OSHA State Plans: In Brief, with Examples from California and Arizona [June 3, 2016] [open pdf - 697KB]
"The Occupational Safety and Health Act of 1970 (OSH Act) authorizes states to establish their own occupational safety and health plans and preempt standards established and enforced by the Occupational Safety and Health Administration (OSHA). OSHA must approve state plans if they are "at least as effective" as OSHA's standards and enforcement. Currently, 21 states and Puerto Rico have state plans that cover all employers, whereas 5 states and the U.S. Virgin Islands have state plans that cover only state and local government employers, who are not covered by the OSH Act. OSHA estimates that 40% of all American workers are covered by state occupational safety and health plans. California's state plan includes specific standards designed to protect workers against heat illness despite OSHA not having a federal heat illness standard, exemplifying a state plan that goes beyond OSHA's standards. In contrast, recent legislation enacted in Arizona creates a residential construction fall protection standard that OSHA has determined is not as effective as the federal standard and has been formally rejected by OSHA, putting the approval of Arizona's state occupational safety and health plan into potential jeopardy."
CRS Report for Congress, R43969
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html