This rule was remanded by the U.S. Circuit Court of Appeals and the limits are not currently in force.
Sodium hydroxide is a severe irritant of the eyes, mucous membranes, and skin.
Because it may be considered public enemy number one for causing chemical burns of the eye, sodium hydroxide has been the chemical caustic most extensively studied in animal and clinical investigations. If not removed from the skin, sodium hydroxide causes severe burns with deep ulcerations. Rats were exposed to an aerosol of 40 percent aqueous sodium hydroxide whose particles were less than 1 um in diameter. Exposures lasted for 30 minutes and were administered twice a week. The experiment was terminated after three weeks because two of the 10 rats died.