What is the difference between primary and secondary ambient air quality standards?

Primary standards relate to federal standards. Secondary standards are those imposed by the states.

Primary standards relate to toxic air pollutants. Secondary standards relate to non$-$toxic pollutants.

Primary standards relate to the protection of human health. Secondary standards relate to public welfare $($e$.$g$.,$ buildings and anesthetics$)$

Primary standards relate to those first established. Secondary standards relate to more recent standards involving other constituents.