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Great Lakes Article:

Steel mill smoke can trigger mutations
Charles Choi
United Press International

HAMILTON, Ontario-- Steel mill smoke can mutate DNA, leading to genetic damage that could persist for generations, Canadian scientists reported Monday.

The new data in mice suggest wildlife and the hundreds of thousands of people who live or work near steel mills worldwide could experience higher-than-expected rates of inherited genetic diseases.

"What is somewhat surprising and concerning is that heritable DNA mutations were significantly elevated after only 10 weeks of ambient air exposure," lead researcher Christopher Somers, an applied ecologist at McMaster University, told United Press International.

The researchers now are conducting experiments to see if filtering chemical-laden soot can dampen its mutative effects.

"If the results are as we expect them to be, a better filtration of emissions would be called for, or a better enforcement of regulations," said senior researcher James Quinn, a molecular ecologist also at McMaster University.

The discovery is backed by nearly 10 years of similar research of Quinn and his team in herring gull flocks nesting around the Great Lakes.

"We knew that birds living near steel mills had elevated rates of DNA mutation compared to those at rural sites," Somers said. "Furthermore, the closer that gull colonies were to steel mills, the higher their DNA mutation rates."

Although Quinn and colleagues had suspected smoke from the mills was responsible, air pollution was hard to nail down as the key culprit. Other factors could not be eliminated, such as contaminated water or disease.

To isolate and analyze the effect of air pollution, Somers, Quinn and others housed lab mice in cages exposed to open air for 10 weeks from September to November 1999. One shed containing 40 mice was placed one kilometer downwind of two steel mills in Hamilton Harbor on Lake Ontario, with another group of mice placed in a rural area about 30 kilometers away. All were kept warm with electric heaters.

In a report published in the Dec. 9 online version of the Proceedings of the National Academy of Sciences, the investigators found mice nearer the mills had offspring with roughly twice as many genetic mutations as the rural mice. The mice near the mills also had slightly smaller litters -- roughly six as opposed to about eight -- although these offspring were not any smaller than normal.

"This study is very important and forms the basis for more of its type, because it shows the actual exposure animals and humans receive in a real world, natural situation," said molecular biologist Bradley White of Trent University in Peterborough, Ont. "Most studies are laboratory based."

Areas of DNA were analyzed that are predisposed to high mutation rates and do not directly affect the health and development of offspring. Although that might be a point of criticism, Somers said, he noted previous studies involving hazardous radiation have provided strong evidence that mutation rates are related in both active and inactive regions of the genetic map.

Somers explained studying DNA that is unusually sensitive to mutation is the same as bringing a canary into a coal mine is to spot deadly gas.

"You don't the canary and the miners to die at similar exposure levels, otherwise the warning system is of little value," he explained. "We want to detect mutations that are of no direct consequence early, in order to prevent those of the more dangerous type later."

The researchers are trying to determine which air pollution components cause this mutation effect. The main ingredients of the smoke are chemicals called polycyclic aromatic hydrocarbons, or PAH. They are byproducts of incomplete fossil fuel combustion and prior studies in bacteria have revealed they are highly mutagenic.

PAH concentrations were 50 times higher near the mill than away from it, researchers found. The compounds usually attach themselves to soot and tend not to travel far, they said. Levels of PAH from car exhaust in urban environments lie somewhere in between.

"Our biggest obstacle is the lack of research funding," Somers said. The projects he described were funded by a Canadian federal program that was discontinued in 2002.


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