PUBLICATION National Post
DATE Tue 09 Feb 1999
EDITION National
SECTION/CATEGORY Discovery
BYLINE Mark Bourrie
COLUMN TITLE Ecology

In the first experiment conducted in Canada to try to map the effects of endocrine disruptors -- chemicals that imitate the female hormone oestrogen -- federal government researchers working near London, Ont., have discovered that pig farm operations are among the sources releasing the hormones into the environment.

The male offspring of animals that are exposed to endocrine disruptors are sometimes born with bizarre deformities, or are sexually scrambled, having both male and female reproductive systems. (Female offspring do not suffer such effects.)

The field experiments for the new study were completed between April and September. It adds to the findings of similar experiments in England, which found the country's rivers are being contaminated with hormones from another source -- sewage treatment plants. Women excrete the natural hormone, oestrogen, in their urine.

A five-member team, comprised of scientists from Environment Canada and from Agriculture and Agri-Food Canada, tested creeks in Ontario's Thames River drainage area last summer to determine if oestrogen in hog manure dumped in fields could seep into streams.

Scientists suspect the agriculture industry is a major source of endocrine disruptors.

Mark Servos, who is head of the project at Environment Canada, said his team kept caged fish near drainage pipes for several weeks last summer, then tested them to see if they had been exposed to oestrogenic compounds.

While the scientists did find the fish were exposed to endocrine disruptors, Dr. Servos said there is no risk to human health at current levels.

``There's a big difference between the way a fish is impacted, and a human is,'' he said.

``Humans are adapted to deal with certain kinds of endocrine disruptors and things. A fish is getting it directly into his gills so something like oestrogen will come into his gills and go directly into his system. We take it in through our food, and it might get degraded in our stomachs or degrade in the liver, and the body can deal with it.''

In humans, high levels of endocrine disruptors are believed to damage foetuses, and the effects can be passed down through several generations.

Sewage treatment plants, which were found by British researchers to be dumping endocrine-disrupting chemicals into rivers, are a cause of concern, Dr. Servos said.

Endocrine disruptors trick an animal's hormone system. Endocrine glands secrete hormones that act as chemical ``messengers:'' By binding to ``receptors'' in cells, the disruptors are able to trigger responses that guide cell development, reproduction, and behaviour.

One way endocrine disruptors interfere with natural hormones is by binding with hormone receptors. Some disruptors then ``mimic'' the natural hormone, producing an identical cellular response. Others act as hormone ``blockers'' that produce no response but prevent the natural hormone from doing its job.

(An endocrine disruptor can also interfere with natural hormones without receptors binding.)

Not only do many industrial and household chemicals mimic female hormones, the synthetic oestrogen of birth control pills tends to survive in the environment.

Those chemicals are causing problems in the ecosystem, Dr. Servos believes, after they travel through women's urine into the sewage system.

Dr. Servos says oestrogen from birth control pills and natural hormones are probably working together to cause responses in fish downstream of sewage outfalls.

In the hog manure, he says, the natural hormone may be acting along with another compound, probably natural plant materials that are oestrogenic, to increase the disruptors' effects.

Dr. Servos said the findings are worrying and scientists need to do more work. But not all scientists, including members of last summer's research team, believe endocrine disruptors are an important problem.

``Preliminary results in studies on endocrine disruptors are mixed,'' says Ed Topp, an Agriculture Canada scientist who was one of the five members studying the pig manure.

``The results are worth following up, but they're not worth panicking over. The whole issue of endocrine disruptors is vague, and I don't believe the causal link [between farm chemicals and animal defects] has been proven.'' Further experiments by the study team will try to determine whether natural hormones are responsible for the abnormalities.

The team is also currently conducting tests to determine whether the disruptors examined in the Thames River study have exhibited any effects on fish.

The federal government is under pressure from environmentalists to take a tougher line on endocrine disruptors.

Back-bench government MPs, the so-called ``Green Liberals,'' are also demanding that the new Canadian Environmental Protection Act regulate the chemicals.