Study Supports Finding of Male Fertility Decline

Offering new evidence that could support a fiercely debated theory that male fertility is decreasing because of environmental pollution, French researchers reported today that average sperm counts of Parisian men have declined by one-third in the last 20 years.

The analysis of more than 1,300 healthy men at a Paris sperm bank confirms the findings of several other European studies that sperm volumes have decreased dramatically over the last 50 years. But the new report goes further by suggesting that the decline is a recent and ongoing phenomenon.

In their study published in today’s New England Journal of Medicine, the French doctors also noted a significant decrease in the vitality of the sperm.

“We conclude that there has been a true decline in the quality of semen during the past 20 years, since the characteristics of semen from a fertile man of a given age in 1992 were significantly poorer than those of a fertile man of the same age in 1973,” the report states.

The findings have triggered a high-profile debate among clinical fertility experts and reproductive scientists. Some remain skeptical that the decline in sperm is real, saying that all the studies have faults that make it impossible to conclude what is happening to the general population.

“My basic gut reaction is that we still don’t have information from a properly done study to know if the sky is falling in regard to sperm counts,” said Dr. Arnold Becker, a clinical professor in the urology division of the University of Louisville School of Medicine.

But Dr. Earl Gray, the U.S. Environmental Protection Agency’s chief of developmental reproduction and toxicology research, said the new evidence is persuasive, especially because it is unlikely that several research teams are wrong.

“This is about the fourth paper that’s come out and reported that sperm counts are declining, each using a slightly different approach,” said Gray, whose EPA laboratory researches the effects of hormone-like environmental pollutants. “When you get four of these, you can’t refute all of them with these types of criticisms. . . . It’s really possible this is real.”

The study seems to add weight to an emerging but highly controversial theory that some pesticides and other chemicals that are widespread in the environment imitate estrogen or block testosterone in the womb, disrupting sexual development.

Studies of alligators in a Florida lake born with half male, half female sex organs, as well as tests on other animals in the wild and in laboratories suggest that DDT, PCBs and some popular pesticides are feminizing male fetuses and embryos by mimicking hormones. Some scientists speculate that man-made hormone disrupters in food and water may be responsible for falling sperm counts and increased testicular cancer in men.

The French doctors said they do not know the cause of the apparent sperm decline, but because the loss coincides with the use of modern chemicals this “could implicate factors affecting all the inhabitants of an area, such as the water supply or environmental pollution.”

However, in an editorial in the medical journal, Dr. Richard J. Sherins of Genetics and IVF Institute in Virginia, cautioned that the men studied were all sperm donors or men about to undergo vasectomies, so they may not represent the general population.

Sherins also said the studies may be inadequate because abstinence, age and other factors can make a major difference in sperm counts. Becker said it was unclear how many times the men in the Paris study were tested, but he said each subject should undergo sperm counts at least three times over a three-month period because counts fluctuate greatly.

In 1993, Danish researchers who reviewed the medical records of 15,000 European men reported a 42% decline in sperm counts between 1938 and 1990. But that study was widely disputed because it appeared that the decrease had occurred before 1970 and that sperm had increased in the last two decades.

The latest study by Dr. Jacques Auger and three other doctors analyzed the records of 1,351 sperm donors at the Center for the Study of the Conservation of Human Eggs and Sperm at a university hospital in Paris between 1973 and 1992. All were healthy and had previously fathered at least one child; 85% lived in the Paris area, and they represented a variety of occupations.

The research team reported that the 1992 concentration of sperm was 32.5% lower than 20 years earlier.

The French team also analyzed a smaller group of 382 men who were the same age--30--and who had abstained from sex for three to four days. The rate of decline in sperm count of these men was more pronounced than in the larger group.

The French researchers reported that they decided to analyze sperm bank records because they were skeptical of the earlier Danish results.

“They thought it was out in left field and they deliberately set out to discredit it, but they had to eat their words,” said Theo Colborn, a World Wildlife Fund biologist who monitors international research on hormone-like pollution.

Reproductive health experts who remain skeptical say that if sperm counts have been falling so dramatically, there should be a corresponding increase in male infertility. Some recent studies show male and female infertility rates appear constant over the last three decades.

“Despite the declining sperm concentrations reported . . . there is little evidence that male fertility is declining,” Sherins said.

Nonetheless, noting that the studies “heighten our awareness of the potential risks of environmental factors that can adversely affect reproductive function in both men and women,” Sherins called for a more thorough study that can monitor trends and causes of infertility.

However, some scientists say infertility may not be a reliable way of judging whether sperm counts are dropping.

If a man’s sperm volume is one-third lower than the past generation, he would still most likely have enough normal sperm to remain fertile and father a child. But a gradual decline in volume and quality could push some men who are borderline because of genetic factors into the ranks of the infertile.

Perhaps, Gray said, the impact is that some modern couples must try much longer to become pregnant.

If sperm counts are decreasing, many researchers suspect pollution could be to blame because similar reproductive problems have been found in many wild birds, reptiles and fish in heavily contaminated waters, such as the Great Lakes, and in laboratory animals exposed to certain pesticides.

Gray said although there is absolutely no scientific proof that human sperm counts are falling because of the pollution, it is a viable hypothesis because laboratory animals exposed in utero to hormone-imitating chemicals experience sperm and genital abnormalities.

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