Abstract
Particle size distributions and hygroscopic growth were studied in a town in Sweden with extensive emissions from wood combustion. The average deposited fraction of particle number, surface area and volume dose in the human respiratory tract was estimated using the data set, as well as the typical deposition pattern of the two dominant particle source types: wood combustion and traffic exhaust. As far as we know, this is the first report on the deposited fraction and hygroscopicity of ambient particles from domestic wood combustion in the literature. The use of PM2.5 as a substitute for the deposited dose was also tested. Source/receptor modeling and the hygroscopicity measurements showed that wood combustion and traffic exhaust are dominant sources, and that these particles have a low water uptake. Number fractions of 38 and 69% of the wood combustion and traffic particles, respectively, were deposited in the respiratory tract, and 53% of the particles were deposited as an average for the whole period. The deposited fraction of the surface area and volume dose was also calculated for wood combustion particles, with the result being 22% for both parameters. The results also revealed that the PM2.5 average over more than 10 hours correlated well (r(2) > 0.80) with the deposited surface area and volume dose. This means that PM2.5 can be used as proxy for the deposited dose when examining health effect relationships during short-term exposure studies if the averaging time is sufficient, while a PM2.5 proxy is not recommended for shorter averaging times.
Highlights
The average deposited fraction of particle number, surface area and volume dose in the human respiratory tract was estimated using the data set, as well as the typical deposition pattern of the two dominant particle source types: wood combustion and traffic exhaust
Residential wood combustion has been associated with adverse health effects on a societal level in epidemiological studies as well as with more limited number of subjects in chamber exposure studies (Boman et al, 2003; Barregard, et al, 2006; Sehlstedt et al, 2010)
Air was drawn through the inlet (16.7 L/min), and a fraction of 5 L/min was directed to a differential mobility particle sizer (DMPS) used for the particle number size distribution measurements
Summary
Residential wood combustion has been associated with adverse health effects on a societal level in epidemiological studies as well as with more limited number of subjects in chamber exposure studies (Boman et al, 2003; Barregard, et al, 2006; Sehlstedt et al, 2010). The main route of exposure is deposition in the respiratory tract during breathing. The dose is often not linearly related to particle concentration as might be expected as a first approximation, since the respiratory tract deposition could vary substantially. Neither provide information about how deposition is related to particle concentrations as function of time, which is important for dose estimates in exposure-response time-series studies. In a recent study, Ham et al (2011) showed that filter measurements of toxic PM components have a potential to improve the correlation with adverse health effects compared to PM2.5. Et al (2011) have developed a lung deposition model of the particle number size distribution that can be used in epidemiological studies
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