Exposure to Crystalline Silica at Alberta Work Sites Occupational - - PowerPoint PPT Presentation

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/m3

• 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/m3 (quartz) and 0.05 mg/m3(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/m3 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/m3

*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
• ccupational 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

• 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) In the same 10-year period:

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

• ccupations (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

• ccupation

– 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

• f controls

– Employer provides feedback to workers on results – Employer reviews controls/systems in place to protect workers

• Do we have all the elements needed?

Occupational disease rates are not a good indicator for how well we are doing now!

BUT…

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/m3 (48%) – 105 samples above NIOSH REL of 0.05 mg/m3 (28%)

• Total of 48 work sites evaluated (29

fixed, 19 temporary)

Industry (# work sites) N Low (mg/m3) High (mg/m3) GM (mg/m3) %Above 0.025 %Above 0.05 Sand and Mineral Processing (2) 16 0.024 1.7 0.090 94 81 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 Building (3) 24 ND 0.068 0.013 25 13 Cement Plant (3) 26 ND 0.061 0.0090 15 4 Limestone Quarry (1) 6 ND 0.016 0.0062

• Occupational Exposure, by Industry

Occupations with Potentially High Exposures

Occupation N Low (mg/m3) High (mg/m3) GM (mg/m3) % above 0.025 Concrete Cutting, Coring, Finishing 10 0.033 1.0 0.13 100 Blaster (Abrasive Blasting) 11 0.019 0.34 0.087 91 Electrician 7 0.0042 0.064 0.029 71 Equipment Operator (mining, underground) 10 ND 0.21 0.034 70 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

Company N Low (mg/m3) High (mg/m3) GM (mg/m3) % Above 0.025 Manufacturing (other) 1 11 ND 0.011 0.0036

• 2

12 0.012 3.5 0.085 83 Oil and Gas 1* 10 0.0076 0.048 0.021 50 2 12 0.0033 8.6 0.086 58 3 6 ND ND

• Mining

1 13 ND 0.21 0.030 62 2 13 ND 0.012 0.0055

• 3

13 ND 0.064 0.017 54 4 5 0.015 0.13 0.042 60 5 6 0.0059 0.054 0.018 33

Variability of Exposure within Industry Groups

Industry (# work sites) N Low (mg/m3) High (mg/m3) GM (mg/m3) %Above 0.025 %Above 0.05 Commercial Construction (4) 44 ND 1.0 0.055 77 50 Demolition (1) 10 0.017 0.065 0.027 40 20 Residential Construction (8) 34 ND 0.38 0.020 26 9 Earth Moving/Road Building (3) 24 ND 0.068 0.013 25 13 Overall 112 ND 1.0 0.028 48 26

Variability of Exposure in Construction

Impact of Drywall Results on Silica Exposures in Residential Construction

*Result is uncertain as it was below detection limit

Industry (# work sites) N Low (mg/m3) High (mg/m3) GM (mg/m3) %Above 0.025 %Above 0.05 Residential Construction w/o Drywalling 16 0.0042 0.38 0.020 31 13 Drywalling only 18 ND 0.23* 0.020 22 6 Overall 34 ND 0.38 0.020 26 9

Note: for respirable dust exposures—mean about 10 times higher for drywallers compared to other workers

Exposure in Abrasive Blasting

Abrasive Product Used N Low (mg/m3) High (mg/m3) GM (mg/m3) %Above 0.025 Ground Glass* 4 0.016 0.18

• 75

Garnet 10 0.011 0.035 0.019 40 Silica Sand 9 0.0076 0.069 0.045 89 Silica Sand 6 0.0074 0.34 0.032 50 Nickel slag, Vitreous Smelter Slag 8 0.0014 0.27 0.058 88 Overall 37 0.0074 0.34 0.038 68

*Blasters were cleaning concrete.

Silica Content of “Non-Silica” Abrasives

Product Quartz Content (w/w%) MSDS Disclosure of Quartz/Crystalline Silica (%w/w) Ground Glass* 0.1-0.5 Not disclosed Aluminum Oxide 0.09 “crystalline particles: no” Garnet1* 0.76 <0.5 Nickel Slag* 0.30 ”no crystalline silica” Vitreous Smelter Slag* 0.28 <0.1 Staurelite 0.32 0.5-1 Garnet2 1.64 Not disclosed, but silicosis noted as a chronic health effect Garnet3 0.08 <0.5% Coal Slag 0.18 0-10 (silica as metal silicates) Glass Beads 0.23 Not disclosed

Controls: Common Themes

• Build-up of visible dust on surfaces even where

ventilation systems were in place

• Enclosures and barrier systems often ineffective

(incomplete, tied back, damaged or ignored)

• Lack of facilities for basic hygiene
• Use of inappropriate work procedures (e.g. dry

cleaning methods)

• Lack of worker training
• Inadequate decontamination (facilities not used

even if available)

Controls: Common Themes

• Personal protective equipment

– Respirators not properly cleaned and stored – Clothing and other equipment not decontaminated – Workers needing respirators not always using it

Key Findings

• Worker exposure was highly affected by work

activity and potential for incidental exposure

• Elevated exposure to silica was found in
• ccupations where it was not anticipated
• In many cases, the companies evaluated had

controls in place but they were not always used

• r used properly
• Work procedures may have a large impact on

workplace exposures

• Lack of awareness of the hazard likely

contributed to issues with work practices

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Food for Thought

• Occupational disease reporting processes

need to be improved; must ensure that all

• f the parties who have responsibility are

involved

• When considering worker exposure,

attention must be paid to the activity the worker will be doing (not just occupation) and their potential for incidental exposure

• Hazard awareness is still poor

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Food for Thought

• There is a lot of focus on engineering

controls and their efficacy – Engineering controls are only as good as the people who use and maintain them – Administrative controls such as work practices, housekeeping and training can have a large impact on exposures – Cost-benefit?

Questions?

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