TORONTO - Humans and wildlife have an increasingly difficult time reproducing and growing as more toxic chemicals are dumped into the environment, a U.S. scientist says. Cancer has long been considered the most serious result of pollution, but recent research has shown that may not be the case, said Theo Colborn, a senior fellow at the World Wildlife Fund in Washington.

"The really devastating problem is the functional effects - systems (in the body) don't function properly, so they don't function properly," she said in an interview. The most dramatic sign of trouble is that some male birds, animals and humans - exposed to toxic chemicals in the egg or womb have much lower sperm counts than normal adults. Male also develop some female characteristics and females often become less feminine, Colborn said.

The chemicals, including dioxin and polychlorinated biphenyls, are getting into the air, water and food from car exhaust, sewage and industrial pollution, garbage burning and the use of pesticides on, farms, golf courses and lawns Colborn said.

The latest findings on how chemicals affect health are to be published in a book with chapters by 21 North American scientists. "We've been hung up on cancer or gross birth defects," such as birds with thin eggshells, missing wings or twisted beaks, Colborn said.

But the impacts many scientists are now concerned about are more subtle. As pollution levels fell in the 1980s, "eggshell thinning went away and we though the problem was finished," she said. "But it wasn't." When the body is developing either during pregnancy or after birth - it's like a computer being programmed, Colborn said. Tiny changes in chemistry can have a big impact on how the brain, thyroid gland, reproductive system and other parts of the body work. Although the changes are subtle, results can be dramatic, according to several studies Colborn cited:

One U.S. study suggested that men exposed to a banned hormone that was used to speed the growth of cattle have reduced sperm counts.

Studies in Michigan and North Carolina found slower physical and mental development in children whose mothers had high PCB counts in their body fat and breast milk.

Some female beluga whales in the heavily contaminated St. Lawrence River estuary develop breasts before puberty.

Roosters given one dose of dioxin didn't grow cumbs or learn how to crow.

Some bald eagles returning to nest near the Great Lakes are giving up after two or three years because they don't reproduce.

Male rats given a single small dose of dioxin produced sperm that can't penetrate female eggs.

A species of Great Lakes tern exposed to chemicals in the wild fails to look after its young or protect its nest.

The solution is to stop the release of chemicals into the environment. Colborn said.