All the above have been blamed for a fall in the number of men able to produce sperm in normal quantities at some time in the past five years. Low sperm counts are a characteristic of Mafia members, according to one, somewhat suspect, study, while men who eat organic vegetables can, it is claimed by other, more reliable researchers, boast dizzying amounts of super-sperm.
Sperm is always good for a laugh - or a headline - and the latest research from Finnish scientists is no exception. Examination of testicular tissue revealed a dramatic drop in the number of middle-aged men capable of producing normal sperm, from 56.4 per cent in those who died in 1981 to just under 27 per cent in those who died in 1991. The weight of the men's testicles also diminished over the decade; their seminiferous tubules were smaller, and there was increased fibrotic (useless) testicular tissue.
With falling sperm counts and more defective sperm being reported throughout Europe and North America, the study, published last week in the British Medical Journal, appears to furnish more evidence that not only is the very essence of masculinity threatened, but also the future of humankind. Or is it?
The contribution of Dr Jarkko Pajarinen and his team at Helsinki University is yet another piece of the complex puzzle that is the Great Sperm Debate. It is significant because the scientists looked at sections of testes removed from more than 500 cadavers. They did not rely on sperm counts, which are unreliable, subject to numerous confounding factors and with wide variations in methodology. The changes they observed between the two groups of men also took place over a short time span, which added to the enormous scientific and public interest.
The findings are "quite dramatic", says Dr Stewart Irvine, director of the Medical Research Council's reproductive biology unit in Edinburgh, which is at the forefront of research into the potential sperm crisis. "It suggests there is something interesting about the population they were looking at."
And yet there is no hard evidence so far that fertility is declining. "That might be because we are well within safety margin [of sperm levels]. It is anybody's guess what level of sperm is too low," Dr Irvine says. In addition there have been about 10 good papers published, most notably from scientists in New York and Seattle, which have reported no drop in sperm counts or semen quality - though medical journals are less keen to publish, and newspapers less keen to report, findings which detract from the doomsday scenario.
That is not to say that something worrying is not going on in the reproductive tracts of men worldwide. Fewer, less mobile sperm, more defective sperm, together with escalating rates of testicular cancer, undescended testes in childhood and other testicular abnormalities, suggest that something is amiss.
Later this month the United Nations will host a two-day conference in Washington DC when around 70 experts will debate the need for global co- ordination and research into sperm counts, semen quality, and testicular abnormalities and disease. The most likely outcome is that the UN will endorse such a project and one of the research priorities will be the "oestrogen hypothesis", still the most promising explanation for the changes being observed.
It was Dr Richard Sharpe, a male fertility specialist at the MRC's Edinburgh unit, and Professor Niels Skakkebaek of Copenhagen University, who, in a paper published in The Lancet in May 1993, first proposed that the female hormone oestrogen was implicated. Professor Skakkebaek is the man credited with alerting the world to the possibility of falling sperm counts in 1992, when he showed that sperm counts in healthy men appeared to have dropped by more than half in 50 years.
The Skakkebaek team reviewed studies involving almost 15,000 men between 1938 and 1992 and found that the average sperm count had fallen from 113 million per millilitre in 1940 to 66 million in 1990. The definition of a "normal" sperm count fell from 60 million per millilitre to 20 million in the same period. Two studies in France and Belgium in 1994 confirmed and strengthened the original findings.
In their Lancet paper, Sharpe and Skakkebaek proposed that exposure to more than the normal level of oestrogen - in natural or synthetic forms - in the womb at a critical period of foetal development could be responsible for the abnormalities of the reproductive tract. A possible culprit was a drug known as DES (diethylstilboestrol), taken by six million women worldwide between 1945 and 1971 to prevent miscarriage.
Moreover, the exposure to oestrogen of the general population has increased significantly since the Forties through the consumption of hormone-boosted dairy produce, the contraceptive pill, other drugs containing synthetic oestrogens and a wide range of man-made chemicals that mimic the effect of oestrogen. These so-called "gender-bending" chemicals occur as phthalates in plastics and food packaging, in detergents and pesticides such as DDT, in exhaust fumes, as PCBs in electronics - and, at very low levels, in some baby milks, which prompted a scare last year.
These "false" oestrogens are difficult to break down and persist in body fat longer than natural oestrogen, to levels 100 or 1,000 times greater than background levels. The result may be devastating for oestrogen-sensitive tissues in the body: the reproductive tract, the breast and womb, and, most worryingly, the developing foetus.
In July 1995 Professor Lewis Smith, director of the Institute for Environment and Health at Leicester University, reported on a review he has conducted of international research. He found an abundance of circumstantial evidence for the oestrogen hypothesis. There was no direct causal link but he did not rule it out, and the Government gave an undertaking to scrutinise more closely the gender-bending chemicals.
The starting point for the oestrogen hypothesis was a wildlife haven called Lake Apopka, near Orlando. Between 1980 and 1984, the death rate for alligator eggs on the lake was found to be running at around 96 per cent, compared to a figure of 57 per cent for lakes nearby. Scientists called in to investigate found numerous sterile male alligators with shrunken, useless penises. A tentative link was made with an accidental spillage of thousands of gallons of DDT into the lake in 1980.
Similar phenomena were then reported in the Great Lakes of North America. Then on the south coast of Britain female dog-whelks developed "pseudo- penises" and "feminised" male fish were found near the sewage outlets in British rivers. Oestrogen was blamed again.
These pieces of the puzzle have fitted together neatly enough to please the environmental lobbyists, who now blame gender-bending chemicals; but scientists have yet to be convinced. A conclusion may be some way off.Reuse content