OVER the Christmas holidays, the sleepy Okanagan Valley town of Valley town was covered with a layer of sparkling white snow Above it, hanging invisibly in the stagnant air, was a second layer of nasty pollutants.
During this period, smoke from wood stoves and fireplaces laced the air with contaminants, some so small they could pass directly into lungs The weather was "a classical episode" of pollution from residential woodburning, says Peter Reid, a regional airquality meteorologist with the B. C. government.
The warmth of a blazing fire holds a special appeal for romantics, outdoor enthusiasts and golden retrievers, but recent research shows that its smoke poses serious health risks "It's not an insignificant problem especially for those with respiratory difficulties, says Scott McDonald, executive director of the B.C Lung Association.
Cleanair activists have been saying exactly that for the past 15 years. A study published in 1980 by John A. Cooper, titled Environmental Impact of Residential Wood Combustion Emissions and Its Implications, described more than 100 chemicals associated with wood smoke, including carbon monoxide, formaldehyde gas, nitrogen oxide, tiny particulate matter and polycyclic aromatic hydrocarbons.
Many of the pollutants are similar to those produced by burning tobacco, and some U.S researchers say breathing in wood smoke is comparable to inhaling secondhand cigarette smoke.
The threat to human health comes from the fine particulate matter tiny particles 200 times smaller than raindrops Several epidemiological studies have concluded that inhaling wood smoke particulate matter increases the incidence, duration and severity of respiratory disease, striking hardest at children, the elderly and those with lung or heart disorders.
Concerns over wood smoke
in the mid eighties put a damper on residential wood burning in
some areas. In the Colorado ski town of Telluride, for example,
several air-quality-conscious homeowners went so far as to put
legal restrictions on their property deeds that would require
their heirs never to allow "solid fuelburning devices.
on the property But most of North America was cold to the idea
of putting controls on wood burning smoke. The Seattle region
created smoke police to hand out tickets to polluters However,
a recommendation from Vancouver's medical health officer to impose
a ban on all woodburning fireplaces and stoves in new residential
construction was dismissed by a local alderman as "imbecilic"
and rejected by city council.
John Blatherwick, Vancouver's medical health officer, proposed the failed ban on fireplaces and stoves in 1991. But despite ridicule by city aldermen, Dr. Blatherwick still holds the same views, and feels vindicated by a report on the health effects of wood smoke that was completed two years later for B. C.'s health officer.
The report, by Sverre Vedal an associate professor with the University of British Columbia's lungdiseases research unit, said studies show that children living in = affected by wood smoke have lower levels of lung function during and following the wood burning season. It also said children have lower lung function the day after exposure to high concentrations of wood smoke.
Researchers have found that fine particulate matter lodges in and alters lung tissue, increasing the incidents of respiratory illness, cardiovascular stress and aggravating asthma, particularly for children. Only particles smaller than 10 micrometers in diameter can be inhaled into the lung without being intercepted by the nose or pharynx and only these smaller particles pose a threat to the respiratory system
Dr. Vedal says that almost all particles generated by wood combustion are smaller than 10 micrometers. Information on physician visits "strongly suggests" that woodsmoke exposure can increase the risk of respiratory illness.
He also reported some good news: There is little evidence that exposure to wood smoke at North American concentrations can be linked to an increased risk of cancer in a healthy person. [ See rebuttal to this point by Mary J. Rozenberg]
He cautioned that any attempt to estimate the health effects of wood smoke involves many assumptions. Generally speaking, he said, air has fewer than 50 micrograms of tiny particulate matter per cubic metre.
With this benchmark Dr. Vedal decided to calculate the impact of a 50 micrograms-percubicmetre increase in tiny particulate matter due to wood smoke. The results showed that 25 per cent of children in the exposed population experienced a slight decrease in lung function; twice as many children experienced lower respiratory symptoms; four times as many were absent from school; and emergency visits for asthma increased by 20 percent.
About 400,000 Canadian homes use wood as the primary heating fuel, and many more use fireplaces and wood stoves as supplementary sources of heat or because they enjoy the esthetics of wood burning.
Environment Canada meteorologist Fred Conway says pollution from residential woodburning is not high on the agenda in Ontario. Wood is not used widely as a fuel in the large urban areas, he says, and the smoke disperses quickly in rural regions.
The Atlantic provinces are more dependent on wood for home heating than else where, but it is in British Columbia that smoke from residential woodburning poses the greatest threat to health. Here, inversions in weather patterns frequently warm the air on mountainsides, trapping cooler air and smoke at ground level in valleys and allowing the concentration of pollutants to build up.
B. C. Hydro has estimated that about 100,000 homes in B. C. use wood as the primary fuel; an additional 200,000 use fireplaces and woodburning stoves occasionally, Several valley communities have air quality problems on cold, clear nights.
Vernon, a city of 31,000 located at the confluence of two valleys has among the highest concentration of fine particulate matter in the province, especially during the cold months, but scientists are still searching for a conclusive link to a source. Analysis of airquality samples from 1992 to 1994. though, found that the air quality is poor for at least 61 days a year.
Mr. Reid and other researchers say more work on air monitoring is necessary before conclusions can be drawn about Vernon. Meanwhile, in other woodburning areas, the impact of wood smoke may be mitigated by new wood stoves and fireplaces that ensure more complete combustion, which prevents unburnt gases from going up the chimney. More people are also using dried wood, which creates fewer pollutants.
Cleanair activists, however, say the research results are enough to allow regulatory agencies to set policies dealing with chronic exposure to wood smoke. The smoke may not be the largest source of pollutants in the atmosphere, activists say, but wintertime woodburning produces them right under people's noses.
Mary J. Rozenberg, a former New York cellist whose health is affected by wood smoke, lives in Point Arena, Calif., and is using the Internet to mobilize U.S. public opinion to push for a ban on woodburning in fireplaces and stoves. Her homepage, Burning Issues, carries references to articles and technical papers, including one of her own on inhalation toxicology.
Her paper presented the results of a study of airborne particulates smaller than 2.5 microns in diameter, which were measured in a residential neighbourhood in the San Francisco Bay area. The study showed that particulate concentrations increased most rapidly in the early evening, with the highest concentrations occurring after 11 p.m.
Ms. Rozenberg concluded that the particulates were generated by nonindustrial, nonautomotive sources, and the most likely source was residential woodburning.
She says that when she
started her research in 1991, everyone said there was no problem
and I was nuts. But when they saw the charts, they were shocked
how big wood pollution is"
* Indicates a chemical also found in cigarette smoke
Cyclic di and triterpenoids:
dehydroabietic acid, isopimaric acid, lupenone, friedelin
*Aldehydes: formaldehyde, *acrolein, propionaldehyde, butryaldehyde, acetaldehyde, furfural
Alkyl benzenes: toluene
Acetic acid, Formic acid
Oxygenated monoaromatics: guaiacol and derivatives *phenol and derivatives, syringol and derivatives, catechol and derivatives
*Particulate organic carbon
Oxygenated polycyclic aromatic hydrocarbons (PAHs):
fluorene, phenamhrene, anthracene, methylanthracenes, fluoranthene ,
*pyrene, benzo(a)anthracene, chrysene, benzofluoranthenes, *benzo(e)pyrene, *benzo(a)pyrene, *perylene, ideno (1,2,3cd)pyrene, *benz(ghi)perylene *coronene, dibenzo(a,h)pyrene, retene, dibenz(a,h)anthracene
Trace elements: including sodium, magnesium, aluminum, silicon
Source: U. S. Environmental Protection Agency
Above table published with
The Globe and Mail Canada's national newspaper
"Ah, Lovely wood smoke Wheeze, gasp" 2/10/96 by Robert Matas, Environmental
Letter to the Editor:
This letter was written by Mary Rozenberg to the Globe in an attempt to correct a glaring error made by Dr. Sverre Vedal. Unfortunately, the letter was never published by the paper.
Thank you for the excellent
article by Robert Matas "Ah, lovely wood smoke. Wheeze, Gasp"
on Feb. 10,1996.The article quotes Dr. Sverre Vedal where he incorrectly
states that "there is little evidence thatexposure to woodsmoke
at North American concentrations can be linked to an increased
risk of cancer ina healthy person." We now have more than
30 references linking wood smoke to increased cancer
risk.Due to similar publication times these were most likely
not available to Dr. Vedal at the time of his report
One of the papers stating that woodsmoke causes cancer at North American concentrations is Mutagenicity, Tumorigenicity and Estimation of Cancer Risk from Ambient Aerosol and Source Emissions from Woodsmoke and Motor Vehicles #91131.6 , 1991, by Dr.Joellen Lewtas of the US EPA. Dr. Lewtas states "These figures indicate that the worst contribution that an individual is likely to make to the mutagenicity of the air is using a woodstove for heating, followed by driving a diesel car." She lists 14 papers on the subject in her bibliography.
In a study, Pulmonary Arterial Hypertension and Cor Pulmonale Associated with Chronic Domestic Woodsmoke Inhalation, Chest 1993 researchers indicated that "findings raise the possibility of a cause-andeffect relationship between longterm woodsmoke inhalation and lung cancer. Given the mutagenic and airway irritant effects described for wood smoke (4 references given) we believe that this possible deleterious relationship needs to be addressed in future studies regarding risk factors for lung cancer in nonsmokers."
I have measured polycyclic aromatic hydrocarbons (PAH) for several weeks. PAH are know cancer causing agents The exposure to PAH from woodburning was longer in duration than that from traffic and on many days it was also higher in the amount of the concentration. My study was published in Inhalation Toxicology is being followed by a current study by Dr. Wayne Ott of the US EPA that includes 15 minute averages by 2 PAH machines (one Indoors one Outdoors) for a full year of data. Already the data reveal that neighborhood exposures produce a huge mountain of PAH pollution in the evening in the burning months and that when there is no burning in the late spring there is almost no detectable neighborhood exposure to PAH.
Further analysis of woodstove incinerators reveals that because of the way wood is burned in them they produce more carcinogens. With an oxygen starved fire, they produce more PAH emissions than from a fireplace.. So the irony is that while the wood is burned more efficiently to create more heat the byproducts are far more carcinogenic. The fact is that wood is an inefficient and dirty fuel. On the energy ladder wood is one step above dung. Dr. Judith T. Zelikoff published research in 1994 showing that just one hour of exposure to woodsmoke altered immune defense mechanisms. Dr. Wm Pryor showed that the cancer causing free radicals from woodsmoke are chemically active in the body 40 times longer than tobacco smoke. Even if there were not over 100 toxic chemicals including dioxin, in the smoke, there is evidence linking ingestion of asbestos sized particles such as those from woodsmoke with cancer.
We do not recommend new woodstoves as the solution to a dirty fuel. To learn more please visit our internet home page at "http://BurningIssues.org".
Sincerely, Mary J. Rozenberg, President Burning Issues/Clean Air Revival
In Chemical Deception Sierra Books, 1991, Dr. Marc Lappe writing about Nasopharyngeal Cancer statesthat in addition to diet, virus, and genetic make up, there is a fourth factor in cancer risk for this disease.In his words "the inhalation of certain chemicals found in the environment, particularly inwoodsmoke"..."What is clear is that synthetic substances generated either through food preparation orwood burning contribute far more to this tumor than does any unadulterated "natural" substance."
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