摘要：Objectives. We assessed child care facilities’ proximity to heavily traveled roadways in an attempt to estimate the extent of potential exposure of young children to vehicle-related pollution in this understudied microenvironment. Methods. We examined approximately 24 000 licensed child care facilities in California located within 200 m of heavily traveled roadways. Results. Approximately 57000 of the available slots in California child care centers (7% of the overall capacity) are in facilities located within 200 m (650 ft) of roadways averaging 50000 or more vehicles per day, and another 172000 (21%) are in facilities located within 200 m of roadways averaging 25 000 to 49 000 vehicles per day. Facilities providing care to infants or preschool-aged children and facilities located in disadvantaged areas were more often situated in medium-or high-traffic areas. Conclusions. Additional research is needed to further clarify the significance of the child care microenvironment in terms of potential childhood exposures to vehicle-related pollutants. Design strategies, notification standards, and distance-based siting restrictions should be considered in the facility licensing process and in land use and transportation planning. Given the potential significance of the child care microenvironment for young children’s overall air pollution exposure, there is a need for new insight into the extent to which child care facilities are located in near-roadway areas with potentially high concentrations of harmful vehicle-related pollutants. Young children are particularly susceptible to air pollution given their narrow airways, higher breathing rates, and developing lungs and immune systems. Few studies, however, have examined air pollution effects among toddlers and pre-school-aged children, in part because few registries exist for children 1 to 5 years of age. Available evidence shows that, among girls aged 4 months to 4 years, exposure to nitrogen dioxide (NO2) near their home or day care center may be associated with the development of wheezing bronchitis 1 ; higher levels of traffic-related air pollutants (NO2, PM2.5 [particulate matter 2.5 micrometers or smaller in size], and “soot”) are associated with wheezing, physician-diagnosed asthma, flu, serious colds, and ear, nose, and throat infections 2 ; and exposure to air pollution (including NO2), particularly in combination with exposure to environmental tobacco smoke, increases the risk of recurrent wheezing in children. 3 A study of infants revealed significant associations between traffic-related air pollutants (PM2.5 and NO2) and cough without infection and dry cough at night in the first year of life. 4 Recent studies suggest that vehicle-related pollutants and associated health effects in children are highly concentrated near heavily traveled roadways. Ultrafine particles, black carbon, and carbon monoxide drop to near-background levels at 200 m (650 ft) downwind from major roadways and are indistinguishable from background concentrations at 300 m downwind. 5 , 6 An analysis of hospital admissions among children younger than 5 years in Great Britain revealed that children admitted with an asthma diagnosis were significantly more likely than children admitted for nonrespiratory reasons or children from other parts of the community to live less than 500 m from a roadway with high traffic flow (more than 24 000 vehicles per day). 38 Another study showed that children of color residing in California were 3 to 4 times more likely to reside in high-traffic areas than White children, and the potential for exposure to vehicle-related pollution was higher among low-income children. 7 Previous exposure assessment and time activity studies have demonstrated that significant exposures of infants and children to air pollution can occur at home as a result of indoor pollutants produced by environmental tobacco smoke, cooking, and cleaning; such exposures can also stem from outdoor sources through the intrusion of outdoor air. 8 – 15 Outdoor air pollutant concentrations may be heightened in homes in close proximity to major roadways, and children may also experience significant exposures in other microenvironments such as portable classrooms, 16 school buses, 17 and passenger vehicles. 18 Although children only spend a portion of their day in child care facilities or preschools, the hours spent in these facilities could represent a significant proportion of their overall daily exposure to air pollution, especially if they spend part of the day in moderate or rigorous play outdoors in high-traffic areas. Because many working parents rely on child care, the hours a child spends in a care facility often correspond to the morning or afternoon periods of peak traffic volumes when pollution levels near roadways are most elevated. Given the potential significance of the child care microenvironment for a child’s overall exposure to air pollution, we assessed the degree to which child care facilities are in close proximity to heavily traveled roadways. To our knowledge, our analyses provide the first estimations of the degree to which young children may be exposed to vehicle-related pollution in this understudied microenvironment, and these estimates have important implications for facility licensing and siting as well as transportation and land-use planning nationwide. Furthermore, an understanding of exposures of children in the child care microenvironment is especially important given initiatives in California and other states to substantially expand existing child care and preschool systems to ensure that all children aged 1 to 5 years receive early education before entering kindergarten.
