Wood smoke harmful to health and DNA, study finds
AIR POLLUTION Wood smoke can hurt DNA
Published 4:00 am, Monday, March 14, 2011
Nevada County - On a frosty evening in the Sierra Nevada, smoke curling from the chimney of the Clair Tappaan Lodge is a welcome sight for chilly snowshoers and cross-country skiers. Gathering by the massive stone hearth at this landmark Sierra Club mountain hostel, guests relax in the warmth and aroma of the crackling log fire.
Woodsy scents waft across the region, as millions of fireplaces and wood stoves are lit by people seeking environmentally friendly sources of heat and ambience. But new research is raising concerns about the toxic substances in that smoke.
Tiny airborne specks known as particulate matter produced by wood-burning stoves appear to be especially harmful to human health. Small enough to deeply penetrate the lungs, they contain high levels of carcinogenic chemicals. They're capable of damaging DNA and activating genes much like car exhaust and tobacco smoke, according to a new study in Denmark. Another new study, conducted in Canada, found that infants and toddlers were significantly more likely to get ear infections if they lived in an area with a lot of wood stoves and fireplaces.
Because wood is a natural material and has been an integral part of human existence for so long, many view it as a benign, cheap and renewable energy alternative. But wood smoke can exacerbate asthma symptoms, and is especially harmful to children and older people. The emissions also have been linked to respiratory disease, atherosclerosis and other coronary problems, and early deaths among people with cardiovascular or lung disease.
"We know there's a lot of bad stuff released when wood is burned," said Dr. John Balmes, a professor of medicine at UC San Francisco and professor of environmental science at UC Berkeley's School of Public Health. "It's actually not that far away from tobacco smoke and smoke from fossil fuel combustion engines. They're in the same ballpark."
Bay Area bans
March 1 marked the seasonal lifting of the nine-county Bay Area Air Quality Management District's ban on wood-burning during Spare the Air alerts. The Bay Area is home to an estimated 1.7 million fireplaces and wood stoves. The most frequent violations of the fireplace and wood-stove restrictions in the past two years came from bucolic Sonoma County.
Because the smoke vents outside, health risks from the particles given off by fireplaces and wood stoves can be greater for the neighborhood than for the people sitting fireside.
Until recently, little was known about the specific harmful agents in wood smoke. The University of Copenhagen project is one of the first to characterize the minute particles and droplets of pollution released by wood fires.
The researchers analyzed air samples from a Danish village where most homes used wood-burning stoves, and compared it to background particles outside the smoke area. They determined that wood smoke was more likely to comprise extremely small particles that can lodge in lungs and pass into the bloodstream.
When added to cultures of human lung cells, the particulates from wood smoke generated large amounts of powerful oxidants that are able to injure cells, damage DNA and trigger oxidative stress, the authors reported. This can set off an inflammatory reaction that scars tissues and interferes with the body's mechanism for fighting off infection. The researchers concluded that wood smoke particulates were more powerful in damaging DNA, activating genes linked to disease and weakening immune response than were the background air pollution particles from a variety of sources.
Risk of ear infections
This may explain what happens with otitis media - a painful middle-ear infection. Researchers from the University of British Columbia compared doctor visits for children ages 2 and under in the Vancouver area to wood smoke pollution levels during the same period.
Children with the highest exposures "were 32 percent more likely to visit the doctor for otitis media compared to children" with the lowest exposures, said lead author Elaina MacIntyre, a scientist at the University of British Columbia's School of Environmental Health.
The California Air Resources Board estimates that breathing fine particulates from all sources contributes to about 9,200 premature deaths from cardiopulmonary disease every year. About a third of the Bay Area's wintertime fine particle pollution comes from residential wood-burning.
So is it safe to cozy up to that inviting hearth at the mountain lodge or fireplace at home?
"If you don't have asthma I think it's OK," Balmes said. "If it's an efficient fireplace with good updraft, it doesn't expose the people sitting near the fireplace."
Rather, "it's the people downwind" who are exposed, he said.
MacIntyre cautioned that families with young children in wood-burning areas should keep the windows closed and use a HEPA air filter.
"Parents should be aware that wood smoke is an important risk factor in the development of childhood respiratory infections and that wood-burning increases the risk of these infections, not only for their own children, but also for children in their neighborhood," she said.
At the Clair Tappaan Lodge, guests use the fireplace almost every night. The wood is dried and cut into small pieces to minimize smoke, said Peter Lehmkuhl, the lodge's general manager.
"There's just something about a fire," Lehmkuhl said. "It's very meditative to sit there and think about your day and stare at that fire and reflect on where you are. Dealing with a very primal element there, the fire."
For more on this story, go to www.environmentalhealthnews.org.