As previously reported in the April 2016 Synergist, a team of researchers at NIOSH has been investigating occupational exposures to diacetyl and 2,3-pentanedione, a common diacetyl substitute, in coffee processing facilities. Diacetyl and 2,3-pentanedione are volatile organic compounds known as alpha-diketones. They are widely-used flavorings that impart a buttery taste and smell. The flavorings are sometimes used in coffee processing facilities and are also generated naturally by coffee roasting and grinding. Thus, there may be an exposure risk for workers in coffee processing industries.

Previously, a team of NIOSH staff assessed exposures at a coffee processing facility (facility #1) where two former workers were diagnosed with obliterative bronchiolitis. Both were non-smokers in their 30s and had worked in the facility’s flavoring room. Obliterative bronchiolitis is a rare and irreversible lung disease that affects the small airways. It can occur as a result of acute chemical exposures, such as to sulphur mustard gas or chlorine gas, or with more chronic exposure to diacetyl and 2,3-pentanedione. These chemicals may be encountered by workers who process coffee. Patients with obliterative bronchiolitis develop progressively difficult or labored breathing along with a nonproductive cough. A patient’s bronchiolar wall will thicken from fibrosis and the airway lumen will narrow. Initially, it may be difficult to diagnose, yet early diagnosis and elimination of harmful exposures are key to treatment.

After the initial survey at facility #1, NIOSH staff have since been to 15 additional coffee facilities in response to requests from coffee processing facility management and workers submitted through NIOSH’s Health Hazard Evaluation program. At a popular session at AIHce EXP 2017 in Seattle, Washington, three NIOSH industrial hygienists presented their methods and initial findings from exposure assessments at facility #1 and a recent survey at second facility.

Collecting Samples

The IH survey team collected area and personal air samples; full-shift and task-based, time-integrated samples for alpha-diketones and VOCs; and real-time samples for total VOCs, carbon monoxide, carbon dioxide, and ventilation assessment when appropriate. Area air sampling baskets were placed in locations of interest throughout the facility, such as the roasting, grinding, green bean storage, roasted bean storage, flavoring, packaging, administrative areas and quality control. Participating employees were fitted with a vest containing two sampling pumps—one for collecting a time-weighted average sample and one for collecting task-based samples.

Despite facility #1’s efforts to source only diacetyl-free flavorings and install local exhaust ventilation, “the exposures remained elevated,” said Ryan LeBouf, PhD, CIH, research industrial hygienist for NIOSH’s Respiratory Health Division. “We saw a pattern where 2,3-pentanedione was higher than diacetyl in the flavoring areas, and diacetyl was higher than 2,3-pentanedione in the grinding and packaging areas.” The elevated levels of 2,3-pentanedione in the flavoring areas may have been due to the attempt to minimize diacetyl in flavorings by substituting 2,3-pentanedione for diacetyl.

An exposure assessment at facility #2 yielded additional insights. “Flavoring and grinding tasks were the highest measured exposures for alpha-diketones. When we compared flavoring task levels to the flavoring room time-weighted average area levels of both diacetyl and 2,3-pentanedione, those air concentrations jumped about tenfold when a worker was actually performing the flavoring task,” said Brie Hawley, MS, PhD, a research industrial hygienist also on the survey team. For the flavoring task, “a mixer would be filled with coffee and a worker would stand at the mixer while the flavoring slowly poured out and was mixed with the coffee.” After learning of the elevated exposures during the flavoring task, the facility automated the system.

The Importance of Properly Designed Ventilation

“What was surprising to us was that the administrative areas of facility #2 had comparable levels of both diacetyl and 2,3-pentanedione as some of the areas on the production floor, which spoke for the potential of entrainment of air from the production space into the administrative areas,” said Hawley. “This highlighted a need for a pressure gradient to ensure their production space was maintained under negative pressure such that the administrative spaces are under positive pressure. Also, this highlighted a need for separate handling systems to ensure that air from the production space is not recirculated into the administrative spaces.” The facility proactively moved the administrative staff out of those areas until the issue was resolved.

Additional Hazards

“We learned with additional facilities that coffee roasting and grinding releases carbon monoxide and carbon dioxide,” said Alyson Johnson, MPH, one of the NIOSH research industrial hygienists on the survey team. “Carbon dioxide degasses from roasted coffee and is commonly used in the decaffeination of green coffee beans.” NIOSH staff have also been collecting exposure measurements for carbon monoxide and carbon dioxide during coffee processing.

Next Steps

Results from the initial surveys allowed for the design of targeted engineering controls to mitigate exposures to diacetyl, 2,3-pentanedione, and carbon monoxide, but more investigation is necessary to better understand relationships between exposures and health outcomes for workers in the coffee processing industry.