Exposure to Crystalline Silica at Alberta Work Sites Occupational and Environmental Medical Association of Canada September 29, 2014
Outline • Silica Project Overview • Alberta Occupational Exposure Limit for Silica • Occupational Disease from Silica Exposure in Alberta • Occupational Exposure to Silica • Next Steps
Silica Project
Silica Project • Began April 2010 • Objective: gather information to address challenges related to crystalline silica exposure in Alberta workplaces • Participants: – Alberta Jobs, Skills, Training and Labour – Workers Compensation Board – Alberta Health – Alberta Health Services – Various stakeholder associations
Project Objectives • Gather information on where and how workers are exposed and ranges of exposure • Identification of occupational disease rates in Alberta due to silica exposure • Evaluation of technical feasibility of OEL and OEL adjustment method • Improved level of understanding on compliance with legislation
Occupational Exposure Limit
Occupational Exposure Limit (OEL) for Crystalline Silica • OELs are airborne concentrations of substances to which it is believed that most workers can be exposed without suffering adverse health effects • The current Alberta OEL for crystalline silica (silica) is 0.025 mg/m 3 • Value is based on the 2006 ACGIH TLV – High risk for development of silicosis and lung cancer at the former OEL levels of 0.1 mg/m 3 (quartz) and 0.05 mg/m 3 (cristabolite)
Occupational Exposure Limit (OEL) for Crystalline Silica • OELs should not be considered fine lines between safe and unsafe conditions • Even at 0.025 mg/m 3 there is still an excess risk for silicosis in occupational settings over a working lifetime (>1/1000) * *National Institute of Occupational Safety and Health, Health Effects of Occupational Exposure to Respirable Crystalline Silica, 2002-129 (2002) Park et al. Exposure to Crystalline Silica, Silicosis, and Lung Disease Other than Cancer in Diatomaceous Earth Industry Workers: A Quantitative Risk Assessment, Occup. Envir. Med. 59(1): 36 – 43 (2002)
Size Selective OELs • Inhalable (100 µm cut-point), hazardous when deposited anywhere in the respiratory tract • Thoracic (10 µm cut-point), hazardous when deposited in the lungs • Respirable (4 µm cut-point), hazardous when deposited in the gas exchange regions of the lungs The silica OEL is based on respirable particulate
Adjustment of OELs • OELs are intended for exposures of 8 hours/day, 40 hours/week • For work shifts longer than 8 hours, OELs must be adjusted • What does this mean? – The OHS Code requires the use of the Brief and Scala* formula (Section 18) – For a 12 hour work shift, the OEL for silica is reduced to 0.0125 mg/m 3 *Brief R.S., Scala R.A. Occupational Health Aspects of Unusual Work Schedules: A Review of Exxon’s Experiences, Am Ind Hyg Assoc J., 47(4):199– 202 (1986)
Is Adjustment Necessary? • A weekly adjustment, such as the Quebec model, should be used rather than a daily adjustment – when the Quebec model* is applied, there is typically little or no adjustment • Where the biological half-life is less than three hours or more than 400 hours, adjustments to the OEL may not be necessary* *IRSST, Guide for the Adjustment of Permissible Exposure Values (PEVs) for Unusual Work Schedules, Technical Guide T-22, 200 Verma, Dave, Adjustment of Occupational Exposure Limits for Unusual Work Schedules, AIHAJ, 61:367-374 (2000)
OEL Adjustment for Silica • Recommendation that the OHS Code be amended: – A notation “4” (do not adjust) should be added to the substances interaction column in Table 2, Schedule 1 for crystalline silica • The department will, by policy, allow employers to follow this recommendation when assessing workplace exposure to silica until the legislation is amended
Occupational Disease from Silica Exposure
Cost of Occupational Disease • A recent study* identified that the number of fatal and non-fatal occupational illnesses in the United States was estimated at more than 53,000 and nearly 427,000, respectively – For fatal illnesses, 1.8% were pneumoconiosis, 34% were COPD – Medical costs for injuries and illnesses estimated at $67 billion – Indirect costs (lost earnings, fringe benefits, home production) estimated at almost $183 billion – By comparison, costs for cancer estimated at $219 billion; cost for coronary disease estimated at $152 billion *Leigh, J.P. Economic Burden of Occupational Injury and Illness in the United States, The Millbank Quarterly, Vol 89, No 4, pp 728-772 (2011)
Occupational Disease Reporting • It is important to have accurate reporting for occupational disease – Ensures that impact of over-exposures are properly understood by stakeholders – Helps identify industries and occupations at risk – Ensures that the costs are attributed correctly • Typically, in jurisdictions with “good” reporting systems, about 40% of occupational disease cases are submitted to the worker compensation system • How do we perform in Alberta?
Occupational Disease Rates in Alberta In the same 10-year period: • Alberta Jobs, Skills, Training and Labour – 2 cases of silicosis were reported to the Director of Medical Services • WCB – WCB accepted 29 claims for probable/confirmed silicosis • Alberta Health – Over 850 cases of silicosis reported from emergency, hospital or physician claims data (based on diagnosis coding)
Does Alberta Have an Occupational Disease Issue? • If we look at employer data, the answer is no • If we look at JSTL data, the answer is no • If we look at WCB data, the answer is there is some occupational disease from silica exposure in certain high-risk occupations (e.g. abrasive blasting) • Do we really know if this is an issue given the inconsistencies in reporting?
Occupational Disease Reporting • What do we need for better reporting? – Employers must be aware of and comply with the legislative requirements – Employers/workers must have an awareness of the hazards in their occupation – Medical professionals must recognize and diagnose the condition – Worker or medical professional must file a claim/report
Elements for Occupational Disease Surveillance • What do we need? – Standardized way to evaluate worker health – Worker made aware of the outcome of the assessment – Follow-up done with the worker – Results reported to work site (with consent) – Physician provides feedback on the effectiveness of controls – Employer provides feedback to workers on results – Employer reviews controls/systems in place to protect workers • Do we have all the elements needed?
BUT… Occupational disease rates are not a good indicator for how well we are doing now!
Silica Exposure in Alberta
Exposure Assessments • 2009/2010 Coal Mining • 2010/2011 Construction – Asphalt and cement plants – Sand and gravel operations – New commercial construction • 2011/2012 Construction and Abrasive Blasting – Sand and mineral processing – Demolition – New commercial construction – Road building – Abrasive blasting • 2012/2013 Manufacturing and Oil and Gas – General manufacturing – Foundries – Well-site servicing operations – Bulk plants • 2014 Residential Construction
Description of Exposure Assessment Studies • Detailed collection of field data: – Environmental conditions – Number of workers and worker tasks – Observation of work activities during the measurement period – Full-shift breathing zone measurements for airborne respirable crystalline silica and total respirable dust – Use of controls documented
Occupational Sampling Results, Overall • 377 samples collected (315 workers) – 180 samples above 8-hour OEL of 0.025 mg/m 3 (48%) – 105 samples above NIOSH REL of 0.05 mg/m 3 (28%) • Total of 48 work sites evaluated (29 fixed, 19 temporary)
Occupational Exposure, by Industry Industry N Low High GM %Above %Above (mg/m 3 ) (mg/m 3 ) (mg/m 3 ) (# work sites) 0.025 0.05 Sand and Mineral 16 0.024 1.7 0.090 94 81 Processing (2) Commercial Construction (4) 44 0.014 1.0 0.054 77 50 Sand and Gravel (3) 22 ND 0.19 0.047 82 59 Abrasive Blasting (5) 37 0.0074 0.34 0.038 68 41 Demolition (1) 10 0.017 0.065 0.027 40 20 Oil and Gas (5) 28 ND 8.6 0.023 43 21 Foundry (4) 44 ND 0.48 0.020 41 25 Residential Construction (8) 34 ND 0.38 0.020 40 20 Manufacturing (2) 23 ND 3.5 0.019 43 26 Mining (5) 50 ND 0.21 0.016 40 16 Asphalt Plant (2) 13 ND 0.074 0.014 38 31 Earth Moving/Road 24 ND 0.068 0.013 25 13 Building (3) Cement Plant (3) 26 ND 0.061 0.0090 15 4 Limestone Quarry (1) 6 ND 0.016 0.0062 -- --
Occupations with Potentially High Exposures Occupation N Low High GM % above (mg/m 3 ) (mg/m 3 ) (mg/m 3 ) 0.025 Concrete Cutting, 10 0.033 1.0 0.13 100 Coring, Finishing Blaster (Abrasive 11 0.019 0.34 0.087 91 Blasting) Electrician 7 0.0042 0.064 0.029 71 Equipment Operator 10 ND 0.21 0.034 70 (mining, underground) QC/Lab. Technician 5 0.011 0.074 0.032 60 Labourer (non-mining) 106 ND 3.5 0.033 59 Plant Operator 21 ND 1.7 0.036 57 Painter 7 0.0085 0.12 0.031 57 Maintenance 6 0.0067 0.053 0.014 50 Carpenter 11 0.013 0.041 0.023 45 Mechanic/Technician 11 ND 0.068 0.018 45 Drywaller 18 ND 0.23 0.023 28
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