Phil McKenna, New Scientist 1 May 09;
Smoke from forest fires may contain potent mutagenic compounds that can damage human DNA, according to a controversial new study of fire emissions.
Researchers found nitrogen-rich alkaloids in smoke billowing from a controlled burn of Ponderosa pine trees in Missoula, Montana.
The findings could have significant health implications for those downwind of forest fires, especially smouldering, low-temperature fires such as prescribed burns that produce more smoke than higher-temperature wildfires.
The presence of alkaloids – naturally occurring toxins produced by trees and other plants – has long been suspected in smoke from forest fires, but the new study is the first to detect the compounds coming directly from a blaze.
Julia Laskin of the Pacific Northwest National Laboratory in Richland, Washington, and colleagues made their discovery using a specialised device to collect ultra-fine particles from the smoke of a forest fire. They then used high-resolution mass spectrometry to determine which molecules the particles contained.
Laskin says the alkaloids can be transported hundreds or even thousands of miles and play an important role in cycling nitrogen through ecosystems, but also have the potential to be quite harmful.
"Some of them are really toxic," says Laskin. "It's very well known that when cows, for example, eat pine needles they die. In a forest fire you emit aerosols into air that contain those same compounds."
'Warning flag'
Ralph Propper, an air pollution specialist at the California Air Resources Board isn't so sure.
"I'd be more concerned about eating heavily charred meat," says Propper, referring to the well-documented carcinogenic affects of burnt food.
He says the study's claim that alkaloids produced by plants can alter or damage genes is an overstatement. "That's just not accurate, a very minor percentage of alkaloids are mutagenic," he says, noting that caffeine and cacao (the key ingredient in chocolate) are also alkaloids.
Propper, emphasising that he is stating his opinion and not that of the CARB, goes on: "The pine needles of Ponderosa pine are toxic to some degree – that's how they defend themselves, with alkaloids – but there isn't anything in this paper to show that they are mutagenic."
The study's main shortcoming is that it identifies classes of compounds found in smoke rather than specific compounds, he says. "It certainly gives a warning flag that the possibility for mutagenic or carcinogenic compounds exists, but they need to do a lot more work to establish that," says Propper.
Journal reference: Environmental Science & Technology (DOI: 10.1021/es803456n)
