Impact of Wood Combustion for Secondary Heating and Recreational Purposes on Particulate Air Pollution in a Suburb in Finland

Little information is available on the concentrations of ambient fine particles (PM_2.5) in residential areas where wood combustion is common for recreational purposes and secondary heating. Further, the validity of central site measurements of PM_2.5 as a measure of exposure is unclear. Therefore, outdoor PM_2.5 samples were repeatedly collected at a central site and home outdoor locations from a panel of 29 residents in a suburb in Kuopio, Finland. Source apportionment results from the central site were used to estimate the contributions from local sources, including wood combustion, to PM_2.5 and absorption coefficient (ABS) at home outdoor locations. Correlations between the central and home outdoor concentrations of PM_2.5, ABS, and their local components were analyzed for each home. At the central site, the average PM_2.5 was 6.0 μg m^–³ during the heating season, and the contribution from wood combustion (16%) was higher than the contribution from exhaust emissions (12%). Central site measurements predicted poorly daily variation in PM_2.5 from local sources. In conclusion, wood combustion significantly affects air quality also in areas where it is not the primary heating source. In epidemiological panel studies, central site measurements may not sufficiently capture daily variation in exposure to PM_2.5 from local wood combustion.