Document bypZ3KRwQLwxbY6O27N6KDk33

j -- w .. .*.-i rai.s'c.Tiej Messrs: t-.V .'a C. Benjamin T. F. Frangos B. E. Godard J. L. Myers J. A. Riddle N. J. Setter J. T. Sinclair J. R. Stickney W. S. Young 270 PARK AVENUE, NEW YORX. Nr.V YORK 1C017 Data Originating Deal. Answering latlar data Subject April 3, 1969 Medical Department Asbestos r-ZD u. 1533 PLASTICS Gentlemen: Both because of changes in regulations and availability of data developed after the issuance of our report in 1964, Dr. Dernehl and I have revised the asbestos memorandum. A copy of the revision is enclosed. The major changes are the decrease in the Threshold Limit Value from 5 million particles per cubic foot of air to 2 million particles per cubic foot of air. (There is also a provision for another method of counting but it does not appear applicable to our short fiber asbestos.) We briefly discuss mesotheliomas, but data is too scanty as yet for a definite policy to be established. It is worth mentioning that the American Conference of Governmental Industrial Hygienists considered in 1968 a requirement that airline respirators be required for all contact with crocidolite asbestos. The resolution did not pass, but may come up again in future meetings. Any questions or comments will be welcome. Very truly yours, KSL:lk Enclosure Assistant Medical Director S35ST0S TOXICOLOGY ?.7.?C~:T It has been known for years that some persons working in asbestos production were prone to develop a disabling lung disease. In time, this condition became known as asbestosis and was related to exposure to high concentrations of asbestos dust. With further experience, it was found that men could work with asbestos without development of lung disease if dust concentrations were kept below a certain level. It has been generally accepted that a 'worker will not develop asbestosis if he is exposed to no more than 5 million particles per cubic foot of air, even if this exposure con tinues for his entire working lifetime. Although no cases of asbestosis are known to have occurred when exposures have been maintained at or below this level, the ACGIH (which sets the threshold limit value (TLV) in the U. S. A.) has indicated they intend to lower the TLV for asbestos to 2 million particles per cubic foot in an effort to increase * the safety factor incorporated in the limit. The U. S. Department of Labor has already issued a regulation under the v/alsh-Healy Act placing the TLV for asbestos at 2 million particles per cubic foot for public contracts in which they have jurisdiction. This concentration of dust is generally not visible in the average work area unless a 2- - beam of light causing a Tyndall effect is present. Usually the dust concentration must be from 8-10 million particles per cuibc foot (MPPCF) before its presence it visible in average lighting conditions. Several years ago, it was reported that there was an increase in the incidence of cancerous tumors, especially of the lung, associated with asbestosis. Recently there have been reports of some cancers occurring in individuals exposed to asbestos dust, but who have not developed clinical asbestosis. It is believed by most authorities that these cases have been associated with exposures significantly exceeding the Threshold Limit Value. A type of cancer named mesothelioma has been noted to be associated with asbestos exposure in recent years. These manors, -while rather few in number to date, may occur in individuals with histories of only slight exposures, and that as much as twenty to forty years earlier. There is considerable evidence that crocidolite is most frequently associated with mesotheliomas. From the data available it appears that the TLV of 5 MPPCF is not low enough to protect against mesothelioma, and it is quite possible that 2 MPPCF is not, either. Research on the problem continues. Control of asbestos dust exposure is therefore necessary. The control methods are the standard ones applicable to a variety of dusty operations.They include closed flow systems. *1*w*> ^W" wO\b. n V LCl ^c VO JQ t/.VfVi e possible, and adequate exhaust ventilation v;hcre openings in the system are necessary. Pelletizing is sor.eei:r.es used to improve the handling characteristics c-f otherwise dusty ma terials. Where satisfactory containment to stay v:ithin the Threshold Limit Value is impractical or impossible, efficient and reliable respirators are available for the protection of the employee. A program of environmental monitoring is highly desirable to determine that Threshold Limit Values are not being exceeded. In paper manufacturing, it would be desirable to know the dust con centrations where the asbestos is dumped from bags info the . pulp slurry. Concentrations should also be determined where sours m x inisnxrw 'oducts. While initial dust determinations should be made at frequent intervals, once the level has been established as satisfactory, the frequency may be extended to occasional tests to assure continuation of a satisfactory condition. Pre-employment and periodic physical examination of 4 workers are desirable. These should include chest X-rays to insure that the worker has no chest condition prior to work with asbestos and to determine that no lung changes are resulting from work with asbestos. It is believed that the addition of asbestos at the proposed levels during the manufacture, of paper products wcula be harmless to the consumer. Total dusting 'would \ i. > have so bo well in excess of any levels accept^ ClVWO^ ow o*1/ the cons' for the asbestos concentrations to approach the Threshola lir.it Value. Jm* i 'W V^> .elusion, while asbestos oust in excess of the ir.it Value is potentially harmful, as are many Co-COr CC... encountered in industry, it is as readily conor died as other such dusts ar.d it can be used safely O* VO -riate orecautior.s. Industrial Medicine And lexicology Department Union Carbide Corporation