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

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 dpaustenbach@chemrisk.com International Conference on Chrysotile Montreal May 23-24, 2006

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

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)

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

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

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

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

Asbestos in Gaskets and Packing Materials

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

Gaskets in Automobile Exhaust Systems 0.120 0.100 OSHA PEL (1994-current) Concentration (f/cc) 0.080 0.060 0.040 0.020 0.022 0.013 0.012 PCM TEM 0.004 0.005 0.002 0.004 0.0008 0.000 Worker (N=23/25) Bystander (N=38/41) Remote-Indoor (N=21/22) Background-Outdoor (N=14/13)

Time-Weighted Average (8-hr) Asbestos Concentrations Associated with Gasket Work on Automobiles 0.12 Concentration (f/cc) 0.10 0.08 0.06 0.04 0.02 0.00 0.006 Single Exhaust (4 cars/day) 0.003 0.002 0.001 OSHA PEL (1994-current) Dual Exhaust (2 cars/day) Worker Bystander

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

Simulation Study (1982): Airborne Asbestos During Removal and Installation of Different Types of Gaskets TWA (8 hr, f/cc) 0.25 0.20 0.15 0.10 0.05 0.00 0.004 0.005 0.005 0.002 0.004 0.004 Spiral Wound Metal Encased Braided Gasket Type Encapsulated Sheet Worker (N=4) Area (N=4) OSHA PEL (1986-1994) OSHA PEL (1994 - current)

Simulation Study (1989): Airborne Asbestos During Different Methods for Gasket Formation and Flange Cleaning TWA (8 hr, f/cc) 0.25 0.20 0.15 0.10 0.05 0.00 0.005 0.005 0.005 0.005 0.005 0.005 0.007 0.009 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 (1986-1994) OSHA PEL (1994 - current) Power wire brush (N=8)

Simulation Study (1991): Airborne Asbestos During Packing Removal and Installation 0.25 TWA (8 hr, f/cc) 0.20 0.15 0.10 0.05 0.00 0.011 0.009 0.004 Worker (N=1) Bystander (N=1) Area (N=8) Sample Location OSHA PEL (1986-1994) OSHA PEL (1994 - current)

Asbestos in Coatings, Mastics and Adhesives

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

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 0.009 to 0.03 f/cc

Results of 452 TEM Air Samples (No measurable asbestos in 446 samples) Product Activity Sample Type Asbestos Fiber Count Asbestos Concentration (f/cc) 41-96 Abrading Personal 0.5 0.0078 41-96 Abrading Perimeter 0.5 0.0017 41-96 Sweep cleaning Perimeter 1 0.0035 81-27 2-hour spill cleanup Personal 1 0.0184 81-27 8-hour splatter cleanup Perimeter 1 0.0035 31-95 Abrading Perimeter 1 0.0033

Fiber Concentration Measurements

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

Asbestos in Bakelite (Phenolic Molding Compounds)

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

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 0.006 to 0.08 f/cc

Results Compared to Current and Historical Standards 100 10 8-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 1 0.1 0.01 0.2 f/ml (June 1986) 0.1 f/ml (August 1994) 2 f/ml (July 1976) 0.001 0 0.5 1 1.5 2 2.5 Band Sawing Belt Sanding Press Drilling Sweep Cleanup OSHA PEL TWA

Bakelite Study Findings The 8-hour TWAs calculated were: 100-fold less than the permissible exposure limit (PEL) set by OHSA in 1972 50-fold less than the PEL in 1976 3-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

Asbestos in Brake Dust

Simulation Studies of Brake Repair Work Asbestos exposures (8-hr TWA) support historical industrial hygiene estimates of 0.04-0.05 f/cc for brake repair work Simulation work includes alleged short-term high exposure tasks Compressed air blow-out Grinding Filing/sanding

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.

Brake Job Asbestos Concentrations

Garage Mechanic Asbestos Exposures (8-hr TWA)

What about health effects at these low exposures?

Epidemiologic Studies of Mesothelioma in Garage Mechanics

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

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

References 1. Paustenbach DJ, Madl AK et al. 2006. Chrysotile asbestos exposure associated with removal of automobile exhaust systems (ca. 1945 1975) by mechanics: results of a simulation study. J Expo Sci Environ Epidemiol. 2006 Mar;16(2):156-71. 2. Mangold C., K. Clark, A. Madl, and D. Paustenbach. 2006. An exposure study of bystanders and workers during the installation and removal of asbestos gaskets and packing. J Occup Environ Hyg 3(2):87-98. 3. Paustenbach, D.J., A. Sage, M. Bono, and F. Mowat. 2004. Occupational exposure to airborne asbestos from coatings, mastics, and adhesives. J Expo Anal Environ Epidemiol 14: 234-44. 4. Mowat, F., M. Bono, R.J. Lee, S. Tamburello, and D. Paustenbach. 2005. Occupational exposure to airbone asbestos from phenolic molding material (Bakelite) during sanding, drilling and related activities. J Occ Environ Hygiene 2: 497-507. 5. Weir FW, Tolar G, Meraz LB. 2001. Characterization of vehicular brake service personnel exposure to airborne asbestos and particulate. Appl Occup Environ Hyg 2001 Dec;16(12):1139-46. 6. Blake CL, Van Orden DR, Banasik M, Harbison RD. 2003. Airborne asbestos concentration from brake changing does not exceed permissible exposure limit. Regul Toxicol Pharmacol Aug;38(1):58-70. 7. Paustenbach, D.J., R.O. Richter, B.L. Finley, and P.J. Sheehan. 2003. An evaluation of the historical exposures of mechanics to asbestos in brake dust. App Occup Environ Hyg 18(10):786 804.

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