Pollution swapping can be defined as the increase in one pollutant as a result of a measure introduced to reduce a different pollutant. Although pollution swapping is widely understood it has received relatively little research attention and receives little consideration in agri-environmental policy. Evidence of pollution swapping in constructed wetlands, riparian buffer zones, cover crops, crop residue retention and no-tillage is examined in this paper. These widely used mitigation options are all successful at reducing diffuse pollutants but literature review shows that there is potential for them to increase levels of one or more other pollutants. There is potential for the widespread adoption of mitigation options to result in unexpected increases in some pollutants. There are a number of barriers to the recognition of pollution swapping in agri-environmental legislation including a lack of tools to evaluate the relative impacts of different pollutants, gaps in our knowledge of the impacts of mitigation measures on non-target pollutants and institutional barriers.