Introduction: While there is mounting evidence supporting the association of traffic-related air pollutants and pediatric asthma morbidity, few studies have examined how land use policies, and especially the proximity of industrial zoning to schools and home residences, influences pediatric asthma outcomes among minoritized communities. The goal of this study was to characterize the association between industrial zone proximity and asthma prevalence, physical fitness, and academic outcomes for children in the Santa Ana Unified School District (SAUSD).
Methods: This is a cross-sectional analysis of school records for students enrolled in SAUSD over the 2018-2019 school year, including demographics, school medical records, physical fitness test scores, attendance records, and standardized exam scores.
Results: The study included a total of 44,641 individual student records. The odds of having an asthma diagnosis were 21% greater for children living in the closest tertile of proximity to the nearest industrial zone (range 0.004-0.534 km) compared to children living in the farthest tertile (> 1.051 km) (adjusted OR 1.21, 95% CI 1.10 to 1.33, p<0.001). Among students with asthma, there was increased likelihood of being overweight or obese for children living in the closest tertile of proximity to industrial zones (adjusted OR 1.50, 95% CI 1.04 to 2.17, p=0.029), an increased likelihood of an unhealthy score on the aerobic fitness test (adjusted OR 1.42 per each additional km of proximity, 95% CI 1.13 to 1.83, p=0.005), but a paradoxical decrease in asthma events with each kilometer of increased proximity (adjusted b = -0.027, p=0.020). Associations of industrial zone proximity with absences or standardized test scores were mostly non-significant, as were most associations between freeway exposures and poor academic/health outcomes.
Conclusion: This school-district-based study found that industrial zone proximity was significantly associated with higher asthma prevalence after controlling for available socioeconomic factors, suggesting that city zoning may be an important variable to consider when studying patterns of asthma among school-age children. Within the population of children with asthma, the effects of industrial proximity on health and academic outcomes are not clear but may be confounded and/or mediated by overweight or obese weight status. Overall, these study findings establish the importance of comparing health disparity distributions to city zoning maps and show how the distance-gradient method can be a useful tool to both inform city policy and generate new hypotheses for additional epidemiologic investigation. Future studies should include improved controls for socioeconomic status and health care access, as well as more sensitive exposure variables incorporating air monitoring data as well as trunk road proximity. Additionally, future studies should investigate the possible protective effect of green space and/or other recreational areas on asthma and weight-related outcomes.
