Sunday, December 26, 2004
Pollution alters body chemistry
Substances in environment upset hormonal balance
By Brian H. Jensen
For the Poughkeepsie Journal
Scientists have begun to recognize that chemical contaminants in the environment have far-reaching effects on the endocrine systems in living creatures. The effects are most striking in animals that live in the water, but there may be implications for human health.
The endocrine system is the group of organs, including the thyroid and pituitary glands, that produce hormones that regulate mood, growth and development, tissue function, and metabolism, as well as sexual function and reproductive processes.
Chemicals that may disrupt the endocrine system are present in the Hudson Valley -- and around the world. As open space is replaced by suburbia, we are more and more likely to be exposed to these chemicals, as are the animals that live in the environment around us. That's because the sources for chemicals that disrupt the endocrine system can enter water from many dispersed sources.
Endocrine disrupting chemicals are any chemicals that interfere with the normal function of endocrine glands. These chemicals can affect any gland, but most research has been done on chemicals that act as estrogen, known as environmental estrogens.
There are many known environmental estrogens, some of which are quite common. Some of the most common environmental estrogens are:
- PCBs (Polychlorinated Biphenyls) are a cocktail of many different chemicals that studies show can affect the thyroid and reproductive functions. PCBs were once used widely in industry as a fire suppressant, but were banned in the United States in 1977 and worldwide this year.
- PAHs (Polyaromatic hydrocarbons) form as a result of the degradation of petroleum products like gasoline and motor oil. Some of the effects that have been attributed to these chemicals include increased risk of cancer in mammals and inhibition of ovulation in fish.
- Some pesticides are also known to act as environmental estrogens. For example, the pesticide atrazine has been shown to have estrogenic effects in fish, and a byproduct of the banned pesticide DDT, DDE is know to be a potent environmental estrogen. Some of the effects that have been attributed to these chemicals include behavioral changes, feminization and malformation of the phallus in male reptiles.
- Pharmaceutical drugs like the birth control pill and estrogen replacement pills have been found not only in wastewater, but also in trace amounts in drinking water. Scientists have only identified trace amounts of these chemicals in recent years, and there have not been studies to determine what, if any, effect they have. Plastics contain chemicals that slowly leach out of the plastic and, some studies show, these chemicals in their pure form have biological effects very similar to estrogen.
These chemicals can enter the environment in a variety of ways. PCBs in the Hudson River are there largely because of General Electric Co.'s manufacturing plants north of Albany. Now-banned pesticides were used widely on farms. PAHs enter the environment whenever petroleum is burned. Plastics slowly degrade, leaching out chemicals. Pharmaceuticals originate in homes, and enter the environment through septic and sewage systems.
There have been some who suggest environmental estrogens are responsible for low sperm counts in men and earlier onset of puberty in females.
However, it is very difficult to say exactly what effect endocrine disrupting chemicals have on humans and there have not been any conclusive studies.
Although the effects of endocrine disruptors have not been demonstrated, there are some very clear examples of endocrine-disrupting chemicals having profound effects on other animals.
The most striking, but not only, of these examples is Lake Apopka in central Florida. In 1980 there was a chemical spill near the lake that included the pesticide DDT. The chemicals from the spill have been seeping into the lake and have had severe effects on the alligators living there. Male alligators in Lake Apopka are very frequently born with small malformed penises. In addition to the problems with their phalluses, they also have testes that are feminized and do not function properly.
Although less dramatic, but more relevant to the animals in the Hudson Valley, there have been several studies done that found that male trout caged in polluted streams produced a protein called vitellogenin that is normally only produced by female fish as part of the egg-making process. Laboratory studies have also shown a broad range of effects of low levels of environmental estrogens, including deformation of testes and behavioral changes.
Endocrine-disrupting chemicals cannot be classified based upon their chemical structure because there is so much variability between different chemicals. Therefore, scientists have been working to develop tests to determine if a chemical has an endocrine effect.
For environmental estrogens, one of the most popular techniques involves exposing male fish to the chemical in question and then determining if the males fish produce a female specific protein called vitellogenin. If they produce vitellogenin, it can be concluded that the chemical is having an estrogenic effect.
Other scientists are using model systems that only used cells grown in the lab, or single-celled organisms to try and identify endocrine-disrupting chemicals. Currently, however, animal models appear to show the most promise because the complexity of the endocrine system and the chemicals acting on it.
There is action being taken to limit the amount and number of endocrine disruptors in the environment.
DDT, PCBs banned
There have been some great successes in dealing with endocrine-disrupting chemicals such as DDT and PCBs, both of which are now banned, but there is still much to be done.
For chemicals that have been identified as endocrine disruptors, government intervention is needed. Maybe more importantly, scientists need to continue their work to identify potential endocrine-disrupting chemicals and better understand how they act.
Thankfully, local professionals, led by Pace University, have organized the Environmental Consortium of Hudson Valley Colleges to begin working together to find solutions to our many environmental problems.
Brian Jensen is an assistant professor of biology at the College of Saint Rose in Albany.
Endocrine system in humans
The endocrine system regulates a variety of bodily functions by secreting hormones into the blood stream.
The pituitary gland controls many functions of the other endocrine glands.
Parathyroid glands regulate the body's calcium and phosphate.
The thyroid regulates metabolism and the body's calcium.
The thymus produces white blood cells that fight infections and destroy abnormal cells.
Adrenal glands help the body to deal with stress, regulate metabolism, produce sex hormones, and regulate sodium and potassium.
The pancreas plays a role in digestion, as well as hormone production.
The ovaries produce estrogen and progesterone.
Sources: World Book Encyclopedia; http://www.umm.edu
; Journal research
Effects of environmental estrogens on male trout
Scientists have identified several ways certain chemicals affect the endocrine systems of aquatic animals, like fish and amphibians. Effects, if any, on the human endocrine system have not been proven.
- Brain: the trout's behavior changes and "sex drive" is reduced.
- Testes: become reduced in size, produce egg-like structures and sperm count decreases.
- Liver: the female specific protein vitellogenin is produced.
Sources: Brian H. Jensen; Journal research
Informant: Teresa Binstock