§ Mr. Ron Daviesasked the Secretary of State for the Environment what distinction his Department makes between total hydrocarbon emissions including gas leakage, and that fraction of emissions considered to be reactive in giving rise to ozone in photochemical reactions; and if he will give figures for the emission of reactive hydrocarbons in each of the last 20 years for which figures are available.
Mr. WaldgegraveHydrocarbons emitted because of gas leakage are all essentially non-reactive. In 1983 (the latest year for which figures are available) these accounted for 64 per cent. of total emissions. Scientific knowledge about the types of hydrocarbons emitted from other sources, and their degree of reactivity in each case, is not sufficiently advanced to provide realistic estimates of the percentage of the remainder which give rise to ozone in photochemical reactions. Figures for total estimated hydrocarbon emissions, however, are published in my Department's Digest of Environmental Protection and Water Statistics, No. 7, 1984.