The Urban Exposome during Pregnancy and Its Socioeconomic Determinants

Abstract

Background: The urban exposome is the set of environmental factors that are experienced in the outdoor urban environment and that may influence child development.

Objective: The authors' goal was to describe the urban exposome among European pregnant women and understand its socioeconomic determinants.

Methods: Using geographic information systems, remote sensing and spatio-temporal modeling we estimated exposure during pregnancy to 28 environmental indicators in almost 30,000 women from six population-based birth cohorts, in nine urban areas from across Europe. Exposures included meteorological factors, air pollutants, traffic noise, traffic indicators, natural space, the built environment, public transport, facilities, and walkability. Socioeconomic position (SEP), assessed at both the area and individual level, was related to the exposome through an exposome-wide association study and principal component (PC) analysis.

Results: Mean±standard deviation (SD) NO₂ levels ranged from 13.6±5.1 μg/m³ (in Heraklion, Crete) to 43.2±11 μg/m³ (in Sabadell, Spain), mean±SD walkability score ranged from 0.22±0.04 (Kaunas, Lithuania) to 0.32±0.07 (Valencia, Spain) and mean±SD Normalized Difference Vegetation Index ranged from 0.21±0.05 in Heraklion to 0.51±0.1 in Oslo, Norway. Four PCs explained more than half of variation in the urban exposome. There was considerable heterogeneity in social patterning of the urban exposome across cities. For example, high-SEP (based on family education) women lived in greener, less noisy, and less polluted areas in Bradford, UK (0.39 higher PC1 score, 95% confidence interval (CI): 0.31, 0.47), but the reverse was observed in Oslo (-0.57 PC1 score, 95% CI: -0.73, -0.41). For most cities, effects were stronger when SEP was assessed at the area level: In Bradford, women living in high SEP areas had a 1.34 higher average PC1 score (95% CI: 1.21, 1.48).

Conclusions: The urban exposome showed considerable variability across Europe. Pregnant women of low SEP were exposed to higher levels of environmental hazards in some cities, but not others, which may contribute to inequities in child health and development. https://doi.org/10.1289/EHP2862.

Figure 1.

Overview of area locations.

Figure 2.

Heatmap showing Pearson’s correlation of environmental indicators measured as part of the urban exposome. See Table 2 for exposure short names. Distance to nearest road, major green and blue spaces presented as inverse for interpretability.

Figure 3.

Heatmaps showing Pearson’s correlation of environmental indicators, within each city. See Table 2 for exposure short names. Questions marks are shown for noise in Gipuzkoa and Valencia since this exposure was not available for these cities. Distance to major green spaces presented as inverse for interpretability.

Figure 4.

Volcano plots showing exposome-wide associations with family education level, by city. Y-axis shows strength of association ($-\log \mathrm{p}\text{value}$) and x-axis shows effect size, presented as difference in standard deviation (SD) of each exposure (for that city) between high SEP women (based on family education level) and lower SEP women, adjusted for age, ethnicity and marital status. Positive SD scores indicated higher exposure levels in high SEP women. Dotted horizontal black line shows $p\text{value}=0.05$. Y-axis differs between city depending on range of p values observed. See Table 2 for exposure short names. Distance to nearest road, major green and blue spaces presented as inverse for interpretability.

Figure 5.

Associations by city between SEP and first four components of PCA, on 18 exposures mean-centerd within each city. (A): Heatmap showing exposure loadings of first four components. See Table 2 for exposure short names. Distance to nearest road, major green and blue spaces presented as inverse for interpretability. (B): Forest plots, showing associations with family education level by city and overall meta-analysis. (C): Forest plots, showing associations with area level SEP by city and overall meta-analysis Models compared high SEP women and lower SEP women, adjusted for age, ethnicity and marital status.