OSHA formerly had no exposure limit for this substance. The ACGIH has established a limit of 0.1 mg/m3 as a ceiling that should not be exceeded during any part of a working day, and has added a skin notation to indicate that substantial percutaneous absorption can occur through the eyes, mucous membranes, and skin. OSHA proposed a ceiling of 0.1 mg/m3 for this substance, with a skin notation, and NIOSH (Ex. 8-47, Table N1) concurs. These limits are established by the final rule. m-Xylene alpha, alpha'- diamine (MXDA) is a colorless liquid.
Animal studies have demonstrated that MXDA is strongly irritating to the skin (Haskell Laboratory 1973, Sherwin-Williams Company 1978, both as cited in ACGIH 1986/Ex. 1-3, p. 638). Research at du Pont (Haskell Laboratory 1973, as cited in ACGIH 1986/Ex. 1-3, p. 638) showed that pure MXDA was corrosive when applied to the skin of guinea pigs, and a 50-percent MXDA solution caused severe irritation in these animals. In a separate study (Sherwin-Williams Company 1978, as cited in ACGIH 1986/Ex. 1-3, p. 638), a 10-percent mixture of MXDA caused severe skin irritation and erythema in guinea pigs. Sherwin-Williams (1978, as cited in ACGIH 1986/Ex. 1-3, p. 638) also reported that rats exposed to levels of MXDA ranging from 1.74 to 6.04 mg/liter even for one hour sustained liver, kidney, and lung damage, as determined at necropsy. One study showed mild sensitization when MXDA was applied to guinea pig skin, but this effect was not observed in a second study (Sherwin-Williams Company 1978, as cited in ACGIH 1986/Ex. 1-3, p. 638). NIOSH was the sole commenter on this substance.
OSHA concludes that a ceiling limit of 0.1 mg/m3 and a skin notation are necessary to protect against the significant risk of skin irritation, percutaneous absorption of MXDA, and potential systemic effects, all of which constitute material impairments of health. The Agency has determined that these limits will substantially reduce this significant risk.