Every state must comply with federal environmental regulations, but they are free to create their own regulations that are more strict than their federal counterparts. For example, the EPA publishes a list of hazardous waste on their website, but states may consider some substances hazardous even if they are not specifically mentioned on the EPA’s list. States may also require more frequent reporting for activities related to hazardous waste.
Although the EPA has regional offices that direct the activities of several states each, it is most often the state-level agencies that carry out the directives from the EPA. The EPA acts as a regulating body, but companies must comply with the more demanding state agencies.