Sperm Shortage?

"Toxic Shock," in The Economist (Aug. 3, 1996),27 St. James's St., London SW1A 1HG

In the Great Lakes, female gulls have been found nesting with other females, having apparently given up on the males. In a Florida lake contaminated by pesticides, alligators have abnormally small penises. These and other strange incidents-along with studies claiming to show dramatic declines in human sperm counts and increases in testicular can- cer-have given rise, the Economist reports, to a new scare: the fear that artificial chemicals are wreaking havoc with the reproductive sys- tems of man and other animals.

"Many studies do indeed show sperm counts to be falling," the British news-magazine says. A 1992 review in the British Medical Journal of 61 such studies, involving a total of 15,000 men from around the world, concluded that the average sperm count had dropped by 42 percent since 1940-from 11 3 million sperm per milliliter of semen to 66 million. Suspicion has been cast on a num- ber of synthetic chemicals-including the insecticide DDT (which is now banned in many developed countries) and phthalates (widely used to make plastics softer)-that are believed to mimic estrogens, the female hormones.

"But the evidence looks messier on closer inspection," the Economist observes. One recent study showed slight rises in the sperm counts of men in various American cities since 1970. The fact that sperm counts, for reasons unknown, often vary hugely from region to region may explain the decline found in the British Medical Journal survey, since a large proportion of its early samples were taken from New York City, where men in the recent study had by far the highest sperm counts, while later samples were from outside the United States.

Even if "gender-bending" is going on, man-made chemicals may not be responsi- ble. Many naturally occurring chemicals also can act as hormone mimics. In a study pub- lished this year, the skeptical scientists of the European Science and Environment Forum say the estrogenic effects in the human diet from naturally occurring chemicals far out- weigh those of artificial chemicals, and no solid evidence exists that either sort poses any risk to human health. Other than chemicals, some possible "gender-bending" suspects are stress, global warming, and even, according to one recent study, tight underwear.