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THE SAFE USE OF "CALIDRIA" RG-244 IN CORROSION RESISTANT TANK FABRICATION 1. Introduction Asbestos has received a great deal of attention and publicity in the last several years and has becomme the first substance covered by new OSHA health regulations. Unfortunately, much of the media treatment of the subject has been emotionally oriented and distorted and in some cases has bordered on the sensational and untrue. Many users of asbestos and products containing asbestos have been mislead regarding the safety of asbestos and what is needed to comply with the OSHA requirements. It is accepted that asbestos, like many other foreign bodies, can cause disabling lung damage which for asbestos is commonly referred to as asbestosis. It is important to note, however, that asbestosis and statistical excess occurrences of bronchogenic carcinoma (lung cancer), the two most common asbestosrelated diseases, have occurred only in workers with long-term exposures to massive concentrations of asbestos dust. The risk of this type of exposure is usually in asbestos mines and mills and in large manufacturing operations that use quantities such as 20,000-30,000 pounds per day. Long-term, massive exposures are, of course, not typical of polyester tank manufacturing operations utilizing RG-244 where at most a few bags are used per day. Much has also appeared in the public press regarding the relationship between asbestos and mesothelioma, a rare type of cancer of the pleura. In almost all cases where there is a strong statistical relationship between mesothelioma and the inhalation of asbestos, crocidolite and/or amosite have been involved. Where asbestos exposure has been limited to chrysotile asbestos (RG-244 is chrysotile) there is strong evidence that no excess mesotheliomas will occur. 2. OSHA Regulations After extensive hearings, a new standard for Exposure to Asbestos Dust was published in the Federal Register, Volume 37, No. 110 on Wednesday, June 7, 1972. The basic exposure standard is an 8-hour time-weighted average (TWA) of 5 fibers, longer than 5 micrometers, per cubic centermeter of air. The fiber limit is to be reduced to 2 on July 1, 1976. A peak concentration of 10 fibers per cc., longer than 5 micometers is not to be exceeded at any time. Note particularly the use of the time-weighted average over the 8-hour shift. An operator performing one or two short additions of RG-244 per shift, as is typical of polyester tank manufacturers, would have his exposure during this dumping time averaged with zero (or a low-background level) for the rest of the shift. It is important that this concept be understood for interpreting the effect of intermittent exposures. Improper interpretation of the regulations has created many miscon ceptions about the equipment and procedures needed to use asbestos. If exposure limits are not exceeded, the main further compliance requirement is medical examinations. Medical examinations are required for all employees in any A08826 "occupation exposed to airborne concentrations of asbestos fibers." Some definition of "exposed" is necessary since evidence indicates that small amounts of asbestos fiber have existed in the atmosphere for millions of years. The source of these fibers would be from the weathering of naturally occurring surface outcrops. Interpreted literally, the regulation would require physical examinations for everyone in industry. In its criteria document on asbestos, NIOSH recommended that "exposed to asbestos" be defined as "average exposures above one fiber per cc. or peak exposures above five fibers per cc." 3. "Calidria" RG-244 in Polyester Resin During the last six months, a major asbestos manufacturer has made asbestos dust count measurements at eight major polyester processing plants. Counts have also been made during the sanding and grinding of parts produced from such resin. In all cases, sampling and counting were done with the equipment and techniques prescribed in the OSHA regulations. The results of dust counts taken in the breathing zone of the operator at eight manufacturing locations are shown in Table I. Samples were collected during the dumping of the bags of RG-244 and represent ceiling concentration (not TWA) fiber counts. Examination of the data shows that in all cases the asbestos dust levels were far below the allowable ceiling concentration of 10 fibers/cc. >5x prescribed in the OSHA regulations. Normally, the operator makes only one such dump in his 8-hour shift so that the peak levels shown would be averaged with much lower values in finding his time-weighted-average (TWA) exposure. For example, if the operator were exposed to the highest level found, i.e., 2.8 fibers/cc., for even as much as one half hour during the dumping operation and to a background level of 0.5 fibers/cc. for the other seven and one half hours of his shift, his timeweighted average would be: TWA = (0-5) (2.8) + 8 (7.5) (0.5) = 0.7 fibers/cc.>%m This is well below both the current 5 fibers/cc. and the 1976 level of 2 fibers/cc. and the NIOSH definition of "exposure to asbestos." The OSHA regulations prescribe special precautions for the disposal of empty asbestos bags and containers if in any reasonable foreseeable use and handling dust levels above the allowable limits will be generated. In two of the plant surveys, dust counts were made during the handling of the empty RG-244 bags. The results given in Table II show levels well below the OSHA limits. As with the dumping data given previously, these values were obtained during active handling of the bags and would represent peak rather than time-weighted average exposure. The data presented in Table I and II are for polyester manufacturing operations and thus should represent much more severe conditions than would be found in tank and equipment manufacturing. The dust levels, nevertheless are well below OSHA limits-. As long as this is true, dust masks, protective clothing, change rooms, warning signs and special bag disposal are not required. Dust measurements are required, however, to demonstrate that the levels in a specific location are within the OSHA standards. -2- A08827 In the manufacture of fiber glass reinforced polyester objects, the edges anc some portion of the surface are frequently sanded or ground with a rotary disc grinder. This generates a cloud of visible dust and it is necessary to determine whether any free asbestos fiber is present in the cloud. To check this, samples were collected at four locations during the sanding or grinding of finished polyester parts. The results, given in Table III, show no free asbestos fibers in any of the operations. All of these data are based on Millipore filter counts by the OSHA procedure. In addition to this, larger samples of airborne dust were collected during Operation K and were studied by special staining and microscopic techniques with various types of illumination at magnifications up to 1000X. These, too, failed to reveal any free asbestos fiber. These data essentially confirm that polyester resin containing the usual levels of RG-244 will not yield asbestos fiber counts exceeding the allowable values. 5. Dust Control Although the data presented herein indicate that RG-244, as it is typically handled in polyester tank manufacturing, gives dust levels within the OSHA standards, asbestos is an emotional subject; and the lowest practical levels are most desirable. For small operations, an air- or fluid-operated aspirator with a flexible pickup hose can be used to remove the thixotrope from bags. This would preclude the need for cutting the end of the bag completely open, and would eliminate the subsequent dumping and bag-shaking operation. The dust from the discharge of an air-operated aspirator would, of course, require adequate collection. Empty bags can be disposed of by packaging them in plastic bags. Each bag of RG-244 is over-slipped with a polyethylene bag which can be used for this purpose. Larger plastic bags are commercially available if the RG-244 bags are not saved. Waste bags can subsequently be burned or given to a regular trash pickup service. Dust which accumulates on tanks, floors, etc. should be removed with a vacuum hose or washed down with water. Blowing with air can only relocate the dust and may cause airborne concentrations to exceed the prescribed limits. Excessive dust can be created by poor work or housekeeping practices. Workers should be instructed to handle dusty materials with care and to avoid undue creation of dust by shaking bags, throwing them, etc. Respirators can be worn if desired and should be approved for the dust encountered. Except for special circumstances, respirators cannot be used to achieve compliance with OSHA regulations. -3- A08828 TABLE I AIRBORNE ASBESTOS DUST COUNTSt1) DURING PULPING OF RG-244 Plant A B C 0 E F G H Data Reference -- 1929-46-2 1929-30-2 1929-56-1 1929-50-3 1929-26-3 1929-24-2 1929-16-1 Descrioti on of Operation Oujnp Sample Bags Time Time Dumped (Min.) (Min.) Special Ventilation(2) 10 10 10 None 14 9 9 None 15 21 21 Hood over thin tank opening 36 12 12 None 15 8 8 None 45 20 20 None 10 24 24 Hood over mixing area 28 15 15 None CEILING Concentration Fiber Count (Fibers/cc. >5^) 0.7 1.2 0.7 2.4 0.5 1.6 0.8 2.8 ^All samples collected in the breathing zone of the operator dumping the RG-244. ^Special ventilation refers to dust collection eauipment at or near the dunning area that is specifically intended for dust control during the dumping operation. All plants had varying measures of overall building ventilation. TABLE II AIRBORNE ASBESTOS OUST COUNTS DURING EMPTY BAG REMOVAL Plant A B B Data Reference -- 1929-40-3 1929-40-5 Description of Operation Sample taken 3 feet above waste disposal drum for empty bags. (During dumping.) Directly over empty bag stacking area. Taken during dump. Empty bag storage area. Taken during aump as bags were put in. Sample Time (Min.) 10 23 24 Fiber Count (Fibers/cc. >5*,) 0.4 0.6 0.4 A0882 ~ } TABLE III AIRBORNE AS3EST0S DUST COUNTS^1) MADE DURING SANDING OR GRINDING OF POLYESTER PARTS CONTAINING RG-244 Data Time Special Plant Reference Description of Operation (Mi n.) Ventilation!2/ I 1929-40-4 Operator sanding finished (Furniture polyester furniture parts Molder) containing~0.52 RG-244. 23 Hood directly over grinding area. J 1929-42-7 Operator edge grinding on (Boat hull containing-*0.5Z Yard) RG-244. (-202 fiberglass) 12 None (Outdoors) K Operator edge grinding on 13 None part containing-0.72 (Closed room RG-244, 202 fiberglass. 8'x8` 8'.) K Operator edge grinding on 4 None part containing 22 RG-244 (Closed room 31x81x8') L (Furniture Molder) Operator hand sanding polyester parts containing -0.052 RG-244. General area sample. 45 None L (Furniture Molder) Large power sander smoothing polyester parts containing -0.052 RG-244. 45 Integral hood Fiber Coi (Fibers/cc. 0 0 0 0.2 <0.01 <0.01 ^Unless otherwise noted, all samples collected in the breathing zone of the operator during the sanding or grinding of parts containing "Calidria" RG-244. (v21'Special ventilation refers to dust collection equipment at or near the dumping area that is specifically intended for dust control during the dumping operation. All plants had varying measures of overall building ventilation. A0883C -5-