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WHAT'S NEW
Now available: MP3 recording and other resources from the July CHE Partnership Call on how industrial animal production impacts health and the environment" - July 15, 2008
5/9/08: CHE featured in AARP: "The Body Toxic" 5/9/08: CHE Partner Dr. Philip Landrigan interview in Discover: "How Much Do Chemicals Affect Our Health?"
4/15/08: Now available: State of the Evidence 2008: The Connection Between Breast Cancer and the Environment 2/20/08: CHE LDDI scientific consensus statement on environmental factors. 9/1/07: The BioInitiative Report: A Rationale for a Biologically-based Public Exposure Standard for Electromagnetic Fields
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Infertility: What We KnowIn both men and women, many factors can undermine fertility and thus it is not surprising that infertility is a common problem, affecting as many as one in ten couples in the United States, one in six in Britain, and even more in some other parts of the world. Experts estimate that somewhere between twenty and forty percent of infertility cases are linked to men while another third are due to female problems. For the remaining cases, the causes either aren’t known or involve both partners. The most basic cause of infertility is ageing. Chances of becoming pregnant decrease with age, as does the success rate for fertility treatments. What about preventable causes of infertility? Many have been identified, and they vary in importance around the world. In regions with poor health care, infections affecting the reproductive organs are a major contributor. Sexually-transmitted diseases take their toll. Hence good health care and safe sexual practices are important to avoiding infertility. Fertility impairment can begin, literally, in the womb. Early in fetal life, the embryo’s genes have begun to send out instructions that guide development of the reproductive tract. If something goes wrong with those instructions—for example, a mutation, a chemical insult, an imbalance in hormones—then when the affected individual reaches reproductive age they may not have all the pieces in place and prepared for procreation. Infertility can also be caused in adulthood. Diseases can scar the reproductive tract, cause hormone imbalances that interfere with key steps in reproduction, or induce harmful immune system responses that contribute to infertility. Certain chemicals have been proven to be highly toxic to sperm, perhaps most notoriously, the pesticide DBCP (dibromochloropropane), whose use in banana fields caused sterility in the workers and ultimately resulted in a $40 million settlement by three US companies. It is not known if infertility is becoming more common. The data available simply aren’t sufficient to be sure. What is certain is that many more people are seeking treatment now that new techniques for overcoming infertility have become available. These treatments are expensive and prospects for success are far from certain. No doubt some of this surge in treatment demand is a result of couples delaying having children long enough so that ageing becomes a problem. But over the past decade, studies have also suggested that certain conditions which have the potential to undermine fertility are becoming more frequent. Endometriosis has almost certainly increased in frequency. Once thought to be very rare, this painful, debilitating disease now affects 10-15% of all women of reproductive age in the US. It can cause scarring and blockages that interfere with reproduction. Several disorders of the testes have increased substantially. Scientists now link four of them—low sperm quality, undescended testes, hypospadias (a birth defect of the penis) and testicular cancer—into a single disorder: testicular dysgenesis syndrome. Low sperm count is surprisingly common in certain countries in northern Europe, for example, Denmark, in some regions in the United States, and in several Asian countries. Analyses of historical data from Europe indicate that counts have fallen there; data from the US and elsewhere are also suggestive of declines. Testicular cancer has increased dramatically in some regions: for example, up 300% over the past two decades in northern Europe. Do preventable, environmental exposures contribute to infertility? Unquestionably. Many documented examples can be found in the scientific and medical literature. The strongest cases involve industrial and occupational exposures, such as the DCBP case mentioned above. These usually involve small numbers of people exposed to high levels of contamination. The bigger question, however, one that is now being pursued intensely by scientists, is whether every-day exposures undermine human fertility: large numbers of people exposed to low levels of contamination. Laboratory experiments with animals reveal exquisite vulnerabilities to low-level exposures that lead to reproductive impairment. The most eye-opening cases involve exposure in the womb to substances that interfere with natural hormone action. Some of the chemicals implicated are used commonly in consumer products, like phthalates and bisphenol A, or as pesticides. Others are industrial chemicals and industrial byproducts, like dioxin. Several human health trends, including testicular dysgenesis syndrome, alterations in the ratio of boys and girls born, and endometriosis, are predicted by these animal experiments and by widespread patterns of human exposure. The scientific jury on this question is still out. The research is complex and reaches across human generations. To achieve certainty using human studies alone will be decades in the making, at best. Summaries of the latest and best studies are posted regularly at this website. Good public health standards can't wait for that certainty, but instead should be based upon precautionary extrapolation of the animal studies and information about human exposures and human health trends.
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