Endocrine Disrupters

Everything from obesity to prostate cancer. That's what researchers say could be triggered by prenatal exposure to an array of chemicals suspected to be endocrine disrupters.

According to a report on the emerging science of endocrine disruption presented to the International Seminar on Nuclear War and Planetary Emergencies in Italy in 2003, chemical "signaling" determines biological development and regulates cell and organ activity in all living things. Results of research strongly suggest that many environmental contaminants interfere with this process.

Endocrine disrupting chemicals (EDCs) are defined as chemicals that can disrupt thyroid hormones and other endocrine processes. For example, the report states that lifetime exposure to estrogen is the best predictor of breast cancer, and "exposure to EDCs that are environmental estrogens could plausibly increase breast cancer risk." This cause and effect has been confirmed in laboratory rats. The Natural Resources Defense Council (www.nrdc.org) says estrogen is a hormone secreted primarily by the ovaries. It controls the menstrual cycle, fertility, and maintenance of a healthy pregnancy, among other critical activities in adults. In the fetus, estrogen is essential for normal development of both males and females.

Other illnesses and disorders suspected of being linked to exposures in the womb to EDCs include heart disease, decreased fertility, preterm birth, autism and impaired immune systems.

In the developing fetus, the report states that EDCs can act at very low levels of exposure to produce profound effects - as early as the moment of conception, on through various stages of maturity, adulthood and death. Insulin resistance and diabetes are believed to be linked to exposure to EDCs, as are neurological problems such as Attention Deficit Hyperactivity Disorder. According to the report, "the disruptive effects of developmental exposure are permanent and irreversible." Adult exposures, it says, result in measurable but reversible effects.

More and exhaustive research is needed, the report says, to confirm the link between environmental exposure to EDCs and, for example, obesity - but the "underlying biology (of such conditions) suggests that alterations in inter- and intra-cellular signaling processes" from exposure to EDCs "may be causally involved."

Among the chemicals thought to trigger such harmful effects are those in polycarbonate plastics, used to make drink containers, and for resin to line food cans. More than 100-billion such liners are manufactured each year in the U.S. alone. Researchers say the potential endocrine disrupter Bisphenol A can leach from the containers, be ingested by pregnant women and passed on to the fetus.

In addition, the report states, endocrine disrupters are literally being carried with the wind. The report states that large masses of air have been tracked across the Pacific carrying a variety of pollutants from central Asia to the West Coast of the United States, largely undiluted.

More than 80,000 chemicals are registered for commercial use, the report states, adding that few have been tested for endocrine disrupting effects, "particularly," it adds, "during embryonic development, the most vulnerable time in life." The Food and Drug Administration (www.fda.gov), calls research utilizing animals "slow and expensive," and says there is a crucial need to prioritize which of the 87,000 chemicals should be tested first, beginning with those "most likely to possess endocrine disrupting activity."

Researchers say suspected endocrine disrupters can be found in:

• Metals
• Personal care products
• Pesticides/herbicides/fungicides
• Industrial chemicals
• Pharmaceutical drugs
• Synthetic and naturally occurring hormones.

Just how great an impact exposure to an EDC will have will vary, say scientists, depending not only on when in the life cycle the exposure occurs, but the amount of exposure and duration. New data suggest disruption can occur with even low dose exposure to heavy metals such as arsenic. Arsenic can leach into drinking water from improperly abandoned landfills, and even old cemeteries. According to the National Park Service (www.crm.cr.nps.gov), arsenic was the main ingredient in embalming fluids from the Civil War until 1910. Leaching from old cemeteries is a confirmed threat to groundwater.

In 1996, the federal Food Quality Protection Act required a screening and testing program for endocrine disrupters. That year, the Office of Research and Development at the Environmental Protection Agency (www.epa.gov) identified endocrine disruption as one of its top six research priorities.

EPA information offers the following answers to questions about EDCs:

1. What is the endocrine system?

The endocrine system is a complex network of glands and hormones that regulates many of the body's functions; including growth, development and maturation, as well as the way various organs operate. The endocrine glands -- including the pituitary, thyroid, adrenal, thymus, pancreas, ovaries, and testes -- release carefully-measured amounts of hormones into the bloodstream that act as natural chemical messengers, traveling to different parts of the body in order to control and adjust many life functions.

2. What is an endocrine disrupter?

An endocrine disrupter is a synthetic chemical that when absorbed into the body either mimics or blocks hormones and disrupts the body's normal functions. This disruption can happen through altering normal hormone levels, halting or stimulating the production of hormones, or changing the way hormones travel through the body, thus affecting the functions that these hormones control. Chemicals that are known human endocrine disrupters include diethylstilbesterol (the drug DES), dioxin, PCBs, DDT, and some other pesticides. Many chemicals, particularly pesticides and plasticizers, are suspected endocrine disrupters based on limited animal studies.

3. What are some likely routes of exposure to endocrine disrupters?

Exposure to endocrine disrupters can occur through direct contact with pesticides and other chemicals or through ingestion of contaminated water, food, or air. Chemicals suspected of acting as endocrine disrupters are found in insecticides, herbicides, fumigants and fungicides that are used in agriculture as well as in the home. Industrial workers can be exposed to chemicals such as detergents, resins, and plasticizers with endocrine disrupting properties. Endocrine disrupters enter the air or water as a byproduct of many chemical and manufacturing processes and when plastics and other materials are burned. Further, studies have found that endocrine disrupters can leach out of plastics, including the type of plastic used to make hospital intravenous bags. Many endocrine disrupters are persistent in the environment and accumulate in fat, so the greatest exposures come from eating fatty foods and fish from contaminated water.

4. How do we know that endocrine disrupters are dangerous?

Many plant and animal species are showing signs of ill health due to exposure to endocrine disrupting chemicals. For example, fish in the Great Lakes, which are contaminated with polychlorinated biphenyls (PCBs) and other man-made chemicals, have numerous reproductive problems as well as abnormal swelling of the thyroid glands. Fish-eating birds in the Great Lakes area, such as eagles, terns, and gulls, have shown similar dysfunctions.

Scientists have also pointed to endocrine disrupters as the cause of a declining alligator population in Lake Apopka, Florida. The alligators in this area have diminished reproductive organs that prevent successful reproduction. These problems were connected to a large pesticide spill several years earlier, and the alligators were found to have endocrine disrupting chemicals in their bodies and eggs.

5. Should humans be concerned for their health based on evidence that fish, birds and alligators have been affected?

Yes. All vertebrates (fish, amphibians, reptiles, birds, and mammals, including humans) are fundamentally similar during early embryonic development. Scientists can therefore use the evidence acquired on other species to make predictions about endocrine disrupting effects on humans.

6. Is there direct evidence that humans are susceptible to endocrine disruption?

Yes. In the 1950s and 1960s pregnant women were prescribed diethylstilbestrol (DES), a synthetic estrogen, to prevent miscarriages. Not only did DES fail to prevent miscarriages, but it also caused health problems for many of these women's children. In 1971, doctors began reporting high rates of unusual vaginal cancers in teenage girls. Investigations of the girls' environmental exposures traced the problem to their mothers' use of DES. The girls also suffered birth defects of the uterus and ovaries, and immune system suppression.

7. Are children at greater risk from endocrine disrupter exposure?

Yes. Because endocrine disrupters affect the development of the body's vital organs and hormonal systems, infants, children and developing fetuses are more vulnerable to exposure. And as was the case with DES, parents' exposure to certain chemicals may produce unexpected -- and tragic -- effects in their children, even decades later.

8. These days don't chemicals have to be safe to be allowed on the market?

No. The majority of the more than 2,000 chemicals that come onto the market every year do not go through even the simplest tests to determine toxicity. Even when some tests are carried out, they do not assess whether or not a chemical has endocrine interfering properties.

9. What can I do to reduce my risk of exposure?

• Educate yourself about endocrine disrupters, and educate your family and friends.
• Buy organic food whenever possible.
• Avoid using pesticides in your home or yard, or on your pet -- use baits or traps instead, keeping your home especially clean to prevent ant or roach infestations.
• Find out if pesticides are used in your child's school or day care center and campaign for non-toxic alternatives.
• Avoid fatty foods such as cheese and meat whenever possible. EDCs are not flushed from an animal's body. Instead, they are stored and accumulate in fat, which then makes its way up the food chain, to be stored in the fat of humans.
• If you eat fish from lakes, rivers, or bays, check with your state to see if they are contaminated.
• Avoid heating food in plastic containers, or storing fatty foods in plastic containers or plastic wrap.
• Do not give young children soft plastic teethers or toys, since these leach potential endocrine disrupting chemicals.

According to the NRDC, the National Center for Environmental Health at the Centers for Disease Control and Prevention has developed analytic techniques which allow measurements of human exposures to many known and suspected endocrine disrupting chemicals. These measurements, usually done on blood samples, are expensive and not available except for specific research projects. NRDC says it is working to increase funding for this testing so that in the future, people may be able to go to their doctor to find out their exposure levels to some of these chemicals, which could result in better research studies.

In the meantime, the NRDC advocates the "Precautionary Principle" with regard to public health. Instead of waiting for proof that chemicals are hazardous, the council believes exposures should be minimized or eliminated until it's determined they do not hurt human health. The burden of "proof," the NRDC believes, should fall not on the public and on government, but on industry. The NRDC states: "Because we do not perform direct studies on human subjects, it is extremely difficult to produce ‘proof' of human harm. Until we shift the burden of proof from organizations and communities (responsible for proving harm) to industries (responsible for proving harmless), unnecessary exposures to unsafe chemical substances will continue to prevail." It should be noted that such safeguards would likely result in higher food prices.