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Answer: Diacetyl is restricted (not fully banned) in California (occupational exposure limits). The FDA still allows it in US food. Risk level: high. Commonly found in: Act II Microwave Popcorn (historical), Various flavored coffees, Some margarine brands.
TL;DR: Diacetyl is restricted in the EU but allowed in the US (flavoring).
Reviewed for clarity & usefulness by the BannedPantry Parent Panel
Also called artificial butter flavor. CAS 431-03-8.
Other names: 2,3-butanedione, artificial butter flavor, buttery flavoring
| EU status | Restricted |
|---|---|
| US status | Allowed |
| Risk level | high |
| Where it shows up | Act II Microwave Popcorn (historical), Various flavored coffees, Some margarine brands, Butterscotch candies, Some flavored chips |
| CAS number | 431-03-8 |
Diacetyl (2,3-butanedione) is a naturally occurring compound produced during fermentation — it is found in beer, wine, and fermented dairy. Synthetically produced diacetyl is used as an artificial butter flavoring in microwave popcorn, snack foods, and margarines. It provides the characteristic buttery aroma and taste.
Provides butter flavor in microwave popcorn, margarine, flavored coffee, candy, and various snacks without using actual dairy.
Diacetyl is most infamously linked to 'popcorn lung' (bronchiolitis obliterans) — a severe, irreversible obstructive lung disease first identified in workers at a microwave popcorn factory in Missouri in 2000. Multiple epidemiological studies, including NIOSH investigations, have confirmed the link between occupational diacetyl inhalation and bronchiolitis obliterans. At least 30 workers developed the condition. OSHA issued a Permissible Exposure Limit (PEL) recommendation in 2016. Consumer risk from eating foods containing diacetyl is considered far lower than occupational inhalation exposure, but consumer lung injury cases from eating large amounts of microwave popcorn have been reported, including a widely cited 2012 case report in Flavor and Fragrance Journal. California enacted stricter workplace exposure limits.
For educational use only. This page summarizes the regulatory status of Diacetylwith citations to the primary sources below. It is not medical advice. Regulatory status is not the same as a proven health effect — read the cited sources for their exact wording, and consult a doctor for decisions about your or your family's health.
Real butter, coconut oil, or yeast-derived butter-flavor compounds that do not generate diacetyl vapor provide alternative flavoring.
Bronchiolitis obliterans — severe irreversible lung scarring caused by inhaled diacetyl vapors, documented in microwave popcorn factory workers.
Many brands reformulated after the popcorn lung scandal. Check labels — look for 'no artificial butter flavor' or 'diacetyl-free.'
A 2012 case report documented lung damage in a consumer who ate large quantities of microwave popcorn daily for years. The risk from normal consumption is uncertain but much lower than occupational inhalation.
Not banned, but the EU restricted its use and exposure in flavoring applications under Regulation EC 1334/2008.
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