Peter Montague
New York Times writer Gina Kolata on April 29 renewed efforts to discredit the theory and evidence that industrial chemicals interfere with hormones, causing harm to wildlife and humans. [Kolata's article was reprinted in the May 4 Sydney Morning Herald.]
A month earlier, Kolata savagely attacked the new book, Our Stolen Future, claiming that "careful studies" (none of which she cited) had "refuted" the premise of the book.
Our Stolen Future reviewed hundreds of studies published in peer-reviewed journals. The book offers substantial evidence that industrial pollutants may be interfering with the hormones that regulate growth, health and behaviour in wildlife and humans, thus contributing to birth defects, problems of sexual development, breast cancer, prostate cancer and even mental problems like attention deficit disorder, diminished IQ, and violent behaviour.
Among the evidence discussed in Our Stolen Future was declining sperm counts in men in industrialised countries, plus data and hypotheses linking such a decline to hormone-disrupting chemicals. In 1992, a report in the British Medical Journal analysed 61 previous sperm studies conducted in 20 countries, concluding that average sperm counts had declined from 113 million sperm per millilitre of semen to 66 million during the past 50 years, a 42% decline.
Kolata has made this her special cause, evidently determined to convince Times readers that there's nothing to it. On the same day that she maligned Our Stolen Future (March 19), Kolata published a second article in the Times about sperm counts. It is clear from Kolata's March 19 article that she requires little or no evidence to be persuaded that sperm counts are not declining. Instead of evidence, she offers two arguments:
(1) From 1960 to 1970 a million women were exposed to a synthetic sex hormone called DES. Recently, a large study of male offspring of DES-exposed mothers showed that these men are fertile, able to father children. Kolata apparently wants her readers to believe that this means DES did not cause a decline in sperm counts among these men.
(2) Kolata offers her readers the opinion that infertility is not increasing in the US. (There is some evidence that this is untrue. Congress's Office of Technology Assessment reported in 1985 that Americans in their prime reproductive years — ages 20 to 24 — have experienced an increase in infertility in recent years.)
These arguments are both straw men. Neither reveals anything important about sperm counts. The original analysis of 61 studies of sperm counts showed a decline from 113 million sperm per ml of semen in 1940 to an average of 66 million in 1990. Men are able to sire children with a sperm count as low as 20 million sperm per ml, and they are not definitely sterile until their sperm count drops to 5 million.
No-one has ever claimed that average sperm counts worldwide have dropped this low. Kolata has set up a straw man and triumphantly demolished it, but in the process has misled her readers about the question of declining sperm counts. (In fact a decline in sperm quality and quantity has been reported among the sons of DES-exposed women, along with underdeveloped and undescended testicles and stunted penises. These men were not sterilised but the sperm of many of them was definitely diminished by their mother's exposure to DES.)
In the Times on April 29, Kolata reviewed three recent studies of sperm, omitting mention of other recent studies that don't support her bias. She highlighted two new studies that indicate sperm counts have slightly increased over the past 25 years among students in Seattle, and among men preparing to have vasectomies in Los Angeles, New York and Roseville, Minnesota. Kolata describes a third study, by Harry Fisch, which re-analyses the 61 previous studies.
Kolata gives great weight to Dr Fisch's re-analysis of the 61 studies, which concludes that sperm counts may not be declining worldwide. Fisch argues that the "decline" in sperm counts is really just previously unnoticed "geographic variation" in sperm counts. In other words, sperm counts may not actually be declining; instead, they may be holding steady, but appear to be declining because there is so much variation between sperm counts in different locations.
Kolata failed to mention it, but to reach his new conclusions about worldwide sperm counts, Dr. Fisch threw out 41 of the 61 original studies, re-analysing only 20. He says he did this because the study populations in those 41 studies were small, involving all together only 9% of the original total study population. However, in so doing, Fisch reduced the number of countries involved from 20 to only 12. On the basis of the much smaller number of studies, from the much smaller number of countries, he concluded that sperm counts have not declined. Exclusion of so many relevant studies seems dubious at best.
Kolata explains Dr Fisch's findings this way: "Dr Fisch argues that the decline reported was probably a result of previously unappreciated regional variations in sperm counts. Most of the early studies, with the high sperm counts, involved New York men, whose sperm counts have remained among the highest in the world. Most of the more recent studies involved men from developing countries and their sperm counts, for unknown reasons, tend to be lower."
But is this true? Is Paris in a developing country? Is London? Is Brussels? Is Scotland a developing country? These are all places where good recent studies have reported declining sperm counts.
Kolata chose not to tell her readers about these important recent studies.
One new study reveals that sperm quantity has not changed for 20 years in rural Toulouse, France. The authors of the Toulouse study suggest that environmental factors might distinguish Toulouse from Paris, where sperm counts seem to be declining. Combined with the two new US studies, does the Toulouse study mean that all the other recent studies showing declines are wrong?
The US studies do not seem particularly persuasive. Students in Seattle are unlikely to be representative of the general populace. Neither, necessarily, are a self-selected population of men preparing to have vasectomies. A general decline in sperm counts could be occurring, yet might not be revealed by studies of these particular populations.
Based on the Toulouse study, we can say that it is good news that some populations can be found who may not be experiencing declines in sperm. But it is not news that some populations have high sperm counts and others have low. The original analysis of 61 studies in 1992 made this very clear.
No matter what is happening to the worldwide average, the question therefore remains: why is sperm count in some large populations low and/or declining? Gina Kolata seems to want her readers to believe that declines are not occurring and that low counts occur only in developing countries. But in his analysis Harry Fisch acknowledges the problem, and answers it this way: the "geographic variations" in sperm might be caused by environmental factors, nutrition, socioeconomic differences, or some other "unknown causes", he says.
In other words, it is entirely possible that "environmental factors", such as hormone-disrupting chemicals, are affecting some large populations, causing a decline in sperm. Back in 1983, the US Environmental Protection Agency identified 52 chemicals or groups of chemicals that adversely affected sperm (as well as 11 that enhanced sperm). We have already seen that DES had adverse effects on the sperm of sons of DES-treated women. Is there laboratory data supporting such an idea?
Elaborate new studies of mice, reported in Environmental Health Perspectives (a US government publication) in December, reveal that exposing pregnant mice to low levels of an oestrogenic chemical causes their male offspring to develop smaller-than-normal testicles and to produce less sperm than untreated mice.
Three separate industrial chemicals with oestrogenic properties were tested, and they all caused small testicles and diminished sperm counts. (DES was also tested, as a "positive control", and — no surprise — it had the same effect.) The oestrogenic chemicals used in these experiments are industrial pollutants commonly found in food and water.
Gina Kolata chose not to tell her Times readers about these important new animal studies.
[From Rachel's Environment & Health Weekly.]