Degreasing, press cleaning and paint removal

Chlorinated solvents have traditionally been used as metal degreasing agents. Trichloroethylene (TLV 50 ppm the Finnish OEL 30 ppm) and 1,1,1-trichloroethane (methyl chloro- 

1- trichloroethane in blood (FIOH BEI 2 j,mol/l) is recommended for biological monitoring of 1,1,1-trichloroethane because less than 10% of this solvent is metabolized. The ACGIH BEI for urinary trichloroethanol is 30 mg/1 for 1,1,1-trichloroethane. For trichloroethylene, the sum of urinary trichloroethanol and trichloroethanol is used (ACGIH BEI 300 mg/g creatinine the FIOH BEI 1000 J,mol/l). Chlorofluorocarbons (CFCs) are also used but their use is decreasing due to their contribution to the ozone depletion in the stratosphere.  

2- trichloro-l,2,2-trifluoroethane (Freon 113 TLV and the Finnish OEL 1000 ppm) is used especially for ultrasonic cleaning of small metal parts. Alternative degreasing methods using either alkaline aqueous solutions or citrus oil (D-limonene) have been developed. Exposure to trichloroethylene and 1,1,1 -trichloroethane should be avoided especially due to their neurotoxic properties. Some evidence is on the carcinogenicity of trichloroethylene. 1,1,1-Trichloroethane was earlier stabilized with carcinogenic 1,4-dioxane. Nowadays, it has usually been replaced with other stabilizers. 1,1,1 -Trichloroefliane has die skin notation in the Finnish OEL list. 

Methylene chloride (dichloromethane) is most commonly used for paint removal. The stripping solution contains 55-85% methylene chloride. Ethanol (TLV and the Finnish OEL 1000 ppm), methanol (TLV and the Finnish OEL 200 ppm with skin notation), toluene and formic acid arc other common constituents. US National Institute of Occupational Safety and Health has recommended that methylene chloride be regarded as a potential carcinogen and that it should be controlled to the lowest feasible limit. Its TLV is 50 ppm (the Finnish OEL 100 ppm). 

Very high airborne methylene chloride concentrations have been detected in the USA during furniture stripping. The TWA concentration was above 50 ppm in all five plants investigated. The highest TWA level was as high as 854 ppm. In individual samples, concentrations up to 2160 ppm were detected. In Finland, the 8 h TWA concentration has varied from 26 to 380 ppm. The highest sample concentration was 850 ppm. Local exhaust sys- 

Toluene is used to clean the rotogravure presses. High exposure levels, up to 700 ppm, may occur during this task. Offset presses are usually cleaned with chlorinated solvents. 1,1,1-Trichloroethane and Freons were earlier commonly used as cleaning solvents. The mean concentration of 1,1,1-trichloroethane has been 23 ppm. The highest concentration observed in Finland has been 117 ppm. Solvent cleaning is a task where exposure is difficult to control with ventilation arrangements but the use of a respirator is needed. Because it usually lasts only for a short time (typically about 1 hour/week) its use is neither too heavy physically. 

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