David Stonehouse Science & Health

Smokestacks pose hazard to DNA: study

Genetic mutations can trigger cancer, be passed to future generations

By David Stonehouse

A startling new scientific study suggests people living near industrial smokestacks are at risk of passing along genetic mutations that could trigger the onset of cancer.

The study, conducted by researchers at McMaster University in Hamilton and published in a prestigious American scientific journal, found that living near steel mills can damage DNA, causing genetic flaws that can then be passed on to future generations.

The research was conducted on mice, but the scientists say humans living near smokestacks from some industries are likely exposed to the same risk.

"I don't think there is a reason for panic or anything like that," says Christopher Somers, one of the researchers. "But I do think as a resident of Hamilton, I am certainly concerned. I think other people should be as well."

The study discovered that a colony of laboratory mice placed one kilometre downwind from two steel mills at Hamilton Harbour suffered from a higher chance of DNA mutation than another colony set up in a rural area 30 kilometres away.

The mice living near the mills had more mutations in their genes, which could be passed to their young, and had smaller litters than the country mice that were not downwind of the mills.

The study warns that chemical pollutants from steel mills "may pose a genetic hazard to humans and wildlife."

The mutations did not cause any evident diseases or malformations, but the scientists are concerned about what may happen in the future as the defective gene passes from generation to generation.

"It is sort of like a canary in a coal mine situation, where we can see the canary is dying, but we're not yet there. So, we view it as potentially a warning," says James Quinn, another of the researchers.

"This is purely speculation, but the worry would be that it could be genetic changes that would introduce cancers. Some of the cancers are based on genetic mutations," he says.

"That would be the most likely direct impact of mutagens on human populations. But as I say, that's speculation," says Mr. Quinn, an associate professor of biology at McMaster who began studying the effects of steel mill pollution a decade ago.

"I think it is reasonable speculation."

Although the researchers did not blame any specific chemical compound within the steel mill discharges for the genetic changes, they believe their findings would apply to similar industries that burn fossil fuels, such as coal-fired power plants.

The research team urges more study into how air pollution from heavy industry affects the human gene.

"Our results suggest that a thorough investigation of the genetic hazards associated with occupational and incidental exposure to contaminated air in urban and industrial areas is warranted," the researchers declare in a paper published in the latest edition of the Proceedings of the National Academy of Sciences.

The findings also prompted Mr. Quinn to call for more stringent air pollution regulations.

"I feel that the industries need to be regulated a little more heavily," he says.

"There are suspicious compounds. We can't isolate a particular chemical that is responsible for these mutations, but we do have some educated guesses as to what kinds of compounds they could be."

One is polycyclic aromatic hydrocarbons, a group of more than 100 different chemicals formed during the incomplete burning of coal, oil and gas, garbage, or other organic substances.

Past experiments by other researchers exposing lab mice to polycyclic aromatic hydrocarbons showed some cancers as well as birth defects, according to the U.S. Department of Health's Agency for Toxic Substances and Disease Registry.

Mr. Quinn's earlier research looked at how herring gulls nesting near the mills are affected. And while that work found higher gene mutation rates, it was unclear whether the mutations were caused by contamination in the air, water or the gulls' food.

The research with the mice enabled Mr. Quinn and his colleagues to zero in on the potential consequences of air pollution, free of the other factors.

Because of the previous work, the genetic mutations did not come as a surprise to the researchers. But they were surprised by how quickly it happened.

"I was a little surprised that something as short as a 10-week exposure could cause the effect. That's a fairly short exposure, and it is air only -- the same air that I am breathing when I'm down there working on the mice," says Mr. Somers, a doctoral student studying applied ecology.

The scientists are now compiling and analysing results from research examining whether filtering the polluted air eliminates the gene mutation in mice.