globeandmail.com: Environment
Humanity at Risk: Are the Males Going First?
by Martin Mittelstaedt Globe and Mail September 20, 2008
Something is happening to today's boys and men: Fewer are being born compared with girls, they're having more trouble in school, virility and fertility are down and testicular cancer rates are up. Now, scientists say these 'fragile males' may be more vulnerable than females to pollutants, affecting their development as early as the womb. If so, writes Martin Mittelstaedt, it could be a bigger threat to our future than global warming
The first clue was how difficult it was becoming to find enough young boys to cobble together a baseball team.
Then, women in prenatal groups started remarking on how everyone in their groups was having girls.
Jim Brophy remembers those casual observations with vivid clarity, and how they eventually led to one of the most puzzling scientific findings in Canada - the lopsided tally of girls compared with boys being born in the Aamjiwnaang First Nation, a community nearly surrounded by a complex of petrochemical plants.
Mr. Brophy, who runs the occupational-health centre of nearby Sarnia, Ont., was holding discussions five years ago with residents worried over the discovery of elevated levels of mercury and lead in soil on the reserve. Out of the blue, someone asked if anyone else had noticed anything odd going on - like more girls being born than boys.
"It was almost like somebody had told the family secret," Mr. Brophy recalls.
The impression was quickly backed up by a check of band records: In some years, nearly two girls were being born for every boy - a major anomaly given that the normal boy-girl sex ratio is 106 to 100.
The Sarnia area has been prone to many pollution-related woes, but the implications here seem to be arising all over the world: Males may be the more fragile sex when it comes to exposure to modern chemicals, from the embryonic stage on.
The recent sci-fi thriller Children of Men imagined a world population doomed to extinction when, over the coming years, every last human being on Earth becomes infertile. Now, some scientists are painting a similarly frightening picture of a widespread threat to male birth rates and later virility and fertility; what's more, they believe serious damage to men and boys is already occurring.
Researchers tracking childhood behavioural disorders, sperm counts, testicular cancer and even the shrinking size of male gonads are convinced that something is amiss.
The University of Pittsburgh's Devra Davis, in a study issued last year, found that the U.S. and Japan combined had a staggering tally of 262,000 "missing boys" from 1970 to about 2000 because of a decline in the sex ratio at birth. Although it could be a statistical anomaly, she says the figure is "very worrisome."
Dr. Davis, director of the Centre for Environmental Oncology at the University of Pittsburgh Cancer Institute, points out another disturbing trend - the rise in what scientists have dubbed testicular dysgenesis syndrome, a catch-all phrase for a raft of male reproductive-system ailments.
Among them is hypospadias, a disfiguring penis abnormality in babies where the urinary opening is on the underside rather than its normal position on the tip. The condition is not new, but boys today are far more likely than their fathers to be born with it. The incidence, adjusted for population size, is up about 60 per cent since the mid-1970s in Canada. Other countries have also experienced increases.
The incidence rate of testicular cancer in young Canadian men aged 20 to 44, for reasons unknown, has risen 54 per cent from 1983 to 2005, according to figures compiled by Cancer Care Ontario.
And levels of testosterone - the hormone that choreographs male development from libido to muscle mass - have inexplicably declined in U.S. men over the past two decades by nearly 20 per cent.
A recent study found that women in the San Francisco area during the 1960s who had higher levels of PCBs gave birth to a third fewer boys than women with low amounts of the chemical, suggesting in utero exposures to the now-banned toxin were able to cull males.
Oddities among males are also occurring in the animal kingdom. Studies in the laboratory and in the wild show that man-made contaminants often attack males of different species with greater ferocity.
Researchers at the University of Florida found that about 35 per cent of male toads from heavily farmed areas of the state exhibited intersex (or hermaphrobitic) attributes: Males showed female coloration and ovarian tissue growing near their testes. Compared with toads in suburban areas, the farmland males also had lower levels of testosterone, more on par with females, suggesting that something related to agricultural practices was feminizing the male amphibians.
For Dr. Davis, there are just too many peculiar things happening to be mere coincidence. "These things theoretically have a common etiology," she says. "Something is tweaking what we can think of as boy-making cells."
HORMONAL HAVOC
A theory rapidly gaining currency is that man-made substances are upsetting the intricate working of hormones - the chemical messengers that even in mere parts per trillion are able to control key aspects of sexual and mental development.
During fetal development, all humans begin life as female, with some assuming male characteristics only after prodding from hormones. If hormones aren't at precisely the right levels in the womb, something in that process might go awry.
University of Florida zoologist Theo Colborn is often heralded as a modern-day version of environmental prophet Rachel Carson. In 1996, she co-wrote Our Stolen Future, which first raised the possibility that synthetic chemicals may interfere with normal hormone functioning. More recently, she has begun giving lectures on "the Male Predicament."
"I definitely feel that the males are really suffering more," says Dr. Colborn, who is also president of the Colorado-based Endocrine Disruption Exchange.
Among her biggest fears is that some chemicals are able to harm brain development, with greater impacts on males than females. She is worried that this attack on male thinking may pose an even greater threat to society than global warming.
She backs up that astonishing claim in part with the observation that two to four times more boys than girls are afflicted by the modern scourge of attention-deficit and hyperactivity disorders. She also contends that chemical exposures could explain why female enrolment at U.S. and Canadian universities is outstripping male, currently at 60 to 40 per cent. (In the U.S., colleges such as Lake Erie in Ohio are establishing new football teams just to lure more males onto their campuses.)
The most insidious of the hormonally active chemicals may be the ones that mimic the powerful female hormone, estrogen. Compounds as diverse as pesticides, plastics, mercury and uranium are able to fool cells into thinking that they are dealing with estrogen rather than a artificial imposter.
"You don't have to be a PhD biologist or doctor to know that pouring estrogen into a male is not a good idea," says Frederick vom Saal, a U.S. biologist who has done pioneering research into the harmful effects of bisphenol A, which is used in polycarbonate plastics. In April, Health Canada proposed adding it to the country's toxic-substances list.
Dr. vom Saal, a professor at the University of Missouri, fears that male babies are facing "a perfect storm" from a variety of synthetic chemicals that simultaneously boost their estrogen exposure while cutting levels of testosterone and thyroid hormones.
He says the phthalates added to many plastics inhibit testosterone production (and can also, according to some researchers, be associated with irregular genital development, although the industry denies it). Meanwhile, brominated flame retardants (routinely used in products ranging from television sets to mattress foams) may block the thyroid hormone, which is crucial for proper development of both the testes and the brain.
Dr. vom Saal says this mishmash of synthetic hormones - leading to too much estrogen and too little testosterone and thyroid hormone - is making "a mess of sexual development in males."
DOWN ON THE FARM
Shanna Swan, a professor at the University of Rochester, has conducted research on a related topic - the sperm of healthy, seemingly normal young U.S men - and got strange results.
Her research group took semen samples from more than 500 men in New York City, Los Angeles, Columbia, Mo., and Minneapolis who were attending prenatal clinics with their partners - a good indication that the men didn't have fertility problems.
Yet the men in Columbia averaged only 58.7 million sperm per millilitre of semen, while New York City men produced an average of 102.9 million per millilitre; the Minneapolis men averaged 98.6 million and the Los Angelenos, 80.8.
Dr. Swan's research team then tried to take into account factors that might cause different sperm counts, such as age, race and smoking. Even so, they were unable to explain why men in Columbia had about half the sperm of men in New York and far less than those in Minneapolis.
The only explanation that makes sense to Dr. Swan is that Columbia is more of a farming area, suggesting that pesticides are to blame.
"These are very big differences and I believe they're environmental. ... We don't have any other explanation," she says.
Researchers are also investigating a widespread drop in testosterone levels. Thomas Travison at the Massachusetts-based New England Research Institutes is the co-author of a 2007 study in the Journal of Clinical Endocrinology and Metabolism that tracked a group of U.S. men from the late 1980s to 2004.
The researchers found that men in 1987 had significantly more testosterone than men of the same age in 2004. Over a decade and a half, the decline worked out to a dramatic 17 per cent - "certainly something to consider and be worried about, particularly if it is related to fertility," Dr. Travison says.
Obesity may be a factor - extra fat is known to cut testosterone levels, and more people have become fatter since the 1980s - but he adds that the trend could also be related to exposures to hormonally active chemicals that may affect metabolism.
"Some of these endocrine disruptors in the environment could have detrimental effects on weight, which then can affect hormones," Dr. Travison says, but he calls it a theory that needs more proof.
PANIC BUTTON
The whole issue of fragile males is a hotly contested area of modern science.
The declining share of male college enrolment, for example, could stem from complex social and cultural causes rather than just decreased male births.
The possibility that environmental chemicals are harming male brains is "a fascinating idea," says William Pollack, director of the Centre for Men at McLean Hospital in Massachusetts and an assistant clinical professor at Harvard Medical School. But he says it should be viewed as a hypothesis waiting for scientific proof.
The easiest way to settle the issue would be to deliberately expose pregnant women in laboratory settings to hormonally active chemicals and then check out their kids. Needless to say, that wouldn't pass an ethical review.
"I don't think, from the scientific point of view, we can really draw firm conclusions in favour of implicating endocrine toxicants as major determinants of all these health outcomes," says Daniel Krewski, director of the University of Ottawa's Samuel McLaughlin Centre for Population Health Risk Assessment.
The centre maintains a website - funded in part by the chemical industry - that takes a skeptical position on scientific claims about the health impacts of hormonally active synthetic substances. Dr. Krewski says his industrial funders don't vet what is on the site.
His reading of the research is that the weight of evidence is not yet strong enough. The unexplained rise in testicular cancer, for example, might be caused by some as-yet-unidentified genetic or lifestyle factor.
Meanwhile, Nicholas Van Larabeke observes that low sperm counts do not "immediately affect the quality of our life - except for those people who do not get the children they want." The professor at Ghent University in Belgium has studied changes in sex ratios, such as the one in Sarnia, and calls them "sentinel" health events for hormone disruption.
On the other hand, he adds: "If ever the situation would get worse, over a longer period of time, that's about, I'd say, the most efficient way to endanger the future of humankind."
Martin Mittelstaedt is The Globe and Mail's environment reporter.
***
Endangered species?
Here are science's top five worries over the fate of the human male.
1.
Lost boys
Studies on births from the U.S., Japan, and Canada have found a drop in the percentage of boys born compared with girls. The reason isn't known.
2.
Declining harvest
Men in farm country can be half as prolific when it comes to making sperm as their city counterparts, raising the possibility that pesticides undermine male fertility.
3.
Downsizing
It's disputed by chemical companies, but some researchers say they have found an everyday plastic compound - phthalates - that feminizes baby boys, causing penises and other reproductive organs to be smaller.
4.
Hormones not so raging
If you're a middle-aged man, you're likely to be less virile than your father because you make less testosterone. In recent decades, the decline has averaged about 1 per cent a year. If it continues over another generation or two, the consequences could be dire.
5.
Equipment failure
Rates of testicular cancer, hypospadias and other genital abnormalities have soared over recent decades, rising by more than 50 per cent each.
Martin Mittelstaedt
***
Chemical culprits
By some counts, nearly a hundred man-made chemicals either act like hormones or interfere with them, but scientists highlight four as major worries:
Bisphenol A, or BPA, the polycarbonate-plastic and tin-can-lining chemical, has been found in experiments by Frederick vom Saal and others to cause prostate abnormalities and other developmental changes linking to sex hormones in laboratory animals, at levels around and below currently accepted safety standards.
Phthalates (pronounced THA-lates), a family of chemicals used to make polyvinylchloride plastic more pliable, are found in everything from shower curtains, new car interiors to perfumes. It inhibits testosterone synthesis by interfering with an enzyme needed to produce the male hormone. Phthalates aren't embedded in products through strong chemical bonds, making them vulnerable to leaching out.
Polybrominated diphenylethers, or PBDEs, are flame retardants used in plastics, foams and electrical equipment. They are able to interfere with thyroid hormones, which are essential for proper brain and testicle development, and have been linked in animal research to attention-deficit-like conditions.
Polychlorinated biphenyls, or PCBs, are now-banned transformer-oil fluids widely used up to the early 1970s. They have a similar molecular shape to flame retardants and reduce thyroid hormone levels. Research has linked low PCB exposures to reduced impulse control and lower intellectual capacity in children. The most recent study, published in Environmental Health Perspectives in May, found that a mere one-part-per-billion increase in PCB concentration in a baby's placenta was associated with a three-point IQ drop at the age of 9.
Martin Mittelstaedt
Source: Globe and Mail
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