From a small policy issue in the 1990s, air quality suddenly became a hotly debated public problem in the Netherlands from 2004 onwards. During the ensuing political and legal clash over air quality in the years 2004 - 2010, Dutch infrastructure development and road expansion grinded to a halt on account of exceedance of the legal standards for air pollution. Tobias Arnoldussen analyses this sudden emergence of air pollution on the Dutch political agenda by reviewing court cases, policy documents, European Environmental Law and the alarming research dataon a new type of air pollution, Particulate Matter.Using social constructivism and discourse analysis as methods of socio-legalinquiry, Arnoldussen relates the emergence of the clash to innovative legal strategies of the environmental movement, the concerns of epidemiologists, ambitious European policy makers and an activist judiciary wielding its substantial political influence. On the level of law and policy he considers the clash to be the result of the increased Europeanisation of Environmental Law, the failed ecological modernisation of mobility and the growing role of a precautionary approach in European and Dutch law and policy.