U.S. imports of Natural and Modified Natural Polymers (NESOI), in Primary Forms (HS 391390) totaled $32.4M in August 2026, imported from 44 countries.
Importers of Natural and Modified Natural Polymers (NESOI), in Primary Forms paid $4.2M in duties in August 2026, an average duty rate of 12.88% — duty actually collected as a share of the imports that cleared customs, not the published tariff schedule.
Last updated: August 2026 dataA broad residual heading covering biopolymers and chemically modified natural polymers not classified elsewhere, including xanthan gum (3913902015), chemical derivatives of natural rubber (3913901000), and other polysaccharides and their derivatives (3913902090). Xanthan gum — a fermentation-derived thickener critical to food, oilfield drilling fluids, and personal care products — is among the most commercially significant lines, with China the leading supplier across most subheadings. Importers should note that food-grade xanthan gum and other edible polysaccharides are subject to FDA review, while industrial grades used in drilling or coatings face different compliance considerations. Classification disputes can arise at the boundary between this heading and Chapter 35 (modified starches) or Chapter 13 (natural gums), making precise product specification documentation essential.
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901 import shipments a month
Xanthan gum is specifically identified by its own 10-digit line (3913902015) and is classified there regardless of end use — food, oilfield, or cosmetic. Other microbial or plant-derived polysaccharides not specifically named fall under 3913902090. The key is confirming the chemical identity of the polymer; a technical data sheet or certificate of analysis identifying the substance as xanthan gum (produced by Xanthomonas campestris fermentation) supports the specific line.
Chapter 13 covers natural gums, resins, and vegetable saps in their unmodified state, while Chapter 39 applies once those substances have been chemically modified or processed into primary polymer forms. A certificate of analysis showing the degree of chemical modification (e.g., carboxymethylation, esterification) and a product specification sheet are the most effective documents for supporting a Chapter 39 classification and defending it during CBP review.
Subheading 1 of 2 in heading 3913
Subheading 391390 · $32.4M of $38.9M
ImportsExports
Imports
$32.4MYoY · free account
Exports
$28.1MYoY · free account
12-mo low · imports
Low · free accountOver the twelve months to August 2026, the U.S. imported $374.1M of Natural and Modified Natural Polymers (NESOI), in Primary Forms and exported $326.3M.
Through August 2026. Source: U.S. Census Bureau.
Imports · August 2026
origin
Sweden and China together supply 47% of it. China pays 42.5% duty; Sweden 3.4%.
customs district
destination
entry
rate provision · imports
3.5% enters free of duty; duty collected equals 12.88% of imports for consumption.
HS10 import codes under this HS6 parent, each with its own page. Source: U.S. Harmonized Tariff Schedule.
| Code | Description | Imports for consumption | Average duty rate | Dutiable Share | Duty Collected |
|---|---|---|---|---|---|
| 3913902090 | Polysaccharides & Their Derivatives, NESOI | $19.9M | 11.13% | 95.22% | $2.2M |
| 3913902015 | Xanthan Gum | $7.8M | 20.73% | 99.88% | $1.6M |
| 3913905000 | Natural Polymers & Modif Nat Polymrs, Prim Fm, NESOI | $4.2M | 7.00% | 96.35% | $297K |
| 3913901000 | Chemical Derivatives of Natural Rubber | $420K | 10.01% | 99.01% | $42K |
HS10 export codes under this HS6 parent, each with its own page. Source: U.S. Schedule B export classification.
| Code | Description | Export Value |
|---|---|---|
| 3913908000 | Natural Polymers & Modif Nat Polymrs, Prim Fm, NESOI | $26.9M |
| 3913901000 | Chemical Derivatives of Natural Rubber | $1.2M |
Import lines come from the U.S. Harmonized Tariff Schedule and export lines from Schedule B. The two are numbered by different agencies, so the same 10-digit code can appear in both tables describing a different product.
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