Woodsmoke Health Effects: A Review

Abstract

The sentiment that woodsmoke, being a natural substance, must be benign to humans is still sometimes heard. It is now well established, however, that wood-burning stoves and fireplaces as well as wildland and agricultural fires emit significant quantities of known health-damaging pollutants, including several carcinogenic compounds. Two of the principal gaseous pollutants in woodsmoke, CO and NOx, add to the atmospheric levels of these regulated gases emitted by other combustion sources. Health impacts of exposures to these gases and some of the other woodsmoke constituents (e.g., benzene) are well characterized in thousands of publications. As these gases are indistinguishable no matter where they come from, there is no urgent need to examine their particular health implications in woodsmoke. With this as the backdrop, this review approaches the issue of why woodsmoke may be a special case requiring separate health evaluation through two questions. The first question we address is whether woodsmoke should be regulated and/or managed separately, even though some of its separate constituents are already regulated in many jurisdictions. The second question we address is whether woodsmoke particles pose different levels of risk than other ambient particles of similar size. To address these two key questions, we examine several topics: the chemical and physical nature of woodsmoke; the exposures and epidemiology of smoke from wildland fires and agricultural burning, and related controlled human laboratory exposures to biomass smoke; the epidemiology of outdoor and indoor woodsmoke exposures from residential woodburning in developed countries; and the toxicology of woodsmoke, based on animal exposures and laboratory tests. In addition, a short summary of the exposures and health effects of biomass smoke in developing countries is provided as an additional line of evidence. In the concluding section, we return to the two key issues above to summarize (1) what is currently known about the health effects of inhaled woodsmoke at exposure levels experienced in developed countries, and (2) whether there exists sufficient reason to believe that woodsmoke particles are sufficiently different to warrant separate treatment from other regulated particles. In addition, we provide recommendations for additional woodsmoke research.

Personal exposures and indoor, residential outdoor, and urban background levels of fine particle trace elements in the general population

“…Incomplete combustion of biomass produces a multitude of different organic species as well as trace metals, but there have been too few studies to assess the relative toxicity of wood-smoke particles with respect to cardiovascular or cancer outcomes compared with other sources (Naeher et al, 2007). In a review of some epidemiological studies conducted in areas where wood smoke is common, Boman et al (2003) came to the conclusion that PM from wood smoke seems to be at least as harmful as PM derived from other sources.…”

Canadian Forest Fires and the Effects of Long-Range Transboundary Air Pollution on Hospitalizations among the Elderly

“…Most studies addressing health impacts of short-term exposures are related to anthropogenically generated PM, which are commonly associated with automobile combustion and industrial practices. There has been a limited but growing body of literature addressing the impact of shorter-term exposure to smoke from forest and bush fires (referred to as wildfires in this paper) [8,9,11,17,[29][30][31][32][33]. The majority of these studies have examined the impact on nearby local communities of exposures to wildfire aerosols.…”

Biomonitoring of polycyclic aromatic hydrocarbon exposure in pregnant women in Trujillo, Peru — Comparison of different fuel types used for cooking

“…One of the main sources of indoor air pollution, especially in developing countries, is household combustion of unprocessed biomass fuel. It is estimated that approximately 50% of the world's population and nearly 90% of households in rural areas of developing countries still rely on wood, dung and crop residues as their source of energy (Torres-Duque et al, 2008); 1.6 million deaths are attributable to exposure to indoor smoke from combustion of biomass fuel each year and it ranks second among all environmental risk factors for the global burden of disease (Naeher et al, 2007;PerezPadilla et al, 2010).…”

“…Smoke generated by the combustion of wood and other biomass fuels contains many health damaging pollutants including particulate matter, carbon monoxide, aldehydes, nitrogen and sulfur oxides, and polycyclic aromatic hydrocarbons (PAH) (Joshi et al, 1989;Naeher et al, 2007;Venkataraman et al, 2002;Zelikoff et al, 2002;Zhang and Smith, 2007). Household biomass fuel combustion compared to the use of cleaner fuels such as gas could contribute significantly more to indoor levels of these pollutants, including PAHs (Bhargava et al, 2004;Hamada et al, 1991;Oanh and Dungs, 1999;Viau et al, 2000).…”