title: Fine and ultrafine particle decay rates in multiple homes.
abstract: Human exposure to particles depends on particle loss mechanisms such as deposition and filtration. Fine and ultrafine particles (FP and UFP) were measured continuously over seven consecutive days during summer and winter inside 74 homes in Edmonton, Canada. Daily average air exchange rates were also measured. FP were also measured outside each home and both FP and UFP were measured at a central monitoring station. A censoring algorithm was developed to identify indoor-generated concentrations, with the remainder representing particles infiltrating from outdoors. The resulting infiltration factors were employed to determine the continuously changing background of outdoor particles infiltrating the homes. Background-corrected indoor concentrations were then used to determine rates of removal of FP and UFP following peaks due to indoor sources. About 300 FP peaks and 400 UFP peaks had high-quality (median R(2) value >98%) exponential decay rates lasting from 30 min to 10 h. Median (interquartile range (IQR)) decay rates for UFP were 1.26 (0.82-1.83) h(-1); for FP 1.08 (0.62-1.75) h(-1). These total decay rates included, on average, about a 25% contribution from air exchange, suggesting that deposition and filtration accounted for the major portion of particle loss mechanisms in these homes. Models presented here identify and quantify effects of several factors on total decay rates, such as window opening behavior, home age, use of central furnace fans and kitchen and bathroom exhaust fans, use of air cleaners, use of air conditioners, and indoor-outdoor temperature differences. These findings will help identify ways to reduce exposure and risk.
authors.affiliation: Consultant, 428 Woodley Way, Santa Rosa, California 95409, United States.
authors.forename: Lance
authors.initials: L
authors.lastname: Wallace
authors.forename: Warren
authors.initials: W
authors.lastname: Kindzierski
authors.forename: Jill
authors.initials: J
authors.lastname: Kearney
authors.forename: Morgan
authors.initials: M
authors.lastname: MacNeill
authors.forename: Marie-Ève
authors.initials: MÈ
authors.lastname: Héroux
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Wheeler
mesh_terms: D000388:Air; D000393:Air Pollutants / Q000737:chemistry*; D016902:Air Pollution, Indoor / Q000032:analysis*; D002170:Canada; D006801:Humans; D008962:Models, Theoretical; D010316:Particle Size; D052638:Particulate Matter / Q000737:chemistry*; D012621:Seasons; D011795:Surveys and Questionnaires; D001335:Vehicle Emissions / Q000032:analysis
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D001335:Vehicle Emissions