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Why Your Neighbor’s Wood Smoke is Killing You

Wood smoke from wood burning devices is hazardous to healthIn many locations, wood burning is the largest contributor to wintertime particulate pollution (PM2.5). An important new study from scientists at the Harvard School of Public Health demonstrates just how harmful this pollution is to human health.

What they found is alarming. In the study’s sample of 2.4 million people, there were higher death rates in zip codes with higher particulate pollution levels than in those with lower levels. Even small increases in PM2.5 led to higher death rates, with each 10 μg/m3 increase in PM2.5 resulting in a 7.52% increase in mortality. This increase in death rates was seen even in zip codes in which the annual exposures were below EPA standards (the current limit is 35 μg/m3 PM2.5 daily).

The new study used satellite data to determine particle levels and temperatures in every zip code in New England, which is a much larger geographical region than previous studies. It then analyzed the corresponding health data of everyone covered by Medicare ≥65 years old in this area from 2003–2008. The results both confirm and extend previous research that shows a strong relationship between particulate pollution, adverse health effects, and increased mortality.

The findings add weight to charges from the public health community that the EPA standards for particulate pollution are insufficient to protect our health, since the air pollution levels tied to higher death rates were just one-third as high as the current levels mandated by the EPA.

As author Joel Schwartz notes, “This study shows that [current EPA limits are] not enough. We need to go after coal plants that still aren’t using scrubbers to clean their emissions, as well as other sources of particles like traffic and wood smoke.” According to Schwartz, there is no clear threshold below which particle pollution is safe.

Since any increase in PM 2.5 levels result in increased death rates, it means our society must rethink our attitudes toward wood burning. We can no longer afford to regard the smell of wood smoke as something evocative, nostalgic, or natural.

The science is not subject to debate: if someone is burning wood, they are shortening the lives of their neighbors.

Last Chance to Take Action on the Bay Area Wood Burning Regulation

This Friday, May 8th, is the final day to submit public comments on the Bay Area Air Quality Management District’s proposed amendments to the wood burning devices rule. The proposed amendments can be read here.

It’s important that the air district hears from people who are concerned about the hazards of wood smoke pollution—they will certainly be hearing from those who aren’t. If you haven’t already sent in your comments, we urge you to do so before the deadline.

Your comments don’t have to be complicated, and they can simply be emailed to the air district at:


In your comments, we encourage you to mention the following points:

  • You feel that wood smoke pollution is a significant issue for public health and the environment.
  • You are in favor of more stringent regulations to reduce pollution from wood burning devices.
  • You urge the air district to step up it’s enforcement of all wood smoke regulations, especially in regards to those who are burning improperly or burning on days when wood burning is prohibited.
  • You feel there needs to be additional measures to protect people from localized pollution “hotspots” on days when there is no wood burning restriction in place. Local concentrations of particle pollution can be 100 times higher for people living near wood burners than what is measured at the nearest monitoring station.
  • You believe that there should be no incentives offered to encourage people to purchase new wood-burning devices, even if they are EPA-certified.

Thanks for taking the time to stand up for healthy air and a better environment.

Wood smoke pollutionThe EPA’s Rules for New Residential Wood Stoves: A Sell-Out to the Wood Stove Industry?

On February 4, the EPA issued its long-awaited final rules for the manufacture and sale of new residential wood stoves. We weren’t fans of the proposed rule, and we think the final rule is even worse. After intense lobbying, the EPA caved to industry pressure, and the result is a rule that may do more harm than good to air quality.

Cordwood Testing: Up in Smoke

One of the biggest problems with the existing EPA wood stove certification process is that it uses kiln-dried lumber arranged in a crib formation. Since people don’t operate their wood stoves like this in the real world, the proposed EPA rule sought to address this by specifying the use of cordwood in the testing process.

Unfortunately, lobbying from the wood stove industry spurred the EPA to back away from this common sense step forward and to revert to testing with kiln-dried cribwood, not cordwood, for stove certification. This makes it impossible to extend the in-lab findings to the real world. Even in laboratory tests in controlled conditions, emissions from burning cordwood are higher than from burning cribwood (see studies here, here, and here), so in-home emissions will certainly be higher than projected.

Lower Wood Stove Emissions—But For How Long?

The EPA’s decision to lower allowed emissions from wood stoves in the new rules was applauded by health and environmental groups as a way to lower particulate matter (PM) emissions. But a closer look shows that this limit may have no effect—or even the opposite effect—on emissions in the longer term.

To meet these lowered emission limits, wood stove manufacturers are likely to use catalytic wood stove technology. Unfortunately, these catalytic components can break down in as little as two years. And when the components begin to wear out, the PM emissions increase dramatically. Stove maintenance is entirely voluntary; the proposed rule does not address the issues of degradation or proper maintenance of catalytic components.

Clearly there’s no economic incentive for the user of the stove to replace the catalytic components. There is also no functional reason for them to replace the catalytic components: the negative consequences of degraded catalytic components, which are primarily increased emissions, occur mostly outside the end user’s home. Thus, there is no reason to think that owners will replace the degraded catalytic components or expend the effort to maintain them properly.

The EPA states that the lifespan of a wood heater is over 20 years. Therefore, after a few years of use, wood smoke emissions from catalytic wood stoves will potentially be as high as those from an uncertified conventional wood heater. Thus, the unintended consequence of the EPA’s lower emissions limit is likely to be higher emissions.

The Long Phase-Out Period

After lobbying from the wood stove industry, the EPA settled on a generous (to industry) 5-year phase-out period for manufacturers to transition to the new standards and sell off their existing models.

The industry is already leveraging this extended transition as a way to gin up sales of wood stoves by making consumers feel like they must act now before the new EPA rules take effect (and prices increase). One ad for an outdoor wood boiler urges consumers to act now, claiming that they will only be available for a limited time:

Outdoor Wood Boiler Ad

VOCs and Air Toxics

In their summary of the final rules, the EPA claims that the lower emission limits will reduce VOC pollution. Unfortunately, as far as we’re aware, there is no scientific basis for this claim.

The new rules do not test for, or necessarily reduce, VOCs or air toxics (including formaldehyde, benzene, dioxins, and polycyclic organic matter). Importantly, studies show that these are not reduced in parallel with PM emissions (see here, here, and here). One technical report prepared for the EPA concluded, “The data demonstrate that particulate emissions cannot be used as a surrogate measurement for POM [polycyclic organic matter] emissions of woodstoves.”

The EPA’s mission is to protect human health, and this rule was originally intended to reduce wood smoke pollution to decrease the harmful effects of wood smoke. Unfortunately, we have several reasons to fear that these measures may make things even worse.

A Lack of Natural Gas Service is No Longer an Excuse for Wood Burning

Many rural areas in the US still lack natural gas service, and these areas often have the highest rates of residential wood burning (and the highest wintertime air pollution).

The reliance on wood burning for home heating in these areas is rationalized on the basis that the cost of electric heat or propane is too expensive. This rationale has even held sway with air quality regulators, who have exempted areas not serviced with natural gas from wood burning restrictions on days when the air quality is poor or predicted to be poor (see, for example, the policies of the San Joaquin Valley and the San Francisco Bay Area Air Districts).

But now, thanks to advances in technology, heating a home with an electric split ductless heat pump is cheaper than heating with natural gas (see here, here, and here). Sensiblenergy.com provides a detailed four-part comparison of the cost of heating a moderate-sized house in Portland, Oregon using gas vs. oil vs. electricity. (Part 4 is here with links to the other parts.) The conclusion? Using a split ductless heat pump is the cheapest of these options.

Split ductless heat pumps are extremely efficient because they move heat from one place to another rather than generating heat from energy. (A more detailed explanation of how they work can be found here.) Installation does not require ductwork, which can be expensive and difficult to put in. In fact, the cost to purchase and install a split ductless unit is comparable to the purchase and installation of a wood stove. Note that these units can cool as well as heat–try doing that with a wood stove.

Wood burning is one of the most damaging activities an individual can do in terms of the impact on the health of their neighborhood. Now there’s one less excuse for doing it.

Study Shows Wood Smoke Pollution Levels Vary Widely Within a Neighborhood

Proving once again the real estate mantra, “Location, Location, Location,” an important new study raises serious concerns that wood smoke pollution at some residential locations is much higher than previously estimated. Specifically, the study reports huge variations in the exposure levels to wood smoke at different locations within a single neighborhood.

In this well designed field study funded by the California Air Resources Board (CARB), researchers compared measurements of wood smoke pollution within a one-kilometer area of a small California coastal town. The sampling occurred on 15 nights over two winter seasons. Notably, the town has no significant sources of air pollution, such as traffic or industry, other than residential wood combustion.

The researchers found that there were large variations in wood smoke pollution levels even within this small area. How large? Measurements in some locations were up to 300% higher than the area average.

This means that people living in the same neighborhood are being exposed to radically different levels of hazardous air pollution—and that some unfortunate households are being exposed to much higher air pollution levels than shown by centrally located air monitors.

This study illustrates why central air monitoring, which reports the average particulate pollution at a single location, is not an effective tool for measuring wood smoke pollution.

It also lends urgency to the recent call by Utah Physicians for a Healthy Environment to ban wood burning in densely populated areas.