# Socioeconomic Inequalities in the External Exposome in European Cohorts: The EXPANSE Project

## TL;DR

This study explores how socioeconomic factors influence environmental exposures across Europe, revealing regional differences in air pollution and temperature patterns.

## Contribution

The study introduces a novel approach using PCA to characterize the external exposome in a large multicountry European cohort.

## Key findings

- Southern European countries face higher ambient air pollution compared to Northern countries.
- Area-level socioeconomic indicators show stronger associations with the urban exposome than individual variables.
- Cohorts with limited geographical coverage show lower temperature variability in cold seasons.

## Abstract

Socioeconomic inequalities in the exposome have been
found to be
complex and highly context-specific, but studies have not been conducted
in large population-wide cohorts from multiple countries. This study
aims to examine the external exposome, encompassing individual and
environmental factors influencing health over the life course, and
to perform dimension reduction to derive interpretable characterization
of the external exposome for multicountry epidemiological studies.
Analyzing data from over 25 million individuals across seven European
countries including 12 administrative and traditional cohorts, we
utilized domain-specific principal component analysis (PCA) to define
the external exposome, focusing on air pollution, the built environment,
and air temperature. We conducted linear regression to estimate the
association between individual- and area-level socioeconomic position
and each domain of the external exposome. Consistent exposure patterns
were observed within countries, indicating the representativeness
of traditional cohorts for air pollution and the built environment.
However, cohorts with limited geographical coverage and Southern European
countries displayed lower temperature variability, especially in the
cold season, compared to Northern European countries and cohorts including
a wide range of urban and rural areas. The individual- and area-level
socioeconomic determinants (i.e., education, income, and unemployment
rate) of the urban exposome exhibited significant variability across
the European region, with area-level indicators showing stronger associations
than individual variables. While the PCA approach facilitated common
interpretations of the external exposome for air pollution and the
built environment, it was less effective for air temperature. The
diverse socioeconomic determinants suggest regional variations in
environmental health inequities, emphasizing the need for targeted
interventions across European countries.

There is limited evidence on geographical disparities in
the exposome and the role of the social environment. This study shows
regional differences in Europe’s external exposome, with Southern
regions facing higher ambient air pollution. Socioeconomic disparities
vary geographically, with implications for multicountry environmental
health studies.