Safety Considerations for Abrasive Blasting Operations
In this Journal of Protective Coatings and Linings article from the archives, the authors review some of the general requirements of regulations on abrasive blasting and explain how they can help increase job safety.
The Occupational Safety and Health Administration (OSHA) writes and enforces regulations that govern safety and health practices in the work place, with many pertaining to cleaning and painting operations. Most of these regulations are very specific about how to do a job safely.
Their purpose is not to make our job more difficult, but to make it safer. These regulations have been developed over many years through studies on how and why accidents happen, and following these written procedures and regulations should ensure that we don‘t make the same mistakes that have injured others in the past.
Hazards of Abrasive Blasting
When you blast clean surfaces with abrasive driven by air, you have to deal with several hazards to your health and safety. Some of these hazards can be lethal, so it is important that you understand what they are and observe the proper safety precautions. The hazards of abrasive blasting include, but are not limited to: dust, noise and equipment.
The dust produced by abrasive blasting is a very serious health hazard. Dust results from the breakdown of abrasives and the pulverizing of surface coatings, rust, millscale, and other materials on the steel surface being blasted. The individual dust particles vary in size from 1 micron (1⁄25,000-inch) to 1,000 microns (1⁄25-inch) in diameter. Dust larger than 10 microns may be visible and settles quickly. Dust smaller than 10 microns, called respirable dust, is invisible, remains suspended in the air for a longer period of time, and can pass through the respiratory system’s defenses and settle in the small air sacs in the lung called alveoli.
Dust of this size cannot be dissolved by the lung fluids. Because the lung cannot break down or cast out the particles, it does the next best thing in its defense program, which is to isolate the intruder by building a thick, fibrous tissue around it. When too much of this tissue develops, the lung is said to be “fibrotic,” or in a condition of fibrosis.
The routes of entry and the associated health effects depend on the chemical and physical properties of the dust. If the dust is soluble in water and respirable in size, it can enter the alveoli, pass through the walls of the alveoli in the lungs and enter the bloodstream. Once in the bloodstream, dust can be transported rapidly throughout the body and damage various organ systems.
Other health hazards may be present in the dust produced by the abrasive blasting process. These hazards can result from the removal of coatings containing toxic metals such as lead, arsenic, cadmium, and hexavalent chromium. One of the most common toxic metal hazards encountered in the removal of a coatings system is lead, a toxic metal that can damage the body’s blood-forming, nervous, urinary and reproductive systems. Lead also accumulates in the body; thus, exposure to small doses over long periods of time can cause great harm.
Exposure to toxic metals can also directly affect the skin. Metals such as hexavalent chromium can irritate the skin or cause an allergic reaction. Other metals can have an irritant effect on the respiratory tract, such as pulmonary edema (fluid build-up in the lungs) caused by severe cadmium dust exposure. Entry can also occur via ingestion, typically caused by poor hygiene practices such as eating, drinking and smoking in the work area.
To determine the specific toxic metals likely to be present in a coatings system, paint chip samples should be collected from representative areas of the structure. The metals that the samples should be analyzed for would depend on a number of considerations, such as the type of structure and the type of coatings system being evaluated. Sometimes, toxic metal content can be determined based on historical knowledge of the coatings system being evaluated.
Toxic metals can also be present in the virgin abrasive blast media, such as crystalline silica in silica sand abrasive. However, dust-containing crystalline silica also can be produced during other abrasive blasting activities, such as surface preparation of concrete. A study published in the September 2006 issue of the Journal of Occupational and Environmental Hygiene indicated that elevated exposure to crystalline silica exposure also can result when it is present in the coatings system being removed.1
The Safety Data Sheet should be consulted to determine what metals may be present in the abrasive blast media. Recently, OSHA has begun requiring abrasive manufacturers to list toxic metals in their products, even if they are present only in trace amounts. Arsenic is commonly found in steel grit and coal slag abrasives, while beryllium is commonly found in coal slag abrasives. When there is exposure to toxic dust, the primary concern is to control respiratory exposure. Respiratory protection must comply with the OSHA Respiratory Protection Standard (29 CFR 1926.103). This standard requires feasible engineering and work practice controls to be employed before respiratory protection is used by workers. Engineering controls include ventilated abrasive blasting containments and considering alternatives to abrasive blasting, such as vacuum-shrouded power tools, water jetting, and chemical stripping. Job rotation is an example of a work practice control. Note that job rotation is not permitted by OSHA in all cases (if workers are exposed to hexavalent chromium, for instance). If such a control is used, a written schedule must be developed and followed.
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When you blast clean surfaces with abrasive driven by air, you have to deal with several hazards to your health and safety. Some of these hazards can be lethal, so it is important that you understand what they are and observe the proper safety precautions.
Respiratory protection may only be used after engineering and work practice controls are employed and workers are still exposed above the OSHA Permissible Exposure Limit (PEL) for a given toxic dust. Employers must select, use, and maintain respirators in accordance with a written program (the elements of which are specified by OSHA in the Respiratory Protection Standard).
Blasters typically use a Type CE or helmet-type airline respirator. Workers in the vicinity of the blasting area, such as pot tenders and lookouts, are required to wear respiratory protection. Workers engaged in clean-up operations should also be equipped with respiratory protection. These workers are usually assigned a half-mask, air-purifying respirator with high-efficiency cartridges (labeled as N, R, or P 100). However, workers cleaning up abrasive blasting debris when blasting is still in progress (as is often the case when recyclable grit is used) may need a higher level of protection. Such workers may need to wear the same type of respirator as the blasters, as their exposure levels are likely to be similar.
The National Institute of Occupational Safety and Health (NIOSH) conducts research on health issues in the work place, and one of its main functions is to test and certify industrial respiratory protection equipment. All respiratory protection equipment used in the workplace must be approved by NIOSH.
Respiratory protection should continue to be worn after blasting as long as dust-laden air remains. Respirable dust in an abrasive blasting booth or containment can remain suspended for long periods of time after blasting is finished. This time period is largely dependent on the effectiveness of the ventilation system, unless the work is performed outdoors.
A health and safety professional should review all projects that require abrasive blast cleaning to determine what precautions, if any, should be taken to eliminate the hazard of chemical exposure. Examples of these precautions include disposable clothing, boots, gloves, respiratory protective devices, and hygiene practices. Hygiene facilities that can be required by OSHA include hand wash stations and showers. OSHA requires provision of a hand wash station when workers may come into contact with toxic materials. Whether or not showers are mandatory depends on which OSHA standard is applicable. If workers are exposed to lead, showers are required when exposures exceed the PEL.
Most forms of abrasive blasting create the hazard of noise exposure, which will vary depending on the blasting conditions. Regardless of the nature, excessive amounts of noise may require personal hearing protection for blasters and other workers in the general area. Depending on the size of the equipment, the material being blasted, and the location of the blasting operation, noise levels can range from about 90 decibels to more than 110 decibels. OSHA’s limit for noise depends on the duration of exposure. For an eight-hour shift of continuous exposure, the limit is 90 decibels. Personal hearing protection should then be recommended if the level and exposure time of the workers exceed the OSHA standard. Noise protection must reduce exposure to below the OSHA limit.
Note that some abrasive blasting hoods already provide some degree of noise protection, but the manufacturer’s specifications should be checked to see if the degree of noise reduction will be adequate. When there is any question about the existing levels (meaning a noise survey is needed) or the adequacy of hearing protection, a health and safety professional should be consulted.
The equipment used in abrasive blasting operations can create physical hazards that require certain precautions. The following are some examples of equipment commonly used during the abrasive blast cleaning process and the respective precautions that should be taken during their use.
When performing abrasive blasting, safety considerations must be given to hazards including dust, noise, and equipment. Once the hazards are determined, procedures for personnel protection can be developed. In addition to being provided with personal protection, workers must be properly trained in the use, inspection, and maintenance of equipment.
Procedures to control exposure to health and safety hazards must conform to the OSHA regulations that govern blasting operations. Additional regulations from state or local jurisdictions may be in force. Many states have their own version of OSHA, and their regulations are at least as strict and, in some cases, stricter than federal OSHA regulations.
This article should not be considered a comprehensive analysis of abrasive blasting health and safety. When there is any doubt about the nature of the hazard or how to protect workers, assistance should be obtained from a health and safety professional, typically someone who is a Certified Industrial Hygienist or a Certified Safety Professional or possesses a degree from a related field of study.
Editor’s Note: This Applicator Training Bulletin is an update of an original article written by Walter Shuler, certified safety professional and safety consultant; Jeff Theo, Service Painting Company; and Mike McGinness, Custom Process Systems.
The article was originally published in the June 1998 issue of Protective Coatings Europe (PCE) and was updated for this issue by Dan O’Malley, Manager of the Environmental, Health, and Safety Group; and Stan Liang, Director of Health and Safety; KTA-Tator, Inc.
References: 1. Meeker, John D., Pellegrino, Anthony, and Susi, Pam, “Comparison of Occupational Exposures Among Painters Using Three Alternative Blasting Abrasives.” Journal of Occupational and Environmental Hygiene, Volume 3, Issue 9 (September 2006): pp. D80–84.