New Paper Examines Effects of Wood Smoke Pollution on Children’s Health

A paper recently published in a leading American medical journal should be of concern to anyone raising children in a neighborhood where people use wood stoves or fireplaces.

The paper is the result of a systematic review of the scientific literature to explore the consequences that living in areas impacted by wood smoke has on children’s health.

The authors only included studies that focused on the respiratory health effects of wood smoke on children in developed nations. All of the studies met strict inclusion criteria and were published in peer-reviewed journals.

Their findings? The authors concluded that, “Studies found community wood smoke exposure to be consistently associated with adverse pediatric respiratory health.”

The associations between neighborhood wood smoke and negative health effects were observed in children of all ages and included a plethora of respiratory ailments: “When wood smoke was higher, children had more upper respiratory tract infections, bronchitis, bronchiolitis, otitis media [ear infections], and hospital admissions for respiratory illness. Children with asthma had worse lung function when community wood smoke was higher.”

The toxic particles in wood smoke are small enough that even closed windows and doors don’t stop them from getting into nearby houses. In many areas, even if a family doesn’t burn wood, they have no choice but to breathe their neighbor’s wood smoke pollution. And wood stoves and fireplaces produce a lot of pollution, accounting for 30% of the fine particle pollution in many areas. The authors note, “Children living in wood-burning communities, regardless of whether there is a
 wood stove in the home, may be at higher risk for adverse respiratory health.”

The findings offer little comfort to the parents of children who are growing up in neighborhoods with wood burning. Although some sources recommend the use of EPA-certified wood stoves as a panacea for wood smoke pollution issues, the performance of these devices is entirely user-dependent, and the emissions reductions are not nearly as effective as touted. In fact, changeout studies in Montana and British Columbia showed little effect on wood smoke pollution. The most effective solution is for people to stop burning wood.

Unfortunately, far too many people remain unaware that breathing wood smoke is one of the worst things you can do to your health—or your children’s.

More Evidence that “Clean” Wood Burning Isn’t Clean

In an effort to reduce air pollution from wood burning, government agencies worldwide have used public funds to subsidize supposedly cleaner burning devices, such as EPA certified wood stoves.

Replacing old wood stove technology with newer wood stove technology is often touted as the solution to wood smoke pollution, especially by those who manufacture and sell wood stoves. The results of these interventions has been consistently disappointing, and large wood stove changeout programs in Montana and Canada have not improved air quality as projected. Now, from Australia, comes a study  that again shows the folly of subsidizing purportedly cleaner wood burning. In Perth, a town heavily impacted by wood smoke in Northern Tasmania, approximately 80% of the households were supplied with a commercially available catalytic device for their existing wood heater. The manufacturer of the device states that it reduces particle emissions from individual wood heaters by up to 54% in a laboratory setting.

The study measured fine particle pollution levels in Perth before and after the devices were provided.

The results? No significant changes in ambient PM2.5 concentrations were found. These results reflect, once again, the disconnect between lab results and real world results. They show that introducing new “less polluting” technology in the context of continued wood burning is not an effective way to reduce wood smoke.

What does work? The only interventions that have been shown to consistently reduce wood smoke pollution are those that convert households to other forms of heat that—no surprise—don’t involve burning wood.

Catalytic Wood Stoves Shown to Increase Dioxin Emissions

People buy EPA-certified wood stoves with the expectation that they’ll reduce air pollution. Ironically, they may be doing the exact opposite.

A study by Finnish researchers published in the scientific journal Chemosphere found that a wood stove with a catalytic converter emits much higher amounts of highly toxic dioxins and furans than one without a catalytic converter. The study’s authors conclude their article with the warning, “…the usage of platinum and palladium based catalytic converters to reduce emissions from RWC [residential wood combustion] should be critically evaluated before wide-range utilization of the technology.”

Unfortunately, this warning has gone unheeded: While catalytic converters have historically been used in some EPA-certified wood stoves in order to reduce fine particle pollution, the EPA’s new wood stove standards, which are more stringent, are expected to drive more manufacturers to use catalytic technology.

The Finnish study burned birch logs in a wood-fired stove with and without a catalytic converter that used palladium and platinum as catalysts and analyzed dioxin/furan, chlorophenol, and PAH (polycyclic aromatic hydrocarbon) production during combustion.

What they found was shocking: although PAH emissions were 24% lower when the catalytic converter was used, the chlorophenol emissions were 430% higher and the dioxin/furan emissions were a whopping 870% higher.

Dioxins are some of the most toxic chemicals known to science and are a potent carcinogen. In addition to cancer, exposure to dioxins can result in birth defects, immune system impairment and reproductive and developmental problems. Notably, threats to human health occur at extremely low levels of exposure to dioxins.

The study exposes a glaring omission in the EPA standard: while EPA-certified wood stoves are tested and certified for particle pollution emissions, they are not tested for the other highly toxic substances they produce, including formaldehyde, benzene, dioxins, and polycyclic organic matter.

Due to active lobbying by the hearth products industry, government agencies have been using public funds to subsidize sales of EPA-certified wood stoves in an effort to reduce fine particle pollution. Studies about changes in air quality following these wood stove changeouts show that these programs did not improve air quality as expected and do not provide justification for further public funding.

In light of the findings of the Finnish study, an even more sinister picture emerges: wood stove changeouts could be more than just ineffective—they could, in fact, make air pollution far more hazardous.

Wood Burning Causes Climate Change: Incentivizing New Wood Stoves Isn’t the Solution

Tucked away on page 102 of a report recently issued by the California Air Resources Board (CARB) is a remarkable statement: By 2030, residential wood burning is projected to be the single largest individual source of black carbon in California.

When it comes to climate change, black carbon can be considered Public Enemy Number Two, with scientists stating that it is “…the second most important human emission in terms of its climate forcing in the present-day atmosphere; only carbon dioxide is estimated to have a greater forcing.”  In the atmosphere, black carbon absorbs solar heat. This not only heats the atmosphere, it also melts the earth’s snowcaps and glaciers when these particles settle on the ground.

Eliminating or reducing wood burning is one of the easiest and most effective ways to curb climate change, but the same report from CARB goes on to say that they are considering incentivizing the replacement of old wood stoves with—wait for it—new wood stoves. Unfortunately, this cognitive dissonance is not unique to CARB. Ontario, Canada recently unveiled a similar program targeting black carbon and other short-lived climate pollutants that allocated $400 million for replacing old wood stoves with “new high-efficiency wood stoves.” Not surprisingly, the Hearth, Patio, and Barbecue Association, a trade group that lobbies on behalf of the wood stove industry for these wood stove changeouts, has hailed the Ontario program as “providing an economic boost”

While these wood stove changeout programs are undoubtedly good business for wood stove manufacturers and retailers, there are many reasons why they are a terrible idea for climate change.

First, if these programs instead incentivized the replacement of wood stoves with cleaner heating devices that run on natural gas or electricity, the result would be far greater reductions of black carbon and other short-lived climate pollutants. As a bonus, this would also have other benefits, including lower CO2 emissions, lower particulate emissions, and lower toxics emissions. This would be a win not only in terms of climate change, but also in terms of human health.

Second, the realized SLCP reductions from these so-called “wood to wood” conversions will be far lower than the reductions projected by CARB and others. Although EPA-certified wood stoves are predicted to have lower emissions of particulates, including black carbon, based on their laboratory certification values, it is openly acknowledged by the EPA and even by the wood stove industry that certification values do not correlate well with the in-home performance of wood heaters. In other words, the stoves are much dirtier in the real world than in the lab.

Third, the projected black carbon reductions from wood to wood conversions are based on the improved efficiency of EPA-certified wood stoves (i.e. less wood burned per BTU of heat generated) compared to conventional wood stoves—but this efficiency is unlikely to be realized in actual use, especially in temperate climates such as California. A more efficient EPA-certified wood stove may indeed generate more heat per unit of wood burned, but because wood stoves do not have thermostats, they continue to heat the home even after it has reached a comfortable temperature. When a home becomes too warm, the wood stove will be operated at less efficient settings as the user reduces the combustion air to the device. Even worse, the fire may be allowed to die when the house warms up, only to be restarted at a later time–generating massive start up emissions.

Finally, previous government-funded wood stove changeout programs provide sobering cautionary tales by not delivering the expected benefits. For example, every wood stove in the Libby, Montana area was changed out to EPA-certified wood stoves at a total cost of over $2.5 million. The 28% reduction in particulate pollution, which includes black carbon, was nowhere near the expected 56% reduction, and the contribution of wood smoke to ambient PM2.5 levels had not changed several years later.  And in British Columbia, a total of 6067 old wood stoves were replaced as part of a change-out program. An in-depth evaluation of the program several years later noted, “…there has not yet been a clear reduction in fine particulate matter pollution coming from residential wood stoves in BC.” Had either of these programs been conversions to natural gas or electric heaters, the emissions would have plummeted.

It’s good news that governments are finally acknowledging the role that residential wood burning plays in climate change, and are ready to take action. Unfortunately, promoting more wood burning is not the way to do it.