Document 50eDGnbmJEkvnxp7QxBGneNV

50983 DOW CHEMICAL U.S.A. TEXAS DIVISION FREFPOH f, TEXAS 77541 Sutrvnory A survey was conducted to determine employee exposures to asbestos fibers while racking unqucnched ingots at Magnesium Casting B, R-842, during April, 1979. Employee exposures wore about It; of the short term exposure limit, and less than 0.5% of the permissible exposure limit calculated as an 8 hour time-weightea average. Further monitoring is not necessary at this time. Employees should be informed of the results of this survey, and the informing documented. I/O bbs Distribution P. E. Howe B-837 K. T. Kerr B-837 A. L. McDowell B-101 File hf W. Rampy 1803 Midland ^R. R. T.angnor 1603 .Midland Marlene Swank 1803 Midland D. J. Roberts 2020 Midland * F. D. Axe - Pittsburg * C. E. Halphen -- Plaquemine * R. J. McCormick - Strongsville k Neil Murray - Sarnia k R. D. Olson 607 Midland * S. A. Goode - OCD AN OPERATING UNIT 0= THE DOW CHEMICAL COMPANY |JD CD CO IX) "o TsT B8-1818 -2- June 1, 1979 INTRODUCTION A survey was conducted to determine employee exposures to asbestos fibers at Magnesium Casting B, 3-342, on April 18, 1979 . PROCESS DESCRIPTION Molten magnesium from. Magnesium III is transported to Magnesium Casting B in covered crucibles, where .it .i.s rhen poured into furnaces. The magnesium is pumped from the furnaces into molds on conveyors, and is allowed to cool in both air and water as the molds traverse the length of the conveyors. At the ends of three of the conveyors, the ingots are hand- or mechanicallystacked; a towmotor is used to remove and stack the large ingots from the remaining conveyor. Occasionally the magnesium ingots do not fall out of the molds into the water quenchers; as a result they fall under the conveyor as the molds turn upside-down while traveling back to the end of the conveyors to be refilled. Since these ingots have not been throuqh the water quenchers, they are too hot to handle with the cotton gloves routinely worn by the Casting Operators while racking ingots, and asbestos gloves are w'orn during the few moments necessary to retrieve and rack them. METHODOLOGY Since only a few moments are normally required to retrieve arid rack the ingots -which fall under the conveyors, a simulated procedure was used to determine the employee exposures to asbestos fibers ar these times. The water quencher was turned off on conveyor =4, and employees wearing asbestos gloves racked the hot (dry) ingots for periods of 10-25 minutes. Fixed station and personnel samples were collected by drawing a measured volume of air (approximately 1.5 liters per minute) through aerosol filters (Millipore MAWG 937AO) using Bendix Micronair II air sampling pumps. The pumps were calibrated before and after use with a calibrated Gilmont rotameter (S/M B-2241). Sampline times ranged from about 10 to 50 minutes. Analyses were done by optical micx`oscopy at Central Laboratory, B-1225. Sampling locations are shown in Figure 1. EVALUATION CRITERIA <(n ___[ .:;o cd CD go '-J 00 Permissible exposure, limits (PEL's) are concentrations of air borne substances to which nearly all employees may be repeatedlyexposed throughout a working lifetime without adverse effect. File B8-1318 -3- June 1, 1979 EVALUATION CRITERIA (contir.ued) Most FEL's are Lime-weighted average concentrations for 8 to 12 hour work days and 40 hour work weeks. Permissible exposure limits do not represent fine lines between safe and dangerous exposures; they are based on industrial experience and experi mental human and animal toxicological studies, and are intended for use as guides for plant design and for evaluating employee exposures. The permissible exposure limit for asbestos fibers is two fibers per cubic centimeter of air (2 fibers/cc), as an eight-hour time-weighted average. An asbestos fiber is defined as a particle greater than or equal to five microns ir. length. Ten ibers/cc are allowed as a ceiling concentration for periods up to 15 minutes, provided the exposure for the entire 8-12 hour work day does not exceed 2 fifcers/cc, and there are no more than four excursions per day, which are separated by at least an hour. RESULTS AND DISCUSSION Monitoring results are shown in Table I. Employee exposures to asbestos fibers while racking unquenched ingots are significantly below allowed exposure levels. The average employee exposure to asbestos fibers while racking was 0.1 fibers/cc air, substantially less than both the short term exposure limit of 10 fibers/cc air (for periods up to 15 minutes) and the permissible exposure limit of 2 fibcrs/cc air (as an 8 hour time-weighted-average) . The average asbestos concentration in the area surrounding the employee (about 2 feet away) was approximately half of the average employee exposure, or 0.04 fibers/cc air. CONCLUSIONS AND RECOMMENDATIONS Employees at Magnesium Casting B are not being overexposed to asbestos fibers while racking unquenched ingots. Exposure levels are so low that the total employee exposure for racking a full 6 hour shift would be only 5% of the permissible exposure limit. Since racking unguenchcd ingots is not a routine procedure and the time involved is unlikely to exceed 15 minutes per shift, employee exposures are`actually closer to 0.5% of the permissible exposure limit (as an 8 hour time-weightedaverage)*, and 1% of the short term exposure limit for the few minutes spent actually racking. * Calculated using the following equation: 8 hour average exposure = asbesros concentration x duration of cxposure(hr) 8 hr. STC003271) file B8-1818 -4- Juno 1, 1979 CONCLUSIONS AND F.ECCiMMEEDATIQNS (continued] Further monitoring is not necessary at this time. Employees should be informed of the results of this survey, the consequences of overexposure to asbestos fibers (attached) , methods of control, and the care and use of protective equipment. This informing process should be documented. ehs EPW/bbs 6-1-79 c/J --I CD rjD CD CO CD -4 cn B8-131S TABLE I ASBESTOS MONITORING RESULTS EMPLOYEE*/LOCATION 140613 141514 140613 141514 Average employee exposure during racking procedures SAMPLE ?/ B8-1818-1 B8-1818-6 B8-1818-7 B8-1818-10 ASBESTOS CONCENTRATION (FIEERS/CC AIR) .064 .094 .16 .12 .11 On conveyor - to left of employee On conveyor - to left of employee On pallet - behind employee On. pallet - behind employee On pallet - to left of employee On pallet - to left of employee Average area concentration -2 -5 -4 -9 -3 -8 .045 .048 .018 .066 .032 .048 .042 Short terra exposure limit (periods up to 15 minutes) - 10 ibers/ce air Permissible exposure limit (S hour time-weighted average) - 2 fibers/cc air '.ID o CD CD f'O cn * Master numbers are show, for the employees monitored File- - \m Figure l - Asbeslos sampling \oca-Kons; 'B-SH'Sl s * #4 CorWe^o r </i --i (.3 CD CO ro --j * SOirnple. (ooa.4ions O employee po-^VKon 'O \ A \ * CONSEQUENCES OF OVEREXPOSURE COMPOUND! Asbestos >5EXPOSURE LIMIT: 2 fibers/ml , microns in length ODOR: none . ' EYES: `' Contact with the dust can cause irritation SIMILAR TO THAT CAUSED BY SIMILAR FOREIGN BODIES. INGESTION: Some evidence indicates that swallowed ASBESTOS MAY INCREASE CHANCES OF STOMACH CANCER. DUST INHALATION: Short Term: Long Term: Inhalation of high concentrations OF THE DUST MAY CAUSE MODERATE DISCOMFORT. INHALATION OF MODERATELY HIGH CONCENTRATIONS MAY CAUSE MO DISCOMFORT. Inhalation of the asbestos fibers "Tj IN CONJUNCTION WITH SMOKING HAS BEEN0 SHOWN TO INCREASE CHANCES OF LUNG o CANCER BY ABOUT SO TIMES THAT OF A co PERSON WHO NEITHER SMOKES NOR WORKS ro WITH ASBESTOS. CAN ALSO CAUSE A SERIOUS LUNG DISEASE CALLED ASBESTOSES. Can also cause cancer of the chest LINING. COMMENTS: Proper respirator is required when working with ASBESTOS. fr.