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1927 J. W. Trevan in Proc. Royal Soc. B. 101 483 Toxicity should be stated primarily in terms of the ‘median lethal dose’, that is the dose which kills 50 per cent. of a large group of animals. As a convenient abbreviation I would suggest the symbol LD50... For doses which kill other proportions of large groups of animals it is convenient to use the analogous symbols LD75, LD25, for doses which kill 75 per cent., and 25 per cent., and similarly for doses killing other proportions.

1950 Proc. Soc. Exper. Biol. & Med. 73 497/2 Only 4oor of X-irradiation was used. This dose corresponds to LD_85–30 for swine.

1954 H. A. Trenkler in One Year LD-Oxygen Refining Process 11/1 Our method of steel refining with pure oxygen by blowing downwards into a bath of metal..is called ‘LD-process’ (Linzer Düsenverfahren).

1958 Thomson & Straube in W. D. Claus Radiation Biol. & Med. iv. 101 Two-thirds of an LD₅₀ dose will probably kill less than 1 percent of the animals exposed.

1965 New Statesman 7 May 709/3 The building of modern plants, LD converters, bigger blast-furnaces, wider sinter plants, automated soaking pits and rolling mills.

1968 Observer 16 June 9/1 Sarin is 30 times more toxic than phosgene, and the amount necessary to achieve what the experts know as ‘LD50’..is 40 drops on the skin.

1973 Times 30 May (Austria Suppl.) p. iii/7 The Japanese have the highest production of LD steel, and by 1972 51 percent of world steel production was based on the LD process.