U.S. Department of Labor
Process: Surface Preparation and Preservation
Abrasive blasting uses compressed air or water to direct a high-velocity stream of an abrasive material to clean an object or surface, remove burrs, apply a texture, or prepare a surface for the application of paint or other types of coatings. Air pressure is typically high, at 100 pounds per square inch, and nozzle velocities can approach 650 - 1,700 feet per second. Shipyard workers who engage in abrasive blasting, as well as those working in the vicinity, are at an increased risk of exposure to toxic dusts, high noise levels, and a range of other safety and health hazards that include particles becoming embedded in skin, eye damage, severe cuts, burns, loss of body parts (e.g., fingers and hands), and electric shock. Further, where poor housekeeping practices allow for the accumulation of dust particles from the abrasive material used, there exists the potential for explosions.
Commonly used abrasive materials include silica sand (crystalline), coal slag, garnet sand, nickel slag, copper slag, glass (beads or crushed), steel shot, steel grit, and specular hematite (iron ore). The application of many of these materials, blasted at a high velocity, may result in the release of toxic dust that is hazardous to workers.
- Silica sand (crystalline) can cause silicosis, lung cancer, and breathing problems in exposed workers.
- Coal slag and garnet sand may cause lung damage similar to silica sand.
- Copper slag, nickel slag, and glass (crushed or beads) also have the potential to cause lung damage.
- Slags can contain trace amounts of toxic metals (such as arsenic, beryllium, cadmium, chromium, lead, nickel, silver, titanium, and vanadium).
When possible, alternative, less toxic blasting materials should be used to help prevent or reduce worker exposure to airborne hazards during abrasive blasting operations. Some less toxic abrasive blasting materials include plastic bead media, sponge, sodium bicarbonate (baking soda), ground walnut shells, high pressure water, ground corn cob, and other biodegradable materials. However, regardless of the type of blasting material used, employers must perform a hazards assessment of each workplace to determine what hazards are present, and provide workers with the appropriate PPE to protect them from the hazard(s) identified (29 CFR 1915, Subpart I). In determining the hazards for abrasive blasting operations, employers should not only account for the hazardous substances contained in the blasting materials, but the airborne toxins from metals such as lead, chromium, cadmium, and zinc, and any coatings applied to the surface where abrasive blasting is being performed.
Exposure to Noise
Abrasive blasting produces noise levels that can cause permanent hearing loss in unprotected workers and others close to the blasting process. The main source of noise is the discharge of compressed air at the blast nozzle. Other noise sources include: (1) the supply air inside the operator's helmet; (2) the impact of the abrasive on the surface being blasted; (3) air compressors; (4) exhaust ventilation systems; and (5) air released during grit pot blow-down. Small abrasive blasting cabinets are also sources of significant noise exposure for operators. The current permissible exposure limit (PEL) for noise exposure is 90 dBA, with employers required to take action at 85 dBA, both measured as eight-hour time-weighted averages (TWA). Employees who have experienced a standard threshold shift may not be exposed to noise above 85 dBA TWA. However, in this type of operation, noise levels range from 85 dBA (equivalent to that of a lawnmower running) to 145 dBA (equivalent to a shotgun blast). For those workers exposed to elevated levels of noise, employers must implement provisions for engineering and administrative controls (such as limiting frequency and duration of exposure), and/or hearing protectors, as well as a hearing conservation program including worker noise monitoring, audiometric testing, hearing protectors, training, and recordkeeping (29 CFR 1910.95).
Static electricity can be generated by abrasive blasting equipment, the surfaces being blasted, and exhaust ventilation systems (fans and ductwork), resulting in shocks to workers, and fires or explosions when combined with flammable and combustible atmospheres or materials. The buildup of static electricity can be prevented through the proper use of bonding and grounding. Additionally, blast hoses can be constructed with anti-static rubber linings or fitted with a ground wire or similar mechanism to dissipate static electrical charges.
High-speed and High-pressure Hazards
Workers engaged in abrasive blasting can be struck by high-speed particles from the blasting media or the surface being blasted (substrate). In addition, they are exposed to high-pressure hazards through contact with high-pressure air or water streams, uncontrolled high-pressure hoses, and air or water leaks in the equipment. Potential injuries include particles becoming embedded in the skin, eye damage, severe cuts, burns, or loss of body parts.
Reduction of Hazards
Each abrasive blasting operation involves a unique set of circumstances, with different surfaces, coatings, blasting materials, and work conditions. OSHA requires that employers inspect each worksite prior to starting work to determine what hazards exist and what PPE, if appropriate, is necessary (29 CFR 1915.152(b)). Where PPE is required, employers must supply workers with the appropriate equipment, as well as ensure they are trained so that they understand when and what type of PPE is necessary; how to properly don, doff, adjust, and wear PPE; the limitations of PPE; and the proper care, maintenance, useful life and disposal of PPE (29 CFR 1915.152(e)). Further, employers should train all workers involved with abrasive blasting on health and safety hazards, how to use engineering controls, personal hygiene practices, and safe work practices. Manufacturers are also required to include appropriate health hazard information concerning the blasting materials on safety data sheets (SDS) as required by OSHA’s Hazard Communication standard (29 CFR 1910.1200). Employers are responsible for maintaining SDSs for hazardous chemicals used in the workplace and ensuring that the SDSs are readily accessible to workers in their work areas during their work shift (29 CFR 1910.1200(g)(8)). Employers must make sure that workers understand the safety and health hazards associated with the abrasive blasting material and the safety measures that must be taken to protect them from these hazards (29 CFR 1910.1200(h).
To help minimize safety and health hazards associated with abrasive blasting, employers must:
- Inspect all hoses and connections frequently and replace any that are worn or damaged before worker use (29 CFR 1915.34(c)(2)).
- Use metal nozzles and hose couplings (29 CFR 1915.34(c)(1)(ii) and (iii)), as well as equip the nozzle end of the blasting hose with a dead-man control device (29 CFR 1915.34(c)(1)(iv)).
- Provide workers with the appropriate PPE when blasting (29 CFR 1915.34(c)(3)(i) through (v)).
- Use exhaust ventilation systems in containment structures to capture dust (29 CFR 1910.94(a)(3)(i)). See ANSI Z9.2-1960 and ANSI Z33.1-1961 for detailed use of such systems.
- Clean and remove accumulated dust from tarps and other equipment on the worksite (29 CFR 1910.94(a)(7)).
- Prohibit eating, drinking, or using tobacco products in blasting areas (29 CFR 1915.88(h)).
- Provide wash stations so workers can wash their hands and face routinely and before eating, drinking, or smoking, and train workers on the need to remove surface contaminants from skin surfaces by thorough hand and face washing (29 CFR 1915.88(e)(1) and (e)(3)).
Other safety precautions that employers should take to protect workers during abrasive blasting operations include:
- Ensure that only one person operates each blast nozzle, when feasible.
- Install guards to protect the operator from high-speed particles.
- Use hose-coupling safety locks and hose whip checks.
- Substitute toxic or hazardous abrasive blasting materials with less toxic or hazardous alternatives, and use abrasives that can be delivered with water (slurry) to reduce dust.
- Train workers to never point a blast nozzle at a person, and to keep coworkers away from the blaster.
- Perform routine cleanup using wet methods or HEPA filtered vacuuming to minimize the accumulation of toxic dusts. Do not use compressed air to clean as this will create dust in the air.
- Schedule blasting when the least number of workers are at the site.
- Avoid blasting in windy conditions to prevent the spread of any hazardous materials.
- Vacuum or remove contaminated work clothes before eating, drinking or smoking.
- Conduct abrasive blasting activities in a blasting enclosure or use isolated areas for non-enclosed blasting operations (e.g., barriers and curtain walls) and control access. This will reduce the possibility of workers and others being struck by high-speed particles.
For more information:
Abrasive Blasting and Control Measures
Hazard Communication in Shipyards
F-8, F-9, F-10, F-11