Do employees have any recourse under federal laws not enforced by OSHA for retaliation due to occupational safety or health activity?

Possibly. Depending on the facts of the case, laws enforced by other federal agencies may be applicable. For example, if the safety or health activity was undertaken with or on behalf of co-workers, including, but not limited to, the filing of a grievance under a collective bargaining agreement (“concerted activity”), the complainant may file a charge with the National Labor Relations Board (NLRB) within six months of the adverse action.