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From May 21, 2001

Hormone Mimicking Chemicals Effect Test Animals at Low Levels

A panel of academic, government and industry scientists have determined that some hormone-like chemicals can affect test animals' bodily functions at very low levels - well below the "no effect" levels determined by traditional testing. The 36-member panel said the chemicals, often called "environmental estrogens" and endocrine disruptors" deserve greater scrutiny and additional research.

The National Toxicology Program (NTP), headquartered at the National Institute of Environmental Health Sciences (NIEHS), released the experts' draft report on May 14, 2001 for a 60-day comment period before sending it to the EPA, which requested the panel review.

The panel found evidence that increases in prostate weight and/or changes in female reproductive organs can occur in rodents or other test animals from low doses of estrogen and from several other estrogenic compounds, including the insecticide methoxychlor. Five types of studies were recommended for a group of chemicals which are related to testosterone. These chemicals include the fungicide vinclozolin, which when pregnant rats were exposed to it appeared to cause changes in the reproductive organs of both female and male offspring.

The panel said EPA should obtain the best advice of experts who design tests and then consider rewriting the "guidelines" that industry must follow in having their new products tested before EPA approval. The panel said that additional multi-generational studies might use a range of different dosages to better determine if any reproductive problems result in the offspring or grand-offspring of exposed animals.

Some of the hormones, like estrogen and testosterone, occur naturally. Other chemically related substances are manufactured for packaging, plastics, pesticides and other products of modern life.

Kenneth Olden, Ph.D., director of NIEHS and NTP, said, "In a first for this kind of review, the panel was able to obtain the raw data from nearly all of the studies. Nearly 100% of the scientists were able to cooperate in this. This permitted a statistical reanalysis of the data, rather than merely a reliance on the conclusions of published papers."

Because of years of controversy over some of the studies and their meaning the review has attracted attention from environmentalists, industry, as well as government and academic scientists worldwide.

For a copy of the report, see http://ntp-server.niehs.nih.gov/htdocs/liason/LowDosePeerFinalRpt.pdf.

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