Alan Pryor, Yolo Clean Air (September 2008)

Summary of Recent Actions - On July 29, 2008, the Davis City Council voted unanimously to accept the public health-based recommendations of the city's Natural Resources Commission (NRC), a citizen advisory group, to phase-out the use of wood-burning appliances used for space heating in the City of Davis. The Council directed the NRC to draft an ordinance for their consideration that exempts wood-burning in cooking appliances (such as BBQs), during periods of power outages, and for persons with wood as the sole source of heat.

The NRC had grappled with the issue of reducing wood smoke pollution for almost 6 months before sending their unanimous recommendations to the City Council. They explored the published adverse health effects of wood smoke pollution (particularly on children and seniors with respiratory or cardiac impairment) as well as looking at the science of local wood smoke dispersion from different types of fireplaces under different weather conditions. This information was weighed along with various factors such as possible economic impact, ease of enforcement, and relative fairness to parties who may have recently invested in fireplace upgrades.

The timing of the phase-out has yet to be determined and public hearings are not yet scheduled. However, reflective of the fact that open hearth fireplaces emit substantially larger amounts of particulate matter compared to EPA Phase II-Certified stoves, there was a stated intent that users of EPA Phase II-Certified stoves be given a longer phase-out period. During the phase-out period, all wood-burning would otherwise be banned during periods when weather conditions could allow an unhealthy accumulation of wood smoke in neighborhoods. These exact conditions and the tools used to predict them have not been finalized.

Background - With a few exceptions such as in Marin Co. where use of non-EPA Phase II-Certified wood stoves is now prohibited, almost all residential wood burning in California is regulated by regional air quality management districts (AQMDs). When regional airborne particulate matter (PM) concentrations exceed federal air quality standards, by law the AQMDs have to implement an EPA-approved plan to reduce particulate matter in the air. Since wood smoke accounts for between 1/3 and 2/3 of winter PM pollution depending on the area in California, the various AQMD in PM “non-attainment” areas (those regions not meeting the federal PM standards) were forced to implement a program enforcing mandatory cessation of wood-burning during periods of expected poor air quality. The annual number of days and nights that wood-burning is prohibited is a function of the then current regional air quality. In some Valley locations with particularly poor air quality and high urban concentrations of fireplace users (such as Fresno), the newest standards are expected to prohibit burning almost half of the time during the winter.

In contrast, Yolo Co and the eastern portion of Solano Co are in the Yolo-Solano AQMD's jurisdiction and this region enjoys particularly low ambient air PM concentrations compared to other areas of the state. Because the region is in compliance with Federal PM air quality standards, the Yolo-Solano AQMD has not been forced to similarly implement a mandatory wood burning prohibition program. Thus, in Davis there are currently absolutely no restrictions on where or when or with what type of fireplace one can burn wood.

Recently, however, a growing body of evidence indicates that wood-smoke can build-up and concentrate in neighborhoods to levels far in excess of allowable federal standards if mild weather conditions exist - and that this excessive buildup can occur even if regional air quality is almost pristine!

What is the Problem with Wood Smoke – Any wood burning creates smoke particles just as a cigarette produces smoke. These soot or carbon particles are very small in size – generally well less than 2.5 micrometers (and known as PM2.5) but sometimes between 2.5 and 10 microns in size (known as PM10).

According to the San Joaquin Air Pollution Control District, the first AQMD in the state to implement mandatory burn restrictions, “Both PM10 and PM2.5 create health problems related to their ability to penetrate deep into our respiratory system. A number of health studies have established a direct correlation between elevated particulate levels and increased mortality…Children, the elderly, pregnant women and people with respiratory ailments are especially susceptible. Among the health impacts are premature death; respiratory-related hospital admissions; aggravated asthma; acute respiratory symptoms, including aggravated coughing and difficult breathing; chronic bronchitis; and decreased lung function that can be experienced as shortness of breath… Even if you don't burn wood, studies have shown that wood smoke from neighbors' fires can enter your home. Smoke particles are so small they can seep into a home with closed windows and doors. The pollution levels inside a closed home can be up to 70 percent of the levels outdoors” (1) (Underline Emphasis added).

Further, according to an officer of the South Coast AQMD, the largest AQMD in the state covering almost all of Los Angeles and Orange Counties and the Inland Empire, "This [wood smoke] is basically the worst pollution in terms of its health impacts. It has been linked to more than 5,000 premature deaths per year in Southern California” (2) (Underline Emphasis added). Extrapolated from a Southern California population of 20,000,000, this predicts that wood smoke pollution will cause between 12-13 additional premature deaths each year in a city with a population of 50,000!

Comparative Amounts of Particulate Pollution Produced by Different Sources - Most people do not realize that wood-burning produces particulate pollution far in excess of many other sources commonly considered to be very polluting. For comparison, following are the average PM emissions produced from different types of wood-burning appliances, cigarettes, and diesel trucks (1):

On a comparative basis, then, one open hearth fireplace burning for an average of 4 hours produces particulate pollution equivalent to over three new 300-HP diesel trucks running full throttle for the same amount of time or smoking 5,900 cigarettes.

Wood Smoke Mostly Affects Those Closest to the Source - As deleterious as wood smoke is on regional air quality, the effects are much more serious when wood smoke accumulates under stagnant or mild weather conditions in the neighborhood or general vicinity of the wood smoke source. When stagnant, inversion air conditions occur in winter in the Valley with very little to no wind, a blanket of air traps smoke and other pollutants near the ground. These conditions result in the rapid build-up of outdoor smoke that can affect all neighbors within the source's immediate vicinity. Depending on the type of fireplace or insert used and the burning duration, smoke can concentrate under such conditions to many times the allowable Federal 24-hour Particulate Standards within a matter of hours.

For instance, as shown in the following chart, in completely stagnant air a single open hearth fireplace emitting 59.0 grams/hour of particulate pollution per hour into the 100 ft. high environmental envelope surrounding a normal city block will cause the concentration of particulate matter to rise to an average of over 4,500 micrograms per cubic meter in that closed space. This is over 30 times the 24-hour Federal Standard for PM10 pollution of 150 micrograms per cubic meter. It is about 130 times the 24-hour Federal Standard for PM2.5 pollution of 35 micrograms per cubic meter (http://www.yolocleanair.org/woodsmoke.htm).

Even a comparatively clean-burning EPA Phase II – Certified wood stove or insert operating in completely stagnant air conditions will result in PM accumulations in a 1-block area rising to greater than the Federal 24-hour PM2.5 Standard of 35 micrograms per cubic meter in just over 1 hour!

Of course, completely stagnant air conditions extending over a full 24-hour period or of a sufficient duration that can result in these extremely high concentrations are somewhat rare in most locales. However, conditions approaching completely stagnant air can frequently occur during atmospheric inversions in winter months such as often seen in California's Central Valley.

And even with slight winds, wood smoke emitted from a chimney of a wood-burning appliance under relatively stable weather conditions can result in excessive smoke exposure at ground level to downwind neighbors. This can occur as a plume of smoke begins to broaden and disperse at ground level after exiting a chimney. The location, size, and concentrations of pollutants in such a plume depend on the distance from the source and the prevailing atmospheric conditions at the time of release and can be calculated using EPA-approved modeling tools. These results can then be used to predict when excessive ground level particulate concentrations will develop under a variety of atmospheric conditions. Further, much wider plumes with even higher concentrations of ground-level particulate pollution can occur when numerous houses in the same neighborhood are burning wood simultaneously. Under such conditions the wood smoke buildup can build to levels that are immediately dangerous to individuals with impaired respiratory systems.

As quoted from the former chairperson of the Sacramento Air Quality Management District, “Almost half of our particulate matter pollution comes from wood burning fireplaces…This type of particulate matter can be very, very dangerous…For folks with asthma, this can be life-threatening!...Anyone who goes for a walk on a cold evening and all the people in the neighborhood are firing up their fireplaces, they can taste it, they can feel it, it chokes their breathing, it is that noticeable.”(3).

Because a single wood-burning fireplace can produce localized concentrations of particulate pollution that are far in excess of allowable Federal Standards and the potential exists for far greater PM concentration buildup if multiple fireplaces are burning in a single neighborhood and the plumes converge, the NRC determined that an outright prohibition of wood-burning in urban areas is the only reasonable solution that can truly protect susceptible individuals with respiratory problems as well as the general population at large.

Proponents of the measure are cheered that a major public health concern is finally being addressed in Davis. Opponents are dismayed that they may be deprived of the ambiance that their fireplaces provide and the freedom they enjoy with unfettered burning. In weighing these concerns, the NRC and City Council simply determined that health trumps ambiance. It has also been pointed out that the proposed ordinance is hardly the draconian measure that wood-burning opponents claim compared to other rules and regulations designed to protect citizens from smoke pollution produced by others. Indeed, there are currently widespread restrictions against burning of yard waste and smoking is prohibited in some public parks, in almost all indoor public places, and even within 20 ft of an entrance to a public building! Yet wood-burning can produce particulate pollution in quantities thousands of times greater than cigarette smokers and it is completely unregulated. In fact, we are not aware of any other human activity in Davis that produces so much pollution in which there is such a complete absence of regulation governing such activities.

“If you can smell smoke, there is a problem” (4).

References

1. Staff Report on San Joaquin Valley Air Pollution Control District Rule 4901 - Wood Burning Fireplaces-Stoves, June 19, 2003.

2. Sam Atwood, South Coast Air Quality Management District, “Pollution Linked to Premature Deaths”, KABC Channel 7, June 1, 2007.

3. Jeff Starsky, Former Chairperson of the Sacramento Air Quality Management District, Insight, National Public Radio, November 21, 2006.

4. United States Environmental Protection Agency, Consumer Information Sheet, “Reducing Air Pollution from Residential Wood Burning”, September 12, 2005.

Note

The Sierra Club Yolano Group supports vigorous efforts to reduce wood smoke pollution because of the proven adverse health effects on susceptible populations. The management committee has not taken a position on this specific local issue because a final ordinance has not yet been proposed.