Silica Exposure, Disease, and Disclosure of Financial Interest - PDF document

Silica Exposure, Disease, and Disclosure of Financial Interest Prevention: Old and New Updates in Occupational and Environmental  Funded by the Alpha Foundation for the Medicine – San Francisco March 9, 2017 Improvement of Mine Safety and Health  Funded by HHS/HRSA/ORHP/BLCP & BLCE Robert Cohen, MD, FCCP  Employee of NIOSH/DRDS Professor of Medicine  Funded Contractor for USDOL/OWCP & Northwestern University Feinberg MSHA School of Medicine  Provide IME’s for Occupational Lung Disease Clinical Professor - EOHS, University of Illinois School of Public Health Chicago, Illinois Goals For Todays Talk Case 1  Describe recent trends in silica dust  PG 44 year old male with symptoms for more than 3 years. lung disease  Cough, sputum production, DOE  Describe spectrum of disease  Multiple exacerbations with increased  Silicosis symptoms  Lung cancer  Social History – Lifelong non-smoker  NMRD  Occupational History – Makes steel parts for  Renal and autoimmune disease elevators.  Review the new OSHA standard to prevent  Referred for evaluation to r/o Miliary TB disease 1

Case 1 - Occupational History Case 1 – Occupational History  Mr. Gonzalez was born in Celeya,  At age 22 until the present he worked for Guanajuato, Mexico. He came to US at age State Line Foundries in Roscoe Illinois 16, at 1986  Manufacture parts out of steel for elevators,  He came to Rockford where he has lived ever engines, and cars. since. His got his first job at age 16:  Worked a grinder, grinding off residual  2 years - Eckland Metal - Rockford – particles of sand from the steel products. Manufactured metal screws. No significant exposures.  Ingersoll, Inc. - Painting pieces of engines - with brushes - no sprays - 3 months Case 1 – Occupational History Case 1 - Diagnosis  He describes the process as molten steel  Used a paper dust mask 16 years and a half placed into a sand mold which was then face elastomeric respirator for 6 years. cooled and placed in a cleaning machine  There was local exhaust ventilation but he which uses steel shot to remove the sand reports that he feels it did not remove all of mold material. He reports that this process the dust. produces a lot of dust. Then the steel is then cut and ground into final product.  Diagnosis – Simple Silicosis – Category 3 2

Occupations where there is risk for Lung Disease from Silica Exposure silicosis Industry/Activity Operations/Tasks  Results from inhalation of silicon dioxide Agriculture Plowing, harvesting, processing (SiO 2 ) or silica in the crystalline form. Mining Bagging, crusher operator, cleanup,  Chronic simple silicosis bullgang  Usually requires 10 years of exposure Road Tunneling, excavation, demolition, construction maintenance  Subacute/accelerated form Glass Raw material processing, refractory  Acute form installation and repair Ceramics Bricks, tile, pottery, porcelain, dental  PMF Foundries Sand molder, shake out, core knock-out Construction Excavation, blasting, sandblasting, concrete and brick work, roofing Harvesting sand, hydraulic fracturing Fracking Exposure factors in prevalence & Chronic simple silicosis severity of silicosis  3 important forms of “free” crystalline silica:  Usually recognized first  Quartz by abnormal radiograph:  Cristobalite upper lobe nodules  Tridymite  Latency period 20-30  Toxicity is greater with freshly fractured, more highly years reactive particles  Intensity and duration of exposure:  Few symptoms and normal PFTs in early  Prevalence of silicosis increases with increasing exposure. disease  Host factors: Race - (SENSOR data showed 7 x rate in  May slowly progress African Americans; foundry worker study showed 2 x rate of silicosis in AA compared with whites) 3

Silica Exposed Population in US Estimates of over-exposure  OSHA Estimates 2.2 million workers are currently  1.3-1.9% of construction, foundry and metal exposed to silica* service workers estimated to be exposed to  1.85 million in construction silica levels 10 time OSHA guidelines  320,000 in general industry – fracking, foundry, brick, concrete, pottery, mining, tunneling, sandblasting  6% of stone workers exposed to levels above  > 100,000 exposed to levels more than 2 times the NIOSH REL of 0.05 mg/m3 (PEL is 0.1 mg/m3) OSHA standards  Lifetime risk of silicosis after 2mg/m3-years (20 years at 0.1mg/m3) is 0.4% to 11% * (Occupational Exposure to Respirable Crystalline Silica. Federal Register. 81 FR 16285) Linch et.al. Am J Ind. Med. 1998. 34: 547 Enforcement Case 2  Workplace may be tested voluntarily by  RJ was a 47 year old male admitted with a 3 management or by regulatory agencies week history of increasing cough and sputum production.  Agency inspection may occur due to  PMH: Negative except for prior episodes of  routine evaluations chest colds. No meds, NKA. No pets, no  worker complaint travel  detection of sentinel cases  ROS: No fevers, chills, weight loss.  Social: Positive 30 pack year tobacco exposure. ETOH occasionally. No drugs 4

Case 2 – Continued Case 2 – Continued  Real Occupational History:  Occupational History: Worked in “construction”  Left high school and began working at age 17  Began working for demolition companies as  Physical exam: Afebrile Pulse 92, RR 18, BP an independent contractor – now 30 years. 137/84  Tearing down buildings – specialized in taking  Remarkable for coarse breath sounds down concrete walls, floors, and ceilings. otherwise normal  He drilled into concrete walls, inserted hooks, and  CXR and CT scan pulled down walls  Frequently used a jackhammer  Worked on demolition in CTA tunnels, drilling and jackhammering Case 2 – Continued Progressive massive fibrosis (PMF)  Work in Tunnels in Chicago  Mass > 1 cm in diameter CTA and Deep Tunnel Project – Total 9 years  Mixed pattern of  Never used respiratory protection restriction and obstruction  Worked 45 minutes underground and went up for air on PFTs for 15 minutes each hour.  Cicatricial emphysema  Noted he could barely see co-workers working 25 feet may be seen. away  Usually symmetric,  Had frequent cough productive of dusty sputum while occasionally R>L on the job.  Asymmetry, rapid growth,  PPD Negative, AFB X 3 negative, cultures negative – and cavitation possible,  Diagnosis – Silicosis with Progressive Massive but should prompt search Fibrosis for mycobacterial disease or cancer 5

Other silica-related health effects Mechanism  Lung cancer  Silicon (Si) 28%  Adjuvant immune  Industrial bronchitis & COPD earths crust response (Animal models)  Lung Function Impairment  Silica (SiO 2 )=  Activate monocytes  Autoimmune Disorders quartz, flint, sand and macrophages to  Systemic Sclerosis– Erasmus Syndrome (cristobalite, tridymite) release cytokines,  Lupus  Silicates (SiO 4 )= oxygen radicals, and  Rheumatoid Arthritis numerous and  Caplan’ syndrome lysosomal enzymes various  Granulomatosis with Polyangiitis - GPA (e.g. PR3 and MPO)  Pleural abnormalities  Silicic acid  Renal Disease (H 4 SiO 4 )= soil water  Mycobacterial infections: Tb and NTM Cohen Tervaert et.al. Cur Op Rheum. 1998. 10: 12 Gregorini et.al. Clin. Rev. All. Imm. 1997. 15: 21 Lung cancer and silica exposure Silica and Lung Cancer  IARC 1996, 2012: Silica classified as a Group 1  In 1987 The International Agency for substance “carcinogenic to humans”. Research on Cancer (IARC), based on  Association seen in autopsy series, case-control animal experiments, came to the conclusion studies of workers with silicosis, patients with lung that there was sufficient evidence that cancer, population-based studies of silica-exposed workers. Strongest association with lung cancer crystalline silica was a carcinogen in occurs in those with silicosis. experimental animals.  Association seen in miners, foundry, quarry and  Classified as Group 2A carcinogen i.e. diatomaceous earth workers; in multiple countries. probably carcinogenic to humans 6

Lung cancer and silica exposure Confounders  Steenland et. al.* pooled data on 65,890 workers  Tobacco from 10 studies  Radon exposure – underground miners (gold  44,160 miners miners of South Africa  21,820 non-miners  Arsenic  1072 lung cancer deaths.  Quintiles of lifetime exposure  Asbestos – steel workers  Log cumulative exposure was a strong predictor of  Effects of scarring (scar carcinoma) in lung cancer  Lifetime risk through age 75 was 1.1-1.7% above silicosis background of 3-6% Lung cancer and silica exposure  Liu et. al. studied Chinese tungsten and iron miners and ceramic workers  Followed 34,018 workers from 1960-2003  Followed for 34.5 years  Developed JEM  546 Cancer deaths  Quartiles of lifetime exposure  25 year lagged og cumulative exposure was a strong predictor of lung cancer  Smoking and silica were close to multiplicative  Lifetime risk through age 65 was 0.51% above Log lung cancer rate ratio vs. log cumulative exposure background Steenland, K et. al. Pooled Exposure-Response Analyses and Risk Assessment for Liu et al., Exposure-Response Analysis and Risk Assessment for Lung Cancer in Relationship to Silica Exposure: A 44-Year Cohort Study of 34,018 Workers , 178(9) Am. J. Lung Cancer in 10 Cohorts of Silica-Exposed Workers: An IARC Multicentre Epidemiology 1424 (2013) Study. Cancer Causes and Control. 12: 773, 2001. 7