Assessing environmental justice through potential exposure to air pollution: A socio-spatial analysis in Madrid and Barcelona, Spain

•A preliminary analysis of EJ in the two main Spanish cities, Madrid and Barcelona.•Proposal of a baseline methodology for EJ evaluation.•The goodness-of-fit test and an 'EJ scale' are effective tools for comparative assessment.•Elderly people and immigrants' areas tend to bear an unequal level of NO2 burden.

The concept of environmental justice (EJ) has recently gained currency, both as a factor for and a goal of sustainable development. Its implementation in practice implies establishing current environmental injustice patterns and analysing planning policies, with the aim to reduce socio-demographic inequalities in the negative environmental impact borne by different population groups. This paper proposes a method to assess differential exposure to excessive pollution levels by socio-demographic groups in intra-urban spaces.The approach developed in this paper is based upon GIS and quantitative spatial analysis techniques. It incorporates the idea of an 'environmental justice weighting scale' for policy-making, using normative pollution thresholds to measure inequalities more objectively and consistently. Spain's two largest cities, Madrid and Barcelona, have been chosen as case-studies, taking nitrogen dioxide as the pollutant, and the geographic distribution of six vulnerable population groups (children, elderly people and international immigrants) in the year 2010. The results reveal that a large part of these groups suffer exposure to air pollution exceeding the maximum permitted levels disproportionately, which would imply a case of environmental injustice.