Residential exposure to air pollution, access to neighborhood greenspace and their association with hair cortisol concentrations in the second and third trimester of pregnancy

Abstract

Background: Exposure to air pollution during pregnancy has been associated with adverse pregnancy outcomes in studies worldwide, other studies have described beneficial effects of residential greenspace on pregnancy outcomes. The biological mechanisms that underlie these associations are incompletely understood. Recent studies have shown that a biological stress response, with release of cortisol, may underlie associations between air pollution and health effects. The available research on air pollution exposure in relation to biological stress during pregnancy is still scarce. Methods: We explored associations between residential exposure to air pollution, access to neighborhood greenspace and hair cortisol concentrations in a prospective pregnancy cohort study. We modelled participants’ residential air pollutant concentrations (particulate matter with an aerodynamic diameter ≤ 2.5 μm, nitrogen dioxide (NO2), black carbon (BC)), assessed residential distance to a major road and access to a neighborhood greenspace. Hair cortisol concentrations, reflecting cortisol secretion over a period of 3 months prior to sampling, were determined at the end of the second (n = 133) and third pregnancy trimester (n = 81). Results: Three-month mean residential NO2 and BC concentrations were positively associated with third pregnancy trimester hair cortisol concentrations. The residential distance to a major road was negatively associated with second and third trimester hair cortisol concentrations. Access to a greenspace of 10 hectares or more within 800 meters travel distance significantly moderated the association between residential proximity to a major road and second trimester hair cortisol concentrations. At an average residential distance of 304 meters from a major road, mean second trimester HCC were estimated 22% lower for mothers with access to a neighborhood greenspace (3.71 (95% CI: 3.24, 4.24) pg/mg hair) compared to mothers without access (4.22 (95% CI: 3.26, 5.47) pg/mg hair). The moderation tended towards significance in the third trimester (p < 0.10). Conclusions: Increased residential exposure to air pollution and closer proximity to a major road are associated with an increased biological stress response in the second and third trimester of pregnancy, access to neighborhood greenspace may moderate the association. Trial registration: The IPANEMA study is registered under number NCT02592005 at clinicaltrials.gov.