Environmental impacts of China's WTO-accession

China's accession to the WTO in 2001 completed the country's entry into the global economy. We investigate environmental implications of WTO-accession. There are several hypotheses in this area: The scale hypothesis says that production is scaled up and in turn, pollution increases. The technique hypothesis says that production methods become cleaner and pollution decreases. The composition hypothesis says that composition of industries changes and pollution reflects the new composition. We analyse the relative strength of the hypotheses by means of an environmental CGE-model, and in the case of air pollution find support for a composition effect in favour of clean industries. Thanks to the composition effect, emissions to air of greenhouse gases fall. Emissions of particles and SO2 also fall, but emissions of NOx and VOC rise. Since particle and SO2-emissions fall we estimate that public health improves.