Document zQ4bQByby52wjzrXLwoBDgKwa

: -;i.. V i-'; VtX`). . i\i . *i kv1'l , 1 tr IXTZP.XJUU COi^rJEGPOrJD^^CE union c:.v:3:dz co^po^atio^ ro>'j.T>) D.Vi'i'ort io.-ot.\jn Co?fto Mr. J. W. Rawlings Mining & Metals Division 38ch floor New York Office Kr. E. Epremian Mr. B. Ingalls Mr. R. J. Klotzbach Mr. P. J. Morgan Mr. J. L. Myers Mr. H. B. Rhodes Dal* Originating Dept. Answrirtg }*)!/ data Sol>i^ RTCtlVSO ( ,,I.A1ynl'F- EXHIBIT SP 2 7 1971 UCC-CAUDRIA T NjX* UC-2916 270 P7.fi K AVE'.UC. fJEW YC2Z. fit// Y0^:< 10017 September 24, 1971 Dear Mr. Rawlings: Attached is the write-up you requested dealing with asbestos. Also attached are copies of methods for dust determinations referred to in the text. Very truly yours. PWM: dp Attachments Paul W. McDaniel Industrial Hygiene Engineer i UCC 016099 A 2 4- 0 ! 3 A. Standards The present (9-23-71) legal standards for concentrations of air contaminants in work places are given in Part 1910.93 of the Occupational . Safety and Health Act as amended and published in the Federal Register, Volume 36, No. 157 - Friday, August 13, 1971. In this listing, which is informally known as "start-up limits", the standard for asbestos is given as follows: (a) 12 fibers per milliliter of air greater than 5 microns or alternatively, (b) 2 million total particles[including fibers jper cubic foot of air. V The listing further specifies how these values are to be determined. That is, fibers per milliliter of air are to be evaluated by the "membrane filter* method at 430X phase contrast magnification". A detailed description (unofficial) of this method is attached. Total dust particles per cubic foot of air are to be "based on impinger samples counted by light-field techniques' A description of this system as recommended by the U. S. Bureau of Mines is attached. Either method of evaluating dust and fiber is presently acceptable, however it is the general feeling among industrial hygienists that the standard for asbestos will be lowered in the future to 5 fibers greater than 5 microns in length per milliliter of air as determined by membrane filters 'and phase contrast microscopy. When this occurs, the limit for asbestos based on total dust will have to be lowered proportionately or abandoned. There has been no indications which course will be followed with the total dust limit. UCC Q16100 A 24 0 2- - Tha definition of an adequate air sampling program for control and evaluation of exposure of personnel to asbestos will depend on the operations involved. For stable, repeated daily operations the collection of air samples once a month will usually be enough. Samples should be collected in sufficient numbers during the work day to cover the usual variations that occur in the operations. ' For operations that are highly variable samples should usually be collected on each occasion of use of asbestos unless it can be shown by experience that the work atmosphere can be expected to be about the same each time. The number of samples collected at each sampling period should be sufficient to cover the changes that might occur during the operations. B. UCC Program at King City Mill and Mine At King City airborne asbestos is evaluated by collection on membrane filters and counts of fibers according to the procedure given for phase contrast microscopy. Samples are collected once a month at various work locations including the cabs of tractors and other moving equipment and at plant property lines. Three 10-minute air samples collected at an air flow rate of 0.1 cubic foot per minute are usually enough to describe the conditions at each location unless the operation is highly variable. In this case samples are collected until it is felt that the number is enough to fairly represent the work environment. Effort is made to insure that the time of day when samples are collected at each location is varied from month to month. Typical fiber counts at King City are 0-2 per milliliter of air at the wet side process locations and 3-14 per milliliter at dry side process UCC 016101 ft 2 4 0 2 ' -3locations. The broad range of restilts for the dry side reflects the effect of occasional bag breakage during filling or other events that would temporarily change the dust picture. Because of this possible variation in dust concentrations at dry process areas, the wearing of res pirators is mandatory for exposed personnel and for any visitors to these locations. The'respirators supplied at King City are Wilson No. 60QA equipped with Wilson filter No. R501 for dusts not significantly more'toxic than lead. Both the respirators and filters bear the U. S. Bureau of Mines seal of approval. This combination of respirator and filter has been found to be acceptable by employees. Tests with the filters have shown them to be highly efficient (987. ) in retention of asbestos fibers. Control of dust is primarily provided by the application of local exhaust ventilation at points of dust generation. This has been found to be an effective procedure by which dust can be prevented from badly contaminating the work environment when used to best advantages through well designed and well maintained systems. Dust from the exhaust system is collected in bag collectors that have been found to be quite efficient for asbestos fiber. Other control measures involve the wetting of ore piles and the use of covers on ore trucks. Both measures significantly help reduce possible spread of dust in outside areas. UCCA16102 ft 2 4-02 2