Document 93wVo6kRL9xbqO7dKV5aDJNbq

penments (Fig 38-2), and the probable lethal dose for humans can be estimated (Table 38-B) These ratings are based on the results of short-term acute exposures only It is quite possible that actual long-term chronic exposures to a substance could prove highly toxic even though short-term exposure tests indicate a low order of toxicity Brown (see References) states that meas urements of relatively crude physical effects-- such as body and organ weight changes, ana tomical changes, and lethal results--are usu ally involved in tests of toxicity To assess the subtle effects a chemical may have, con sideration must be given to measunng central nervous system effects during toxicity testing Animal experiment data are difficult to in terpret and apply to human exposure 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 investigation. Toxic Substances List The Occupational Safety and Health Act of 1970, Section 20(a) (6), requires that "the Secretary of Health, Education, and Welfare shall publish within six months of enactment of this act and thereafter as needed, but at least annually, a list of all known toxic sub stances by generic family or other useful grouping, and the concentrations at which such toxicity is known to occur " The first such list was prepared in 1971 The 1972 edition represents a substantial revision and expansion of the earlier list Under the OSHAct, the Secretary of Labor must issue regulations requiring employers to monitor employee exposure to toxic materials and to keep records of any such employee exposure This requirement is set forth m Section 8(c) (3) of the act The purpose of The Toxic Substances List is to identify "all known toxic substances" in accordance with definitions that may be used by all sections of our society to describe tox icity It must be emphatically stated that the entry of a substance on the list does not auto matically mean that it is to be avoided A listing does mean, however, that the listed substance has the documented potential of being hazardous if misused, and, therefore, care must be exercised to prevent tragic con sequences The absence of a substance from the list does not necessarily indicate that a substance is not toxic Some hazardous substances may not qualify for the list, because the dose that causes the toxic effect is not known Other chemicals associated with skin sensi tization and carcinogenicity may be omitted from the list, because these effects have not been reproduced in experimental animals, or because the human data are not definitive Of necessity, there had to be rebance on the published comments and evaluations of the scientific community, also, there has been no attempt at an evaluation of the degree of hazard that might be expected from sub stances on the list--that being an ultimate goal of the hazard-evaluation studies It is not the purpose of the list to quantify the hazard by way of the toxic concentration or dose that is presented with each of the substances listed Hazard evaluabon involves far more than the recognihon of a toxic sub stance and a knowledge of its relabve toxic potency It involves a measurement of the quantity that is available for absorption by the user, the amount of time that is available for absorpbon, the frequency with which the ex posure occurs, the physical form of the sub stances, and the presence of other substances, toxic or non-toxic, additives, or contaminants Ventilation, appropriate hygienic pracbces, housekeeping, protecbve clothing, and perti nent training for safe handling may dimmish any hazard that might exist Hazard evaluation requires, therefore, en gineers, chemists, toxicologists, and physicians who have been trained in the fields of toxi cology, industrial hygiene, and occupational health, to recognize, measure, and control these hazards Many companies employ people with this type of professional background, particularly those companies that roubnely handle haz ardous chemicals Other companies acquire occupabonal health services from the many consulbng firms or group medical pracbtioners as well as from some state and community of fices In order that all work-places may be evalu ated properly, there must be standards for the concentrahons of hazardous substances m 1117