Endocrine disrupters and people

Detail from an ad for Grant Chemical Company's DES product, circa 1955. Courtesy Independent Television Service (ITVS), 1997.

Ambiguous, but still worrisome
Although the human harm from endocrine disrupters is not as clear as the animal harm, there's reason to worry. In terms of biochemistry, we're not that different from other mammals, where endocrine disrupters effects are clear, particularly in the reproductive apparatus.

But there was one giant "experiment" with endocrine disrupters on humans. DES was recommended to prevent miscarriages and premature labor Between the 1940s and 1970s, doctors prescribed an artificial estrogen named diethylstilbestrol, or DES, to prevent miscarriages in millions of pregnant women. Only long after the fact did doctors find that DES had caused a rare form of cervical cancer in some of their daughters.

Other evidence is more ambiguous. Several studies -- but not all -- have found a worldwide lowering of sperm counts, and blamed it on the rising concentrations of estrogen mimics in the environment. Some scientists say estrogen mimics could also explain the growing incidence of breast cancer and perhaps prostate cancer as well.

The putative endocrine disrupters have structures akin to real hormones, and seem to include:

			breakdown products of several pesticides that are now banned, such as DDT,
			PCBs, a persistent group of chemicals still found in electrical equipment that pollutes lake and stream sediments in many industrial regions,
			dioxins, a group of toxic chemical byproducts from paper production and incineration, and
			chemicals found in the epoxy lining of "tin" cans, plastics used for storing food, dental sealants, and Vinclozolin, a fungicide used on fruit.

Biochemically, we're not that different from other mammals.

Although some of these chemicals, like the PCBs, are off the market, they break down very slowly. Tests of people living as far from factories as the Arctic have found PCBs at levels that could be dangerous. In animal tests, remember, endocrine disrupters and hormones can act at tiny concentrations -- parts per trillion.

(What kind of fraction is one-trillionth? It's about the width of a magazine page -- compared to the distance to the sun.)

The congressional edict
The growing alarm over endocrine disrupters reached Congress. In September 1996, Sen. Alphonse D'Amato urged funding for a new screening program, citing "a growing concern over the effect of pesticides and other substances on human endocrine systems and their ability to increase the likelihood of disease, such as breast cancer."

The Congressional edict requires EPA to devise a strategy to screen chemicals for endocrine disrupters effects by August 1998. The EPA formed the Endocrine Disrupters Screening and Testing Advisory Committee (EDSTAC) to devise a rational process for assessing the hazards of environmental endocrine disrupters.

While much of the research to date has focused on estrogen disrupters, EDSTAC has chosen to include androgens (so-called "male" hormones) and thyroid hormones, which direct body growth and metabolism.

The screening job is a big order, since there are so many possible effects in so many animals -- from alligators to people wearing alligator shoes. But before we assess their prospects, let's stop back and ask some basic questions.

Like what are we really talking about, anyway?

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