Project at a Glance

Title: Ultrafine particle concentrations in schoolrooms and homes

Principal Investigator / Author(s): Nazaroff, William

Contractor: UC Berkeley

Contract Number: 05-305

Research Program Area: Health & Exposure

Topic Areas: Health Effects of Air Pollution, Indoor Air Quality, Monitoring


Field monitoring of ultrafine particles and copollutants was undertaken at seven houses and six classrooms in the East Bay region near San Francisco, California. At each site, timeresolved measurements were made indoors and outdoors of particle number (PN) concentration in addition to nitric oxide, ozone, carbon dioxide and carbon monoxide. Data were also acquired through the use of questionnaires (houses), observation (classrooms), and temperature and proximity sensors. The information from each site were analyzed to characterize (1) indoor and outdoor PN concentrations; (2) key factors that influence indoor PN concentrations; and (3) the exposure of building occupants to indoor PN and its determinants.

During the observational monitoring periods, the time-average PN concentrations from the primary indoor monitor varied across the seven house sites from 3.7 103 particles per cm3 to 28 103 particles per cm3 with a mean of 14.5 103 particles per cm3. The corresponding outdoor concentrations ranged from 5.5 103 to 23 103 particles per cm3 (averaging 15 103 particles per cm3). For five classroom sites (excluding one at which overnight outdoor data were incomplete), the time-average indoor concentrations ranged from 3.2 103 to 10.5 103 particles per cm3 (averaging 6.9 103 particles per cm3); the corresponding outdoor concentrations ranged from 9.7 103 to 16 103 particles per cm3 (averaging 13 103 particles per cm3).

Overall, the results inform the interplay among building factors, human occupancy, and pollutant dynamics as they influence concentrations of and exposures to ultrafine particles in the studied houses and classrooms. Particle levels in classrooms and in houses were much higher when occupied than when vacant. In houses, important contributions to PN levels were attributable to both outdoor particles and indoor emission sources such as cooking (both with natural gas and electricity) and natural gas furnace use. In schools, the dominant PN source was outdoor air and indoor levels were significantly influenced by time-varying ventilation conditions. Daily average PN exposures per person were much higher in houses than in schools.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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