Transport emissions of acidifying substances, ozone precursors and particulates decreased by 34%, 40% and 30%, respectively, between 1990 and 2003 in the EEA32. This was mostly a result of emission reductions realised in road transport, which in turn was due to the increased use of catalytic converters, reduced sulphur concentrations in fuels and fleet renewal. However, further reductions of all substances will be required from all sectors in order to achieve the various environmental targets set for 2010. Unlike the steady decline of emissions from the EU15 and EFTA4, in the EU10 emissions of acidifying substances, ozone precursors and particulates decreased by 22%, 15% and 16% between 1990 and 1993 but then remained largely stable until 1998 before decreasing further in 1999-2003 to 67%, 73% and 72% of the 1990 levels respectively. The initial sharp decline in the early 1990s was mainly due to the economic recession that impacted strongly on traffic volumes. The stabilisation of emissions, despite rising transport volumes in the second half of the 1990s, was a result of fleet renewal. Emissions from the AC2+CC2 have fluctuated in the same period, with emissions of acidifying substances, ozone precursors and particulates reduced by 16%, 13% and 18% respectively by 2001, but have risen sharply since then to 109%, 125% and 111% of the respective 1990 values by 2003. This rise is almost entirely attributable to significant growth in NOx emissions from Bulgaria and Turkey.