Proposed Priority Product: Nail Products Containing Methyl Methacrylate at Concentrations Greater than 1,000 parts per million (ppm)

On November 1, 2024, DTSC initiated rulemaking to list nail products containing methyl methacrylate (MMA) as a Priority Product under the Safer Consumer Products (SCP) regulations. On February 10, 2025, DTSC initiated a modification to this proposed rulemaking. The proposed modification changes the definition of the Priority Product to exclude nail products containing less than or equal to 1,000 parts per million (ppm) of MMA.

Rationale for Priority Product Listing

Methyl methacrylate is a volatile monomer used in some nail products; MMA is released from these products into air and can be inhaled. Dermal and oral exposure to MMA from nail products can also occur. MMA has been detected in retail nail products for home use as well as in indoor air in nail salons. In the early 1970s, the Food and Drug Administration removed the nail products containing 100 percent MMA from the market and in 2015, California’s Board of Barbering and Cosmetology (BBC) prohibited the use of MMA-containing nail products in licensed hair and nail salons and cosmetology schools through regulation. Despite these regulatory actions, MMA continues to be detected in indoor air in California nail salons.

Exposure to MMA has the potential to cause or contribute to adverse human health impacts, including:

• Dermatotoxicity – MMA exposure can cause skin sensitization, allergies, and irritations, including nail deformities or nail loss.
• Respiratory toxicity – MMA exposure may cause nose, throat, and respiratory irritation, and harm to the respiratory tract.
• Reproductive and developmental toxicity – MMA exposure may cause pregnancy complication and sexual disorders.
• Neurotoxicity – MMA exposure may cause central nervous system symptoms including headaches, sweating, paresthesia, fatigue, loss of appetite, memory loss, sleep disturbance, lightheadedness, difficulty concentrating, and irritability.
• Ocular toxicity – Exposure to MMA may cause eye irritation.

Based on the criteria in the SCP Regulations, we have determined that exposure to MMA through normal use of nail products may contribute to or cause significant or widespread adverse impacts to Californians, including to sensitive subpopulations such as nail salon workers, pregnant people and their fetuses, infants, children, and adolescents. MMA has been detected in air in nail salons at levels above California regulatory standards. Nail technicians (also known as manicurists) have an especially high potential for MMA exposure due to their longer workdays and workweeks compared to employees in other sectors. They are often not provided with adequate information concerning chemical safety, nor with proper personal protective equipment (PPE). Additionally, their workplaces often lack appropriate ventilation.

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