Which of the following monomers is banned by the FDA for salon use?

Methyl methacrylate is the monomer that the FDA has banned for use in salons due to its health risks and potential for adverse effects on clients. This substance has been associated with serious allergic reactions and skin sensitization. Additionally, it can lead to nail-related damage and complications, making it unsafe for both technicians and clients. Regulations are in place to protect consumers from products that can cause harm, and methyl methacrylate's banned status reflects the critical need for safety in salon practices.

Ethyl methacrylate, while it does have safety considerations, is permitted for use under specific guidelines. Vinyl acetate and styrene are not specifically banned by the FDA for salon use, which further clarifies the unique position of methyl methacrylate regarding safety and regulatory concerns.