title: Measurements of personal exposure to nitrogen dioxide in four Mexican cities in 1996.
abstract: Nitrogen dioxide is a ubiquitous pollutant in urban areas. Indoor NO2 concentrations are influenced by penetration of outdoor concentrations and by indoor sources. The objectives of this study were to evaluate personal exposure to NO2, taking into account human time-activity patterns in four Mexican cities. Passive filter badges were used for indoor, outdoor, and personal NO2 measurements over 48 hr and indoor workplace measurements over 16 hr. Volunteers completed a questionnaire on exposure factors and a time-activity diary during the sample period. An unpaired t test, an analysis of variance (ANOVA), and a linear regression were performed to compare differences among cities and mean personal NO2 concentrations involving housing characteristics, as well as to determine which variables predicted the personal NO2 concentration. Sampling periods were in April, May, and June 1996 in Mexico City, Guadalajara, Cuernavaca, and Monterrey. All 122 volunteers in the study were working adults, with a mean age of 34 (SD +/- 7.38); 64% were female, and the majority worked in public offices and universities. The highest NO2 concentrations were found in Mexico City (36 ppb for outdoor, 57 ppb for indoor, and 39 ppb for personal concentration) and the lowest in Monterrey (19 ppb for outdoor, 24 ppb for indoor, and 24 ppb for personal concentration). Significant differences in NO2 concentrations were found among the cities in different microenvironments. During the sampling period, volunteers spent 85% of their time indoors. The highest personal NO2 concentration was found when volunteers kept their windows closed (p = 0.03). In the regression model adjusted by city and gender, the best predictors of personal NO2 concentration were outdoor levels and time spent outdoors (R2 = 0.68). These findings suggest that outdoor NO2 concentrations were an important influence on the personal exposure to NO2, due to the specific characteristics and personal behavior of the people in these Mexican cities.
authors.affiliation: Environmental Health Sciences Department, School of Public Health, University of California, Los Angeles, USA.
authors.forename: Matiana
authors.initials: M
authors.lastname: Ramirez-Aguilar
authors.forename: Pablo
authors.initials: P
authors.lastname: Cicero-Fernandez
authors.forename: Arthur M
authors.initials: AM
authors.lastname: Winer
authors.forename: Isabelle
authors.initials: I
authors.lastname: Romieu
authors.forename: Fernando
authors.initials: F
authors.lastname: Meneses-Gonzalez
authors.forename: Mauricio
authors.initials: M
authors.lastname: Hernandez-Avila
mesh_terms: D000328:Adult; D000393:Air Pollutants / Q000032:analysis*; D016902:Air Pollution, Indoor / Q000032:analysis*; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D008297:Male; D008800:Mexico; D008962:Models, Theoretical; D009585:Nitrogen Dioxide / Q000032:analysis*; D010083:Oxidants, Photochemical / Q000032:analysis*; D011634:Public Health; D014505:Urban Population; D017132:Workplace
chemical_list: D000393:Air Pollutants; D010083:Oxidants, Photochemical; D009585:Nitrogen Dioxide