From a small policy issue in the 1990s, air quality became a hotly debated public problem in Dutch law and politics in 2004. During the political and legal clash over air quality in the years 2004 - 2010, Dutch infrastructure development and road expansion grinded to all but 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 data on a new type of air pollution, Particulate Matter. By using social constructivism and discourse analysis as methods of socio-legal inquiry, 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 the clash is considered to be the result of the increasing Europeanisation of Environmental Law, the failed ecological modernisation of mobility and the increasing role of a precautionary approach in European and Dutch law and policy. [Subject: Environmental Law, Dutch Law, European Law, Public Policy]