While diacetyl occurs naturally as a product of fermentation, it is widely used as a food flavoring ingredient in its synthetic form. The hazards of diacetyl became widely known in the early 2000s when workers making butter-flavored microwave popcorn in the US were shown to have devastated lungs following relatively brief exposure to the diacetyl used to add butter flavor in the manufacturing process. At least 5 workers are known to have died as a result; nearly a thousand of lawsuits are pending. Subsequent research highlighted exposure paths to other groups of workers, including food flavoring ingredient and kitchen workers. In 2012, workers in a Texas coffee roasting facility developed bronchiolitis obliterans as a result of exposure through roasting coffee beans mixed with artificial flavorings, including diacetyl.
In an article published on June 20, reporters at the Milwaukee Journal Sentinel found levels of diacetyl up to 4 times the recommended standard in air samples at facilities producing unflavored coffee, emitted by the beans in the roasting process.
With the exception of California, there are no mandatory exposure levels established by government in the United States. In the European Union diacetyl exposure is completely unregulated.
Click here for the IUF diacetyl safety alert.