Difference between State Environmental Protection Agency & Federal Environmental Protection Agency?

The principal difference is the federal level crosses all states and the state levels must meet the federal standard as a minimum.

Beyond that, the states are free to establish more stringent requirements than the federal level mandates.

California has the strictest environmental protection of any state and exceeds federal standards in air, water and industrial pollution as well as the prohibition of many materials. California has outlawed Styrofoam and recently prohibited plastic bags.