Workers who roast and grind coffee have reason for concern about exposure to lung-destroying chemicals.

A study published by the online journal “Toxicology Reports” found high levels of diacetyl and the related chemical 2,3-pentanedione in the air at a small coffee roasting plant. A second study by some of the same authors, simulating a cafe setting, found the potential for risk to customers.

The research focused on facilities that did not use added flavors with diacetyl and 2,3-pentanedione, known hazards. The research shows that the chemicals are also formed naturally and released from roasting coffee, and to a greater extent from grinding beans.

The Occupational Safety and Health Administration proposed that workers not be exposed to more than 5 parts per billion of diacetyl during an 8-hour workday, or 25 parts per billion during a 15-minute span. The study found workers who ground coffee were exposed to as much as 390 parts per billion of diacetyl in a short-term sample and long-term customer levels ranged from 10 to 14 parts per billion.

It’s impossible to say what the results mean for cafes, as chemical concentrations depend on the volume of coffee roasted and ground, ventilation and other factors.

Milwaukee Journal Sentinel