Evidence is mounting that your morning cup of joe could come with a side of permanent lung damage for the people who roasted the beans. An investigative report and several preliminary studies point to the production of a volatile chemical called diacetyl. This is the molecule that gives butter its characteristic taste, but it’s not good when it gets in your lungs.
The Milwaukee Sentinel-Journal recently conducted an investigation of local small-scale coffee roasters by equipping workers with air sensors that tracked the concentration of diacetyl. According to the report, the sensors detected levels of diacetyl more than five times the tentative limits set by the CDC. These limits are based on preliminary studies carried out some years ago when regulators realized workers in microwave popcorn factories were also being exposed to high levels of diacetyl.
The draft rules for diacetyl exposure released by the CDC last month call for workers to be exposed to no more than 5 parts per billion in a standard 40 hour work week. Exposure to 25 parts per billion of higher is also unacceptable for any 15 minute span under these guidelines. The popcorn incident was a case of flavoring being added, but it now appears that coffee beans themselves have some naturally occurring diacetyl that is released during the roasting process.
Exposure to diacetyl is associated with the development of a lung condition known as obliterative bronchiolitis. The chemical is breathed into the lungs, where it causes tissue damage in the bronchioles. This can eventually prevent the alveoli (the tiny air sacs where oxygen is absorbed) from inflating fully. There is no way to reverse this damage, which can be life threatening.
Coffee producers are remaining cautious for the time being, indicating the evidence for diacetyl exposure from coffee roasting is still limited. Most large-scale operations also use roasters that are externally ventilated, but that’s not the case in your local hipster artisanal coffee house. If evidence continues to mount, these companies might have to make some changes, and possibly address injuries sustained by workers in the past.