title: Comparison of Outdoor and Classroom Ozone Exposures for School Children in Mexico City.
abstract: To evaluate methods of reducing exposure of school children in southwest Mexico City to ambient ozone, outdoor ozone levels were compared to indoor levels under three distinct classroom conditions: windows/doors open, air cleaner off; windows/doors closed, air cleaner off; windows/ doors closed, air cleaner on. Repeated two-minute average measurements of ozone were made within five minutes of each other inside and outside of six different school classrooms while children were in the room. Outdoor ozone two-minute average levels varied between 64 and 361 ppb; mean outdoor levels were above 160 ppb for each of the three conditions. Adjusting for outdoor relative humidity, for a mean outdoor ozone concentration of 170 ppb, the mean predicted indoor ozone concentrations were 125.3 (±5.7) ppb with windows/doors open; 35.4 (±4.6) ppb with windows/ doors closed, air cleaner off; and 28.9 (±4.3) ppb with windows/ doors closed, air cleaner on. The mean predicted ratios of indoor to outdoor ozone concentrations were 0.71 (±0.03) with windows/doors open; 0.18 (±0.02) ppb with windows/doors closed, air cleaner off; and 0.15 (±0.02) ppb with windows/doors closed, air cleaner on. As outdoor ozone concentrations increased, indoor ozone concentrations increased more rapidly with windows and doors open than with windows and doors closed. Ozone exposure in Mexican schools may be significantly reduced, and can usually be kept below the World Health Organization (WHO) guideline of 80 ppb, by closing windows and doors even when ambient ozone levels reach 30Q ppb or more.
authors.affiliation: a Charming Laboratory, Brigham and Women's Hospital , Boston , Massachusetts.
authors.forename: Diane R
authors.initials: DR
authors.lastname: Gold
authors.forename: George
authors.initials: G
authors.lastname: Allen
authors.affiliation: b Department of Environmental Health, Harvard School of Public Health , Boston , Massachusetts.
authors.forename: Andrew
authors.initials: A
authors.lastname: Damokosh
authors.affiliation: c Universidad Autonoma Metropolitana-Xochimilco, Mexico City and the Instituto Nacional de Salud Publica , Cuernavaca , Mexico.
authors.forename: Paulina
authors.initials: P
authors.lastname: Serrano
authors.affiliation: d Health Effects Research Laboratory, U.S. Environmental Protection Agency , Research Triangle Park , North Carolina.
authors.forename: Carl
authors.initials: C
authors.lastname: Hayes
authors.affiliation: e Universidad Autonoma Metropolitana-Xochimilco , Mexico City , Mexico.
authors.forename: Margarita
authors.initials: M
authors.lastname: Castiilejos