Being Too Fair With Carcinogenic Chemicals

Minnesota schoolchildren are finding deformed frogs by the thousand. Frog and toad populations are plummeting mysteriously in many parts of the world. Now comes a report in the Journal of Environmental Toxicology and Chemistry about researchers in Switzerland exposing developing frogs to a fungicide called triphenyltin. (Minnesota sugarbeet farmers use over 100,000 pounds of triphenyltin a year. Georgia farmers use even more on pecans.) The fungicide stunts the growth of tadpoles and retards the sexual development of adult frogs. It acts differently on different species, but, says one of the researchers, the chemical "may contribute to the ... decline of populations of more-sensitive amphibian species."

The Kansas City Star reports that households in northeast Kansas are being supplied with bottled water, because unacceptable levels of a cancer-causing chemical have been found in their drinking water. The chemical, vinyl chloride, was first found to be harmful when it caused cancers in workers in polyvinyl chloride (PVC) plastic factories. The source of the chemical in the Kansas water is PVC piping made before 1975. Those early PVC pipes, it turns out, leach vinyl chloride into water.

An article in press in the journal Environmental Health Perspectives says that a whole family of widely used chemicals tests positive for estrogen mimicry. Estrogen is a powerful hormone, a message-carrier that regulates sexual development and behavior in both males and females. Chemicals that behave like estrogen can mess up the body's signaling systems, especially the system that tells an embryo how to develop into a healthy, functional baby.

The suspicious chemicals are called hydroxylated diphenylalkanes or bisphenols. They occur in plastics used for everything from household dishes to drinking water containers (that Kansas bottled water might have problems of its own) to the enamel substitutes used to fill teeth. The new article says, "Because diphenylalkane derivatives are widespread and their production is increasing, potential exposure to estrogenic diphenylalkanes both in the workplace and the home environment is becoming a significant issue. The hazardous effects of continuous exposure to bisphenol-releasing chemicals in exposed workers and in general populations demand investigation."

Then there are the alligators. A pesticide spill about 15 years ago in a Florida lake called Apopka led scientists to be worried about estrogen-mimicry in the first place. The pesticide caused the alligators in the lake to develop improperly, especially the males, which had shrunken penises and could not reproduce.

New research, published last month in Environmental Toxicology, reveals that it doesn't take a spill to emasculate alligators; agribusiness as usual will do the trick. The male alligators in three Florida lakes, including huge Okeechobee, have depressed testosterone levels. Females have elevated levels of estradiol, the principle estrogen found in all vertebrates. The alligators also have problems with thyroid hormones, which govern brain development and metabolism.

"It raises a major red flag for us," said researcher Louis Guillette to a Reuters reporter. "It could mean that these animals would not mature properly. They could have altered reproduction. They could have altered resistance to disease. In Florida, we have a couple of major problems. We have extensive development taking place that's very rapid. And we have growing seasons that go 12 months out of the year," so there's no let-up in the use of pesticides.

The point isn't to worry about any one chemical. The point is that our "innocent till proven guilty"attitude toward chemicals in general is building up a lengthening history of damage and regret. If we were watching that history from the perspective of a different culture or planet, we would surely wonder whether those crazy folks would ever stop doing chemistry experiments on themselves and their world.