Monthly Round Up of Important Ideas and Standards in
Industrial Hygiene and Safety
IN THIS ISSUE: Paint-Stripping Alternatives to Methylene Chloride
Methylene Chloride (MeCl) has been used in industry as a paint stripper for many years. It works quickly and effectively to remove paint and other coatings, but it is also toxic. Without adequate controls, MeCl can affect the health of workers. Short-term exposure can cause headaches, dizziness, eye, nose and throat irritation, chest pain, and trouble breathing. Exposure to high concentrations can be fatal. Long-term exposure increases the risk of liver damage and cancer.
Less hazardous alternatives to MeCl have been developed to effectively remove paint:
- Mechanical stripping: This method using sodium bicarbonate, dry ice, or high-pressure water blasting has low toxicity to both workers and the environment. It may, however, present mechanical hazards due to the velocity of the stripping method. It uses various types of media to abrade the paint from painted surface. Limitations include the cost, size of the equipment, type of substrate surface, and application.
- N-Methyl Pyrrolidone (NMP): This solvent-based system forms the base of several chemical paint strippers. They have low odor, low evaporation rate with less re-adhesion of the paint, and are non-carcinogenic and water-soluble. On the other hand, NMP takes longer to work than MeCl and still has some harmful effects. NMP is toxic to the reproductive system of male and female test animals, although testing has not been done in humans. Overexposure to NMP irritates the eyes, skin, nose, and throat. It can also affect the central nervous system causing symptoms of drunkenness similar to the effects of drinking alcohol. NMP is easily absorbed through the skin. The ACGIH and Cal/OSHA have adopted occupational exposure limits for this substance.
- Benzyl Alcohol-based Products: These may be the best chemical alternative to MeCl. They require more surface contact time and are more labor intensive but have been shown to work just as well as MeCl based strippers. Benzyl alcohol is a colorless liquid with a mild aromatic odor and sharp burning taste. It is of comparatively low toxicity relative to MeCl. Exposure to benzyl alcohol can occur through inhalation and skin absorption. The vapor is a skin, eye and respiratory irritant. Cases of allergic contact dermatitis have been reported. Animal tests of its reproductive and development toxicity and carcinogenicity are negative.
As with any process change, switching from MeCl to less harmful mechanical processes or alternative chemicals may take considerable investigation, engineering, testing, investment, and training. However, the continued use of MeCl is harmful to both workers and the environment and the switch to an alternate method of paint stripping is necessary.
Chloromethane | From Wikipedia, the free encyclopedia
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