In order to further safeguard the environment, it is necessary to supplement the measures already adopted by Council Directive 77/537/EEC of 28 June 1977 on the approximation of the laws of the Member States relating to the measures to be taken against the emission of pollutants from diesel engines for use in wheeled agricultural or forestry tractors(5) (opacity of exhaust gases) with other measures relating, in particular, to physicochemical emissions.
