The Roles of Dose Reconstruction and Simulation Studies in Understanding Historical Exposure to Asbestos

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1 The Roles of Dose Reconstruction and Simulation Studies in Understanding Historical Exposure to Asbestos Dennis Paustenbach PhD, DABT President and Founder ChemRisk San Francisco, California International Conference on Chrysotile Montreal May 23-24, 2006

2 Simulation Studies Data on airborne concentrations of chemicals collected while simulating conditions involving past actual or alleged exposures Advantages Gives insight on historical exposure scenarios Allows understanding of plausible range of exposures Can apply to risk and causation analyses Meets current court and juror expectations

3 Study Design Considerations Routes of exposure Chemical characteristics and use Volatility Quantity Mixtures Existing work and safety practices Historical work environment Sampling methods (old or modern)

4 Usual Elements of a Simulation Study Worst case and normal scenarios Work parameters Average # of procedures Variety of operations Duration of exposures for different operations Intensity of exposures for different operations Work environment Size of facility Ventilation Use of respiratory protection

5 Usual Elements of a Simulation Study Airborne samples Personal lapel Bystander Background Ambient Analysis of bulk samples of raw materials Collect adequate samples If possible, conduct tests in triplicate Collect 2 samples per worker and bystander Demonstrate expected day to day variability Different workers or workplace settings

6 Usual Elements of a Simulation Study Quantify (continuously) air exchange rate (SF6) Obtain Institutional Review Board approval Perform photography and videography

7 Considerations for Asbestos Simulation Studies Simulation scenarios Appreciate differences between professional vs. hobby applications Evaluate tangential exposure sources Sampling (i.e., contaminated clothing, cleanup, eating lunch) 30-min and 8-hr TWA airborne concentrations Fiber type and size distribution in air NIOSH and ISO analysis methods Total and respirable dust Fiber type in bulk samples

8 Asbestos in Gaskets and Packing Materials

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10 Gaskets in Automobile Exhaust Systems Asbestos-containing gaskets were used in some automobile exhaust systems prior to mid-1970s Some mufflers contained asbestos paper Asbestos exposures have been alleged to occur during automobile exhaust work

11 Gaskets in Automobile Exhaust Systems OSHA PEL (1994-current) Concentration (f/cc) PCM TEM Worker (N=23/25) Bystander (N=38/41) Remote-Indoor (N=21/22) Background-Outdoor (N=14/13)

12 Time-Weighted Average (8-hr) Asbestos Concentrations Associated with Gasket Work on Automobiles 0.12 Concentration (f/cc) Single Exhaust (4 cars/day) OSHA PEL (1994-current) Dual Exhaust (2 cars/day) Worker Bystander

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14 Simulation Study of Gaskets and Packing Materials Simulated formation, removal and installation of gaskets and replacement of packings: Field studies at worksites Simulation studies in a controlled environment Collected over 150 personal and area samples Observed 8-hr TWA exposures consistently below the historical and current OSHA PELs

15 Simulation Study (1982): Airborne Asbestos During Removal and Installation of Different Types of Gaskets TWA (8 hr, f/cc) Spiral Wound Metal Encased Braided Gasket Type Encapsulated Sheet Worker (N=4) Area (N=4) OSHA PEL ( ) OSHA PEL ( current)

16 Simulation Study (1989): Airborne Asbestos During Different Methods for Gasket Formation and Flange Cleaning TWA (8 hr, f/cc) Circular cutter (N=16) Hand shears (N=8) Ball Peen Hammer (N=8) Scribe (N=8) Gasket removal (N=8) Method of Gasket Formation and Flange Cleaning Putty knife (N=8) Hand wire brush (N=8) Worker (N=1) Bystander (N=8) Background (N=1) OSHA PEL ( ) OSHA PEL ( current) Power wire brush (N=8)

17 Simulation Study (1991): Airborne Asbestos During Packing Removal and Installation 0.25 TWA (8 hr, f/cc) Worker (N=1) Bystander (N=1) Area (N=8) Sample Location OSHA PEL ( ) OSHA PEL ( current)

18 Asbestos in Coatings, Mastics and Adhesives

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20 Mastics Exposure Assessment Series of five tests conducted to simulate product usage (tests varied with product) Application: applying test product per manufacturer s instructions Cleanup (spills): cleaning accidental spills and drips of test product Removal/cutting: cutting or sawing test product-coated material Sweep cleaning: sweeping and disposing of debris generated in cutting test Abrading: abrading exterior surface coatings

21 Simulation Study of Mastics, Coatings, and Adhesives Collected over 400 personal and area samples Detected asbestos fibers in 6 of 452 samples Estimated TWAs ranging from to 0.03 f/cc

22 Results of 452 TEM Air Samples (No measurable asbestos in 446 samples) Product Activity Sample Type Asbestos Fiber Count Asbestos Concentration (f/cc) Abrading Personal Abrading Perimeter Sweep cleaning Perimeter hour spill cleanup Personal hour splatter cleanup Perimeter Abrading Perimeter

23 Fiber Concentration Measurements

24 Mastics Study Conclusions Results support OSHA and EPA categorization of no significant risk associated with encapsulated asbestos Data from this study show limited or no release of asbestos fibers (> 5 microns) from these products Measurements are at least 10- to 100-fold lower than ACGIH TLV or OSHA PEL during the 1960s and 1970s Measurements are at least 5- to 10-fold lower than the current OSHA PEL

25 Asbestos in Bakelite (Phenolic Molding Compounds)

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27 BMMA-5353 (Bakelite) Manufactured by client from late 1960s through 1974 Novolac resin and 31% chrysotile asbestos by weight Reformulated in a pilot-plant setting during February and March 2003 based on historical formulation information Molded into 4 in. long, 6 in. wide, ¼ in. deep test panels Clean up of dust generated conducted as separate test

28 Simulation Study of Bakelite Simulated manipulation of phenolic molding materials, including sawing, sanding, drilling, and cleanup Collected over 150 personal and area asbestos samples Estimated 8-hr TWA ranging between to 0.08 f/cc

29 Results Compared to Current and Historical Standards hr TWA, 0.5 hours of activity 8-hr TWA, 1 hour of activity 8-hr-TWA, 2 hours of activity 12 f/ml (May 1971) 5 f/ml (June 1972) Asbestos Fibers/ ml f/ml (June 1986) 0.1 f/ml (August 1994) 2 f/ml (July 1976) Band Sawing Belt Sanding Press Drilling Sweep Cleanup OSHA PEL TWA

30 Bakelite Study Findings The 8-hour TWAs calculated were: 100-fold less than the permissible exposure limit (PEL) set by OHSA in fold less than the PEL in fold less than the current PEL Products of phenolic-molded compounds were molded to fit and crafted for their intended use Even if a worker performed sanding, drilling, and cleaning up (activities with highest exposure) for the entire 8-hour workday, the net exposure still would not have exceeded current or historical standards

31 Asbestos in Brake Dust

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34 Simulation Studies of Brake Repair Work Asbestos exposures (8-hr TWA) support historical industrial hygiene estimates of f/cc for brake repair work Simulation work includes alleged short-term high exposure tasks Compressed air blow-out Grinding Filing/sanding

35 Historical Exposures of Auto Mechanics Analyzed asbestos exposures for mechanics doing brake work Included more than 200 samples collected in 6 different countries over the last 30 years Concluded historical asbestos exposures for automobile brake mechanics are low and consistently below occupational standards in the U.S.

36 Brake Job Asbestos Concentrations

37 Garage Mechanic Asbestos Exposures (8-hr TWA)

38 What about health effects at these low exposures?

39 Epidemiologic Studies of Mesothelioma in Garage Mechanics

40 Risk Of Mesothelioma For Various Occupations Source: Teschke et al. 1997, Table II pg. 165 (most recent 20 years removed)

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51 Summary of the Science Airborne asbestos levels are very low for occupations working with: Gaskets/packings Coatings, mastics, and adhesives Phenolic molding compounds Brakes The duration and frequency of exposure is very low The asbestos fibers are often bound in a resin Airborne asbestos levels for the above mentioned applications are, under any reasonable scenario, too low to cause any asbestos related adverse health effects This has been borne out by many epidemiology studies

52 References 1. Paustenbach DJ, Madl AK et al Chrysotile asbestos exposure associated with removal of automobile exhaust systems (ca ) by mechanics: results of a simulation study. J Expo Sci Environ Epidemiol Mar;16(2): Mangold C., K. Clark, A. Madl, and D. Paustenbach An exposure study of bystanders and workers during the installation and removal of asbestos gaskets and packing. J Occup Environ Hyg 3(2): Paustenbach, D.J., A. Sage, M. Bono, and F. Mowat Occupational exposure to airborne asbestos from coatings, mastics, and adhesives. J Expo Anal Environ Epidemiol 14: Mowat, F., M. Bono, R.J. Lee, S. Tamburello, and D. Paustenbach Occupational exposure to airbone asbestos from phenolic molding material (Bakelite) during sanding, drilling and related activities. J Occ Environ Hygiene 2: Weir FW, Tolar G, Meraz LB Characterization of vehicular brake service personnel exposure to airborne asbestos and particulate. Appl Occup Environ Hyg 2001 Dec;16(12): Blake CL, Van Orden DR, Banasik M, Harbison RD Airborne asbestos concentration from brake changing does not exceed permissible exposure limit. Regul Toxicol Pharmacol Aug;38(1): Paustenbach, D.J., R.O. Richter, B.L. Finley, and P.J. Sheehan An evaluation of the historical exposures of mechanics to asbestos in brake dust. App Occup Environ Hyg 18(10):

53 References (cont.) 8. McDonald JC, Liddell FD et al Dust exposure and mortality in chrysotile mining, Br J Ind Med Feb;37(1): Teta MJ, Lewinsohn HC et al Mesothelioma in Connecticut, Occupational and geographic associations. J Occup Med Oct;25(10): Spirtas R, Heineman EF et al Malignant mesothelioma: attributable risk of asbestos exposure. Occup Environ Med 1994 Dec;51(12): Woitowitz HJ, Rodelsperger K Mesothelioma among car mechanics? Ann Occup Hyg Aug;38(4): Teschke K, Morgan MS et al Mesothelioma surveillance to locate sources of exposure to asbestos. Can J Public Health May-Jun;88(3): Agudo A, Gonzalez CA et al Occupation and risk of malignant pleural mesothelioma: A case-control study in Spain. Am J Ind Med Feb;37(2): Hessel PA, Teta MJ et al Mesothelioma among brake mechanics: an expanded analysis of a case-control study. Risk Anal Jun;24(3): Goodman M, Teta MJ et al Mesothelioma and lung cancer among motor vehicle mechanics: a meta-analysis. Ann Occup Hyg Jun;48(4): Wong O Malignant mesothelioma and asbestos exposure among auto mechanics: appraisal of scientific evidence. Regul Toxicol Pharmacol 2001 Oct;34(2): Laden F, Stampfer MJ, Walker AM Lung cancer and mesothelioma among male automobile mechanics: a review. Rev Environ Health Jan-Mar;19(1):39-61.