The outdoor exposome during pregnancy and its social determinants

Abstract

Background: We define the 'Outdoor Exposome' as the complex mixture of environmental factors that individuals are exposed to in the outdoor environment, which may be determined by socio-demographic factors. It is hypothesized that more disadvantaged social groups are more exposed to environmental hazards resulting in health inequalities. AIMS: To describe the outdoor exposome and its socio-demographic determinants among pregnant women living in nine cities across Europe. Methods: We included 28,710 pregnant women enrolled in six birth cohorts participating in the EC FP-7 HELIX project. Using GIS, we assessed exposure over pregnancy to 26 exposures at the home address including air pollutants, noise, meteorological factors, and natural and built environment characteristics and performed a principal component (PC) analysis. The association between each exposure and ethnicity and education level (low, medium, high) was assessed by within city regression. Results: 3 PCs explained over 50% of variation. Latitude and ‘urbanisation’ could account for observed PC loadings. Meta-analyses showed that higher education levels was associated with exposure to lower level of air pollutants (PM2.5: β = -1.12, 95% C.I.: -1.50; -0.13) and noise (β = -1.30, 95% C.I.: -0.23; -0.03), greater surrounding green space (Normalized difference vegetation index within 100m : β = 0.005, 95% C.I.: 0.003; 0.007), and lower street connectivity (within 100m : β = -3.90, 95% C.I.: -125; -81). Those of native country ethnicity were similarly less likely to be exposed to harmful environments. However there was significant heterogeneity between cities: e.g. higher education was associated with greater NO2 levels in Sabadell, Spain and lower levels in Bradford, UK . Conclusions: Pregnant women from more disadvantaged social groups are more exposed to unhealthy urban environments within some European cities, which may impact on the development of their children.