Relationships of Outdoor and Indoor Ultrafine Particles at Residences Downwind of a Major International Border Crossing in Buffalo, NY

Abstract

PP-31-006 Background/Aims: This aim was to assess the penetration of ultrafine particle (UFP) into homes and the resulting change in particle size distributions as particles move indoors near a major diesel traffic source. Because people spend most of their time in their homes, exposure estimates for epidemiological studies are generally determined using ambient concentrations. The findings of this study will contribute to improved size-resolved UFP exposure estimates for near roadway exposure assessments and epidemiological studies. Methods: During winter 2006, indoor and outdoor UFP size distribution measurements for particles with diameters from 5.6 to 165 nm were made at 5 homes in a neighborhood directly adjacent to the Peace Bridge Complex, a major international border crossing connecting Buffalo, New York to Fort Erie, Ontario. Monitoring with 1-second time resolution was conducted for several hours at each home. Participants were instructed to keep all external windows and doors closed and to refrain from cooking, smoking, or other activity that may result in elevating the indoor UFP number concentration. Results: Overall, particle concentrations indoors were lower and less variable than particle concentrations outdoors, with average indoor-outdoor ratios ranging from 0.1 to 0.5 (mean 0.34) for particles between 5.6 and 165 nm in diameter. Conclusion: With no indoor sources, the average indoor/outdoor ratios were lowest (0.2) for 20 nm particles, higher (0.3) for particles less than 10 nm, and highest (0.5) for particles 70–165 nm.