Document aJN1qL1Zk4QzVOReEjJJxMrpX

% -L TABLE 40-B THRESHOLD UM1T VALUES FOR 1903 E LE M E N TS OF IN D U S T R IA L TO XIC O LO G Y Adopted at the 25th Annual Meeting of the American Conference of Govern mental Industrial Hygienists, Cincinnati, Ohio, May 6-7, 1963 These values should be used as guides in the control of health hazards and should not be regarded as fine hoes be tween safe and dangerous concentrations They represent conditions under which it is believed that nearly all workers may be repeatedly exposed, day after day, without adverse effect The values listed refer to time-weighted average concen trations for a normal workday The amount by which these figures may be exceeded for short periods without in jury to health depends upon a number of factors such as the nature of the con taminant, whether very high concentra tions even for short periods produce acute poisoning, whether the effects are cumulative, the frequency with which high concentrations occur, and the dura tion of such periods All must be taken mto consideration in arnvisg at a deci sion as to whether a hazardous situation exists Because u has been recognized that the threshold limits of certain acute ly acting substances may not provide a safety factor comparable to that of chronically acting substances for which a time-weighted average apphes, a "C" designation or "ceiling" has been affixed to such values indicating that the Thresh old Limit Value should not be exceeded The bases for the "C" listing are given m appendix C Special consideration should be given to die application of these values in as sessing the health hazards which may be associated with exposure to mixtures of two or more substances A bnef discus sion of basic considerations involved in developing threshold lmut values for mix tures, and methods for their develop ment, amplified by specific examples are given tn appendix B Threshold limits are based on die best available information from industrial ex perience, from experimental studies, and, when possible, from a combination of the two These values are based on various criteria of toxic effects or on marked dis comfort, thus, they should not be used as a common denominator of toxicity, nor should they be considered as the sole entenon in proving or disproving diag nosis of suspected occupational disease These limits are intended for use in the field of industrial hygiene and should be interpreted and appbed only by per sons trained in this field They are not intended for use, or for modification for use, (1) as a relative index of toxicity, by making a ratio of two hznlts, or (2) in the evaluation or control of commu nity air pollution or air pollution nui sances, or (3) in estimating the tone potential of continuous uninterrupted ex posures These values are reviewed annually by the Committee on Treshold Ltmifa (or revisions, or additions, as further infor mation becomes available The Commit tee welcomes the suggestion of sub stances to be added to the hst and also comments, references, or reports of expe rience with these materials