Document 6RJ9RMn8KbXbM3rEb2a1oKZYR

\ i Mr. G. H. Reilly Director of Safety Rational Tube Division BUILDING PLAINTIFF'S EXHIBIT ulyl, 1959/ Kenneth M. Morse, Director Industrial Hygiene Toxic Limits As per your request, may 1 suggest you consider including the following information with your transmission of the enclosed tables of '*Thresho'ld Limit Values for 1958." The enclosed list of "Threshold Limits" are known under a variety of nasaes, such as "maximum allowable con centrations/' "toxic limits," etc. They are not exact delinea tions between hazard and non-hazard conditions, since they are derived from a variety of sources. Sosae are based upon studies with human subjects, others upon opinions derived by interpo lating from animal experimental data, while still others are based merely upon unsupported opinions from industrial medical and hygiene authorities. However, the fact remains that these limits are often incorporated into state codes or used by state inspectors as exact numbers above which a condition is dangerous. Therefore, in actual practice, it is important to maintain air concentrations of these gases, vapors, dusts or mists within such levels where possible or protect workers by approved respiratory devices. These data are the maxitann degree of air contamination to which one should be exposed upon a continuous 8-hour daily and 40-hour weekly basis. The data, therefore, are degrees of air contamination which will prevent the development of chronic poisoning arising from continuous day to day exposures. It Is our opinion that short-term exposures also should be maintained within such limits where practicable, because of the absence of good data on safe concentrations for preventing acute (sudden) poisoning. This approach is considered to be the best course of action becauee the human body does nob respond in a direct arithmetic relationship with the amount of contaminant in the air. In other words, it would not be prudent to expose an individual for ona hour to eight times the values shown in the enclosed table without respiratory protection, furthermore, state inspectors would no doubt consider such exposurss as* hazardous to health. mf Mtmo from C. H. REILLY 'JUL. /^ w \ i ^ if 'f -* <y *--<_ cc/ -tf * `^V- vL- Oc^^~ JL<S-. cs^~- **( r .7 K/-Ae> <SgaaF^