Document pp027xrobB6OvGZY3412ebO06

ASBESTOS Here's an update on asbestos... By G.S. Rajhans, P.Eng., Occupational Health Branch, Occupational Health Engineering Services, Toronto. Ontario. There has always been an attempt on the part of scientists to establish a hygienic standard for asbestos that is biologically most appropriate in limit ing the hazard. However, since asbes tos was established as a human carcinogen, it has been difficult to establish a no-risk level, either for occupational exposure or non-occupational exposure. There is always some small risk to health as long as there is any airborne dust in the environ ment. Nevertheless, an allowable exposure level must be set and defined by an index based on the theory that expo sure up to certain levels can be toler ated without incurring undue risks. This article will offer a critical review of the existing and proposed occupa tional and non-occupational standards for asbestos. OCCUPATIONAL STANDARDS The occupational or work-environment level is normally referred to as a Threshold Limit Value (TLV) or Time-Weighted Average (TWA). These values refer to time-weighted concentrations for a 7- or 8-hour work day and 40-hour work week. They refer to airborne concentrations under which it is believed that nearly all workers may be repeatedly exposed day after day without adverse ef fect. In 1946, the American Governmen tal Industrial Hygienists proposed that the TLV for asbestos dust be set at 5 mppcf (million particles per cubic foot), as determined from impingcr samples.' This value was recom mended by Dressen, Dullavallc, Ed wards. Miller and Sayers after a study of 541 employees in three asbestos textile plants using chnsolile asbes tos.-' In 1960 an occupational standard for asbestos was published in the U.K. by the Minister of Labour.1 This was taken from the annual list of TLV's published by the ACGIH. In 1965 The British Occupational Hygiene Society (BOHS) formed a Hygiene Standard Committee.-1 This committee, after critical examination of the ACGIH standards, recommended the use of the ACGIH standard for asbestos for the time being, until they have estab lished their own standard. In 1967, Cooper1 observed that the TLV of 5 mppcf for asbestos rests on shakier evidence than most TLV's. His chief argument was that a large proportion of asbestos fibres have diameters below the resolving power of the light microscope used for impinger counts and are therefore not counted at all. He further reported that asbestosis appeared in insulation workers who were exposed to con centrations much below the timeweighted average of 5 mppcf. Leathart and Sanderson5 also considered the TLV of 5 mppcf to be too high. In January of 1968 the ACGIH issued the following statement: "A limit to 5 mppcf, based on impinger samples counted by light-field techniques is satis factory to control exposures to most forms of asbestos. Crocidolite, however, has been shown to produce mesotheliomas in addition to the common asbestotic inflammations. Since no safe limit can be estalished for this form of asbestos at this time, until more definitive data are obtained, it is recommended that workers exposed to croci. dolite be equipped with air- Hygfene Standards for ABbestos Response to chrysotile asbestos exposure vuc00Ho1 Ms 01 00 4avu<c_0J> owu waW(>0) u-l o 0) Oh 4030- 2010- LAM 004799 Exposure (fibre years/cm-^) TT4 rr I 'Dnciinnon 1000 DPMC-02436 TO OCCUPATIONAL HEALTH AND SAFETY supplied helmets.6 years/cc over 50 years and an extrapo should reduce the likelihood of dis TEXTILE STUDY However, by this lation of the curve shown above would eases (malignant and non-malignant) time, the Hygiene Standards Commit indicate that this would result in more resulting from exposure in excess of tee of the BOHS under the chairman than 2% risk of contracting asbesto 30 years with very long latent periods. ship of Professor Lane had already sis. The U.S. Government published the completed an environmental and med In 1972 NIOSH recommended the following in the Federal Register, Vol. ical study at an asbestos textile following criteria for asbestos dust."1 36, No. 234, December 7, 1971." factory in England, in which investi "Occupational exposure to airborne "The 8-hour time-weighted gations were made of 290 of the men asbestos dust shall be controlled so average airborne concentration employed in the period of 1933-1966/ that no worker shall be exposed to of asbestos dust to which em The asbestos dust concentrations to more than 2.0 asbestos fibres per cubic- ployees are exposed shall not which different workers had been centimeter (cc) of air based on a count exceed 5 fibers per milliliter exposed varied from 1 fibre/cc to 27 of fibres greater than 5 micrometers greater than 5 microns in fibres/cc measured by the membrane (> 5 um) in length determined by the length, as determined by the filter (MF) technique in which the membrane filter method at 400-450 x membrane filter method at 400- number of fibres greater than 5u in magnification (4 mm objective) phase 450 x magnification (4 millime length were counted. contrast illumination, as described in ter objective) phase contrast The problem of relating prevalence Appendix 1, determined as a time- illumination. Concentrations of asbestosis with concentration and weighted average (TWA) exposure above 5 fibres per milliliter but, with duration of exposure was re for an 8-hour work day, and no peak not to exceed 10 fibres per millil solved by assuming that the cumula concentration of asbestos to which iter, may be permitted up to a tive amount of asbestos remaining in workers are exposed shall exceed 10.0 total of 15 minutes in an hour the lungs from a given exposure is fibres/cc greater than 5 um as deter for up to 5 hours in an 8-hour equally dependent on the dust con mined by a minimum sampling time day." centration and on the duration of of fifteen minutes." On June 7,1972" the OSHA promul exposure to that concentration. Thus, Along with the above recommenda gated a standard which limits the the exposure of an individual was tion the NIOSH also issued several worker exposure to an 8-hour time- expressed as fibre-years/cc, that is other statements: weighted average (TWA) of five the product of the average concentra asbestos fibres per cc of air; and the tion during working hours and his years of exposure. Exposure ex pressed in this way was compared to the prevalence of asbestosis and a curve was developed/ (Fig. 1) Category TABLE I Dust Concentration f/cc ceiling limit of 10 fibres/cc. They also mentioned that effective July 1, 1976, the 1972 rule would reduce the expo sure limit to an 8-hour exposure limit of 2 fibres/cc. Selikoff et al'1 criticized One criticism of this curve was the use of a continuous scale starting at zero. Doses which give zero response are never, in fact, known with abso lute certainty since the sensitivity of a Negligible Low Medium High 0-0.4 0.5-1.9 2-10.0 ove' 10.0 the standard on the basis that the fibres are made of fibrils 300 to 350 Angstroms in diameter and cannot be seen with the optical microscope, being far below the limits of its reso measuring instrument is limited. (1) The standard is amenable lution. However, the main conclusion from to techniques that are valid, In 1973 the Hygiene Standard the curve was that for an accumulated reproducible and available to Committee reviewed the 1968 BOHS exposure of 100 fibre-years/cc, it is industry and governmental standard for chrysotile and recom probable that the risk of being affected, to the extent of having the agencies. It will be subject to review and will be revised as mended that no changes be made at the present time, but the standard be earliest clinically demonstrated signs, necessary. kept under review." They also re j is less than ]"*. That is, 2 fibres/cc for (2) The recommended stan viewed the information on the results I 50 years, 4 fibres/cc for 25 years or 10 dard is designed primarily to of human exposure to airborne arao- fibres/cc for 50 years, 4 fibres/cc for prevent asbestosis. For other site asbestos with animal experi 25 years or 10 libres/cc for 10 years. diseases associated with asbes ments. They recommended that the ACGIH In 1909 the ACGIH proposed tos, there is insufficient infor standards for amosite be the same as a TLV of 12 fibres greater than 5 urn mation to establish a standard those for chrysotile. in length per cc by the MF technique to prevent such diseases includ It was further recommended that or 2 mppcf by the impinger technique. ing asbestos-induced neoplasms the following table (Table I) be used to This was probably based on the work by any all-inclusive limit other designate certain ranges of dusti of Lynch. Aver and Johnson' in than one of zero. Nevertheless, a ness. asbestos textile plants where 1 mppcf safety factor has been included On October 9, 1975 the Federal (impinger) was shown to lie equal to in arriving at the concentration Register1' proposed a standard of 0.5 5.9 fibres/cc. In 1970' the ACGIH level that will reduce the total fibres per cc for an 8-hour TWA (or i proposed a lower asbestos dust limit of body burden and should more 500,000 fibres per cubic meter) and ` 5 fibres/cc by the MF technique and adequately guard against neo likewise a reduced ceiling of 5 fibres < eliminated the impinger standard. plasms. per cc (or 5 million fibres per cubic However, this TLV remained on the LATENCY A ceiling value of 10.0 meter) for any period not exceeding , intended changes list until 1973 when fibres/cc that was noL to be exceeded 15 minutes. * it was first adopted as the TLV and was included to reduce the possibility IHPR The proposed standard did not continues to be the one today. This of the short-term heavy exposures to apply to the construction industry and ! TLV, if continued, would result in an asbestos that have been reported to separate rulemaking to revise the accumulated exposure of 250 lihre- cause mcsotholiama. In addition, this asbestos standard for construction J NOVEMBER DECEMBER 1977 DPMC-02437 LAM 004800 I I industry was planned. The Insulation Hygiene Progress Report"' critically reviewed the proposed OSHA stan dard and issued the following state ment: "This recognition that the construction industry is unique is highly desirable. Earlier data on the effectiveness of moni toring in the construction indus try (see Insulation Hygiene Progress Reports, Summer 1973), have shown that few dust counts are ever taken in this segment of the Industry. Thus, specification of procedures is of much greater importance here. Individual workers must be able to judge whether or not they are working in a safe environment on the basis of materials and methods rather than dust counts. "As much of insulation is now asbestos-free, work practices for installation of new material can be developed that would lead to a time-weighted average expo sure less than that proposed in the new standard. With care, even ripout can be done safely, but special precautions must be taken. Wetting techniques have now been developed that would allow removal of asbestos to be accomplished within the pro posed regulations." 2 FIBRE OSHA invited comments on appropriateness and feasibility from the asbestos industry. On February 4, I976,: some 65 representatives from companies and trade associations rep resenting manufacturers and pro cesses of asbestos products in the United States participated in a meet ing held in Washington, D.C. and overwhelmingly endorsed that the "2 fibre" level has been or can be attained by application of engineer ing technology but the proposed "0.5 fibre" level is unnecessary, impractic able and lacks medical justification. In a letter dated December 15, 1976" to the OSHA, Dr. Finklea of the NIOSH recommends that the OSHA reduce the standard for occupational exposure to asbestos to 0.1 fibres per cc. Dr. Finklea said the previous recommendation of a 2 fibrcs/cc was designed primarily to prevent asbestosis since insufficient information then existed to establish a standard to prevent asbestos-related diseases such as pulmonary, pleural and peritoneal neoplasms. The 0.1 fibre per cc recom mendation i based on lowest con centration at 'thick asbestos fibres can be monitored reliably using phase contrast microscopy. Our study1" indi cates that it is not possible to monitor the levels at 0.1 fibres/cc reliably. CANADA In Canada there is no uniform standard, all provinces have their own asbestos standards. An attempt is made here to summarize the provincial standards. Qr/.r-,,-Thc standard to be ap plied is 5 fibres/cc but the Beaudry commission has suggested a reduction to 2 fibres per cc or the equivalent. 0f riV-Thcy followed the ACGIH recommendation until 1972 and then they lowered the standard to 2 fibres/cc for chrysotile mainly due to the following: (1) The U.K. has been using this standard since 1971. (2) The NIOSH criteria docu ment recommended this limit. (3) The toxicities of various types of asbestos is not well understood and hence a built-in safety factor was needed. air as determined by the mem brane filter method of evalua tion at 400-500x magnification using phase contrast illumina tion. British Columbia---The B.C. Government have had a standard of 5 mppcf (impinger) for a long time. However, they have now their stan dard and recommended a TLV of 2 fibres per cc greater than 5 um in length for chrysotile and 0.2 fibres/cc for crocidolite in the Second Draft Amendments, Workmen's Compensa tion Board, Industrial Health and Safety Regulations, February, 1976. They have also mentioned a ceiling of 5 fibres/cc for 15-minute exposure. This is the ceiling level of 10 fibres/ cc recommended by Ontario. Saskatchewan--The province has a TLV of 2 fibres/cc for all asbestos varieties. Nora Scotia--At present, the stan dard is 5 fibres/cc but new facilities TABLE 2 REGULATING AGENCY CALIFORNIA + Air and Industrial Hygiene Laboratory, California State Department of Health CONNECTICUT + Department of Environmental Protection, State of Connecticut ONTARIO Ontario Ministry of the Environment Air Resources Branch ASBES TOS-CONCENTRA TION STANDARD Total fibre count downwind of an asbestos emission source must not exceed 10 times the total fibre count upwind of that source. 30 ng/m1 (based on 30-day average sample) Interim guideline of 5 jig/m' LAM 004801 For crocidolite the standard is 0.2 fibrcs/cc. They also have a ceiling value of 10 fibres per cc for a 15minutc exposure. Alberta---On April 15, 1975 Alberta officially promulgated the following occupational health standards: (A) For asbestos dust or fibre, all forms, the timeweighted average airborne con centration shall not exceed 2 fibres greater than 5 micro meters in length per cubic centi meter of air, as determined by the membrane filter method of evaluation at 400-450 x magni fication using phase contrast illumination. (H) For asbestos dust or fibre, all forms, the maximum (ceil ing) airborne concentration shall not exceed 10 fibres greater than 5 micrometers in length per cubic centimeter of will be required to meet tne standard of 2 fibres/cc. The Working Group on Asbestosis-' recognized the documented and sus pected health hazards associated with asbestos exposures and recommended a uniform early acceptance of a maximum tolerable level of 2 fibres/ ml., time-weighted average. The prac tical objective, however, should be to reduce asbestos dust in the workplace to the lowest possible level. Feasibility o f J fibres/n: Simulant A standard should not be promulgaled on whether it is feasible to meet it or not. Almost anything is feasible if it is necessary. However, it is a worthwhile exercise to analyse if the standard is feasible. It should also be realized that 2 fibres/cc is a TWA over an S-hour period. In other words some excursion during the period ran be permitted, but the excursion is limited to 10 fibres/cc. Now, if one supposes DPMC-02433 The hands-off ear plug Bilsom Propp-o-Plast Handle the toughest hygiene requirements with Bilsom Propp-o-Plast. No shaping required. Ready-to-wear Propp-o-Plast disposable plugs are pre-lormed. A thin plastic Him covering the acoustical fibers maintains the plug shape. Several polyurethane plugs (such as E-A-R. Deei-Dampl require considerable molding and shaping which could easily imbed contami nants into the plug surface. Propp-oPlast plugs remain untouched and hygienic. Comfortable, too. because they fit any size ear and the minute pores in the plastic flim allow the plug to breathe. Economical enough to toss away after each use. Propp-o-Plast is 100% disposable. Bilsom for your comfort liilsoni International, Inc., 118(H) Sunrise Valiev I)r., Reston, VA 22091 Phone (703) 620-3950 Wzm. For more (acts circle 15 on card. that a worker is exposed to 10 fibres/ cc for 15 minutes he could be exposed to 1.7 fibres/cc for the rest of his shift, i.e. 5 x 10 465 x 1.7 = 480 x 2. Lemen et al2` showed that more than 50% of the operations in textile operations were able to meet the 2 fibres/cc limit and control technology to meet the 2F/cc level existing in all operations in the friction product industry. A study has been carried out in Ontario to determine the technolog ical feasibility of the 2 f/cc standard2'1 as is the Beaudry Commission in Quebec.-"' The Ontario report'- shows that the level of 2 fibres per milliliter is technologically feasible in the five major plants studied. COSTS Our studies in Ontario would seem to indicate that the industry is well able to bear significantly in creased control costs without enor mous dislocations in the industry. We enforce asbestos standard as strict as that presently used anywhere in the world. At the present time, it would seem that our asbestos using indus tries are economically healthy and perfectly capable of working under the necessary constraints imposed upon them. Other Occupattonal Standards (1) The BOHS has recommended a level of 0.2 fibres/cc for crocidolile. " (2) The BOHS also gives the follow ing alternative indices for chrysotile asbesots.1'" Respirable mass: -0.03 mg magnesium/m' -0.04 mg SiO./m1 -0.10 mg ash/nT` -0.12 mg asbestos/m1 Thermal Precipitator: 25 ppcc greater than 1 um after incin eration. Impinger: 10 ppcc Royco Particle Counter: 2 ppcc greater than 4 um. It should, however, be realized that the above standards refer to condi tions in textile factories using chryso tile asbestos and the equivalents may not be applicable in other places. The joint ACGIH-AIHA Aerosol Hazards Evaluation Committee-'' af ter reviewing various standards in cluding the mass concentration con cluded that "at present the only practical way to determine fibre concentration is by counting fibres which have been mounted on a suit able substrate so that they can be identified as individual fibres." ENVIRONMENTAL STANDARDS In 1971 the Environmental Protection Agency, U.S. Government proposed emission standards concerning the following: (1) Emissions shall not exceed those which would be emitted from operations if proper engi neering control had been in stalled (i.e. fabric filter, cyclone gas cleaning devices). (2) Visible emissions of par ticulate. (3) Spraying of asbestos. (4) Use of asbestos for surfac ing or resurfacing of roads. The use of procedural standards and visible emissions as the basis for eval uation for compliance with the stan dard arc designed to minimize emis sion to the atmosphere. At about the same time the USA, through the Air and Industrial Hygiene Laboratory, California State Department of Health, asks that the total fibre count downwind of an asbestos source not exceed 10 times the total fibre count upwind of that source. The Depart ment of Environmental Protection, State of Connecticut U.S. Environ mental Protection Agency, had the problem under study, and required only that there be no visible emission or certain specified control equipment must be used, e.g. a baghouse, high energy scrubber, etc. Ontario has an emission guideline7 which is 5 micrograms per cubic metre averaged over a half hour at point of impingement. This guideline refers to NOVEMBER'DECEMBER 1977 A1 DPMC-02439 LAM 00480 the maximum concentration of asbes tos averaged over a half hour result ing from the plume from any source, stack or vent, impinging on any recep tor, a school, shopping centre, ground, etc., at the time when the wind is blowing from the source directly toward the receptor. Since wind direction is variable and since more than one source may impinge on a given receptor at one time, the emission guideline is devel oped to encompass these variables in such a way that, if every source meets the emission guideline, the ambient air quality guideline will not be exceeded. Thus, there is no direct numerical relationship between the emission guideline and the ambient air quality guideline. The ambient air quality guideline is the maximum concentration, averaged over 24 hours, to be found anywhere in the commu nity. Table II summarizes some of the air quality standards in force today. The Final National Emission Stan dards for Hazardous Air PollutantsAsbestos and Mercury, promulgated by the U.S. Environmental Protection Agency, were published in the Federal Register of October 14,1975s* and are effective as of that date. Initially the standards appeared in the Register of Have confidence in your test results: accuhaler 808" the accurate personal sampling pump Precise total volume measuremeiu Sample for Ben/ene. Toluene. Petroleum Distillates, and other organic substances Reproducible and verifiable results Low. adjustable flow rate % cc to 9G/cc/mm For use with Charcoal, Silica Gel and Low Flow Detector Tubes For additional information and your Guide, call or write: Easily calibrated Contiolierl inhalation Will not onerate when flow is blocked MESA approval no 2G 3026 for Methane Atmosphnes BASEEFA apnrovai imminent and CFRCHAR anproval no 776D84X for Hydrogen Atmospheres : copy of the Charcoal Tube User MDK SCIENTIFIC, INC. 8O8BusseHgtTAOYPoikkRROog0ee..llirois6OO68 Phone 312 (fit 4250 lele> 7?-A3W/MDA pro MDhEuropean Subsidiary SCIENTIFIC CUKJLTD. fetndownlTK; E;t 66CcCriamr<-j .v r--<.ne Do'se: Eh2:7'-'S ing.and riK_x*ei?Or F VTY v.r., 229* .i/y.ip April 6, 1973." The amendments thereto were proposed October 25, 1974. The following are some of the high lights of this newr document as it concerns asbestos. (1) The "no visible emissions" clause for the waste disposal of asbestos materials remains in effect. (2) Asbestos mills are exempt from the requirement to wet tailings when disposal site tem peratures are below 15F. (3) Only asphalt concrete manufacturing plants that use commercial asbestos are af fected. (4) Local exhaust ventilation systems may be used during certain renovation operations. (5) Containers of asbestos waste may display either an EPA or an OSH A warning label. (6) Clarification is given of the definitions for "planned renovation'' and "emergency re novation" operations. (7) Wastes generated by op erations that use sprayed-on materials containing less than 1% of asbestos by weight to insulate or fireproof buildings, structures, pipes and conduits are not covered by the new ruling. oh&5 REFERENCES 1. Rajhans, G.S.: Fibrous Dust--Its Mea surement and Control, CIMM Bulle tin., pp. 900-910, August, 1970. 2. Dressen, W.C.. Dallavalle, J.M. Ed wards, T.l. Miller, J.W. Sayers, R.R., Easom, H.F. and Trice, M.F., "A Study of Asbestosis in the Asbestos Textile Industry," Pub. Health Bull. No. 241, Washington, D.C., 1938. 3. Addingley, C.G.: Asbestos Dust and its Measurement, Ann. Occ. Hyg., 9, 2., 1966. 4. Committee of Hygiene Standards of the British Occupational Hygiene So ciety: Hygiene standards (or chrysotile asbestos dust. Ann. Occup. Hyg. 11:47-69, 1968 5. Leathart, G.I., and Sanderson, J.T., "Some Observations on Asbestosis," Ann Occup. Hyg.. 6: pp. 65-74, 1963. 6. "Threshold Limit Values of Airborne Contaminants." Adopted at the 30th i Annual Meeting ot the American 1 Conference oI Governmental Indus trial Hygienists. St. Louis, Missouri, May 13, 1968. 7. "Hygiene Standards for chrysotile asbestos dust," Ann. Occup. Hyg , Vol. 13. pp. 7-15. 1970. 8. Roach, S.A., "Hygiene Standards for Asbestos," Ann Occup Hyg., Vol. 13, pp. 7-15, 1970. For more facts circle 16 on card 42 OCCUPATIONAL HEALTH AND SAFETY