Is Diacetyl banned?
Diacetyl is permitted by the US FDA. Several countries restrict, warning-label, or have reviewed it for safety concerns. The US has more lenient additive rules than the EU, UK, Canada, and Japan, which is why this ingredient remains widely used here.
Why Diacetyl is flagged
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.
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