Burning wood, dangerous? - Page 9

Conclusions
Recognizing the limitations of current knowledge and need
for additional information, we nevertheless offer preliminary
answers to the questions raised in the introduction:
The hazards of woodsmoke as a mixture. Because
woodsmoke is made up of such a large mixture of different
chemicals, it is impossible at present to attempt to accurately
assess its health impacts by simply summing the potential effects of individual constituents. (Indeed, there are few if any
examples in which the effects of mixtures are fully reflected
by the summed toxic potentials.) Particularly in high-exposure
situations with fresh woodsmoke, as with occupational exposures or vegetation fire episodes, there may be a need to derive indices of exposure that take into account a range of toxic
endpoints due to woodsmoke, for example, including acuteacting as well as chronic toxicants, so that appropriate protective actions can be adequately taken. Use of fine particles or
any other single metric by itself may not be sufficient in these
circumstances.
Woodsmoke particles. Nevertheless, at the present time fine
particles may represent the best metric to characterize exposures
to smoke from residential wood combustion and from wildfire
smoke. There is no persuasive evidence that woodsmoke particles are significantly less dangerous for respiratory disease
than other major categories of combustion-derived particles in
the same size range. There is too little evidence available today, however, to make a judgment about the relative toxicity of
woodsmoke particles with respect to cardiovascular or cancer
outcomes.
Table 6 indicates that millions of people are exposed to
smoke from household combustion of wood and other sources
of biomass burning. Given the recent upward trend in the costs
of oil and natural gas, it is likely that residential biomass combustion will become even more widespread throughout both the
developed and developing world. More explicit efforts to reduce
emissions from small-scale biomass smoke sources are likely to
become even more important in the near future in order to meet
air quality goals set to protect health.
Finally, returning to the questions posed at the start, we conclude that although there is a large and growing body of evidence
linking exposure to wood/biomass smoke itself with both acute
and chronic illness, there is insufficient evidence at present to
support regulating it separately from its individual components,
especially fine particulate matter. In addition, there is insuffi-
cient evidence at present to conclude that woodsmoke particles
are significantly less or more damaging to health than general
ambient fine particles.
Nevertheless, given the importance of woodsmoke as a contributor to particle concentrations in many locations, strategies
to reduce woodsmoke emissions may be an effective means of
lowering particle exposures. In addition, given the weight of toxicologic evidence, additional epidemiologic studies are needed
to confirm our conclusions