This article from IEHIAS, the Integrated Environmental Health Impact Assessment System, presents various reasons behind environmental prejudice and injustice, though it suggests we lack definitive explanations.
Issues of environmental justice often arise, although are not always considered, in health impact assessments. In general terms, these relate to the double or triple jeopardy that is commonly seen between socio-economic status, environmental exposures and health. These relationships need to be recognized and allowed for in assessments, because they affect both who is at risk from environmental hazards such as pollution, and the distribution of effects of any policy or other intervention.
The concept of environmental justice is rather poorly defined. A wide range of somewhat different concepts and terms tend to be bound up under the banner of environmental justice. For example:
A large body of studies has been done on environmental justice. These use a wide range of methods both to characterize socio-economic status and environmental inequalities, and the relationships between them. Typically, these have shown that poorer population groups (however defined) tend to live in more polluted environments. Care is nevertheless needed in interpreting these relationships both because the analytical methods used are not always robust, and because the causal mechanisms producing the relationships are not well understood.
Methodologically, for example, problems arise because analysis is done at aggregate (area) level, and relies on measures of proximity to sources as an indicator of risk. This tends to mask the inter-individual variations in experience that may occur within any area (e.g. due to local clustering of emission sources and of different socio-economic groups). Proximity is also often a poor indicator of exposure. More detailed studies (e.g. Briggs et al. 2008, Kruize 2007) have shown that the relationships are, in practice, often complex and non-linear (and in some cases contrary to expectation).
Environmental justice effects may also arise in a number of different ways:
It may also affect different population sub-groups. For example:
Dealing with these socio-economically related environmental justice effects in health impact assessment poses important challenges. Most of epidemiological studies on environmental factors consider socio-economic factors as a confounding variables; synergistic effects are rarely analyzed – although they are of great importance both for scientific and policy reasons. In the case of environmental health impact assessment, care is needed in allowing for these synergistic effects, for they often represent an important influence on who experiences the impacts of environmental hazards (or policies).
The implications in terms of policy are no less complex. They depend on the perspective of the policymakers - i.e. the extent to which priorities are given to reducing social inequalities (see Davy 1997) - which may themselves change over time. Even when policies are aimed at addressing inequalities, moreover, the solutions (or impacts of specific policy measures) may not be clear, because social inequalities are multivariate and multi-causal conditions, that reflect deep-seated social interactions and inter-dependencies. Tackling individual elements within this web of factors may have little effect. Social influences on health, as much as environmental influences, thus need an integrated approach.