Traffic related air pollution and incidence of childhood asthma: results of the Vesta case-control study.

STUDY OBJECTIVE: The Vesta project aims to assess the role of traffic related air pollution in the occurrence of childhood asthma. DESIGN AND SETTING: Case-control study conducted in five French metropolitan areas between 1998 and 2000. A set of 217 pairs of matched 4 to 14 years old cases and controls were investigated. An index of lifelong exposure to traffic exhausts was constructed, using retrospective information on traffic density close to all home and school addresses since birth; this index was also calculated for the 0-3 years age period to investigate the effect of early exposures. MAIN RESULTS: Adjusted on environmental tobacco smoke, personal and parental allergy, and several confounders, lifelong exposure was not associated with asthma. In contrast, associations before age of 3 were significant: odds ratios for tertiles 2 and 3 of the exposure index, relative to tertile 1, exhibited a positive trend (1.48 (95%CI = 0.7 to 3.0) and 2.28 (1.1 to 4.6)), with greater odds ratios among subjects with positive skin prick tests. CONCLUSIONS: These results suggest that traffic related pollutants might have contributed to the asthma epidemic that has taken place during the past decades among children.

[Air quality monitoring and personal exposure of children to NO(2) and fine particles]. / Surveillance de la qualité de l'air. Etude de l'exposition personnelle d'enfants au NO(2) et aux particules fines.

BACKGROUND: Personal exposure to air pollutants and ambient air measurements are poorly correlated in the short term. Nevertheless, air quality surveillance data are often used to characterize exposure in epidemiological studies. This work explores a method to derive exposure estimates for a population of children, through appropriate usage of surveillance data that allows for heterogeneity of life environments. METHODS: Personal exposure (PE) to PM2.5 and NO(2) of 66 to 184 children was measured in 4 French metropolitan areas (Grenoble, Nice, Toulouse and Paris). The proposed approach provides an estimate of a "translator parameter". This method was applied to subgroups of children who differed in terms of daily time spent in areas more or less influenced by traffic emissions. RESULTS: Ambient air concentrations of NO(2) overestimated personal exposures, on average, but children whose life environments are more influenced by traffic exhausts exhibit, on average, greater PE values; as far as particles are concerned, air quality surveillance and PE values are closer. Hence, translation parameters differ according to pollutants, cities and populations. CONCLUSIONS: These results suggest that ambient air monitors can be used to assess exposure of urban populations living in areas with variable traffic intensities. However, usage of these air quality surveillance data should allow for population and pollutant characteristics.

Five epidemiological studies on transport and asthma: objectives, design and descriptive results.

A case-control study was conducted in five French metropolitan areas in order to assess the role of traffic-related air pollution in the occurrence of childhood asthma. This paper presents the study design and describes the distribution of key exposure variables. A set of 217 pairs of matched 4- to 14-year-old cases and controls were investigated (matching criteria: city, age, and gender). Current and past environmental smoke exposures, indoor allergens or air pollution sources, and personal and family atopy were assessed by standard questionnaires. When possible, direct measurements were done to check the validity of this information, on current data: skin prick tests, urine cotinine, house dust mites densities, personal exposures to, and home indoor concentrations of NO(x) and PM(2.5). Cumulative exposure to traffic-related pollutants was estimated through two indices: "traffic density" refers to a time-weighted average of the traffic density-to-road distance ratio for all home and school addresses of each child's life; "air pollution" index combines lifelong time-activity patterns and ambient air concentration estimates of NO(x), using an air dispersion model of traffic exhausts. Average current PM(2.5) personal exposure is 23.8 microg/m3 (SD=17.4), and average indoor concentrations=22.5 microg/m3 (18.2); corresponding values for NO(2) are 31.4 (13.9) and 36.1 (21.4) microg/m3. Average lifelong calculated exposures to traffic-related NO(x) emissions are 62.6 microg/m3 (43.1). The five cities show important contrasts of exposure to traffic pollutants. These data will allow comparison of lifelong exposures to indicators of traffic exhausts between cases and controls, including during early ages, while controlling for a host of known enhancers or precipitators of airway chronic inflammation and for possible confounders.