## Facts

- Aflatoxin is an unavoidable contaminant in some foods and is carcinogenic.
- The Federal Food, Drug, and Cosmetic Act includes 21 U.S.C. § 346, directing the Secretary to promulgate regulations limiting unavoidable poisonous substances “to such extent as he finds necessary for the protection of public health.”
- The FDA treated § 346 as giving discretion whether to issue formal “tolerance” regulations, reading “to such extent as he finds necessary” as qualifying the duty to promulgate.
- Instead of issuing a formal tolerance for aflatoxin through notice-and-comment rulemaking, the FDA set an informal “action level” of 20 parts per billion, indicating it ordinarily would not enforce the adulteration provisions below that level.
- After a particular corn harvest, the FDA published a notice stating it would not enforce the Act for certain corn intended for animal feed with aflatoxin levels up to 100 parts per billion.
- Public-interest groups and a consumer challenged the FDA’s approach, asserting that § 346 required a formal tolerance before shipment of aflatoxin-containing food and disputing the procedures and legality of the action level and exemption.
- The district court upheld the FDA’s interpretation; the D.C. Circuit reversed based on its reading of the statute’s plain language.

## Issues

1. Whether 21 U.S.C. § 346 unambiguously requires the FDA to promulgate formal tolerance regulations for unavoidable poisonous substances whenever present in food.
2. If § 346 is ambiguous, whether the FDA’s longstanding interpretation permitting reliance on informal “action levels” is a permissible construction entitled to judicial deference.

## Decision

- The Supreme Court reversed the D.C. Circuit and reinstated the district court’s judgment.
- The Court held that § 346 contains “inherent ambiguity” regarding whether formal tolerances are mandatory in all circumstances.
- The Court concluded the FDA’s interpretation was sufficiently rational and therefore controlling, precluding the court from substituting its own statutory reading.
- The Court accepted the FDA’s use of action levels as a permissible method of implementing § 346 in lieu of formal tolerance rulemaking.

## Legal Principles

- When statutory text administered by an agency is ambiguous, courts defer to the agency’s reasonable construction rather than impose an alternative interpretation.
- The phrase “to such extent as he finds necessary for the protection of public health” can reasonably be read to condition whether, and to what extent, the agency must promulgate tolerance regulations under § 346.
- An agency’s longstanding implementation practice may support the reasonableness of its interpretation, especially where legislative history does not clearly resolve the statutory meaning.
- Congressional inaction in the face of an established administrative interpretation may be treated as some support for the agency’s reading.

## Conclusion

The Court held that § 346 does not clearly compel the FDA to issue formal tolerance regulations for every unavoidable contaminant and that the FDA’s reasonable, longstanding interpretation permitting informal aflatoxin action levels must be respected by reviewing courts.


Young v. Cmty. Nutrition Inst., 476 U.S. 974 (1986)