Wood Smoke Pollution Kills More than Two Million People a Year

Here in the US, most of us don’t get exposed to extremely high levels of wood smoke inside our homes. But just like studying the lungs of two-pack-a-day smokers tells us about the harms of cigarette smoking, studying the effects of exposure to high levels of wood smoke tells us about the many ways that wood smoke can harm our health.

And what it tells us is not good.

When families in developing countries burn wood and dung in their homes for cooking and warmth, the fires produce levels of pollution that lead to the premature deaths of about 2 million people each year, more than either malaria or tuberculosis.

This disturbing news is discussed in a 2012 interview with Dr. Kirk R. Smith, a member of the National Academy of Sciences and Professor of Global Environmental Health at the University of California at Berkeley. Dr. Smith has spent decades studying the health effects of indoor air pollution due to biomass burning on women and children in developing countries.

Dr. Smith notes that there are parallels between the dangers of cigarette smoke and wood smoke. “Most people recognize that the worst thing you can do is stick burning stuff in your mouth. The second worst thing is to have burning stuff inside your house…”

According to Smith, “A fire in the kitchen, if you’re cooking a meal, produces about the same pollution per hour in a typical house as a thousand cigarettes burning. So, if you think about a thousand cigarettes burning inside your kitchen, it’s not surprising that there are significant health effects. The big difference is that children and babies don’t smoke, but they are in kitchens and are also being exposed to the household pollution, so there’s a large impact on children.”

Smith’s research focuses on interventions in developing countries to reduce the harm from wood smoke. Unfortunately, despite many programs that have introduced supposedly improved stoves, these programs have not been effective.

Smith explains, “…those stoves don’t get rid of the smoke, they just move it around. What you have to do now, I believe, is eliminate it; don’t produce the stuff in the first place.”

For more information about the effect of wood smoke in developing countries, see When Smoke Gets in Your Lungs.

Beyond Particulates: Toxins in Wood Smoke

In many areas, wood burning is the largest single source of particle pollution in winter months.

But what about toxic compounds?

A recent study by the Australian EPA sheds some light on this topic, and it’s an eye opener. For example, look at formaldehyde, which is a potent irritant and carcinogen. The study found that in the Sydney region, 38% of the formaldehyde in the air is generated by residential wood heaters.

Another example is polycyclic aromatic hydrocarbons (PAHs), which also cause cancer: 35% comes from wood burning.

Perhaps most frightening is the data for dioxins and furans, which are some of the most toxic compounds known to man–39% is generated by wood burning.

These numbers are even more troubling when you consider that they are annual figures and that wood burning in the Sydney area takes place for only about a third of the year. During the winter months, residential wood heaters likely account for more than 50% of these toxic compounds in the air.

Before you breathe a sigh of relief that you are not living Down Under, bear in mind that wood burning activity in the Sydney area is not any worse than in many areas in the United States and around the globe.

To date, attention has focused mainly on wood burning as a source of particle pollution. This study makes it clear that wood burning’s role as a source of toxic and carcinogenic compounds may pose an even greater threat to human health and to the environment.

Wood Burning vs. Natural Gas: No Contest

Families for Clean Air recently received a letter that asked for references backing up our assertion that the emissions from EPA-certified wood stoves are greater than those from devices that burn natural gas. This information is available from many sources, including the US EPA, but we think the chart below from the Puget Sound Clear Air Agency illustrates the point in a clear and simple manner (you may click on the image to enlarge):

As bad as this chart may make things look for wood burning devices, we’d like to note that it actually makes the relative performance of wood burning stoves seem more favorable than it actually is. First, the emissions of wood burning stoves are tested under laboratory conditions that bear only a passing relationship to how they are likely to actually be used in the real world. Second, studies have shown that the performance of EPA-certified wood stoves can deteriorate over time.

Thus, the wood stove data probably reflect ‘best case scenario’ stove performance in laboratory conditions.

Any way you slice it, it’s clear that gas burns much more cleanly than wood, leading to less particulate pollution.

New Evidence of the Effect of Wood Smoke on Climate Change

A recent study by scientists at the University of Leeds finds that the influence of soot generated by wood burning on climate change has been greatly underestimated.

This study, which is the first comprehensive and quantitative analysis of the role of soot in the climate system, concludes that particles from wood burning and diesel engines have twice the warming effect calculated in previous estimates. Soot, which is also called black carbon, is second only to carbon dioxide in terms of its effects on warming the climate. This study shows that black carbon has a warming effect approximately two thirds that of carbon dioxide.

Black carbon in the atmosphere absorbs solar heat. This not only heats the atmosphere but also melts the earth’s snowcaps and glaciers when these particles settle on the ground.

Eliminating or reducing wood and other biomass burning may be one of the easiest and most effective ways for us to curb global warming. Co-lead author Dr. Tami Bond notes, “Since black carbon is short lived, the impacts would be noticed immediately.” That’s because while carbon dioxide remains in the atmosphere for relatively long periods, existing black carbon emissions are washed out of the atmosphere in just a few weeks.

“Reducing emissions from diesel engines and domestic wood and coal fires is a no-brainer as there are tandem health and climate benefits,” said Professor Piers Forster from the University of Leeds

This study highlights the fact that not only does wood smoke pollution have harmful effects on human health, wood smoke harms the health of our planet as well.