Deaths from silicosis in the construction industry may be significantly underreported. New proposed rules and current emphasis programs will impact precast concrete producers.
By Don J. Garvey, CIH, CSP
Silica is a chemical compound consisting of oxygen and silicon (silicon dioxide) and is one of the most abundant minerals in the earth’s crust. In the form of sand, it is a critical component of concrete. There are two primary forms of silica: crystalline and amorphous. Crystalline silica is significantly more hazardous than amorphous silica. In this article, “silica” refers to respirable crystalline silica – particles small enough to be inhaled and retained deep within the lungs.
Silicosis: a centuries-old disease
It has been known for centuries that repeated, prolonged exposure to silica-containing dust such as concrete dust can cause silicosis, a debilitating lung disease. Old texts describe grinders’ rot and stonecutters’ disease – names that reflect how certain trades were associated with the disease. Workers with silicosis may suffer from:
• Shortness of breath
• Severe cough
• Loss of appetite
• Chest pains
Excessive exposure may cause lung scarring and interfere with oxygen transfer, which may eventually lead to death. Because it weakens the lungs, silicosis can also increase the risk of contracting tuberculosis. Some occupational health organizations have classified silica as an occupational carcinogen.
While the incidence of silicosis has been greatly reduced over the past 100 years, cases of silicosis still regularly occur. The National Institute for Occupational Safety and Health (NIOSH) states that more than 200 workers die from silicosis annually. While this is already too many fatalities, there is a concern that the actual number of cases may be significantly underreported. In response to this, U.S. OSHA is taking steps to further reduce the occurrence of silica-induced disease. For information regarding laws in Canada, also see the sidebar “Silica Regulations in Canada.”
Notice of proposed rulemaking
In February 2011, U.S. OSHA sent a Notice of Proposed Rule Making for crystalline silica to the Office of Management and Budget for mandatory review under Executive Order 12866. It remains under review. While the specifics of the proposed rules are not known at this time, it is likely they will be similar to other chemical-specific regulations, including:
• Permissible Exposure Limit (PEL) – possibly lower than the current OSHA PEL
• Regulated areas
• Worker exposure assessment
• Methods of compliance
• Respiratory protection
• Worker protective clothing
• Employee information and training
• Record keeping
Currently, the only silica-specific OSHA regulation is the silica PEL. Some states, however, promulgate and enforce their own rules regarding silica. New Jersey law, for example, bans the dry cutting and grinding of masonry materials on construction work sites. Wet methods to dampen dust and prevent exposure to silica must be used whenever feasible. California has similar rules.
National Emphasis Program
While a final silica-specific regulation is likely years away, in 2008 OSHA promulgated a silica National Emphasis Program (NEP), Directive CPL 03-00-007. The intent of the NEP “is to significantly reduce/eliminate employee overexposure to silica and therefore control the health hazards associated with such exposures. This goal will be accomplished by a combined effort of inspection targeting, outreach to employers and compliance assistance.” Targeted industry groups include:
As part of the NEP, during an inspection OSHA will enforce multiple current general safety and health regulations that are applicable to crystalline silica. These general regulations are covered in six key areas:
1. Employee exposure monitoring
OSHA will ask to see any employee exposure monitoring (air sampling) results and may conduct its own monitoring. There is no current silica-specific regulation requiring air monitoring. OSHA regulation 29 CFR 1910.134, “Respiratory Protection,” does require an employee exposure assessment of some kind (usually air monitoring) if respirators are used, to determine whether equipment provides adequate protection. Therefore, if there is an exposure above the PEL, and respirators are used to control that exposure, OSHA will ask to see exposure assessment data used to select the respirator in use. Exposure monitoring and data interpretation can be complex and should be done by a trained safety and health professional such as a Certified Industrial Hygienist (CIH). A listing of CIH consultants can be found on the American Industrial Hygiene Association website (www.aiha.org) under the Consumer Info tab. Several other websites give expected ranges of exposures for various tools such as grinders and saws and can be used for a first approximation of worker exposure.
2. Engineering and work practice controls
If employee exposures exceed the PEL, under 29 CFR 1910.1000 or 29 CFR1926.55, OSHA requires that all feasible engineering controls be used, such as local exhaust ventilation, water sprays, isolated control rooms or enclosures. Feasible controls that significantly lower exposure should be implemented even if they do not reduce it below the PEL. This reduces the need to rely solely on respirators to control exposure and may give employers increased flexibility in respirator selection. Because silica has been classified as an occupational carcinogen by several occupational health organizations, some administrative controls, such as employee rotation to limit individual exposure duration, are usually considered inappropriate to control these exposures.
NIOSH has recently published “Dust Control Handbook for Industrial Minerals, Mining and Processing,” DHHS (NIOSH) Publication No. 2012–112 (www.cdc.gov/niosh). While primarily for the mining industry, the text offers information on basic ventilation system design, air cleaners and wet spray systems that may help in the design of engineering controls.
3. Respiratory protection
If respirators are used to protect workers from silica exposures above the PEL, OSHA will evaluate whether all aspects of the respirator regulation 29 CFR1910.134 are in place. OSHA will ensure that:
• Only NIOSH-certified respirators are used; at this time all NIOSH-approved particulate filters, including N95 particulate filters, are allowable
• Exposure level is within the maximum use concentration as determined by considering the PEL and the assigned protection factor of the respirator
• Employees have been medically evaluated to determine if they can safely wear respirators
• Employees have been fit-tested and trained on the proper selection, use, limitations and care of a respirator
• Only NIOSH-certified supplied air abrasive blasting respirators are allowed for abrasive blasting
In addition, respirator use should always follow the manufacturer’s recommendations.
4. Hazard communication
Any exposure to crystalline silica triggers regulations in 29 CFR.1910.1200, which include:
• Employee training on the hazards of silica and methods to minimize exposure
• MSDS3 for silica readily available; the MSDS must include a warning on carcinogenicity
• Proper labeling of containers or products that contain silica
5. Housekeeping/hygiene practice
29 CFR 1910.141 requires surfaces be kept as free as practical of silica-containing dust. Wet wiping or HEPA (High Efficiency Particulate Air) filtered vacuums should be used. Compressed or forced air should not be used to clean silica-contaminated surfaces, as this can generate significant airborne dust concentrations. Hand and face washing facilities must be readily available.
6. Exposure and medical records
Per 29 CFR 1910.1020, all medical and exposure monitoring records must be kept for at least 30 years. This includes respirator medical evaluations and air monitoring results for silica. When employees are first hired and annually thereafter, the employer must inform all employees of the existence, location and availability of records covered by this regulation and who will provide access to those records.
While OSHA’s revised rules on silica in the workplace may be years away, it is still a continuing threat that must be addressed today. Compliance with general safety and health regulations provides a starting point in controlling this hazard. It also gives employers a head start in anticipating compliance with the new silica-specific regulations when they are published.
Silica Regulations in Canada
Silica and respirator regulations in Canada will vary depending on the province. Two examples are Ontario and British Columbia.
Several regulatory references concern crystalline silica in Ontario:
• Designated Substances (O.Reg.490/09): Workplaces where exposure is possible requires an Assessment and Exposure Control Plan designed to maintain worker exposure as low as reasonably achievable. The quartz silica exposure limit is 0.1 mg/m3.
• Code for Respiratory Equipment for Silica: Assigned Protection Factors, training, facial hair, cleaning, and supplied air systems must meet CSA Z180.1-00.
• Code for Medical Surveillance of Silica Exposed Workers.
• Ministry of Labour Guideline – Silica on Construction Projects (www.labour.gov.on.ca). This classifies silica-generating tasks such as concrete grinding into one of three types. The guidance then lists recommended respirators and other exposure-reducing procedures that should be followed.
British Columbia has general regulations such as Section 5.54 of the Occupational Health and Safety regulations that are applicable to silica (www.worksafebc.com). This requires that an exposure control plan be developed when worker exposure exceeds or may exceed 50% of the allowable limit. Worksafe BC has sample programs on its website to assist employers in developing their own site-specific plan. WorkSafe BC has a crystalline silica occupational exposure limit of 0.025mg/m3.
The bottom line is that in Canada, it is critical for employers to verify silica and respirator regulations for each province in which they have operations.
Don Garvey, CIH, CSP, is a technical service specialist for construction with 3M Occupational Health & Environmental Safety Division in St. Paul, Minn. Previously he was the construction industrial hygienist for the St. Paul Fire and Marine Insurance Co. He is the past chair of the American Industrial Hygiene Association Construction Technical Committee.
1 SIC stands for the Standard Industrial Classification codes
2 NICS stands for North American Industry Classification System
3 Material Safety Data Sheet