Perils of chemicals outlined in lecture

By Meredith Macleod
The Hamilton Spectator(May 8, 2006)

Not all hormones are created equal. Some are the real thing and others are doing a really good impersonation.

Dr. Warren Foster, director of the Centre for Reproductive Care at McMaster University, will be presenting a lecture about how environmental and dietary chemicals can mimic hormones and affect health and fertility as part of the Science in the City series tomorrow night.

It's the last in this year's series, a partnership between McMaster University and The Hamilton Spectator.

Hormones are naturally-made chemicals in our bodies which stimulate and inhibit growth, development, the immune system and metabolism and play vital roles in puberty, reproduction and menopause.

There are several dozen hormones in the human body, but the ones most commonly known are sex steroids such as estrogen, testosterone and progesterone.

For about 15 years, scientists have known that natural and man-made chemicals in food and the environment, can behave like hormones.

The first warning signs, says Foster, were found in fish downstream from pulp and paper mills.

"The male fish started to look like females. Their testes had ovarian cells in them."

Foster explains that hormones bind to cell receptors like a key fitting in a lock. Somehow, outside chemicals can replicate the key.

Studies found that chemicals such as PCB, dioxins and pesticides like DDT could mimic the effects of estrogen. When given to mice and rats, the chemicals could change the structure of ovaries. Research has also found that cigarette smoking has a profound effect on fertility. Women who smoke or are heavily exposed to second-hand smoke are about half as fertile as non-smokers, says Foster.

What's not clear is where in the reproductive cycle the chemicals in cigarettes are causing trouble. Some chemicals, for example, could cause eggs to die, some may interfere with an embryo's ability to attach itself inside the uterus.

But not all impersonators are bad. Some seem to have beneficial effects, says Foster. Most research has focused on estrogen and its mimickers because it is the most "promiscuous," said Foster.

"More chemicals bind with it than with testosterone or others. There's something funny in the chemistry that we can't explain."

That could have huge implications for human health because there are many estrogen-dependent ailments, including breast and testicular cancers, endometriosis, lowered sperm counts and male reproductive abnormalities.

So far, scientists have not been able to find the guilty chemicals, says Foster.

"We have suspicions and chemicals of interest but we couldn't go to a prosecutor and say this is the culprit."

In fact, Foster isn't convinced there is enough evidence to say environmental chemicals are affecting human reproduction and fertility. There are puzzling and troubling signs but no smoking gun, he says. For instance, a study of sperm counts in 13 Canadian cities over 13 years found some had increased counts, others stayed the same and some dropped.

Foster, who has served as associate director of women's health and director of research at Cedars-Sinai Medical Center in Los Angeles and as the head of reproductive toxicology at Health Canada, studied an individual sperm donor. His count varied from zero to 200 million. Many factors, including sexual activity, medications and viruses in the body, can affect the counts.

"This is a very complex puzzle we're trying to tease apart."

The lecture will be held at the Hamilton Spectator Auditorium. Doors open at 6:30 p.m. and the talk begins at 7 p.m. To reserve your seat, e-mail sciencecity@mcmaster.ca or call 905-525-9140, extension 24934.

mmacleod@thespec.com

905-526-3408