LOW FERTILITY and CHEMICALS: A Possible Connection?

Low fertility has many positive effects, including benefits to the health of women and their children. However it is possible that there may be a dark thread in the braid of mostly positive factors currently contributing to the unprecedented rate of fertility decline around the world. Man-made chemicals may be negatively affecting human fertility. This issue merits more attention than it has received.

Declining Sperm Counts

In the late 1980s, Danish researchers, led by Dr. Niels Skakkebaek, noticed an increase in sperm abnormalities and a decrease in sperm count among samples of Danish men. At the same time, a dramatic increase in the rate of testicular cancer and an increase in reproductive organ abnormalities in infant boys were also being observed.

Skakkebaek and his colleagues summarized 61 studies, mostly from Europe and the United States, in which sperm counts had been measured since the 1930's. They reported a decline of almost 50% in average sperm counts over a 52 year period. These findings generated a fair amount of controversy, and therefore media attention, including an article in the New Yorker in 1996 entitled "Silent Sperm" by Lawrence Wright. However, since sperm counts can vary substantially among individuals and countries, it was difficult for specialists or the public to know how seriously to take these studies.

In 2000, another study was published in which all 18 year old Danish men registering for national service were asked to provide a semen specimen, and 20% agreed. The median sperm count for this group was far lower than prior studies for men in the previous generation, and low enough to indicate that in 1998 the average Danish 18 year old man was only marginally fertile.

Endocrine Disrupting Chemicals

In the 1990s, other research documented an apparent increase in aberrations in the reproductive organs and behavior of various animal species, including birds, fish, alligators, marine mammals and polar bears, sometimes resulting in bisexual or sterile offspring. In 1997, Colburn, Dumanowski, and Myers co-authored Our Stolen Future, which brought national attention to the concept of "endocrine disruption," and provided a possible scientific explanation for the many disparate sexual and reproductive anomalies that had been increasingly observed in wildlife and humans exposed to certain man-made chemicals.

Colburn, Dumanowski, and Myers noted that many man-made chemicals mimic human hormones, especially the persistent, bio-accumulative organohalogen compounds often found in pesticides. Some chemicals, for example, are "estrogenic." That is, they act like the specific key that only fits with estrogen receptors. If there is an excess of estrogen or estrogen-like substances in the environment of the developing fetus, it can trigger excessive reactions, or reactions at the wrong time. Other chemicals, like DDE, a breakdown product of DDT, mimic testosterone but act as hormone blockers. That is, they can bind with receptors and prevent the real testosterone from working. Because these synthetic chemicals act on the endocrine system to interfere with and alter the body's normal messaging system, they are referred to as "endocrine disruptors."

Colburn, Dumanowski, and Myers also highlighted research documenting that:

1. endocrine disrupting chemicals can cause damage even in very tiny concentrations;
2. these chemicals may be able to be passed from one generation to the next; and
3. they pose a special threat to the developing fetus.

Some of the endocrine disrupting chemicals specifically affect the process of sex organ development. Perhaps the best known endocrine disruptor is diethylstilbestrol, or DES, a synthetic estrogen prescribed starting in 1947 to prevent miscarriages. The alarming discovery in 1971 that DES caused an extremely rare vaginal cancer in the daughters born to women who took DES ended its use in the United States (although it continued to be used elsewhere into the 1980's). Recent research suggests that negative effects from DES may even occur in the third generation.

In 2000, researchers suggested a possible linkage between endocrine disrupting chemicals and a well-documented increase in birth defects of the male reproductive system, particularly hypospadias (abnormal placement of the urethra) and possibly cryptorchidism (undescended testes). The researchers found that one in three samples of amniotic fluid taken from 51 women in Los Angeles tested positive for at least one endocrine disruptor, primarily DDE. If DDE were present in the fluid surrounding a developing male fetus during the 52nd or 53rd day of its existence, when the cells that would become that baby's sex organs were being formed, it is possible that the DDE could interfere with the masculinization process in ways that might not become apparent until many years later, when that individual was trying to produce a baby himself.

Possible Effects on Human Reproductive Health

Since current social, economic and cultural factors undoubtedly influence fertility much more than environmental factors, verifying if there is a connection between fertility and environmental exposure to certain chemicals is likely take a lot of research and a long time. Humans, like all mammals, have a substantial "cushion" of excess eggs and sperm, so the average sperm count could decrease significantly before we would necessarily notice it.

Some research suggests that unwanted infertility is increasing, although it is difficult to know how much this trend may be influenced by voluntarily delayed childbearing and the availability of various forms of assisted reproduction, including in vitro fertilization. While more couples and women are reporting impaired fecundity, it may be that in the past a comparable number of women who had difficulty getting pregnant quietly stopped trying, resigned themselves, or adopted children, and hence were excluded from the statistics.

Perhaps the most dramatic study with regard to impaired fecundity was by Chandra and Stephen in1998. Their research showed an increase of 5.8% in impaired fecundity in women in the United States aged 35-44 over the period 1982-1995. The next younger cohort, aged 25-34, showed an increase of 12%, and in the youngest cohort (15-24), the increase was a whopping 41.9 percent over the thirteen year period.

If endocrine disrupting chemicals are affecting human reproductive health, we would expect to see larger effects in younger populations. Because these chemicals are accumulating in the environment, and in our bodies, younger people have not only what they absorb just by living in today's world, but also increasingly the effects passed on to them in utero by their mothers.

If this is the case, we might also expect the increasing concentration of estrogenic chemicals to show up as an increase in endometriosis, as well as an earlier age of onset of puberty in girls. In older women, we might expect an increase in the rate of breast cancer. An excess of estrogen or the presence of testosterone-blocking hormone mimics could cause a gradual increase in infant male reproductive organ anomalies. In older men we might expect to see an increase in prostate and testicular cancer. We would expect to see a sustained and continuing decline in teen pregnancy rates. And we would expect to see more of these things in those countries in which humans spend more money putting bio-accumulative chemicals on their crops, especially when those crops are grown close to areas of high population density.

In fact, all of these things are happening.

What Should Be Done?

An appropriate response to the potential threats posed by endocrine-disrupting synthetic chemicals should include at least three elements: 1) a call for greatly increased research in order to establish whether and how human health is being affected; 2) ratification of the Persistent Organic Pollutants Treaty by Congress; and 3) the enactment of a broad and effective precautionary principle.

Endocrine disrupting chemicals have now become global. It will take a long time to reduce their presence in the environment. As a result, the speed with which we can identify whether they are affecting us is crucial. However we don't have to start at the national level. Small, "rifle-shot" research projects, such as determining if there is a correlation between the presence of DDE in the amniotic fluid of a mother and reproductive organ anomalies in her newborn baby boy, would be very useful. We can encourage Planned Parenthood clinics to offer sperm count services, and urge them to pool their data. We can ask for better data collection by local and state funded health clinics with regard to all kinds of fertility problems and trends.

Concerned citizens can also lobby for ratification of the Persistent Organic Pollutants treaty by Congress. Under the Clinton administration, the Environmental Protection Agency created a task force in 1999 to develop priorities and a protocol to begin testing the chemicals of greatest potential concern. In the spring of 2001 President Bush signed the first international agreement to ban chemicals labeled Persistent Organic Pollutants, the so-called "POPS" treaty. However, this treaty has yet to be ratified by Congress. It will take concerted action by many people to get the legislation passed. In the meantime, as individual citizens, we could all adopt the "do no harm" credo and stop using pesticides � in our homes, gardens and places of work.

Entities responsible for releasing persistent chemicals into the environment should be held to the "do no harm" credo through the enactment of a legally binding "precautionary principle," similar to one recently adopted in Sweden. This would require that all new chemicals be tested before being released into the environment, and that existing harmful products be phased out and replaced by safe alternatives. The effort to develop a precautionary principle in industry will require leadership from many fronts, including population groups, environmental organizations, and public health advocates.

An emerging grassroots environmental health movement is increasingly active in the area of endocrine disruptors and chemical pollution. Leading organizations include "Healthcare Without Harm," which has lobbied with some success to remove dioxin from hospital waste streams, and the women's breast cancer prevention movement. If the connections between synthetic chemicals in the environment and reproductive health become clearer, it is reasonable to anticipate that more and more people will become active environmentalists, willing to change their own lifestyles, and willing to push their elected officials to initiate real change.

* Edith Eddy is Executive Director of the Compton Foundation. This paper reflects her personal opinions and not necessarily the priorities of the Compton Foundation.