Presented by: Donna M. Ringo, CIH. DMR & Associates, Inc., Louisville, Kentucky

Transcription

1 New Considerations for: If It s Silica It s Not Just Dust Presented by: Donna M. Ringo, CIH DMR & Associates, Inc., Louisville, Kentucky

2 Honorable Mention OSHA / NIOSH updates Disclaimer : I am not a toxicologist. The information presented here is the viewpoint of one industrial hygienist to the best of my Knowledge.

3 Power Generation Coal Dust Fly Ash

4 Navy Documents before WW II Silicosis: major concern with shipbuilding Asbestosis few cases

5 Navy Documents before WWII Silicosis: major concern with shipbuilding, pages Asbestosis one short paragraph

6 Patty s 1 st Edition pages silica 6 pages asbestos

7 OSHA Table Z-3

8 Silica, Silicosis, and Cancer

9 Carcinogenicity 1997, the International Agency for Research on Cancer (IARC) reviewed the available animal and human studies and came to the conclusion that there was sufficient evidence in experimental animals for the carcinogenicity of inhaled silica, and there was sufficient i evidence in humans for the carcinogenicity of inhaled crystalline Silica from occupational sources. [ACGIH].

10 Documentation of TLV s

11 Documentation of TLV s (cont.) The consensus among a number of U.S. and international agencies is that a positive association exists between silica exposures and lung cancer, but not all have decided d that t silica is a confirmed human carcinogen... (and)

12 Documentation of TLV s (cont.) There is little support for the hypothesis that occupational silica exposure is a direct-acting initiator, while at the same time, there is compelling evidence that many forms of pulmonary fibrosis constitute major risks for human lung cancer. Available data do not prove that the fibrosis associated with silicosis leads directly to lung cancer among silica- exposed workers.

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15 Crystalline SiO 2 Factors Particle size < 10 microns respirable Freshly Cleaved Edges Enzyme stimulated Quartz vs Cristobalite Exposure and Latency Period

16 Basics of Dusty Lung Diseases Effect of dusts/particulates Body s natural defenses Nasal hairs U i Upper respiratory curve Mucocilliary escalator

17 Basics of Dusty Lung Diseases Air sacs or alveoli

18 Body Response(s) Cellular actions Macrophage attempts but fails Macrophage succeeds then ruptures L l i fl ti Local inflammation Scaring occurs

19 Fibrotic nodules Scar tissue build-up

20 Fibrosis Scar tissue linking

21 Lung Damage Results Scar Tissue reduces O 2 -CO 2 exchange Fibrosis i Progressive and usually non/reversible Debilitating Silicosis loss of elasticity Stages: Category 1 through 4

22 Symptoms Shortness of Breath Fatigue Coughing Wheezing Chest Pain From the loss of gas exchange and the loss of elasticity of the lung

23 Inflamation/Fibrosis Silica Asbestos Iron oxide Cotton dust Beryllium Pumice Silicosis Asbestosis Siderosis Bysinosis Berylliosis Pseudopneumovolcanoconiosis

24 How much dust does it take?

25 How much dust does it take? Cumulative dose information A cumulative exposure of <2,000 ug/m3-year did not result in an increase in silicosis prevalence in either smokers or nonsmokers. Cumulative exposures in the range of 2000 to 3000 ug/m3-year resulted in a prevalence of 0.9 in nonsmokers and 1.8 in smokers. (54) 54. Cherry MN; Burgess GL; Turner S; McDonnald JC:.Crystalline silica and risk of lung cancer in the potteries. Occup Inviron Med. 55: (1998).

26 Cumulative dose as threshold for minimum risk of disease development: Smoking and Lung Cancer 10 pack year history : increased risk 10 years of 1 pack per day or 5 years of 2 packs/day *Risk increases with increased pack years

27 Cumulative dose as threshold for minimum risk of disease development: Asbestos and Mesothelioma 5 fiber-year history : increased risk 1 years at 5 f/cc daily exposure, or 5 years at 1 f/cc daily exposure, or 50 yrs at 0.1 f/cc daily exposure

28 Cumulative dose as threshold for minimum risk of disease development: Silica and Silicosis < 2,000 ug/m 3 -year : No increased risk = 2 mg/m 3 -years = mg/m 3 daily exposure = mg/m 3 daily exposure Numerous research publications have higher and lower cumulative doses reported.

29 Cumulative dose as threshold for minimum risk of disease development: Using New Threshhold Limit Value mg/m 3 for a working lifetime (40 yrs) => 1 mg.m 3 -yr cum. dose Dose should prevent silicosis and therefore prevent any risk of lung cancer from crystalline silica.

30 Lung disease Book

31 Mesothelioma NIOSH/CDC

32 Silicosis NIOSH/CDC

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34 Prevention of Silicosis Ventilation Isolation Dust Suppression Substitution Respiratory Protection

35 Litigation/Expert Witness

36 Questions and Answers

37 Silica 3D