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EPA Misses Historic Opportunity to Reduce Wood Smoke Pollution

The William Jefferson Clinton Federal Building, Washington, D.C., which is the headquarters of the U.S. Environmental Protection Agency. Image: U.S. EPA

On February 7, following a multi-year process, the U.S. Environmental Protection Agency announced an update of the National Ambient Air Quality Standards for Particulate Matter. These standards set the maximum allowable levels of fine particulate matter (PM2.5). 

Scientists acknowledge that PM2.5 is one of the most hazardous of all air pollutants, and the standards are meant to protect the public by ensuring air pollution is kept below levels that are known to harm health. Under the Clean Air Act, the EPA is supposed to review, and revise if necessary, the standards every five years based on current scientific evidence. 

First for the good news: the EPA announced it is planning to lower the annual PM2.5 standard from 12 μg/m3 (micrograms per cubic meter) to 9 μg/m3.

However.

There are actually two PM2.5 standards. The second (and arguably more important standard) is measured over a 24-hour period. The 24-hour standard hasn’t been changed since 2006, the year the Dow Jones Index first crossed 12,000 (it’s now above 38,000). Since then, there has been a deluge of scientific evidence linking PM2.5, even at extremely low levels, to serious health problems and premature death.

Last year, thousands of people and organizations, including ours, submitted comments to the EPA urging them to lower the 24-hour PM2.5 standard. We pointed out in our submission that lowering the 24-hour standard was critical for protecting public health from wood smoke pollution.

During the rule-making process, the EPA acknowledged that the 24-hour standard is the more important one in communities affected by wood smoke pollution. They noted that in areas affected by localized sources of pollution, including wood burning, that the “24-hour standard is generally the controlling standard,” meaning it is the more relevant one for protecting air quality. 

The majority of the EPA’s own Clean Air Scientific Advisory Committee (CASAC) recommended lowering the 24-hour standard. They specifically expressed concern that the annual standard did not protect people in areas affected by wood smoke pollution.

So how did the EPA respond?

By deciding to leave the 24-hour standard unchanged at a whopping 35 μg/m3, the same level that was set back in 2006.

To put that in perspective, the World Health Organization recommends a 24-hour standard of 15 μg/m3.

This is not good news for the significant numbers of Americans affected by pollution from wood burning. 

According to the EPA’s own National Emission Inventory, more PM2.5 pollution in the U.S. comes from wood burning than from motor vehicles or from industrial processes. Wood burning is the largest source of PM2.5 pollution in many communities, such as the San Francisco Bay Area.

During the 18 long years since the 24-hour PM2.5 standard was last updated, the scientific evidence of harms from PM2.5 has only grown stronger. Will we have to wait another 18 years before the EPA finally lowers the 24-hour PM2.5 standard? 

And more importantly: how many people will needlessly suffer or die from wood smoke pollution in the meantime?  

Do Wood Stove Changeout Programs Actually Work?

We recently came across a page on the British Columbia Lung Association website that touts the success of their long-running wood stove changeout program. The page claimed that the program, which began in 2008, has “reduced particulate matter emissions by over 400 tonnes per year.”

This claim struck us—to put it politely—as surprising, so we wrote to the Lung Association asking them for details. They never replied.

What made us so skeptical of this claim? For one thing, an in-depth evaluation of the British Columbia wood stove exchange program published in 2014 noted that 6 years after the program began, “…there has not yet been a clear reduction in fine particulate matter pollution coming from residential wood stoves in BC.” Another study that compared pollution levels in homes before and after the program concluded, “There was not a consistent relationship between stove technology and outdoor or indoor air quality indoor concentrations of PM2.5.”

Perhaps things had turned around since those studies were published? Apparently not, since the BC Lung Association’s own 2018 “State of the Air” report shows that there were no significant decreases in PM2.5 (particulate matter smaller than 2.5 microns in diameter) from 2008 to 2017.

One might reasonably ask: What’s going on here?

Our educated guess is that the BC Lung Association’s claimed reduction in PM2.5 of 400 tons per year is likely a calculated reduction based on taking the certification values of EPA wood stoves and multiplying them by the number of wood stoves that have been changed out through the program.

This is like claiming that you lost 20 pounds based on counting how many calories you ate last month rather than actually weighing yourself.

So why wasn’t the program as effective in reducing wood smoke pollution as it was projected to be? The answer is simple: EPA-certified wood stoves do not perform as well in the real world as they do under the laboratory test conditions that are used to produce their certification values. Indeed, it is widely acknowledged by the EPA—and even by the hearth products industry—that wood stove certification values do not correlate well with the in-home performance of wood stoves.

One study found that certified wood stoves operated by homeowners in their own homes produced up to 30 times more particle pollution than their certification value.

The Trouble with EPA Certified Wood Stoves

There are many reasons why EPA certified wood stoves perform differently in the real world than they do in the test lab. In the real world, people burn wood that isn’t perfectly dried. They “damper down” their wood stove overnight or when their home gets too warm. They overfill the firebox with logs. In reality, it takes a lot of work to burn wood properly—and the end user doesn’t have a lot of incentive for doing so, since the majority of the pollution they create disappears up their chimney and out into the neighborhood.

While EPA certified wood stoves have been aggressively promoted as a panacea, in reality an improperly operated EPA certified wood stove emits more pollution than a properly operated conventional wood stove. Even if EPA certified wood stoves performed as well in real life as their lab certification values would suggest, a single stove would emit more fine particle pollution than hundreds of homes using a gas furnace (electric heat pumps produce almost no particle pollution).

Largely due to industry influence, the EPA test method is gamed to present an unrealistically optimistic picture of wood stove performance. For example, rather than logs, it uses kiln dried lumber that is arranged in a crib formation and specifically excludes the massive amount of pollution that is created when the wood stove is started up.

Wood Stove Changeout Programs: Disappointing Results

The sad reality is that the effectiveness of wood stove changeout programs that incentivize the sales of new EPA certified wood stoves has never been adequately demonstrated in real world studies. Yet in spite of this, due to pervasive industry influence, wood stove changeout programs have become the de facto response by air quality regulators to the problem of wood smoke pollution.

The Hearth, Patio and Barbecue Association is the main lobbying organization for the wood stove industry. On a website they host dedicated to wood stove changeout programs, there is a section dedicated to “success stories.” While these success stories include details about capturing “congressional earmarks” to fund new wood stove sales, they curiously do not include data showing actual air quality improvements (other than, once again, calculated estimates).

The one program that is constantly cited in favor of wood stove changeout programs was subsidized by the wood stove industry and took place in Libby, Montana. From 2005–2007, 95% of all the non-certified wood stoves in the community were replaced. In the year following the changeout, PM2.5 levels fell by 27%. But this was less than half the reduction that would be expected if the new, certified stoves actually emitted 70% less particulates than the old stoves, a figure cited by the EPA.

Notably, the relative contribution of wood smoke to PM2.5 levels was unchanged following the changeout, raising the question of whether the PM2.5 reduction was due to changes in wood stove technology or to another factor, such as newer cars on the road. Moreover, a study of air quality at two schools found that “…the changeout did not result in a measurable improvement on school indoor air quality.” When researchers looked at air quality inside houses following the changeout, 5 of 21 houses actually showed increased PM2.5 levels.

A Better Solution to Wood Smoke Pollution

If changeout programs that subsidize sales of new EPA certified wood stoves don’t work, what does?

Somewhat ironically, the 2014 report on the British Columbia program showed the way forward, stating: “For many communities, the elimination of wood burning for heating may be the desired path to reduce exposure to pollutants.” In other words, if you want to eliminate wood smoke pollution, don’t encourage or subsidize the use of new wood stoves. Instead, subsidize only cleaner heating devices, such as electric mini-split heat pumps or gas heaters.

A changeout program in Launceston, Australia attempted to do just that, offering incentives to encourage homes that were heating with wood to switch to electric heat. Even though only half of the homes that were using wood heat converted to electric heating, particle pollution levels fell by 40%.

Despite the evidence that the British Columbia wood stove exchange program has not reduced particulate matter pollution from wood smoke, the 2014 report on the British Columbia wood stove exchange program states that “…the program has been very successful.” If PM2.5 levels haven’t dropped, how is success measured? Apparently by the number of stoves that are exchanged, even if air quality isn’t improved. This might be a win for the wood stove industry, but it isn’t a win for the residents of British Columbia who must live with the harmful effects of wood smoke pollution.

It’s not difficult to see why the wood stove changeout scheme rolls on: it gives regulators an easy way out by allowing people to continue burning wood. In reality, however, the idea makes as much sense as using public funds to subsidize light cigarettes for tobacco users instead of encouraging them to quit smoking.

(Photo: Kim Nilsson)

Families for Clean Air Launches Air Monitoring Network Focused on Wood Smoke Pollution

Map of air monitors designed to detect hazardous wood smoke pollution.It has been well documented that wood burning devices create localized air pollution hot spots—but these neighborhood hot spots are often located far from official government air quality monitoring stations.

The result? A large number of households may be breathing highly polluted air, even when the established monitoring networks are showing the air quality to be good.

In an effort to address this discrepancy, Families for Clean Air has recently launched an air monitoring network in the San Francisco Bay Area.

The network utilizes PurpleAir PA-II air monitors to analyze the air quality of neighborhoods where there are currently no EPA or local air district monitors. The PA-II contains a sensor that uses a dual laser beam to count particles based on their reflectivity and provides real-time information about PM1.0, PM2.5, and PM10. This information can then be viewed on a map online—you can see air quality data at your home in real time, as well as information from other PA-II sensors.

Sound complicated? It isn’t. You simply attach the sensor to the outside of a structure, plug it into a power source, and connect it to your home’s Wi-Fi network. Readings are uploaded to the cloud every 80 seconds or so, where they are stored for download and displayed on the PurpleAir map.

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

House with wood stove drawn by a child

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

wood burning stoves cause air pollutionIn 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.