Research suggests that people living in deprived areas of the UK are more likely to be exposed to hazardous environments than those in more affluent areas, but the mechanism behind this trend is not clear. Discrimination in the siting of undesirable land uses has often been blamed, leading to claims of environmental injustice. However, environmental inequalities may also arise through postsiting processes that lead to selective migration: the presence of an undesirable land use may devalue local property, encouraging affluent households to move away and deprived households to move in to surrounding areas. Ascertaining the underlying process at work is important as this has significant implications for guiding policies aimed at delivering environmental justice. We investigated the distribution of municipal landfill sites in Scotland and local exposure to their airborne emissions. Geographical information system techniques were used to construct a wind-weighted, emissions-weighted, and distance-weighted model with which small-area exposure to landfills could be classified. This model gave the exposure classification a degree of realism not generally incorporated in similar studies. We found clear evidence of environmental inequality: socially deprived areas of Scotland are disproportionately exposed to municipal landfills and have been since at least 1981. We then asked which came first, the deprivation or the landfill? Our results suggest that both disproportionate siting and postsiting market dynamics may play a role: area deprivation may have preceded disproportionate landfill siting to some extent, particularly in the 1980s, but landfill siting also preceded a relative increase in deprivation in exposed areas. Areas that became exposed to a municipal landfill in the 1980s were subsequently 1.65 times more likely to be classified as deprived by 2001 than areas that remained unexposed.