Document 6B8bORLBGaaXGrYkOjgK1EmrR

ELEMENTS OF INDUSTRIAL TOXICOLOGY TABLE 40-A COMBINED TABULATION OF TOXICITY CLASSES Commonly Used Tern Extremely toxic Highly toxic Moderately toxic Slightly toxic Practically nontoxic Helatively harmless Single Oral Dose for Bats (gm/Es) 0 001 or less Vapor Exposure Causing E to 4 Deaths in 6Bai Group (ppm) More than 10 0 001 to 005 10 to 100 005 to 05 100 to 1,000 0 5 to 5 0 1,000 to 10,000 50 to 150 10,000 to 100,000 More than 15 0 More than 100,O00 LD Skin for Babbits (cm/Kg) 0005 or less 0 005 to 0 043 0044to 0 340 0 35 to 2 81 < 2 82 to 22 6 More than 22 6 Probable Lethal Dose for Man Taste (1 gram) 1 tsp (4 cc) 1 oz (30 gm) 1 pmt (250 gm) 1 quart More than 1 quart From Handbook of Toxicology, Vo) 1 "Acute ToxnatieB *' W. S Soector. ed Ptuladetahia, Po, W B Sannders Co 1866 The commonly used expressions are. Ml .O--minimum lethal dose, the smallest dose which kills one of a group of test animals LDm --lethal dose for 50 per cent, the dose that kills one-half of a group of test nmmole (usually ten or more) LD,to--lethal dose for 100 per cent, the dose that kills all of a group of test animals (usually ten or more). These doses may also be expressed as lethal concentrations (LC) for airborne toxic sub stances Substances can then be "rated" according to their relative toncity as shown in animal experiments and the probable lethal dose for humans estimated (Table 40-A) These rat ings are based on the results of short term exposures only It is quite possible in actual long term "chronic*1 exposure for a substance to prove highly toxic even though short term exposure tests indicated a low order of toxicity However, animal-experiment data are dif ficult to interpret and apply to human expo sures Such data are valuable only as guides to be used by the industrial toxicologist in estimating the gross toxicity of a substance and as leads for further investigations. It is from a variety of sources, Including animal experiments, lab studies on humans, and field and mplant investigations of expo sures, that the two prevailing concepts for expressing safe concentrations--threshold limit value and maximal acceptable concen tration--have been taken. Threshold limit values The American Conference of Governmen tal Industrial Hygienists (ACGIH) adopts an annual list of threshold limit values (TLV) for about 300 substances (Table 40-B) These are expressed as parts of va por or gas per million parts of air by volume (ppm) at 25 C and 760 mm Hg pressure or as approximate milligrams of particulate per cubic meter of air (mg cu/m) Mineral dusts are expressed as millions of particles per cu ft (mppcf) based on impinger sam ples counted by light field techniques TLVs represent time-weighted average concentra tions for a normal workday. Most of die values averaged in the thresh old limits may fluctuate a reasonable amount above the recommended TLV providing an equivalent fluctuation below the limit oc curs A major change In the TLV table for 1963, however, limits fluctuation for some substances to below the TLV. These "C" or "ceiling" values, as well as the concepts 40-2