Does Low Exposure to Chrysotile Pose a Health Risk?

Dr. Tom Hesterberg Principal Toxicologist Center for Toxicology and Environmental Health

American Conference Institute’s Claims and Litigation January 30-31, 2014 San Francisco, California

5120 North Shore Drive | North Little Rock, AR 72118 | Main Line: 501.801.8500 Overview of Toxicology Studies

• Basics of Fiber Toxicology • Chromosomal Effects • Fiber Biopersistence • Rodent Inhalation Studies • Thresholds for Fiber Toxicity

2 Basics of Fiber Toxicology

3 Dose The Cornerstone of Toxicology

“All substances are poisons; there is none which is not a poison. The right dose differentiates a poison from a remedy.”

Paracelsus (1493-1541).

4 Definition of Threshold

The dose below which a given effect is not observed

A threshold is a result of our bodies’ protective mechanisms

5 Doses of Common Substances

Substance Normal Lethal

Water 1.5 qts 15 qts

Aspirin 2 tablets 90 tablets

Table Salt 3 tsp. 60 tsp.

Cyanide in Lima Beans 0.5 cups 11 cups

Toxicity is the adverse effect caused when a chemical reaches a sufficient dose—threshold.

6 Asbestos Types

Chrysotile Asbestos Crocidolite Asbestos The Three Ds of Fiber Toxicology

Dose - Amount reaching the deep lung

Dimension - Thin deposit in the deep lung; long fibers are more toxic

Durability - Dissolution and breakage; more durable fibers are more toxic

Hesterberg and Hart., Inhal. Tox., 2001

8 Biopersistence Determines Toxic Potential of Fibers

Long Fiber (> 20 µm)

Incongruent Dissolution Congruent Dissolution

Transverse Breakage

Complete Altered Biological Translocation Dissolution Reactivity Macrophage Uptake

Mucociliary Clearance Epithelial Cell Uptake Intracellular Degradation Translocation to Interstitium

Hesterberg and Hart., Inhal. Tox., 2001 9 Important to Link Exposure and Dose and to the Lung’s Response to Asbestos Fibers

Exposure

Dose

At High Doses: Response Inflammation Fibrosis

10 What happens to fibers in the lung?

Movement Up the Mucociliary Escalator

Macrophage with fiber Asbestos in the Lung

Macrophage Exposure Early Clearance of Short Fibers Soluble Long Fibers Rapid Recovery of Normal Durable Long Fibers Chronic Inflammation Chromosomal Effects of Fibers in Cells Grown in Culture Dishes

17 Asbestos Fibers are Taken Up by Cells Grown in Culture and Accumulate in the Perinuclear Region of the Cell

Hesterberg, Oshimura, Brody and Barrett, 1986 Asbestos Induces Anaphase Abnormalities in Syrian Hamster Embryo (SHE) Cells in Culture Dishes

Hesterberg and Barrett, 1985 Asbestos and Fiber Glass Induce Cytogenetic Effects in SHE Cells in Culture Dishes

Hesterberg et al., 1985 But Asbestos Does Not Induce Cytogenetic Effects in Primary Cultures of Human Bronchial Epithelial Cells Grown in Culture Dishes

Kodama et al., 1993 Toxicity of Asbestos to Primary Cultures of Mesothelial Cells

Untreated Mesothelial Cells

Apoptosis in Asbestos-Treated Mesothelial Cells

Broaddus et al., 1996

22 Toxicity of Asbestos to Primary Cultures of Human Mesothelial Cells • Induced apoptosis, not chromosome effects Broaddus et al., 1996: • All cells die within one week Yang et al., 2006 • Programmed necrosis Yang et al., 2010 How can asbestos cause mesothelioma if human mesothelial cells exposed to asbestos die? Yang et al., 2006

23 Fibers With the Same Length Have the Same Toxicity to CHO Cells in Culture

Hart et al., 1994 No Correlation Between Cell Culture Chromosomal Effects and Inhalation Toxicity of Fibers

In Vitro Toxicity Rat Inhalation Toxicity Fiber Chromosome Effects Fibrosis Tumors

Crocidolite Yes Yes Yes Chrysotile Yes Yes Yes RCF1 Yes Yes Yes 475 Fiber Glass Ye s Yes No MMVF 22 (Slag Wool) Yes No No X607 Fiber Yes No No MMVF10 (Fiber glass) Yes No No MMVF22 ( wool) Yes No No

Hesterberg and Hart, 2001 Hart et al., 1994

25 Fiber Dissolution and Biopersistence Studies

26 Measurement of In Vitro Dissolution of Fibers Simulated Lung Fluid

Fibers

Analyze Solutes: Outflow Na +,Ca +2 , etc. Leaching of the Outer Layer of a Fiber Glass Fiber Leaching of Metals From Fibers Leaving Weakened Dioxide Matrix

Na+ Ca+2

Mg+2

K+ B+3

SiO2 Matrix Vitreous Fibers Dissolve and Break

Glass Fibers Lung Macrophage After 3 Days in Lung Fluid with Fiber

30 Asbestos Physical/Chemical Structure Determines Biopersistence

Chrysotile Asbestos Crocidolite Asbestos

31 Inhalation Biopersistence Study Protocol

32 Biopersistence of Fibers in the Lung

120

100

80

60 % of Day 1 Day of % Amosite

40

Fibers/Lung >20 µm >20 Fibers/Lung E Glass 20 475 Glass Cert. Glass 901 Glass 0 0 90 180 270 360 Recovery Days Biopersistence of Amosite and Chrysotile

Bernstein and Hoskins, 2006

34 Rodent Studies of Lung Disease

35 Advantages of Rodent Inhalation Studies

• Respirable fibers used • Exposure determined • Dose = Lung burdens • Fibrosis, lung cancer, and mesothelioma • Biopersistence • Determine threshold • Relationship between fibrosis and tumors

36

Lungs 14 Days After Similar Exposures to or Chrysotile

Tremolite Chrysotile

Bernstein, 2003 Chronic Inhalation Studies of Fiber Toxicity and Tumorigenicity

At Risk Animals

Inhalation Exposure Recovery

3 Mo 6 Mo 12 Mo 18 Mo 24 Mo 20%

Recovery

Lung Histopathology and Burden Rodent Chronic Fiber Inhalation Studies

Fiber Type Species Fibrosis Lung Cancer Meso

Air Control R - 1-3.7 0 Asbestos Amosite H + 0 26* Asbestos Amosite R + 38* 5 Asbestos Crocidolite R + 13.2* 0.9 Asbestos Chrysotile R + 18.5* 1.4 Asbestos Chrysotile H + 0 0 FG-SA MMVF32 R + 23* 4.7 Ceramic RCF1 R + 12.4* 1.6 Ceramic RCF1 H + 0 41* FG-SA MMVF33 H + 0 1.2 Rock MMVF21 R + 4.4 0 FG-BI MMVF10 R - 5.8 0 Hybrid X607 R - 0 0 FG-BI MMVF11 R - 2.6 0 Slag MMVF22 R - 2.6 0 HT MMVF34 R - 0 0

Hesterberg and Hart, CRT, 2001 39 If Chrysotile is Biosoluble in the Lung, then Why did it Produce Lung Disease in the Animal Studies?

40 Lung Dose = Deposited Dose – Amount Cleared Lung Burdens of Chrysotile and Other Fibers During a Chronic Inhalation Study

Two Year 6 Month Lung Burden Recovery Percent Retained Produced Fiber Exposure Fibers/Lung Fibers/Lung After 6 Mo Lung

Type Fibers/cc (X 106) (X 106) Recovery Disease X607 174 58 15 26% No RCF 187 143 61 58% Yes Chrysotile 10,600 1,600 216 14% Yes

Hesterberg et al., 1998 Lung Burdens of Chrysotile and Other Fibers During a Chronic Inhalation Study

Two Year 6 Month Lung Burden Recovery Percent Retained Produced Fiber Exposure Fibers/Lung Fibers/Lung After 6 Mo Lung

Type Fibers/cc (X 106) (X 106) Recovery Disease X607 174 58 15 26% No RCF 187 143 61 58% Yes Chrysotile 10,600 1,600 216 14% Yes

Hesterberg et al., 1998 Chrysotile Does Not Cause Mesotheloimas in Hamsters

Num ber Lun g Mesoth elial Group Animals Fibrosis Hyperplasia Meso thelioma Control 83 No No No MMVF 10a 81 No No No Chrysotile 49 Yes No No MMVF 33 83 Yes Yes Yes RCF 1 102 Yes Yes Yes Amosite 83 Yes Yes Yes

McConnell et al., 1995

Hesterberg et al., 1999

McConnell et al., 1999 Chronic Bioassays of Chrysotile Asbestos

• Chronic exposure resulted in lung fibrosis, cancer and a single mesothelioma in rats • Chrysotile exposure levels were very high — 10,600 f/cc • This is 100,000 times the OSHA PEL of 0.1 f/cc • Massive dose to the lung target tissues • Lung clearance likely impaired due to “overload”

Hesterberg et al., 1993

45 Threshold for Chrysotile-Induced Lung Disease is Above 500 f/cc

• Three month rat inhalation study of chrysotile • Exposure to 536 WHO fiber/cc • No lung fibrosis was observed at this level • 200-fold lower than tumorigenic exposure of 10,500 f/cc • Lack of fibrosis suggests no lung cancer or mesothelioma • This study indicates a threshold of > 500 f/cc

Bernstein et al., 2006.

46 Fiber Biopersistence Correlates with Inhalation Toxicity of Fibers

Biopersistence Rat Inhalation Toxicity Fiber Half-Life (Days) Fibrosis Tumors Crocidolite 817 + + Amosite 418 + + MMVF32 79 + + RCF1 55 + + MMVF33 49 + - MMVF21 67 + - MMVF 10 (Fiber glass) 14.5 - - X607 9.8 - - MMVF11 (Fiber glass) 9 - - MMVF22 (Mineral wool) 9 - - MMVF34 (Mineral wool) 6 - -

Hesterberg and Hart, 2001

47 Fiber Biopersistence Correlates with Inhalation Toxicity of Fibers

Biopersistence Rat Inhalation Toxicity Fiber Half-Life (Days) Fibrosis Tumors Crocidolite 817 + + Amosite 418 + + MMVF32 79 + + RCF1 55 + + MMVF33 49 + - MMVF21 67 + - MMVF 10 (Fiber glass) 14.5 - - Chrysotile (Canada) 11.3 X607 9.8 - - MMVF11 (Fiber glass) 9 - - MMVF22 (Mineral wool) 9 - - MMVF34 (Mineral wool) 6 - - Chrysotile (Brazil and CA) 1.3, 0.3 Hesterberg and Hart, 2001

48 Lung Fibrosis Occurs Before Lung Cancer and Mesothelioma in Rodents

Hesterberg and Hart, 2001 Airborne TWA Fiber Concentrations from Drywall Workers (fibers/cc ≥5 µm) Study TWA

Contemporary Studies

Brorby et al. (2013) (respirable PCM 0.26 (median) fibers, enclosed space)

Brorby et al. (2013) (respirable PCM 0.078 (median) fibers, nonenclosed space)

Contemporary Estimates of Historical Exposures

Brorby et al. (2013) 0.11 (median)

Historic Studies

Rhodes and Ingalls (1976) 0.1 to 0.9

Rhodes and Spencer (1977) 0.005 to 0.3 (personal TWAs)

Verma and Middleton (1980) 2.1 to 4.5

Verma and Middleton (1981) 4.2

National Loss Control Service None Corporation, 1972

Soule (1973) None

Rohl et al. (1975)/Fischbein et al. (1979) None

PCM=phase contrast 50 Low Exposures to Chrysotile Do Not Result in Lung Disease

12000

10000

8000

6000

4000

Exposure Levels in Fibers/cc in Levels Exposure 2000

0 Lung Disease in No Lung Disease in Drywall Installers Animals Animals

51 Summary and Conclusions

• In vitro studies in non-lung rodent cells and cell lines have shown chromosomal effects, but – These effects are not seen in primary cultures of human lung cells – In vitro chromosome studies were invalidated by chronic animal inhalation studies • Chrysotile is very biosoluble in the lung • Threshold for chrysotile disease > 500 f/cc • Low chrysotile exposures do not cause disease

52 Does Low Exposure to Chrysotile Pose a Health Risk?

Dr. Tom Hesterberg Principal Toxicologist Center for Toxicology and Environmental Health

American Conference Institute’s Asbestos Claims and Litigation January 30-31, 2014 San Francisco, California

5120 North Shore Drive | North Little Rock, AR 72118 | Main Line: 501.801.8500