PCBs and Other Industrial Chemicals Linked to New Health Risks
Concerns are growing that chlorinated organics, such as PCBs, and other chemicals with the ability to mimic natural hormones, are causing cancer in adults and adverse health and reproductive effects in the offspring of both humans and wildlife.
According to an article in an industry publication, Chemical and Engineering News (April 19, 1993), "An increasingly prominent element of the argument against these chemicals is that many of these compounds cause non-cancer health effects--endocrine, immune and neurological problems--principally in the offspring of the exposed humans and wildlife, and seem to create these problems at extremely low exposure levels."
Recent scientific findings that support these concerns are widespread and compelling:
- Boys in Taiwan exposed to PCBs while in their mother's womb (their mother's had eaten rice oil contaminated with PCBs) develop smaller penises as they mature; according to a study reported in Scientific American Science News reported that male alligators exposed to pesticides in Florida are having difficulty reproducing, partly because their penises are not developing to normal size.
- 15 of the Taiwanese children were evaluated 6 years after their mothers were exposed to PCBs; they were found to be less developed than a control group of children for 32 of 33 different measures of physical and mental abilities.
- Endometriosis, a painful disease that affects women in their reproductive years, frequently leading to infertility, was formerly a very rare condition but now affects 6 to 9 million women in the United States. Lab studies with Rhesus monkeys have shown a definite link between exposure to dioxin and PCBs and development of endometriosis. A 1992 study revealed that endometriosis is linked with exposure to PCBs in humans.
- Since the 1940's, the incidence of female breast cancer in Western Europe and the U.S. has risen significantly. Today, the chances of a woman developing breast cancer in her lifetime are one in nine. Researchers at Mt. Sinai School of Medicine in New York City have found a correlation between the incidence of breast cancer and DDB levels (a breakdown product of DDT) in breast tissue.
- Over the same period of time sperm counts in men worldwide have fallen about 50%, the incidence of testicular cancer has tripled and that of prostate cancer has doubled. There also appears to be a significant increase in the occurrence of birth defects of the male reproductive system.
- Researchers have found that prenatal (before birth) exposure to very low levels of dioxin feminized the behavior of male rats during adulthood and sharply reduced their production of sperm.
- Female common terns nesting near a PCB contaminated waste site in New Bedford, Massachusetts are sharing nests and exhibiting other abnormal reproductive behaviors. Research has also shown a high incidence of abnormalities in the embryos taken from these nests.
- Since 1987, communities of marine mammals such as dolphin, seal and whale have experienced wide-scale die-offs around the world. Researchers believe exposure to organochlorines weakens the creature's immune systems, making them more susceptible to infectious disease. In some cases, this has been supported by findings of increased levels of PCBs in the tissues of dead animals.
- Studies in North Carolina found a correlation between a mother's exposure to PCBs and poor muscle tone at birth weight and poor muscle coordination in their offspring at 6 and 12 months.
- In Michigan children born to women who ate as few as two to three meals per month of Lake Michigan fish (contaminated with PCBs) preceding their pregnancies were smaller than average at birth, and had behavioral, motor and learning problems. Negative growth and behavior effects were still observable when the children were tested again at age four.
According to an article in Chemical and Engineering News (January 31, 1994), "Some scientists say at least part of the reason for the increase in these conditions may be man-made chemicals introduced to the environment since 1940 that mimic or block the action of the natural hormone estrogen. Such chemicals may act on the adult human or animal and cause cancer or endometriosis. The consequences may be even more widespread and devastating when estrogen mimics accumulate in the mother and are then transferred to the egg or the fetus, disrupting the hormone balance of the developing offspring and causing reproductive abnormalities or changes that set the stage for cancer in adulthood."
Researchers believe organochlorines can promote cancer by mimicking natural estrogen; high natural estrogen levels have long been known to be a risk factor for breast cancer. Interfering with the endocrine system in a fetus can have devastating effects on offspring because it is the balance of hormones that dictates normal development of the reproductive, nervous and immune systems. Fetal exposure to endocrine mimics could also "program" the fetus to be more susceptible to environmental toxics (including estrogen mimics) later in life, thereby increasing the cancer risk factor.
According to Dr. Theo Colburn of the World Wildlife Fund, at least 45 widely used industrial chemicals and pesticides have been shown to disrupt the endocrine system in fish, birds and mammals, including humans. Examples of estrogen mimics are DDT, kepone, dieldrin (pesticides) and some PCBs. These chemicals all tend to be persistent and prone to accumulate in fatty tissues of animals and humans over full lifetime. Most can cross the placental barrier and pass from the mother to the developing fetus.
Levels of many persistent toxics, particularly organochlorines, peaked in the 1970's, but have leveled off since. Some have increased in recent years. EPA has banned only a small fraction of the 15,000 or so chlorinated organics that are used in commerce. Even chemicals that have been banned (such as PCBs) are still a problem. According to some estimates, as much as 70% of the total global production of PCBs is still in use or in stock and could reach the environment in the future.
Given the growing evidence of widespread and potentially devastating health effects being linked to persistent, bioaccumulative chemicals, it is clear that more needs to be done to prevent ongoing exposures to wildlife and humans. And it can be done. The standard for appropriate governmental response is being set by the International Joint Commission (IJC), a governmental agency of representatives from Canada and the U.S. which is responsible for maintaining and restoring environmental quality in the Great Lakes. The IJC is calling for an entirely new approach to the problem of controlling persistent toxic chemicals. Specifically, the IJC has called for:
- the phase out of all persistent toxic substances from the Great Lakes,
- a ban on the manufacture and use of chlorine,
- a reversal of the policy that assumes chemicals are innocent until proven guilty,
- adoption of the principle of "precautionary action" which acknowledges that a practice which could cause harm, even without conclusive scientific proof, should be prevented and eliminated.
The IJC's 7th Annual Report states, in part, "We do not know what all of the effects of human exposure will be over many years... For the Commission, however, there is sufficient evidence now to infer a real risk of serious impacts in humans. Increasingly, human data support this conclusion."
Faced with emerging evidence of human health risks associated with PCBs, General Electric, which dumped over a million pounds of PCBs into the Hudson River, said:
"Scientists have begun to change their minds about PCBs. New information shows PCBs pose much lower risks to public health and the environment." -- General Electric, July, 1991.
The endocrine system is a complex set of bodily organs and tissues whose activities are coordinated in wildlife and humans by chemical messengers, called hormones, that control growth, development and behavior. Estrogen is one such natural hormone, present in both males and females, which dictates sexual development and behavior. Other roles of estrogen are just starting to be understood. Much of the ongoing research focuses on a diverse group of chemicals which appear to "mimic" or interfere with estrogen.
Information used in this article came from articles in Chemical and Engineering News (cited) and several issues of the Environmental Research Foundation's,
Hazardous Waste News
, Reprints of these articles are available by contacting Clearwater's Environmental Action Program at (914) 454-7673.
Source: Hudson River Sloop Clearwater, Inc.
Reprinted from the Clearwater Navigator -March/April 1994
By Bridget Barclay, Clearwater's Environmental Director
Brought to the Web by the
Environmental Studies Program at Rensselear (10/94).