asked Her Majesty's Government:What criteria they are to observe in determining which technologies "entail excessive costs", in relation to the "control of the most dangerous substances whose long-term effects on the environment are uncertain", (Lord Belstead's answer to Viscount Mersey, HL Deb,, 19th November 1987, col. 404).

The process of arriving at a judgment in the circumstances of each case will be similar to that already used by HM Inspectorate of Pollution in enforcing the requirement to use best practicable means under Section 5 of the Health and Safety at Work etc. Act 1974.