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Copyright Applied Industrial Hygiene ISSN: 1047-322X print/1521-0898 online DOT: 10.1080/10473220390192881 An Asbestos Job Exposure Matrix to Characterize Fiber Type, Length, and Relative Exposure Intensity Carol Rice1 and Ellen F. Heineman2 1 University ofCincinnati College ofMedicine, Cincinnati, Ohio; 2Occupational and Environmental Epidemiology Branch, Epidemiology and Biostatistics Program, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department cf Health and Human Services, Bethesda, Maryland No job exposure matrix (JEM) was identified that included The relationship between asbestos exposure and disease has been well documented, although questions persist as to variation in risk by the type and length of fiber. For a series of jobs with potential asbestos exposure, the primary fiber type (e&, amosite, anthophylite, chrysotile, crocldolite, of tremolite) and fiber length were identified and the relative information on exposure intensity and asbestos fiber type and length. Thus the work presentedwas undertakentoprovidealink between job title or activity reported, in a work history and the type and length of asbestos fibers that could present a potential for exposure. The JEM was developed for exposure assessment for an epidemiologic study. exposure intensity was estimated. The resulting job expo sure matrix may be useful in epidemiological studies where asbestos is an exposure of interest. METHODS Potential asbestos exposure situations were grouped broadly Keywords Asbestos, fiber Type, Fiber Length, Exposure Intensiiy into primary or secondary use in product manufacture, shiprelated occupations, mining and milling, and end-user/ Exposure to asbestos has been associated with an increased risk of adverse health effects in a number of populations es pecially since the early 1960s/1"65 In addition to employment as an insulator or shipyard worker/7"105 exposure may occur in a widerange ofotherindustries/11-175 Nicholsonetal/185 provided a detailed listing of occupations where workers may be exposed to asbestos. Work activities andjobs reported to involve asbestos exposure include a range of duties, such as laborer, supervisor, and handyman that may be conducted in industrial and non industrial settings/19-2*5 Evidence from some reports suggests that the risk of disease and the latency may vary depending upon the type of asbestos fiber exposure and length/25-345 In animal experiments, diam eter and length of inhaled fibers have been shown to be im portant determinants of die site of deposition and subsequent translocation/35-375 maintenance activities/185 Industries orjobs associated with po tential asbestosexposure werelisted within eachofthesegroups. Primary or secondary manufacturing industries cover a gamut ofproducts, including friction products, paints and sealants, and electrical appliances. Among ship-related occupations, several groupings are relevant First are those jobs with potential for direct contact with asbestos, for example, welder or electrician. Bystander occupations, in which employees might receive ex posure as a result of the work conducted by tradesmen using asbestos-containing materials can also be identified/38,395 One group of bystanders includes occupations that work routinely on or near the ship, for example, riggers. The second bystander group includes employees who mightperiodically go to the ship construction area, but work routinely in office areas adjacent to the yard. A major component ofthe end-user/maintenance groupis the buildingconstruction trades thatare identifiedby craft;forexam ple, carpenter, painter, tiler. Otherend-user andmaintenancejob titles include activities that may bring a worker in contact with ElIenRHeinetnan's present address is Epidemiology and Genetics. Research Program, Division of Cancer Control and Population Sci ences, National Cancer Institute, National Institutes ofHealth, Depart ment of Health and Human Services, Bethesda, MD 20892. asbestos-containing products; these include elevator manufac ture, installation, or repair; power generation; steam locomotive repair/overhall, and brake manufacture or repair. Exposure may occur during other types of work activities, such as inspecting 506 w `*5 AN ASBESTOS JOB EXPOSUREMATRIX 507 foldings, fire fighting, or diamond cutting. Exposure may also be used for a project manager. If the work involved purchasing occur through the use ofproducts potentially contaminated with of material at distribution centals, the job would be assigned to asbestos (e.g., industrial use of talc). category 1 (low); ifthe job involved onsite oversight ofoverhaul Literature sources woe reviewed to identify the likely fiber of an insulation-cladboilerin 1955, exposure would be assigned types used for various applications andthe relative lengths ofthe to category 3 (medium). fibers.17,10,4<M) The type offiber was characterized as amosite, A wide variety of industries and operations associated with anthophylite, chrysotile, crocidolite, or tremolite. Many uses potential exposure are listed. The majority ofjobs were included of asbestos involve more than ace fiber type; for example, in the a priori list; those added during the review of the work ftiRimal pipe insulation frequently contains amosite and chiy- records from the epidemiology study were milling or other use sotile fibers while reinforced plastic may contain chrysotile, oftalc, shipyard painter, shipyard mechanic/machinist, train en crocidolite, and amosite. Thus, die JEM was constructed to in gineer, building inspector, longshoreman, renovation, use of as dude multiple types of fibers, as appropriate. bestos products NOC, sale of asbestos products NOC, and iron The type and length of fiber were inferred for operations in worker. Examples of jobs associated with the "use of asbestos which products containing asbestos were used. For example, products, NOC" included laboratory technician and household from the documented use of chrysotile and amosite in building appliance repair; the category "sale of asbestos products, NOC" construction and pipe insulation, the potential far exposure to included workers in hardware, plumbing supply, automotive these fibers during building demolition was inferred. Similarly supply, and flooring businesses. For these activities, the fiber for building renovation activities, potential exposure to tremo type is listed as "variable" to allow for assignment using more lite and anthophyllite was inferred because of the presence of specific informationin theworkhistory; toexample, the specific these fibers in drywall materials. When potential exposure re product used, sold, or repaired might be available in the history. sulted from use of a product containing asbestos, fiber length was assumed to be equal to that in the original product Forintensity during the period ofexposure, a four-level scale was developed: very low, low, moderate, high- Very low was considered below the limit of detection using phase-contrast microscopy;*45 low was assigned for exposures likely to be above the limit of detection but below 2 fibers/cc (free); medium, 2-7.9 f/cc; and high, 8 or more free, during the mea surement period. The extensive compendium ofexposure levels reviewed by Nicholson et al.(18) was used as benchmark values. The inclusion ofacategory for verylow-exposurejobs/activities allows evaluation ofthe potential effects of work in many occu pations that might otherwise be excluded, such as building in spection and sale of asbestos-containing materials such as floor coverings, wherecutting wouldbe unlikelyto resultindetectable concentrations of airborne fibers. For these low-exposure jobs, potential contact with an asbestos-containing material was required. DISCUSSION Calendar dates were not included in the JEM; however, use requires somehistorical perspective. The numbers ofemployees in eachoftheseindustry sectorshaschangedovertheyears as the use ofasbestos rose and felL Approximately 6,000metric tons were used in the United States in 1910, increasing to 300,000 metric tons in 1940 and, by 1950, use bad more than doubled to 700,000 metric tons, in part reflecting shipyard use/425 Use peaked in about 1970, and has subsequently declined. Anumber ofkey dates are usefulinevaluatingthe potential forasbestos ex posure. For example, insulation walk was an established skilled trade in the early part of the centuiy, when a New York local joined others to foam the Asbestos Workers Union/25 The years of spray application as a fireproofing material on structural steel are 1958-1972.*185 During tire 1950s, the change from steam to diesel locomotives decreased the numbers of persons exposed RESULTS Jobs with potential asbestos exposure included in this JEM, and fiber types and lengths are shown in Table I. Definitions to file abbreviations and symbols are given in the key at the end " r-of the table and summarized here. Fiber length for chrysotile is ' ^ I shown as grade, with Grade 3 being the longest and Grade 7 the shortest. Amosite and crocidoliteare characterizedas extralong, . long, medium, or short. No length data were found to tremolite or anthophylite. The four-point scale for relative exposure intensity is shown as 1 (very low) to 4 (high) to most jobs; for a small number of a, jobs, the letterD is listed, indicating that the duties performed by . a person with this job title could result'in exposure from none _ to high, depending upon the activities conducted. For exampie, construction work not-otherwise-classified (NOC) would This JEM was developed to use with occupations held through the early 1980s reported by subjects in an epidemiology study; therefore, it does not include all possible jobs or exposure scenarios. Application to later dates should follow a review of the relative exposure intensities to relevance to the timeperiod. Additional jobs or activities might be added to reflect chang ing uses ofasbestos-containingmaterials. Fbr example, asbestos abatement work tasks are not included here. The exposure intensities are relative categories and are set arbitrarily. An exposure of 2 flea was recommended as the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold limit Value (TLV) for chrysotile in 1979.*515 Quantitative exposure assessment studies in the as bestos textile industry showed that quadrupling the endpoints ofan exposure group resulted in statistically different means for W55'"'* 508 C RICE Aram f, heineman , ' . ' . . ; . . TABLE I ... ' product manufactured or jcfo with potential asbestos exposure, length of primary fiber type(s),and relafiveexposure intensity Manufacturing sector/ ... product orjob ... ... -:. Uses .... - ... ; Primary or secondary manufecturingindustrie : lection products ' Clutch/transmission, .. Fibdf'i^ieflraigfiA V Grade:7C . Relative exposure . ' intensity. .3 Pipe . Textiles Tiles Roofing felts Other building materials Paints/coaiings/sealants Reinforced plastics Industrial faction materials Water supply . Conduits for electrical wife Roofing materials Fire/heaf-profective clothing Diyerfelts Electrical wire arid pipe insulation Fireproof diaperies/curtains ' Office, commercial, and " . residential applications Roofing felts Roof coalings ' Roofpatching compounds Auto/truck body coating Roofcpating^patching compounds Hi-strcpgth molded .components r Gaskets, pacMng.and sealing Valve, flange, pump, tank assembly - Building paper/bdard . ' . .. . Paper: ducts, pads/mats : Underlay for floor Beverage filter . Appliancg/eiecftic instdadon Gaskets Heat/fire protective Board: hoods/vents ' Gheinical tnnks. = Residentml/cpminercial/ - '` . Gpsde^C.' LCr . Grade 3C Grade 5/6 C . MA : } Gfoded'{-7)C Grade 5/6 C Grade 7,C Cade3C LCr' : . . -sA Grade 3 G . Grade 5/6 C . L/M/SA 3 3 3 3 3 . :3 3 3 .. Heating boilejs, domestic furnaces, burners Boileishops fodustrial fumaces/ovens Electric housewares and fans Cigarette filter Molten metal handling equipment Fife protection " : Insulation. Small appUance/eiectric motor components, Lab furniture, cqoling towers . ' Grade3C EL/L/SA Grades C EL/L/SA Grade 3 C ELji/SA Graide3C EL/LCr . .- 3 4 3 2 2' (Coptinued on nextpage) AN .ASBESTOS job exposure mahux .509 . . TAB^EI . . Product manufactured orjob with potential asbestos exposure, lerigthdfprimary fiber type(s), and relative exposure intensity . .. , . (Continued) .. Manufacturing sector/ product orjob Fiber type/length* Relative exposure intensity8 Ship-related occupations Shipbuilding and repair, NOC Fumace/bofler maker Welder/cutter/bumer Electrician Plumbing Mechanic/machinist Bystander Group 1 Joiners Riggers Sandblasters Fitters Shipwrights Painters Bystander Group 2 Draftsmen Handymen EL/USA Grade 3 C . v , '" 3 4 4 4 4 4 3 2 Estimators Ship operation, NOC Engine room Marine engineer Mining and Milling Mining, asbestos Milling, asbestos Talc End users/maintenance/asbestos as a contaminant Construction, NOC General contractors Water, sewer, pipe Welding/metal cutting Plumbing/heating (except electric) and cooling Electrician Carpenter/flooring Paint/paperhang/decorating Tile/floor/teiraazo EL/L/SA Grade 3 C Grade 5 C T Grade 3 C T T, An (short) Grade 5/6 C EL/L/SA T, An Grade 4 C CrM Grade 3 C EL/L/SA Grade 3 C EL/L/SA Grade 3 C EL/L/S A Grade 3 C EL/L/SA Grade 5/6 C T,An Grade 3C .2 3 3 2 4 4 D 2 2 2 3 '3 2 3 1 (Continued on nextpage) 510 C. RICE ANDE. P. HEtNEMAN TABLE I Product manufactured orjob with potential asbestos exposure, length ofprimary fiber type(s), and relative exposure intensity (Continued) Manufacturing sector/ product orjob Elevator; NOC Manufacture InstaU/repair Power generation, NOC Stationary engineer Maintenance Firefighter Electric, gas, and combination utilities Train engineers Steam locomotive repair/oveihaul Brakes, NOC Manufacture Vehicle repair/maintenance Uses Fiber type/lengthA Grade 5/6 C Grade 5/6 C L/M/S A Grade 3 C EL/L/S A Grade 3 C EL/L/SA Grade 3 C EL/L/S A Grade 3 C Grade3 C Grade 3,7 C Relative exposure intensity D 1 2 D 2 4 4 2 1 4 3 3 2 Talc use Skilled trades/maintenance, NOC Building demolition Renovation Use of asbestos products, NOC Sales of asbestos products, NOC Ironworkers Longshoremen Building inspection- Sheetmetal Roofing/siding Glass and glaring Jewelry soldering/diamond cutting Firefighter , Other, NOC T, An (short) Grade3C . EL/L/S A Grade 5/6 C EL/L/S A Grade 5/6 C el/l/sa Variable Variable Grade 5/6 C EL/L/SA Grade 3C EL/L/S A Grade S/6C EL/L/SA Grade 5/6 C EL/L/SA Grade 5/6 C L/M/S A Grade 5/6 C EL/L/SA Grade 5/6 C GrQde5/6C EliL/SA Variable D D 3 3 2 1 D 2 I 4 2 2 1 D Note: The letter designation that follows is the usual fiber type (C = chrysotile, A s= amende, T = Hematite, An == autbophyllite, Cr = croddolite), .. AGrade refers to the usual length for chrysotile, 3 is longest, 7 is shortest Amosite and croddolite are designated by: EL = extra long; L = long, M=Medium, S -- sbort.See references.^ 1 BRange -- 1 (very low) to 4 (high). D indicates that exposure levels arediverse and avalue is assignedafter review ofthe work record. Extended as described elsewhere.0 AN ASBESTOS JOB EXPOSURE MATRIX 511 adjacent groups/525 Whileno mean ofdie categories in this JEM can be calculated, the guidance regarding setting midpoints is a useful template; therefore, die value of 8 f/cc, or four times die exposure ofthe lower group, was used as the lower bound of die high exposure group. Investigators who have quantitative data for some jobs held demiological study. The combination of asbestos type, length, and relative exposure intensity have not previously been avail able in a single JEM. Whenused during review ofwork histories by individuals experienced in occupationalepidemiology expo sure evaluation, this characterization of asbestos fiber exposure may be useful in exposure reconstruction. by subjects should compare those data with the categories pro vided here for the sampling period and adjust as appropriate. Because of die extensive sampling of asbestos exposures, it is likely that values outside the ranges citedhere will be identified; higher or lower estimates should be incorporated according to the professional judgment of the user. It is also noted that the user must provide an exposure intensity estimate for jobs cat-, ACKNOWLEDGMENT The review by and suggestions from John Dement are gratefully acknowledged. This workwasconductedwhile funded through an Interagency Personnel Agreement at the National Cancer Institute (CJL). "egorized as "D." For example, the end user category "skilled trades/maintenance, NOC" would include gasket removal ac tivities by pipe fitters and machinists. Here literature would be used to document the intensity of exposure, depending upon the methods used for removal/28'31*545 The assignment of fiber type (chiysotile) and length Gong) inferred from the listing for gaskets, packing and sealing, in the primary or secondary man ufacturing industries in the first part of the Table is consistent with data from Millette et al./495 who report difficulty id charac terizing the long, thin chrysotile fibers by electron microscopy. The summary offibertypes and lengths shownallows consid REFERENCES 1. Wagner,J.C.; Sleggs,C-A4Marchand,?.: DiffusePleur&lMesothe- lioma and Asbestos intheNorth Weston CapeProvince. BrJIndus Med 17:260-271 (i960). # 2. Selikoff, LJ.; Churg, J.; Hammond, E.C.: Asbestos Exposure and Neoplasia. J Am Med Assoc 188:22-26 (1964). 3- Selikoff, IJ.; Churg, J.; Hammond, E.C.: Relation Between Expo sure to Asbestos aqfl Mesothelioma. N Engl J Med 272:560-565 (1965). 4. 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