EPA has designated PFOS and its precursors as persistent, bioaccumulative, and toxic (PBT) chemicals under TSCA, with significant use restrictions. Import is not categorically prohibited, but it is limited to specific exempted uses authorized by EPA. Importers must confirm that the intended application falls within a current EPA exemption and should be prepared to provide end-use documentation at entry.

Pharmaceutical sulfonamides such as sulfamethoxazole are classified under 293590 and, when imported as active pharmaceutical ingredients, are subject to FDA drug import oversight rather than EPA TSCA restrictions. The foreign manufacturer must be registered with FDA, and the product must comply with current Good Manufacturing Practice (cGMP) standards. The PFOS subheadings, by contrast, trigger EPA review focused on environmental and health risk rather than drug-quality standards.