Infertility is a devastating health problem that affects 15-20 per cent of couples in the developed world and these rates are on the rise. While many experts blame the trend towards later motherhood for this pattern, others suspect that something far more difficult to control is responsible: our exposure to an increasing array of toxic chemicals.
Scientists have known for some time that certain chemicals can cause reproductive problems in wildlife and laboratory animals, but only now are they beginning to discover the impact of such agents on humans. As the latest research shows, even at relatively low levels, common chemicals found in the food we eat, the water we drink and the air we breathe-can have dramatic consequences for our reproductive health.
Infertility which refers to the inability to either conceive or carry a baby to term can be due to both male and female factors. However, recent studies have focused on women, showing that everyday chemical exposures could be destroying their reproductive health.
US scientists looked at the perfluorinated chemicals (PFCs) perfluorooctanoate (PFOA) and perfluorooctane sulphonate (PFOS), ubiquitous man-made compounds used in a variety of consumer goods from nonstick cookware (Teflon) and carpets to pesticides and personal care products. PFCs, already known to contaminate food and water supplies, are persistent in the environment and have been detected at worrying levels in wildlife and humans around the world (Environ Sci Technol, 2004; 38:
On analyzing data from more than 1200 women in the Danish National Birth Cohort study (1996-2002), the researchers found that those who had high blood levels of PFOA and PFOS took significantly longer to become pregnant than those with lower levels.
Alarmingly, compared with women who had the lowest levels of exposure, the likelihood of infertility defined as taking more than 12 months to become pregnant or having to use infertility treatments to establish the current pregnancy increased by 70-134 per cent and 60-154 per cent for women in the higher three quartiles of PFOS and PFOA exposures, respectively.
The study concluded that exposure to these chemicals at levels commonly seen in the general population could affect a woman’s ability to reproduce (Hum Reprod, 2009; 24: 1200-5).
Although such results are not proof of cause and effect, they add to the convincing evidence showing that PFCs can cause abnormal hormone levels and spontaneous miscarriages in animals, effects that might explain the mechanism by which such chemicals reduce fertility. According to the researchers, “PFCs may interfere with hypothalamic-pituitary-ovarian regulation, possibly causing irregular menstrual cycles, delayed ovulation or early abortions not recognized by the mother.”
Although more studies are needed before PFCs can be added to the current list of risk factors for infertility, for couples trying to become pregnant, detoxing from these chemicals may be a case of better safe than sorry.
Another chemical that appears to be wreaking havoc on the female reproductive system is bisphenol A (BPA), used in the production of plastic consumer products, and in the epoxy resins used to line the inside of food and drink cans. Like PFCs, BPA is pervasive in the environment and in people, too mostly because it leaches from containers into the food we eat (for more information on BPA, see WDDTY vol 18 no 8). Indeed, US studies have found detectable levels of BPA in more than 90 per cent of the general
population (JAMA, 2008; 300: 1303-10).
Concerns that BPA could be damaging to reproductive health were first raised in 2003, when scientists from Case Western Reserve University in Cleveland, OH, observed a sudden, dramatic rise in chromosomal abnormalities in the oocytes (eggs) of mice they were studying. Such abnormalities lead to a condition called ‘aneuploidy’ that, in humans, can cause early miscarriages and birth defects such as Down’s syndrome. The surprising pattern was eventually traced to the use of a harsh detergent to wash the animals’ polycarbonate plastic cages and water bottles. Follow up experiments revealed that the detergent damaged the plastic, causing BPA to leach from the bottles and cages, and it was this exposure to the hormone disrupting chemical that had caused the sudden increase in aneuploidy (Curr Biol, 2003; 13: 546-53). Although such animal findings may not apply to humans, studies in women have also suggested that BPA is a potent reproductive toxicant.
Indeed, Japanese scientists found that women who’d suffered recurrent miscarriages had significantly higher levels of BPA in their blood than women with no history of infertility (Hum Reprod, 2005; 20: 2325-9). Blood levels of BPA in women have also been linked to endometrial hyperplasia, where the lining of the womb becomes thickened, and to polycystic ovarian syndrome, one of the most common causes of female infertility (Endocr J, 2004; 51: 595-600; Endocr J, 2004; 51: 165-9). The most worrying aspect is that, while traditional toxicology asserts that the higher the dose, the greater the harm, BPA tests show that low doses may be the most toxic of all. This suggests that it might well be BPA even at extremely low concentrations that is contributing to the increase in infertility rates worldwide (Endocrinology, 2006; 147 [6 Suppl]: S56-69).
Yet another chemical or, rather, group of chemicals linked to female infertility is chlorinated hydrocarbons (CHCs), a class of persistent agents that includes dioxins, polychlorinated biphenyls (PCBs) and organochlorine pesticides. Widely used in industry and agriculture for decades, they are known to make their way into our food and so, eventually, our bodies (J Lipid Res, 1982; 23: 474-9).
In women with occupational and accidental exposures to CHCs, a wide range of reproductive effects has been observed, including miscarriages, a prolonged
time to achieve pregnancy and endometriosis, frequently linked to infertility (Environ Health Perspect, 2008; 116: 599-604; Ann Epidemiol, 2007; 17: 503-10; Environ Health Perspect, 1998; 106: 675-81).
Even more worrying, however, is the evidence that CHCs may be harmful at levels commonly seen in the general population. When the blood levels of various CHCs in 89 women with repeated miscarriages were compared with those of a reference population, more than 20 per cent had at least one CHC level that exceeded the reference range. Significant correlations were also found between increasing CHC levels, and immunological and hormonal changes, which may explain how CHCs have the potential to affect the course of pregnancy (Environ Health Perspect, 1998; 106: 675-81).
In another study by the same team of researchers, a considerably larger group of women was analyzed to see how CHCs affected various aspects of fertility. What they found was that women with uterine fibroids, endometriosis, miscarriages, hormonal disturbances and persistent infertility had higher concentrations of CHCs in their blood. The study concluded that CHCs may be an underlying factor in certain gynecological
conditions, and may play a significant role in female infertility (Environ Res, 1999; 80: 299-310).
However, it’s not only women who are vulnerable to the effects of toxic chemicals in the environment. Many of the chemicals known to damage women’s reproductive health have also been found to affect male fertility, primarily by reducing sperm quality. Indeed, in industrialized countries, the evidence suggests that sperm quality has been steadily decreasing over the past 50 years, and a number of experts claim that environmental contaminants could be to blame (J Androl, 2009; 30: 566-79).
The most consistent evidence implicates CHCs and, in particular, PCBs. Several studies show that men with elevated levels of PCBs in their blood have reduced sperm motility, which hinders its ability to propel itself towards an egg (Semin Reprod Med, 2006; 24: 156-67). In one study of 212 men attending the Massachusetts General Hospital for fertility treatment, a significant dose response relationship was found between sperm motility and blood levels of an agent known as PCB-138 in other words, the higher a man’s PCB-138 levels, the lower his motile sperm count (Environ Health Perspect, 2003; 111: 1505-11).
In addition, PCBs can affect other sperm parameters such as ejaculate volume, total sperm count, normal morphology (shape) and fertilizing capacity. These compounds, found at particularly high concentrations in fish-eaters, “may be instrumental in the deterioration of semen quality in infertile men without an obvious etiology”, the researchers concluded (Fertil Steril, 2002; 78: 1187-94).
As if that’s not bad enough, PCBs have also been found to interact with other chemicals to produce even more damage. Scientists at the Harvard School of Public Health looked at male fertility in relation to PCBs and another family of ubiquitous pollutants: the phthalates (Environ Health Perspect, 2005; 113: 425-30). Used to make plastics more flexible and also as solvents, phthalates are found in a huge array of consumer items-from toys and food packaging to cosmetics and detergents. They’re also inside us.
A US study found detectable levels in more than 75 per cent of the people tested (Environ Health Perspect, 2004; 112: 331-8).
On their own, phthalates have been linked to poor sperm quality in infertile men at levels similar to those seen in the general population (Hum Reprod, 2007; 22: 688-95; Epidemiology, 2003; 14: 269-77). But the Harvard team then also found that they are particularly potent when combined with PCBs. Using data from over 300 men from couples seeking infertility treatment, they found evidence of interactions between certain PCBs and phthalates in the men’s blood that were associated with a “greater than additive” risk of poor sperm motility (Environ Health Perspect, 2005; 113: 425-30). In other words, some PCBs alone correlate with decreased sperm motility and some phthalates correlate with decreased sperm motility but, when they’re mixed together, the impact of the interaction is greater than the sum of the two.
The implications are alarming, as most men are likely to be exposed to both pollutants. Other chemicals in the body are also probably adding to the toxic mix. A wide variety of common contaminants are linked to poor sperm quality, including pesticides, heavy metals, solvents and cigarette smoke.
A Chemical Legacy
While infertility is clearly an adult problem, its causes may have their roots in fetal development. Indeed, mounting evidence in animals shows that chemical exposures in the womb (in utero) or during the early stages of development can cause abnormalities at birth or later that have impacts on adult reproductive functioning.
Some of the latest evidence concerns BPA, which has been detected in urine, breast milk, maternal and fetal plasma, amniotic fluid and placental tissues in various populations worldwide. Scientists at the US National Institute of Environmental Health Sciences (NIEHS) investigated whether prenatal BPA exposure at “environmentally relevant” doses levels seen in the general population could cause long term adverse effects in the reproductive tissues of female mice. After dosing pregnant mice with either BPA or corn oil (the control group) for eight days and evaluating their offspring after 18 months (young adulthood), they found that, compared with the controls, the pups of the mothers given BPA were significantly more likely to have both benign and malignant lesions, such as ovarian cysts, in their reproductive tissues (Environ Health Perspect, 2009; 117: 879-85). These effects could ultimately have a negative impact on fertility.
The results add to previous animal evidence showing that very low doses of BPA can cause abnormalities in the uterus, vagina and ovary when those exposures take place during early development (Environ Health Perspect, 2009; 117: A256).
And it appears that even male reproductive health can be affected, too, as recently revealed by scientists from the National Institute for Research in Reproductive Health in Mumbai, India. When they injected newborn male rats with relatively low doses of BPA, they found dramatic effects on fertility in adulthood. Females mated with these male rats had significant increases in pregnancy loss and decreases in litter size, while the males themselves had altered sperm counts and hormonal imbalances. What’s more, the BPA-exposed rats showed changes in the expression of Sertoli cell junctional proteins in the testes. These proteins are crucial for sperm production, and their altered expression by BPA could be the mechanism by which the chemical contributes to infertility (Toxicology, 2009 Sep 24; Epub ahead of print).
Besides BPA, a variety of other chemicals, such as pesticides, CHCs, perfluorinated compounds and heavy metals, appears to have an impact on adult reproductive health when animals are exposed to them early on in life.
Our Toxic Future
Although the evidence linking chemicals to infertility is still in its early stages, there’s already a compelling case to be made against many of the contaminants we encounter on a daily basis. This suggests that, along with factors such as age, nutrition and body weight, other influences are clearly involved in whether or not a couple successfully makes a baby, including the increasingly polluted world in which they live.
While more research is needed, the current facts suggest that if we don’t start cleaning up our act, we’re not only risking our health, but our entire human existence.
A World of Chemistry
Every year, around 100,000 different types of chemicals are produced and used around the world, many of which eventually find their way into our environment. Even chemicals that were banned from manufacture years ago can still be lingering in the atmosphere, soil and water. As a result, we’re now being exposed to tens of thousands of chemicals that were never part of the environment in which our ancestors lived. The impact of all this pollution on our health is not yet known, but a number of experts claim that it may well be behind the growing fertility problems worldwide. Data from the US National Center for Health Statistics 2002 National Survey of Family Growth revealed that almost 7.3 million women reported impaired fecundity (the biological capacity to have children) compared with 6.1 million in 1995 and 4.9 million in 1998. Although this could perhaps be explained by the trend of more couples waiting until they are older before trying to have children, surprisingly, the survey found that the most striking increase in self-reported problems was in women aged under 25 who showed a 42 percent increase between 1982 and 1995. Results from more surveys suggest this pattern is continuing
“What is clear,” the report states, “is that many chemicals commonly found in the environment and in human bodies have shown themselves in laboratory tests to be capable of causing the type of effects which may underlie the trends in reproductive human health that we are witnessing across the globe.”
This laboratory evidence together with observations made in wildlife, numerous occupational studies, and more and more research in the general population-suggests that chemical exposures should now be recognized as one possible factor underlying human infertility.
What Doctors Don’t Tell You
Vol. 20 08 November 2009
Part 2 will involve a patient case and my functional medicine approach to this topic.