Natural, Yes, But Wood Smoke is Toxic, Too

Science is swiftly turning upside down the common notion that a fire built with wood is kinder to humans’ well-being than gas and other modern fuels.

From California to Sweden and China, researchers are reporting that wood smoke contains large amounts of harmful pollutants, including some of the same toxic chemicals found in cigarette smoke.

Those reports seem counter-intuitive. After all, wood is a natural substance, a heat source since prehistoric times and a seemingly safe alternative to dirty fossil fuels.

But natural does not necessarily mean harmless, and a growing number of published studies are associating wood smoke with asthma, other lung problems and heart disease — some of the same illnesses associated with smoking and with heavy exposure to car and truck pollution.

“Is it as toxic as something coming out of the tailpipe? We’re not sure yet,” said Robert Devlin, senior scientist in the environmental public health division of the U.S. Environmental Protection Agency in Washington, D.C.

But the new consciousness of wood smoke’s dangers is spurring scientific inquiries in communities across the West where wood heat is popular: in California, Montana, Idaho, Seattle and British Columbia.

Wood consists largely of two relatively harmless ingredients, cellulose and a strengthening substance called lignin.

If the wood burned completely, it would turn into simple water and carbon dioxide. But instead it forms what scientists call “products of incomplete combustion” — thousands of chemicals, including certain toxic and carcinogenic substances.

Many of the same chemicals form during the burning of other organic matter — whether waste from orchards and rice fields or tobacco leaves wrapped up in cigarettes.

That is why some scientists compare wood smoke to second-hand smoke and cigarette smoke.

“It’s not the nicotine in cigarette smoke that kills you. It’s the other stuff,” said Kirk R. Smith, a professor of global environmental health at the UC Berkeley School of Public Health who has studied smoke’s health effects around the world.

“The worst thing that you can do with this stuff is stick it in your mouth,” Smith said. “The next worst thing is to have it in your house. The next worst thing is to have it in your neighbor’s house.”

Researchers can rattle off long lists of dangers in wood smoke.

They often focus on the tiny particles — a mere fraction of the width of a human hair — that can lodge in tissue and blood vessels and disrupt lung and heart functions. Some are so small that they can pass right through the walls of blood vessels. Wood smoke also contains well-known cancer-causing chemicals such as benzene and formaldehyde.

Scientists have published dozens of studies on the human health effects of wood smoke. In 2007, a 40-page review of those studies in the journal Inhalation Toxicology concluded, “It is now well established … that wood-burning stoves and fireplaces as well as wildland and agricultural fires emit significant quantities of known health-damaging pollutants, including several carcinogenic compounds.”

Today, most U.S. regulators focus largely on the fine particles in wood smoke to measure its potential for harm, rather focusing on its cancer-causing ingredients as they did with tobacco smoke a generation ago.

The same is true in California.

“The main issue is that it has particulate matter. When it comes to particles, we treat all particles the same. We feel that all particulate matter is bad for you,” said Linda Smith, head of the health impacts section at the state Air Resources Board.

International public health officials have gone further. In 2006, wood smoke was labeled “probably carcinogenic in humans” by the International Agency for Research on Cancer, part of the World Health Organization.

But the 2007 journal review concluded that it was too early to formally link wood smoke and cancer, and that more research is needed.

An American Cancer Society advisory group recommended several years ago that the society not take a position on the issue, deciding “that the evidence linking wood burning smoke to cancer was much weaker than that for heart and lung disease,” the society’s statistics director, Kenneth M. Portier, wrote in an e-mail note.

Some activists believe California should act more aggressively and treat wood smoke just as it does second-hand smoke or fumes from diesel-burning trucks. The state has classified both “toxic air contaminants.”

Wood smoke deserves the same label, said Jenny Bard, regional air quality director for the American Lung Association in California.

“We’re going after tobacco smoke in all sorts of ways,” Bard said. “We’ve banned it from workplaces and restaurants. And the exposures to wood stove pollution can be so much more concentrated in localized situations.”

This story is a result of a partnership between the Center for Health Reporting and the Chico Enterprise-Record.

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5 comments to “Natural, Yes, But Wood Smoke is Toxic, Too”

  1. cynthia

    • Wood smoke from Pizza, steak and BBQ contains carcinogenic chemicals, gas and may have synergistic affect. Should be 700 feet and properly vented –from unenclosed mobile homes. (Huntington Beach -South Coast Air Coast Mgmt. District) Signs should be placed in RV parks and areas where toxic chemicals trespass, hang out with soot (ppm) in humid climates. Research may be needed to show that one street block has, for example, 60% more heart attack death and illness than another. Officials need to become familiar with the new second-hand smoke ie. Wood Smoke. It is magnified the closer one is to the source–Bonfire, fire rings, restaurant smoke stack. Plumes from the smoke drift and become stuck in between buildings and trees. Half gas mask works for daytime for a little while. What do we wear at night to sleep to mimimize the effect?

  2. Maria

    This has nothing to do with nuclear power or gas! The vast majority of wood fires are in people’s homes for pleasure only—not for heat or power! This huge source of pollution and disease could be eliminated over night with no side effects and no need for any sort of replacement if we just…stopped building fires in fire places.

  3. joe Provey

    Good info here, but measuring harm to humans caused by various heat sources is an enormous task. Consider the cost of one major nuclear power plant accident (and don’t tell me it can’t happen given the increase of bozos in our society). It could contaminate an entire state for 100s of years. And what about storing the nuclear waste and decommissioning spent nuclear power plants. Everyone forgets to mention that when discussing nuclear and pollution.

    Then consider gas. Green, right? No, not for the people who live in areas where it’s drilled. The new drilling methods pioneered by Haliburton are fouling water wells in 34 states. (Watch the documentary “Gas Land.”) And then there’s oil. No need to look beyond the latest spill. The dispersants and oil WILL get into the food chain. Is it any wonder that diseases like pancreatic cancer are on the rise. Burning wood seems like the lesser of the evils IF a clean-burning appliance is used.

  4. David

    This is a good reason to go with Nuclear power. No air pollution at all. It is far safer than any other type of power production as proven by the actual number of deaths, illness and injuries over the past 60 years of civilian power production in the west. There are designs that are passively safe such as the Adam’s Atomic Engine, or the new B&W MPower design.

    Frankly, this “study” seems exaggerated. It does not jive with the real life experience I have had with fire places and says nothing about the impact of a wood burning power plant that uses scrubbers.

  5. steve laiken

    I agree 1000000%. I’ll be filing complaint against neighbor this fall. Local air agency appears to be ‘employed’ by wood and hearth industry & has reputation of being useless at the neighborhood level. I saw a site last week that was featuring stickers to put on street sign posts: it said: ‘WOOD SMOKE IS TOXIC WASTE’. I tried to order some but I think I failed. Does anyone know where/how to get some of these stickers? Thanks, Steve in Bothell WA 425-481-5077.

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