Standard Industrial Hygiene Practices for Spray Painting
Spray painting can refinish old and coat new products with bright new and various colors, satisfying millions of customers. While these paints provide protection to underlying surfaces of automobiles, boats, appliances and many other consumer products, they also can cause harm to workers exposed to the multitude of solvents, pigments, inhibitors and other additives that enhance the appearance and resistance of the finished product. Although spray paint booths, respirators and protective clothing are recommended for minimizing inhalation exposure and dermal contact, many spray painters neglect to utilize ventilation systems and appropriate protective equipment.
The United States Occupational Safety and Health Administration (OSHA) regulates worker exposure to many of the substances used in spray painting and more recently adopted a personal protective equipment standard requiring a hazard assessment of tasks followed by justification for selecting appropriate protective equipment. This standard also requires documentation and training of workers potentially at risk who will use or who are currently using protective equipment. The purpose of this paper is to review the potential hazards of spray painting, assess the risks and provide a recommended best practice.
The principal hazard in spray painting is the paint, its components and the form or state in which it is applied. Since paint is a mixture of solvents, pigments and other additives, the spray consists of aerosols, mists and vapors. Depending on the type of spray gun, pressure and nebulizer, various airborne contaminant concentrations are produced in and around the breathing zone of the painter. A combination type high efficiency particulate air filter (HEPA) and organic vapor respirator is recommended to provide protection from inhalation of this component mixture. Some paints contain additives such as isocyanates which require the use of an air supplied respirator because of individual sensitivity, reactivity and irritation to low concentrations. In many cases individual threshold limit values (TLVs) have been set for specific solvents and vapors. These exposure values and guidelines may require exposure monitoring to determine the appropriate respirator selection based on respirator protection factors. In addition, respirator fit testing is required to assure proper fit and comfort.
Paint can also come in contact with skin and other body surfaces if not protected. Although dermal contact is not a major route of exposure, it can enhance the overall body exposure if solvents effectively permeate the skin carrying potentially harmful pigments and additives. In order to provide adequate protection, clothing should be worn that resists penetration through seamed and zippered areas and also resists chemical permeation through clothing materials. A number of protective clothing manufactures have developed permeation guides that list chemical resistance breakthrough times and permeation rates. By checking the paint manufacturer's material safety data sheet (MSDS) and comparing the components to breakthrough times listed in permeation guides, appropriate resistant clothing can be selected.
Since not all clothing is impervious to permeation and contaminated clothing should not be re-worn, it would seem prudent to wear disposable items of clothing that could be discarded after use. Furthermore, cleaning of reusable clothing contaminated with paint is costly and in many cases would require using solvents used to get the paint into solution. Besides the exposure problem, paint also gets on everyday clothing worn to work and could be brought home to be laundered with family clothing, where it could contaminate household laundry. One last but not likely hazard of paint spraying is the potential for oral ingestion of paints that are sprayed in work shops, garages and rooms where food is allowed. Many small paint spray operations are done in facilities where separate lunch rooms for eating and for storing food are not provided by employers. No eating or drinking should be permitted in work areas where spraying is being done.
There are two primary occupational diseases associated with paint spray operations. These are painter's asthma and dermatitis. While neither of the two have significant statistical data to determine their risk, there is enough evidence to warrant concern. The combination of different chemical solvents, pigments and other additives in paints that become airborne in spraying operations make it difficult to quantitate the risk based on a specific hazard assessment, although career spray painters tend to have a predisposition to these diseases.
Besides the chemical hazards of paints there is also the potential risk of fire from the solvents used in spraying operations. In many cases pretreatment with appropriate solvents is required to prepare surfaces for the paint. These solvents typically are volatile and have low flammable flash points. Careful storage and housing of paints and their solvents is required to prevent the possibility of ignition and explosion. Ventilated solvent sheds, diked with concrete and restricted to nonsmoking areas, are recommended. Typical paint spray operations are done in a ventilated area adjacent to the paint storage room. The areas have access to an air supply for pressurizing the paint sprayers and supplying breathing air for respirators. Intake air for the respirators should be checked for breathing air quality and an alarm system set up to warn of carbon monoxide, particularly if oil is used as a lubricant for the compressors.
Depending on the size of the product to be painted, spraying operations may take anywhere from 15 minutes to several hours. During this time painters are moving about in respirators and protective equipment that provides protection but also adds to the burden of heat stress and comfort. The risk of heat stress can be minimized by wearing light weight disposable garments that breathe, yet are chemically resistant to the solvents.
Spray painting can be done safely with minimal risk and exposure to hazardous components in paints following these recommended practices.
First, obtain and review a copy of the paint's MSDS. Check those sections for specific recommendations for personal protective equipment.
Second, all spray painting operations should be done in well ventilated areas equipped with breathing air lines for respirators. Respirator selection and use should be based on a hazard assessment of the components in the paint and protection factors required. Fit testing and training must be provided and documented for regulatory compliance.
Third, lightweight disposable protective clothing should be provided to prevent dermal exposure and contamination of work clothes. This lightweight clothing will also eliminate potential heat stress and fatigue associated with the burden of wearing protective equipment. It can also be readily disposed of as waste at the end of the day. Selection of the clothing should be based on the chemical resistance guides for solvent breakthrough and permeation.
Fourth, separate locker, storage and lunch rooms should be provided for keeping personal protective equipment, paint supplies and food respectively. This will eliminate contamination and the potential fire hazards in paints with flammable solvents.
By following these practical recommendations spray painters can reduce their exposure to occupational hazards.
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