TSCA applies to chemical substances and mixtures not excluded by statute (such as pesticides, foods, and drugs). Importers of novel or non-exempt chemical preparations under NAICS 325998 must certify TSCA compliance at entry—either that the substance is on the TSCA Inventory or that it is exempt. Failure to certify correctly can result in refusal of admission.

Natural origin alone does not determine HTS classification; the product's chemical composition, degree of processing, and end use govern heading assignment. However, naturally derived preparations may qualify for different duty rates than their synthetic counterparts under certain HTS headings, and some may trigger USDA APHIS phytosanitary review if derived from plant material. Consulting a licensed customs broker is advisable for complex natural preparations.