What condition allows states to maintain their safety and health enforcement activities under the OSHA Act?

States can maintain their safety and health enforcement activities under the Occupational Safety and Health Administration (OSHA) Act primarily because their programs must be "at least as effective" as the federal program implemented by OSHA. This condition ensures that state-level regulations provide a level of protection for workers that is comparable to or greater than the standards set by federal authorities.

This concept is crucial because it fosters a consistent and protective environment for worker safety across the nation while still allowing states the flexibility to address specific local conditions and needs. States can develop their own regulations and enforcement mechanisms as long as they meet or exceed the effectiveness of federal regulations, thereby promoting a high standard of occupational health and safety.

The other options suggest various forms of approval or authorization that do not align with the fundamental requirement established by the OSHA Act for state programs. The emphasis on effectiveness ensures the primary objective of worker protection is maintained without unnecessary bureaucracy in certifying state programs.