According to detailed particulate analysis of the smoke produced by previous California wild fires, the composition posed more serious potential threats to health than is generally realized.
For the study Constantinos Sioutas and colleagues from USC Viterbi School of Engineering, the University of Wisconsin-Madison and RIVM (the National Institute of Health and the Environment of the Netherlands) analyzed the particular matter gathered during the fall 2007 blazes.
Fire emissions produce a significantly larger aerosol in size than typically seen in urban environments during periods affected by traffic sources, which emit mostly ultrafine particles, Sioutas said.
Staying indoors may not provide protection from smoke particles in the absence of air conditioning or the ability to recirculate filtered indoor air. This is because the fire particles can penetrate indoor structures more readily than particles from vehicular emissions, Sioutas added.
Sioutas said that the fires produce a dangerous mix.
The chemical composition of particles during the fire episodes is different than that during 'normal' days impacted by traffic sources. Tracers of biomass burning (e.g. potassium and levoglucosan) were elevated by two-fold during the fire period, he said.
Water-soluble organic carbon (WSOC) was also higher during the fire event. This makes these particles from wood smoke more bioavailable, thus more readily absorbable by our system than particulate matter from traffic sources, he added.
The study will appear in Environmental Science and Technology.