A conference committee considered the final bill in early December 1970. Union leaders pressured members of the conference committee to place the standard-setting function in the Department of Labor rather than an independent board. In return, unions agreed to let an independent review commission have veto power over enforcement actions. Unions also agreed to removal of a provision in the legislation which would have let the Secretary of Labor shut down plants or stop manufacturing procedures which put workers in "imminent danger" of harm. In exchange for a Republican proposal to establish an independent occupational health and safety research agency, Democrats won inclusion of the "general duty" clause and the right for union representatives to accompany a federal inspector during inspections. The conference committee bill passed both chambers on December 17, 1970, and President Nixon signed the bill on December 29, 1970. According to the "New York Times", labor and environment activist Tony Mazzocchi was a "principal force behind the legislation".