Assessment," he added.

While food packaging is under the jurisdiction of the FDA, the U.S. Environmental Protection Agency (EPA) has the broader regulatory role when it comes to EDCs. The EPA says that because BPA is a reproductive, developmental and systemic toxicant in animal studies and is weakly estrogenic, there are questions about its potential impact, particularly on children's health and the environment.

"Studies employing standardized toxicity tests used globally for regulatory decision-making indicate that the levels of BPA in humans and the environment are below levels of potential concern for adverse effects. However, results of some recent studies using novel low-dose approaches and examining different endpoints describe subtle effects in laboratory animals at very low concentrations. Some of these low-dose studies are potentially of concern for the environment because the concentration levels identified with effects are similar to some current environmental levels to which sensitive aquatic organisms may be exposed," notes the EPA.

These concerns also appear in a study to be published in June in The Endocrine Society, Chevy Chase, Md., journal Endocrine Reviews. The study says the EPA's current definition of low-dosage doesn't fully take into account the unique influence that low doses of EDCs, such as BPA, have on disease development in humans ("Hormones and Endocrine-Disrupting Chemicals: Low-Dose Effects and Nonmonotonic Dose Responses," June 2012).

It found that low doses of EDCs, which are comparable to the average person's environmental exposure to these chemicals, can result in significant health effects.

"Whether low doses of EDCs influence disorders in humans is no longer conjecture as epidemiological studies show that environmental exposures to EDCs are associated with human diseases and disabilities," said Laura Vandenberg of Tufts University, Medford, Mass., and lead author of the study. "Current testing paradigms are missing important, sensitive endpoints and fundamental changes in chemical testing and safety determination are needed to protect human health."

In this study, researchers reviewed current EDC literature and explored the relationships between dose and effect. They found this relationship could be non-linear; meaning the EDCs' effect on the body varied within the range of doses examined. The report provides a detailed discussion on the mechanisms responsible for generating this phenomenon, plus hundreds of examples from cell culture, animal and epidemiology literature.

"Low-dose effects are remarkably common in studies of natural hormones and EDCs," said Vandenberg. "We recommend greatly expanded and generalized safety testing and surveillance to detect potential adverse effects of this broad class of chemicals. Before new chemicals are developed, a wider range of doses, extending into the low-dose range, should be fully tested."

SEÁN OTTEWELL is Chemical Processing's Editor at Large. You can e-mail him at [email protected].

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