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Intersections as hot spots: assessing the contribution of localized non-tailpipe emissions and noise on the association between traffic and children’s health

Principal Investigator: 

University of Southern California

This study will assess the effects of metals from nontailpipe emissions on asthma and lung function in the most recent cohort of the Children’s Health Study in Southern California (recruited during 2002-2012), using available filters with particulate matter samples. The investigators will estimate exposure to several pollutants and transportation noise and evaluate the roles of socioeconomic status, green space, physical activity, diet, and stress.

Funded under

Abstract for the 2019 Annual Conference

Environmental factors affecting stress in children: interrelationships between traffic-related noise, air pollution, and the built environment

Meredith Franklin, Xiaozhe Yin, Robert Urman, Rebecca Lee, Scott Fruin, Rob McConnell

University of Southern California, Los Angeles, CA, USA

Background. There is a growing body of research linking several aspects of the physical environment to children’s mental and physical health. Stressors such as traffic-related noise have been associated with decrements in children’s mental health, and air pollution has been shown to modify neurocognitive development and behavior. Exposure to artificial light in the built environment can lead to circadian disruption and stress, while studies have shown that living near greenspace reduces stress and has a wide range of other health benefits for children and adolescents. Chronic stress in childhood may contribute to direct and indirect health effects such as asthma, cardiovascular disease, and obesity.

Methods. When aged 13-14 and 15-16 years, participants in the longitudinal Southern California Children’s Health Study (CHS) responded to four questions pertaining to stress. An individual’s combined responses to these questions resulted score from 0 to 16 on the Perceived Stress Scale (PSS-4). Residential exposures were derived for traffic-related noise from the Traffic Noise Model, freeway and non-freeway NOx from the CALINE line dispersion model, greenspace from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations of enhanced vegetation index (EVI), and artificial light at night (ALAN) from Visible Infrared Imaging Radiometer Suite (VIIRS) satellite observations in the day-night band. We assessed the marginal and joint associations with these exposures using mixed effects models with adjustments for subject-specific characteristics and confounders.

Results. Overall, PSS-4 is significantly higher (p<0.001) for girls [mean (s.d.) = 5.8 (3.4)] than boys [mean (s.d.) = 4.9 (3.2)]. From ages 13-14 to 15-16, stress significantly increased in girls from 5.6 (3.3) to 6.0 (3.4), but for boys stress did not change.  Marginally, all of the environmental factors were significantly associated with stress after adjustment for sex, height, weight and trouble initiating sleep. Greenspace showed a -0.33 (95% CI: -0.49, -0.18) decrease in stress per IQR (0.06) increase in EVI. All other environmental factors have positive associations with stress, including a 0.22 (95% CI: 0.05, 0.40) increase in stress per IQR (22.6 nW/cm2/sr) increase in ALAN. Jointly, we found similar patterns with a -0.23 (95% CI: -0.43, -0.03) decrease in PSS-4 per IQR increase in EVI, together with a 0.15 (95% CI: 0.03, 0.27) increase in PSS-4 per IQR increase in freeway NOx. In this model traffic-related noise was only statistically significant with PSS-4 at the community level, with some Southern California communities showing stronger associations than others. Furthermore, due to the strong negative correlation between EVI and ALAN (r= -0.67) it was difficult to tease out their joint association with stress.

Conclusions. The physical environment consists of a complex mixture of factors that can both positively and negatively affect health. We find evidence that residential greenspace may mitigate the impact of traffic–related air pollution and noise on perceived stress in a longitudinal cohort of children in Southern California.


Poster by Franklin et al., 2019 HEI Annual Conference