The OSHA regulations pertaining to employee footwear are found at 29 CFR 1910.132 and 1910.136. In general, the standard requires that foot protection be used whenever it is necessary by reason of hazard of processes or environment which could cause foot injury. Normally, the employer will determine which, if any, of the employees are exposed to a foot injury hazard. When employees are exposed to the possibility of foot injuries, foot protection shall be worn. When employees are not exposed to possible foot injuries, foot protection is not required by the OSHA standard, which then becomes solely a matter of employment conditions existing between the employer and the employees, and where applicable, subject to any labor/management contractual agreement.
www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.136
The employer shall ensure that each affected employee uses protective footwear when working in areas where there is a danger of foot injuries due to falling or rolling objects, or objects piercing the sole, or when the use of protective footwear will protect the affected employee from an electrical hazard, such as a static-discharge or electric-shock hazard, that remains after the employer takes other necessary protective measures.