Final report of the safety assessment of methacrylic acid.

Methacrylic Acid is an organic acid used at concentrations between 50 and 88 percent to pretreat the nail and maximize the adhesion between the nail and artificial nail extender. Methacrylic Acid is readily absorbed through mucous membranes of the lungs, the gastrointestinal tract, and the skin; and is distributed to all major tissues. Oral LD50 values for rats ranged from 277 to 2260 mg/kg; acute toxicity symptoms included severe gastric irritation, gasping, labored respiration, prostration and hematuria. In a short-term inhalation study, rats exposed to Methacrylic Acid at 1300 ppm showed nose and eye irritation and weight loss, while necropsy results and blood and urine tests were normal. Methacrylic Acid is an ocular toxicant in animals. Undiluted Methacrylic Acid is corrosive to the skin of rabbits and guinea pigs. Exposure as limited as 3 minutes can cause severe erythema and slight to moderate edema. Exposure from 15 minutes to 24 hours under occlusive patches can cause marked to severe discoloration, slight to severe subcutaneous hemorrhages, necrosis, ulcerations, severe erythema, edema and concave eschar. Methacrylic Acid was irritating and caused strong rubefaction and scab formation in a guinea pig maximization test at challenge concentrations from 10 to 100 percent. It was difficult to determine if the results were type IV hypersensitivity reactions or simple irritation. In three other studies, guinea pigs were not sensitized. Methacrylic Acid was not a reproductive/developmental toxicant in rats or mice. Methacrylic Acid was negative in Salmonella typhimurium mutagenicity tests using strains TA98, TA100, TA1535 and TA1537 both with and without metabolic activation, but was positive in a DNA-cell-binding assay. Case reports involving Methacrylic Acid often involve children. Effects from ingestion include drooling, gagging, and vomiting. Children exposed to Methacrylic Acid as a result of accidental spills caused first and second degree burns to the eyes, face, hands, arms, and chest. The Consumer Product Safety Commission has required child-resistant packaging for liquid household products containing more than 5 percent Methacrylic Acid (weight-to-volume) in a single package. Since Methacrylic Acid is an extremely corrosive chemical, a primary concern about its use as a cosmetic ingredient was the ability to limit exposure to the nail when pretreating the nail prior to application of an artificial nail extender. A videotape presentation demonstrated that a trained professional could use a small applicator brush to dab a limited volume of Methacrylic Acid only to the center of the nail, allowing the monomer liquid to diffuse down the nail without any exposure to the skin. There were no available data to demonstrate that an individual consumer could apply Methacrylic Acid and avoid inadvertent skin contact. In order to minimize any exposure to the acid, the Expert Panel concluded that nail primers containing Methacrylic Acid could be used safely by trained individuals instructed to ensure that there be no contact with the skin. The CIR Expert Panel recognized that there are no chronic inhalation toxicity data on Methacrylic Acid, but was concerned that inhalation of Methacrylic Acid could affect the respiratory tract. Since the inhalation exposure time is significantly increased in a commercial setting, the Panel was more concerned about the safety of the nail technician than the consumer. The Expert Panel concluded that the current NIOSH recommended exposure limit of 20 ppm would provide adequate protection.