The links between birth defects and men's exposure to harmful substances are woefully under-reported, says Cynthia Daniels.
Imagine that every pub in Britain posted signs warning men that excessive use of alcohol can lead to increased risks of miscarriage and birth defects in the children they father. And imagine that every packet of cigarettes carried warnings that the use of tobacco can cause sperm abnormalities that can result in childhood cancers.
In fact, hundreds of studies have shown significant associations between men's exposure to toxic substances and foetal health problems, while 60 per cent of all birth defects remain of "unknown origin" and the cause of the majority of miscarriages is also unknown.
Yet almost no public attention has been paid to this evidence. It remains ignored because it threatens to undermine our most basic assumptions about manhood - that men are virile, less vulnerable to harm than women and distant from children and their health problems. Indeed, they are ultimately assumed to be providers and protectors. But both men and their children pay a serious price for this willful ignorance.
As early as the mid-19th century, studies found high rates of birth defects in the children of men who were exposed to lead. Now, human and animal studies show statistically significant associations between male exposures to alcohol, tobacco, pesticides, herbicides, anaesthetic gases, chemotherapeutic drugs, opiates and other "recreational" drugs and miscarriage, low birth weight, stillbirths, birth defects and childhood cancers in the children that men father.
US veterans of the Vietnam War experienced dramatically higher rates of spina bifida in their offspring after returning from the conflict, presumably from exposure to the 19 million gallons of dioxin sprayed on the jungles - and soldiers - from the air. In 1996, after three decades of intense lobbying, the US Government finally agreed to extend veterans' benefits to such children as "victims of war". One politician noted: "The Government ought to treat these children as if they had been shot in Vietnam." This remains the only formal US government recognition of the link between paternal exposures and foetal harm.
The male reproductive system is quite vulnerable to toxic damage. Sperm are continuously produced, taking about 72 days to develop inside the body. Cells that are developing and dividing are at higher risk for mutagenic damage than those that are at rest, such as eggs in the female reproductive system. We know that sperm can be damaged by toxins, that damaged sperm can fertilise eggs and that sperm carrying mutagens can produce children with birth defects. Seminal fluid can take toxins directly into the female system: alcohol can be transferred by semen, lead can be carried by seminal fluid and the metabolites of cocaine can bind to sperm as well. Yet, except for the forward-looking scientists carrying out research in this area, we choose to virtually ignore this evidence in deference to myths of men's invulnerability to harm and distance from responsibility for the health of their children.
This reluctance to see men's connection to human reproduction has also produced a profound neglect of other male reproductive health issues. Men exposed to dioxin after an explosion at an Italian factory in 1977 produced no baby boys for seven years. Exposed women who fathered children with unexposed men produced children of both sexes.
Studies worldwide also show that testicular cancer rates have risen by 50 per cent or more since the 1970s. We have also witnessed increases in reproductive malformations in men, perhaps due to the exposure of the male foetus to plastics in the environment that mimic estrogen as they break down. This evidence paints a picture of a male reproductive system that is highly sensitive to toxic damage. Yet there are almost no reproductive protections for men at their workplaces, in the environment or on the battlefield.
What happens when men rendered infertile from toxic exposures end up with their partners at sperm banks? There they face another kind of reproductive belittlement. In the US, sperm has been reduced to a commodity like any other supermarket product. While the UK has imposed restrictions on sperm marketing, American reproductive consumers can "shop" for sperm based on ideal traits of masculinity. Donors who are tall and muscular, who possess high IQ scores and chiselled jaws and who rank high on the "tanability" scale are bestsellers. But banks rarely screen donors for exposure to toxins. Again, we see the perpetuation of ideals of masculinity at the expense of real men.
Were we to take off our gendered blinkers, we might see that men are equally important to the making of healthy children, equally in need of protection from substances that are toxic to the reproductive organs. But this would require the dismantling of ideals of masculinity that now both privilege and burden men. It would require an affirmation of the notion that men and women are equal partners in the reproduction of the species. That would be truly revolutionary.
Cynthia R. Daniels is professor of political science at Rutgers University in the US and author of Exposing Men: The Science and Politics of Male Reproduction , published by Oxford University Press, £17.99.