SEX RATIO OF FISH IN ALBERTA RIVERS RAISES RED FLAGS
Researchers say skewed sex ratio of fish in Alberta rivers raises red flags
at 18:55 on July 29, 2010, EDT.
Shannon Montgomery, The Canadian Press
CALGARY – Alberta researchers say gender-bending fish swimming in the province’s southern rivers raise serious questions about whether the water is safe for people to drink.
Two University of Calgary professors have been studying how a small species of minnow reacts to a wide variety of hormone-altering chemicals detected in several rivers.
They found sexual changes both in the wild populations of the fish and under controlled lab experiments with the same chemicals, said co-author Hamid Habibi.
He said while it’s not known whether the levels are high enough to hurt humans, there is a possible risk the chemicals could increase cancer rates or developmental abnormalities.
“We think there’s a health concern,” he said Thursday. “We’d like to be able to predict these things and reduce that kind of risk.”
In some locations, female fish accounted for as much as 90 per cent of the minnow population, far higher than the normal 55 to 60 per cent.
At many of the sites studied, male fish showed elevated levels of a protein normally high only in the blood of females. Other areas have produced male fish with female eggs in their testes.
Habibi and co-author Lee Jackson found a large variety of chemicals that affect hormones in the water. They include synthetic estrogens, such as the birth control pill and bisphenol A — a chemical used in making plastics — as well as agricultural byproducts.
The disturbances in fish populations were greater downstream from cities than upstream and were most notable around several major cattle feedlots.
One area of high concentration was interrupted by a normal region where the river is joined by several tributaries from Waterton National Park.
The researchers managed to replicate many ofMoneygram money orderthe changes in a lab environment by combining the chemicals in the same ratio as found in the river.
They also discovered that while a single chemical might affect a fish one way, the combined effect with another chemical might be much greater than expected.
In one case, two chemicals might each have a one-fold effect on a fish, while in combination the effect might be nine times bigger.
“The potency of these chemicals improves significantly if they are present in a mixture. That is new information,” said Habibi.
“Which means some of the data used by Health Canada and EPA (the Environmental Protection Agency in the United States) may need to be revised, because they’re based on individual studies for those chemicals.”
Jackson said most wastewater treatment plants don’t get rid of many of the chemicals.
The researchers have partnered with the City of Calgary to begin work at a new treatment plant investigating how engineering can keep the chemicals from flowing back into the water.
He said it’s too early to tell whether the current levels in water might have anything to do with a rising trend of cancers that are under hormonal control, but he added that a possible link should be studied.
“I think we need to look at this a little more carefully and ask, what is the message the fish are telling us,” he said.
“If the fish are showing bent genders and people are drinking the same water … we need to try to evaluate that risk.”
Part of the research is to be published in the journal Environmental Toxicology and Chemistry.