21 CFR 176.170: Paper and Paperboard Migration Limits and PFAS

21 CFR 176.170 is the FDA regulation that governs paper and paperboard used in contact with aqueous and fatty foods. It limits chloroform-soluble extractives migrating from the packaging into food to 0.5 milligrams per square inch of the food-contact surface, and it sets that ceiling regardless of which specific chemical is doing the migrating.¹ To show a package meets that limit, a manufacturer has to identify the food type, match the correct conditions of use, run migration testing against the right simulants, and keep documentation tying every substance in the sheet back to a recognized authorization.

The 0.5 mg/sq in Migration Limit

The compliance measurement is straightforward in concept. Expose the paperboard to a food simulant under the time and temperature conditions the package will actually see, then measure what came out. The chloroform-soluble extractives cannot exceed 0.5 milligrams per square inch of food-contact surface under any required combination of simulant and condition. Passing every other combination does not rescue a failure in one.¹

If packaging releases a substance that isn’t authorized under this section, an effective food contact notification, or another recognized exemption, the food inside is treated as adulterated under 21 U.S.C. § 342.² A first criminal violation can bring up to one year of imprisonment and a $1,000 fine; a repeat violation or one involving intent to defraud raises the ceiling to three years and $10,000.³

Substances Authorized in the Paper or Paperboard

The regulation contains a table of additives permitted as components of coated or uncoated food-contact surfaces. It runs from processing aids such as slimicides, used to prevent bacterial growth during papermaking, to functional chemicals like sizing agents that control liquid penetration in the finished sheet. Each listed substance carries identity specifications and concentration limits tied to the finished weight of the paper or paperboard, and in some cases molecular weight floors or purity requirements meant to keep the chemical stable at the temperatures and moisture levels it will meet in use.¹

If a substance isn’t listed, using it anyway isn’t an option. The alternatives are an applicable GRAS determination, a threshold-of-regulation exemption, or a food contact notification (FCN) to the FDA. One quirk of the FCN system worth knowing before you buy or sell a chemical: an effective notification is proprietary to the manufacturer or supplier named in it. A customer buying from that named manufacturer can rely on the FCN, but a competitor producing the identical chemical independently cannot, and would need its own submission.⁴ The FDA maintains a searchable inventory of effective notifications, which is the first place to check before starting a new submission.

Food Type Classifications

The regulation sorts food into nine categories in Table 1, because different food chemistries pull different substances out of paperboard at different rates. A high-fat food extracts oil-soluble chemicals that water-based foods leave alone; an acidic food accelerates leaching that a neutral food would not.⁵

Type I: nonacid aqueous products with a pH above 5.0, such as plain water or broth-based soups.
Type II: acidic aqueous products with a pH at or below 5.0, such as fruit juice or vinegar-based sauces.
Type III: aqueous products containing free oil or fat, including oil-in-water emulsions.
Type IV: dairy products and modifications of dairy products.
Type V: low-moisture fats and oils.
Type VI: beverages, subdivided to include Type VI-A for beverages containing more than 8 percent alcohol.
Type VII: dry solids with no surface fat or oil, such as flour or sugar.
Type VIII: moist bakery products.
Type IX: dry solids with surface fat or oil present.

Choosing the wrong type isn’t a filing error. Packaging an acidic juice (Type II) using paperboard tested only as Type I skips the more demanding extraction, and the product may release substances above the legal limit without anyone noticing until an inspection.

Conditions of Use

Temperature drives migration, so Table 2 assigns the environments a package encounters letters A through H, from most to least aggressive.⁶

Condition A: high-temperature heat sterilization above 212 °F, used in retort or canning.
Condition B: boiling water sterilization.
Condition C: hot-filled or pasteurized above 150 °F.
Condition D: hot-filled or pasteurized below 150 °F.
Condition E: room-temperature filling and storage.
Condition F: refrigerated storage.
Condition G: frozen storage.
Condition H: frozen or refrigerated storage for ready-prepared foods reheated in the container.

The condition you test under must match the most extreme temperature the packaging will realistically see over its life, from the filling line to the consumer’s kitchen. Two further conditions appear in FDA guidance beyond the A–H range: Condition I for irradiation and Condition J for cooking above 250 °F.⁷

Microwave containers don’t have their own letter. FDA guidance treats them as a subset of Condition H, and testing done for Condition H is generally adequate for microwave-only containers. If the packaging is specifically sold for microwave use, the FDA recommends migration testing in a food oil or fatty-food simulant at 266 °F for 15 minutes and in an aqueous-food simulant at 212 °F for 15 minutes.⁷ Marking a paperboard container “microwavable” without running that protocol is a compliance risk that can surface in an inspection.

Migration Testing and Food Simulants

Because testing with real food would be inconsistent, the regulation specifies laboratory simulants matched to each food type. Distilled water simulates aqueous foods. Ethyl alcohol at 8 percent or 50 percent by volume simulates beverages, with the higher concentration standing in for more aggressive products like alcoholic drinks.¹

Fatty-food simulation has changed. Older protocols used n-heptane as a stand-in for oils and allowed the resulting migration values to be divided by five to correct for heptane’s aggressiveness relative to real food oil. The FDA no longer recommends that. Studies found heptane’s exaggeration effect varies dramatically depending on the polymer, sometimes by orders of magnitude. Where n-heptane is still used, on inorganic adjuvants or highly cross-linked polymers for instance, the FDA generally will not allow any reduction factor without specific justification from the manufacturer.⁷ Applying the old factor-of-five without that justification is a fast way to have test data rejected.

PFAS Grease-Proofing Is No Longer Authorized

Per- and polyfluoroalkyl substances (PFAS) were used for decades as grease-proofing coatings in paper food packaging. That authorization is gone. In February 2024, the FDA announced that all PFAS-based grease-proofing substances had been voluntarily withdrawn from the U.S. market by their manufacturers. On January 6, 2025, the FDA formally determined that 35 food contact notifications authorizing these coatings were no longer effective, with a compliance date of June 30, 2025, to let existing inventory be exhausted.⁸

Any PFAS-coated paper food packaging produced or supplied after June 30, 2025, lacks a valid authorization and cannot legally be used for food contact in the United States. Alternatives in use include polyethylene film laminates, polylactic acid (PLA) coatings, wax coatings, and bio-based barriers from starch or cellulose derivatives. Each of these must independently satisfy 21 CFR 176.170 or hold its own food contact authorization. Swapping out PFAS does not by itself make the replacement compliant; the migration testing described above still applies in full.

Documentation an FDA Inspector Will Expect

The FDA does not require a specific format for compliance certificates, but manufacturers commonly provide letters of guaranty certifying that packaging is acceptable for its intended food-contact use. Whatever the format, the documentation for each substance in the packaging needs to address three things: the identity of the chemical, its purity or physical property specifications, and the limitations on its conditions of use.⁹

Every substance must trace back to a recognized authorization: a Title 21 regulation such as 176.170 itself, a GRAS determination, a prior sanction letter, a threshold-of-regulation exemption, or an effective food contact notification. When the authorization is an FCN, the paper trail has to connect the substance to the specific manufacturer named in the notification, since FCNs are proprietary.⁹

An inspector asking about a specific resin in your paperboard expects three things on the table: migration test data, the regulatory authorization that covers the substance, and proof it meets its concentration limits. A gap anywhere in that chain leaves the packaging open to being classified as containing an unauthorized food additive, which makes the food itself adulterated under 21 U.S.C. § 342.²

1
eCFR. 21 CFR 176.170 Components of Paper and Paperboard in Contact With Aqueous and Fatty Foods
2
Office of the Law Revision Counsel. 21 USC 342 – Adulterated Food
3
Office of the Law Revision Counsel. 21 USC 333 – Penalties
4
U.S. Food and Drug Administration. Inventory of Effective Food Contact Substance (FCS) Notifications
5
eCFR. 21 CFR 176.170 Components of Paper and Paperboard in Contact With Aqueous and Fatty Foods – Section: Table 1
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eCFR. 21 CFR 176.170 Components of Paper and Paperboard in Contact With Aqueous and Fatty Foods – Section: Table 2
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U.S. Food and Drug Administration. Guidance for Industry: Preparation of Premarket Submissions for Food Contact Substances (Chemistry Recommendations)
8
U.S. Food and Drug Administration. FDA Determines Authorization for 35 Food Contact Notifications Related to PFAS Are No Longer Effective
9
U.S. Food and Drug Administration. Determining the Regulatory Status of Components of a Food Contact Material