In May 2000, eight former employees of a microwave popcorn packaging plant were reportedly diagnosed with a pattern of respiratory symptoms “consistent with” respiratory obliterative bronchiolitis (OB), a severe and sometimes fatal lung disease.

It was suggested that the symptoms were a result of exposure to diacetyl, a chemical used in the popcorn butter flavorings. Since that time the National Institute of Occupational Safety and Health (NIOSH) has conducted cross-sectional industrial hygiene and medical investigations in six microwave popcorn facilities.

The conclusions offered in the NIOSH reports appear to generally support the belief that respiratory disorders are elevated in certain workers and that diacetyl appears to be a likely candidate for the causative effects.

This analysis summarizes the strengths and weaknesses of the existing information and identifies key data gaps. In addition to a detailed analysis of the NIOSH reports, we reviewed the PUBMED and MEDLINE databases for studies that reported animal toxicology and epidemiology results for diacetyl and artificial butter, and known or suspected causes of OB.

There exists little toxicology or epidemiology literature for diacetyl, although cases of OB have been noted in agricultural workers and attributed to oxides of nitrogen.

There are significant gaps in our knowledge of the effects of diacetyl and definitive conclusions regarding its toxicity to occupationally-exposed workers are difficult to offer.

Click on links below or articles to view abstract.

Popcorn lung and bronchiolitis obliterans: a critical appraisal.
Bronchiolitis obliterans syndrome in chemical workers producing diacetyl for food flavorings.
Respiratory toxicity of diacetyl in C57BL/6 mice.