Proximity of California public schools to busy roads - Children's Health

Environmental Health Perspectives, Jan, 2004 by Rochelle S. Green, Svetlana Smorodinsky, Janice J. Kim, Robert McLaughlin, Bart Ostro

Residential proximity to busy roads has been associated with adverse health outcomes, and school location may also be an important determinant of children's exposure to traffic-related pollutants. The goal of this study was to examine the characteristics of public schools (grades K-12) in California (n = 7,460) by proximity to major roads. We determined maximum daily traffic counts for all roads within 150 m of the school using a statewide road network and a geographic information system. Statewide, 173 schools (2.3%) with a total enrollment of 150,323 students were located within 150 m of high-traffic roads ([greater than or equal to] 50,000 vehicles/day); 536 schools (7.2%) were within 150 m of medium-traffic roads (25,000-49,999 vehicles/day). Traffic exposure was related to race/ethnicity. For example, the overall percentage of nonwhite students was 78% at the schools located near high-traffic roads versus 60% at the schools with very low exposure (no streets with counted traffic data within 150 m). As the traffic exposure of schools increased, the percentage of both non-Hispanic black and Hispanic students attending the schools increased substantially. Traffic exposure was also related to school-based and census-tract-based socioeconomic indicators, including English language learners. The median percentage of children enrolled in flee or reduced-price meal programs increased from 40.7% in the group with very low exposure to 60.5% in the highest exposure group. In summary, a substantial number of children in California attend schools close to major roads with very high traffic counts, and a disproportionate number of those students are economically disadvantaged and nonwhite. Key words: air pollution, children's health, environmental justice, ethnicity, schools, socioeconomic status, traffic.

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Vehicular-traffic-related emissions are a major source of air pollution, especially in urban areas. Epidemiologic studies of the relationship between asthma prevalence or morbidity and traffic-related exposures have recently been reviewed (Delfino 2002). Residential proximity to busy roads has been associated with respiratory symptoms (Ciccone et al. 1998; van Vliet et al. 1997; Venn et al. 2000, 2001), asthma hospitalizations (Edwards et al. 1994), and decreased lung function in children (Brunekreef et al. 1997). A study in San Diego, California (English et al. 1999), found increased risks for medical visits for asthmatic children associated with residence near at least one busy street. Some studies have found associations between proximity to traffic and higher rates of childhood cancer (Pearson et al. 2000; Raaschou-Nielsen et al. 2001; Savitz and Feingold 1989), whereas others have failed to show any association (Langholz et al. 2002; Reynolds et al. 2002).

A study of vehicular traffic density in census block groups in California (Gunier et al. 2003) found that children of color were about three times more likely to live in high-traffic areas than were white children. Researchers examining stationary sources of air pollution, such as Toxic Release Inventory (TRI) facilities, have found evidence of disproportionate exposures by race and socioeconomic status (Maantay 2002; Morello-Frosch et al. 2002a). Another study found that nonwhite students in southern California were more likely than non-Hispanic whites to attend schools in locations with higher respiratory risks, estimated from modeled concentrations of hazardous outdoor air pollutants emitted by both mobile and stationary sources (Morello-Frosch et al. 2002b).

School location may be an important determinant of exposure to traffic-related pollutants because children spend much of their time at school. There are more than 8,000 public schools in California, but to date no one has assessed either the spatial distribution or the demographic profiles of schools in relation to nearby vehicular traffic volume. The goal of this study was to examine the characteristics of public schools in California by proximity to busy roads and to determine whether there are disparities in proximity of schools to high traffic volumes by race/ethnicity and socioeconomic status.

Materials and Methods

School data and selection. For this study, we used the most current database available from the California Department of Education (CDE) as of December 2000 (CDE 2000). From this statewide school database of approximately 8,200 schools, we selected all open public schools, grades K-12, excluding alternative and special education; 7,515 schools met the eligibility criteria. The school database also included a) school address, b) school district, c) county, d) census tract in which the school was located, e) type of school (e.g., elementary school, middle school, high school), f) total enrollment by grade and race/ethnicity, g) number of students eligible for flee/reduced-price meals (which is related to household income and size), h) number of children 5-17 years old residing in the school's attendance area who are eligible for the California Work Opportunity and Responsibility to Kids program (CalWORKS; aid for families and welfare-to-work program), and i) total number and native language of English learners (i.e., children whose primary language is not English and who have been assessed to lack English language skills). Except for the CalWORKS indicator, all other demographic data are based on student enrollment information obtained by the school.