NIOSH Announces Recommended Exposure Limits for Diacetyl and 2,3-Pentanedione

October 31, 2016
NIOSH Update:
Press Contact: Christina Spring (202) 245-0633

Washington, D.C. –The National Institute for Occupational Safety and Health (NIOSH) has released formal recommendations for controlling workplace exposures to diacetyl and 2,3-pentanedione, widely-used food flavoring compounds that have been associated with decreased lung function in exposed workers. The recommended exposure limits (RELs) were published today in the document, Criteria for a Recommended Standard: Occupational Exposure to Diacetyl and 2,3-Pentanedione.

Flavorings used in food products are often complex mixtures of natural and manmade compounds. While considered safe to eat, these compounds might still be harmful to breathe in the forms and amounts to which workers in the food and chemical industries may be exposed.

To protect workers, NIOSH recommends a REL of 5 ppb for diacetyl as a time-weighted average (TWA) for up to 8 hours/day during a 40-hour work week. To further protect against effects of short-term exposures, NIOSH recommends a short-term exposure limit for diacetyl of 25 parts per billion for a 15-minute time period.

Additionally, NIOSH recommends keeping exposure to 2,3-pentanedione below 9.3 ppb as an 8-hour TWA during a 40-hour work week. This REL is slightly higher than the REL for diacetyl due to analytical method limitations. NIOSH also recommends a short-term exposure limit for 2,3-pentanedione of 31 parts per billion during a 15-minute period.

“We know these flavoring compounds can pose a great risk for workers who may be exposed on the job, causing serious and irreversible damage to their lungs,” said NIOSH Director John Howard, M.D. “This Criteria Document reflects not only our review of the science and understanding of the hazard, but also outlines our recommendations for controlling workplace exposures to these compounds. With the release of this document, NIOSH is taking an important step in protecting the health and safety of all those who may be exposed to these compounds while on the job.”

In addition to presenting RELs, the Criteria Document summarizes current scientific knowledge and proposes measures, such as engineering controls, for curbing work-related exposures to both compounds, based on the current state of knowledge.

An important piece of the NIOSH assessment focuses on workplace exposures to diacetyl and the development of an uncommon, severe lung disease known as obliterative bronchiolitis. This severe respiratory impairment was recognized among workers at microwave popcorn packaging plants beginning in the mid-2000s. Since then, NIOSH has worked to advance research on the occupational safety and health aspects of diacetyl and 2,3 pentanedione.

Leading to the publication of the REL, NIOSH has conducted numerous studies, reviewed the scientific literature on exposures, toxicology, engineering controls, and subsequently conducted a quantitative risk assessment. The criteria document has undergone a rigorous scientific process including peer, stakeholder, and public review.  NIOSH continues to collect information through its Health Hazard Evaluation program for companies where workers may be exposed to these compounds.

For more information and resources to reduce the risk of obliterative bronchiolitis associated with occupational exposures to flavorings, including research updates, scientific findings, and recommendations, visit NIOSH’s topic page on flavorings-related lung disease.

NIOSH is the federal institute that conducts research and makes recommendations for preventing work-related injuries, illnesses, and deaths. For more information about NIOSH, visit

Page last reviewed: October 31, 2016