Most DCM that enters the body is expelled on the breath, but some is converted to carbon monoxide and this could affect people with a heart condition. The safe working level in air is 100 parts per million (ppm), well below the 2,000 ppm level that causes headaches and vomiting, and the 20,000 ppm that will cause death. A high- purity grade of DCM is used extensively by pharmaceutical and cosmetic manufacturers."As with all volatile solvents, DCM is tightly regulated by the UK Health & Safety Executive. Worldwide production is around a million tons a year, with ICI producing a fifth of this. Dr Martin Smith, ICI's Safety, Health and Environment Manager, said: "DCM was first introduced as a safer alternative to ether, an equally volatile, but dangerously flammable liquid that was common in hospitals and laboratories until the 1960s. Although DCM was also tried as an anaesthetic it was not widely used, but it has proved very popular in other ways.

It is essential for the manufacture of viscose yarns, cigarette filters and cellophane, which are made from DCM solutions of cellulose acetate.ICI's Chlor-Chemicals plant at Runcorn, Cheshire, is Britain's largest producer of DCM, which is made from methanol. It is used industrially on a large scale to clean metal surfaces and to dissolve oils, fats, waxes, resins, rubber and tar. It has the molecular formula CH2Cl2, with two hydrogens and two chlorines attached to a carbon atom. DCM has a remarkable ability to penetrate hardened paint films and lift them off. Throughout these scares DCM continued to be the active ingredient in DIY paint strippers. Ironically, research has since shown that DCM does not cause cancer in humans, nor does it damage the ozone layer.DCM, also known by its older name of methylene chloride, is a clear, volatile, non-flammable, colourless liquid with a not unpleasant odour. Unfortunately, as we now know, the BSE agent survived the new treatment. DCM was also attacked from another quarter: environmentalists accused it of damaging the earth's atmosphere because, like CFCs, it contains ozone-depleting chlorine atoms.

This used lower rendering temperatures, and pressed the grieves to extract the fat. It was producing high-grade fat and cattle cake, free of the BSE agent. However, before the process could be scaled up, a report from the US Environmental Protection Agency reported that DCM caused cancer in mice. British firms that processed abattoir waste abandoned the new solvent, and went over to a non-solvent process instead. The fat used to be removed from grieves with either hexane, a highly flammable solvent, or trichlorethylene, which was safer but contaminated the product. In the early 1980s, the rendering industry had already built a pilot plant using DCM as the solvent. When the grieves have been de-fatted, the high-protein residue is sold as cattle fodder.