Background Inequities in the distribution of environmental exposures may add an extra burden to socially disadvantaged populations, especially when acting during vulnerable periods such as pregnancy and early life, but such inequities may be more complex and uncertain than is generally assumed. We therefore examine whether socioeconomic inequities exist in pregnancy exposures to multiple common environmental contaminants in air, water and food.
Methods A Spanish population-based birth cohort study enrolled over 2000 pregnant women between 2004 and 2008. Questionnaires assessed parental education, occupation, country of birth, diet and many other factors. Environmental pollutant assessments included nitrogen dioxide as a marker of traffic-related air pollution, trihalomethanes as a marker of tap water disinfection by-products, organochlorine biomarkers measured in maternal serum during pregnancy (polychlorinated biphenyls (PCB), dichlorodiphenyl dichloroethylene (p,p′-DDE), hexachlorobenzene and β-hexachlorocyclohexane) and mercury concentrations measured in cord blood.
Results Associations between socioeconomic status indicators and nitrogen dioxide and trihalomethanes were generally weak and inconsistent in direction. Concentrations of PCB, hexachlorobenzene and mercury were higher in higher social classes than lower social classes. p,p′-DDE and β-hexachlorocyclohexane were not related to social class. Social class explained between 1% and 5% of the variability in pollutant concentrations, much less than other variables such as region of residence, country of birth and maternal age.
Discussion This study demonstrates that the general assumption that more disadvantaged populations have higher levels of exposure to environmental pollution does not always hold and requires further elucidation in different international settings.
- Child health
- environmental exposure
- environmental health
- social inequalities
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Funding The INMA project is funded by grants from Instituto de Salud Carlos III (Red INMA G03/176 and CB06/02/0041) and Fundación Roger Torné Fundació Privada. The studies in the specific regions were funded by the Spanish Ministry of Health (FIS 03/1615, 04/1436, 04/1509, 04/1112, 04/1931, 05/1079, 05/1052, 06/0867, 06/1213, 07/0314, 08/1151, 09/02647), the Generalitat de Catalunya (CIRIT 1999SGR00241), the Diputación Foral de Gipuzkoa (DFG06/004), the Department of Health of the Basque Government (2005111093) and the Conselleria de Sanitat Generalitat Valenciana.
Competing interests None.
Ethics approval This study was conducted with the approval of the hospital ethics committees in the participating regions.
Provenance and peer review Not commissioned; externally peer reviewed.