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Open Access Research article

Relationship between area-level socioeconomic characteristics and outdoor NO2 concentrations in rural and urban areas of northern Spain

Ana Fernández-Somoano12*, Gerard Hoek3 and Adonina Tardon12

Author Affiliations

1 Spanish Consortium for Research on Epidemiology and Public Health (CIBERESP), Instituto de Salud Carlos III, C/Melchor Fernández Almagro, 3-5. Pabellón 6, planta baja, 28029, Madrid, Spain

2 Preventive Medicine and Public Health, University of Oviedo, c/Julián Clavería, 33006, Oviedo, Spain

3 Institute for Risk Assessment Sciences, Environmental Epidemiology Division, Universiteit Utrecht, 3508 TD, Utrecht, Netherlands

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BMC Public Health 2013, 13:71  doi:10.1186/1471-2458-13-71

Published: 25 January 2013

Abstract

Background

Socioeconomic variables are associated with mortality and morbidity in a variety of diseases at both the individual and neighborhood level. Investigating whether low socioeconomic status populations are exposed to higher air pollution has been an important objective for the scientific community during the last decade. The goal of this study was to analyze the associations between outdoor nitrogen dioxide (NO2) concentrations in an area of Asturias (Spain) and two socioeconomic indexes—one based on occupation and the other on educational level—at the census-tract level.

Methods

A map of NO2 concentration was obtained from a land-use regression model. To obtain a census-tract average value, NO2 was estimated at the centroids of all 50 × 50 m grids within a census tract. Standard socioeconomic variables were used from the Census of Population and Housing 2001. We analyzed the association between NO2 concentration and socioeconomic indicators for the entire area and stratified for more urban and more rural areas.

Results

A positive linear relationship was found between the levels of education and NO2 exposure in the urban area and the overall study area, but no association was found in the rural area. A positive association between socioeconomic index based upon occupation and NO2 concentration was found in urban areas; however, this association was reversed in the rural and overall study areas.

Conclusions

The strength and direction of the association between socioeconomic status and NO2 concentration depended on the socioeconomic indicator used and the characteristics of the study area (urban, rural). More research is needed with different scenarios to clarify the uncertain relationship among socioeconomic indexes, particularly in non-urban areas, where little has been documented on this topic.

Keywords:
Air pollution; Socioeconomic factors; Education; Nitrogen dioxide