AIR pollution could be harming future generations as well as those directly exposed to it. A small study in Canada suggests pollution from coal fires can trigger genetic defects that are passed down the generations.
鈥淚t鈥檚 important work,鈥� says a US government scientist who did not want to be named. 鈥淥f course, here we have an administration that is rolling back pollution controls on coal-fired power plants, so they aren鈥檛 going to be happy to hear this.鈥�
Air pollution causes many health problems but the question of whether it has any inherited effects is difficult to study. James Quinn at McMaster University in Hamilton, Ontario, found genetic effects in herring gulls exposed to polycyclic aromatic hydrocarbon pollution. PAHs, produced by burning coal and many other fuels including diesel, cause mutations in lab animals exposed to large doses. But the gulls also consume contaminated water and fish.
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To find out if simply breathing in such pollution every day has any effect on DNA, Quinn鈥檚 team set up two 鈥渕ouse hotels鈥� near local steels mills that run on coal. Many coal-fired factories and power plants throughout the world produce the same type of pollution as these mills.
The 鈥渉otels鈥� were heated and ventilated sheds, each containing 20 male and 20 female rodents. One shed was 1 kilometre downwind of two steel mills, while the other was in a rural area 30 kilometres away, in a direction perpendicular to the prevailing winds. For ten weeks, the mice were exposed to the air while being fed clean food and water. They were then brought back to the lab, mated and their progeny examined for genetic changes.
Even after that brief exposure, the genetic impact was easy to detect. As a sensitive measure of mutations, the researchers examined small, repetitive DNA sequences that often mutate. While these sequences don鈥檛 have a vital function, increases in their mutation rate should reflect those elsewhere in the genome.
About 20 per cent of the rural controls had mutations in chromosomes inherited from their fathers. In the mice exposed to the pollution, however, the rate was 30 per cent. No significant effect was found in maternal sequences, suggesting the pollution mostly affected the cells that give rise to sperm. The litter size of the pollution-exposed mice also tended to be smaller, suggesting that lethal mutations had killed some fetuses.
Since species as diverse as gulls and mice are affected, it seems likely that people would be too. 鈥淚 work in these areas all the time for my research,鈥� says team member Christopher Somers. 鈥淵ou can鈥檛 help but wonder what is happening to your own sperm.鈥�
Such pollution could increase the risk of cancer during people鈥檚 lifetime as well as causing mutations passed on to children. How serious it is isn鈥檛 clear 鈥� the effects of radiation, a far better studied cause of mutations, are still controversial.
Since PAHs and other toxic chemicals tend to cling to tiny particles, the team want to see if filtering the air will lower the mutation rate. 鈥淣ow that we鈥檝e found the problem, we鈥檇 like to find a solution,鈥� says Somers.