Estimating hourly exposure to residential wood combustion for human health

During the last decade, there has been a substantial rise in the use of wood for space and water heating in North America, in addition to recreational burning. While there are national, state and regional programs to improve efficiency and reduce emissions from wood burning appliances, wood combustion remains a major source of airborne particulate matter (PM) and related pollutants during the heating season. While current regulatory air monitoring for PM2.5 provides daily measurements, with one monitoring site representing a relatively large area, health outcomes may be triggered by hourly pollutant exposures. For example, acute myocardial infarctions (MI), were found to be triggered within hours of short term increases in ambient PM2.5 concentrations (Gardner et al., 2014). Thus, more temporally and spatially resolved estimates of wood smoke exposure are needed to assess whether health outcomes may be impacted by this source specific PM a few hours after exposure, rather than after a few days or weeks. For this study, continuous 1-minute indoor and outdoor PM and indoor carbon monoxide (CO) concentrations were measured from November through April of 2015/16 and 2016/17 at 50 residences across Monroe County, near Rochester, New York (25 residences per season). Inclusion criteria for the study were that homes had wood burning appliances or were located in ‘high wood smoke’ areas of Monroe County. Although wood combustion in most Monroe County residences is recreational only, we found that wood smoke can represent up to 30% of the winter-time PM2.5 concentrations there (Wang et al., 2012a,b). Results from the first heating season validate the importance of including indoor exposure to combustion appliance emissions when assessing cumulative inhalation exposure to wood smoke. A regular daily cycle of PM was observed at all homes, with peaks associated with human activity, cooking, and wood burning appliance use. Indoor/outdoor PM concentration ratios were significantly higher when the carbon monoxide measurement indicated the presence of a combustion source. Most of the sites showed clear diurnal patterns with higher PM concentrations and indoor/outdoor PM concentration ratios in the late afternoon and evening hours. Monitoring data were used as input for a land use regression model to predict hourly ambient PM2.5 concentrations across the region. Raster surfaces (spatial resolution 10 x 10 m) were developed for a series of predictors, including the number of bedrooms, fireplaces, and kitchens, as well as the property value, year the property was built, nearby road type and road traffic densities, railways, elevation, and density of various land cover data features. In general, the relationships between PM concentrations and the predictors were moderate and results were similar to a previous study predicting 24-h concentrations (Su et al., 2015). References: Gardner B, Ling F, Hopke PK, Frampton MW, Utell MJ, Zareba W, Cameron SJ, Chalupa D, Kane C, Ku-landhaisamy S, Topf M, Rich DQ. 2014. Ambient fine particulate air pollution triggers ST-elevation myocardial infarction, but not non-ST-elevation myocardial infarction. Particle & Fibre Toxicology, 11, pp. 1. Su JG, Hopke PK, Tian Y, Baldwin N, Thurston SW, Evans K and Rich DQ. 2015. Modeling particulate matter concentrations measured through mobile monitoring in a deletion/substitution/addition approach. Atmospheric Environment, 122, pp.477-483. Wang Y, Hopke PK, Rattigan OV, Chalupa DC and Utell MJ. (2012a) Multiple-year black carbon measurements and source apportionment using delta-C in Rochester, New York. J Air Waste Manag Assoc. 62:880-887. Wang Y, Hopke PK, Xia X, Rattigan OV, Chalupa DC and Utell MJ. (2012b) Source apportionment of airborne particulate matter using inorganic and organic species as tracers. Atmospheric Environment. 55:525-532. Acknowledgements: This work was supported by the New York State Energy Research and Development Authority (NYSERDA) under agreement 63040.