Antidumping duty orders on sodium dithionite (sodium hydrosulfite) from China have been in place historically. Importers should verify the current status of any active orders and applicable duty rates with CBP, as orders are subject to periodic sunset and administrative reviews.

Dithionites (S₂O₄²⁻) and sulfoxylates (RSO₂⁻ or related anions) are chemically distinct reducing agents, but both are captured within heading 2831. The split between subheadings 283110 and 283190 is based on whether the compound is a sodium salt, not on whether it is a dithionite or sulfoxylate.