Sperm Wars


Here's some good news from the frontiers of science: Sperm counts are not declining. Then again, what's good news for most people is bad news for environmentalists who want to scare people out of their wits.

In recent years, Greenpeace and other groups have pointed to an apparent decline in sperm counts in America and elsewhere as evidence of the dangers posed by man-made chemicals. Citing the threat of hormonal problems and infertility, activists have called for sweeping bans on entire classes of pesticides, plastics, detergents, and other products. Products that contain chlorine have been singled out as particularly dangerous.

When it was pointed out that no clear link had been established between sperm counts and consumer products, environmentalists countered with the "Precautionary Principle"–the idea that possibly harmful products should be banned even before the evidence is in, just to be on the safe side. (See "Precautionary Tale," page 36.) To drive home the point, environmentalists conjured up nightmare scenarios of the human race becoming unable to reproduce in the 21st century.

Dubious though such arguments were, there did seem to be at least some reason for concern: Sperm counts had apparently dropped from the late 1930s to the mid-1990s. But in the February issue of the Journal of Urology, researchers at Columbia-Presbyterian Medical Center document that the decline was only a statistical illusion.

The confusion arose from an intriguing fact: Sperm counts vary from one city to another. The reasons for such geographic variation are not yet understood–they may have to do with climate and seasons, or with factors such as demography and nutrition. They may be partly due to different methods used to select volunteers in different times and places. In any event, it so happens that most men studied in the early decades came from a single city, the one that has the highest measured sperm counts in America: New York.

To be precise, 87 percent of those studied before 1970 were from New York. After 1970, as more wide-ranging research was conducted, New York's share of the studied population shrank to 25 percent. On average, New York-based studies showed sperm levels about a third higher than non-New York studies (the New York effect skewed international statistics as well). After correcting for the disproportionate emphasis on New York in the early data, the downward trend disappears. As the Columbia-Presbyterian researchers put it, "there appears to be no significant change in sperm counts in the U.S. during the last 60 years."

New York's high rank in sperm counts may boost a few egos or lead to some jokes (at the very least, we can expect Mayor Rudolph Giuliani to take most of the credit). But the findings are no laughing matter. Neither is the answer to the serious question raised by them: Will environmental groups retract their unsupported claims that man-made chemicals are wreaking hormonal havoc?