The National Institute for Occupational Safety and Health (NIOSH) invites public comment on a draft document, "Criteria for a Recommended Standard:nioshOccupational Exposure to Diacetyl and 2,3-pentanedione.”

For public review and comment, the draft document summarizes current scientific knowledge about the occupational safety and health implications of the food flavorings diacetyl and 2,3-pentanedione, and recommends occupational exposure limits and measures for controlling work related exposures to diacetyl and 2,3-pentanedione, based on the current state of knowledge.

The draft document is available at  for written public comment until Oct. 14, 2011. NIOSH will also hold a public meeting to discuss and obtain comments on Aug. 26, 2011, in Washington D.C.

"Occupational exposure to diacetyl has been associated with severe obstructive lung disease, bronchiolitis obliterans, and decrease in lung function," said NIOSH Director John Howard, M.D.  "NIOSH has provided over a decade of research and leadership in this important scientific area.  In addition to the recommended exposure limits (RELs), this draft document provides for public comment a comprehensive review of scientific literature, a quantitative risk assessment, and valuable guidance to reduce occupational exposures to diacetyl and 2,3-pentanedione.  We invite public comment on the draft Criteria Document to help us develop final recommendations."
The draft document includes, for comment:

  • For Diacetyl, a recommended exposure limit (REL) of 5 parts per billion (ppb) as an eight-hour, time-weighted average, (TWA) during a 40-hour work week. To further protect against effects of short-term exposures, NIOSH recommends in the draft document a short-term exposure limit (STEL) for diacetyl of 25 ppb for a 15-minute time period.
  • For 2,3-pentanedione, a recommended exposure limit (REL) of  9.3 parts per billion (ppb) as an eight-hour, time-weighted average, (TWA) during a 40-hour work week.  The REL for 2,3-pentanedione in the draft document is based upon the lowest level at which the substance reliably can be detected using the existing analytical method, and should not be misconstrued to imply that 2,3-pentanedione is of lower toxicity than diacetyl. Further, NIOSH recommends a STEL of 31 ppb to limit peak exposures for 2,3-pentanedione on the same basis of analytic method limitation.

NIOSH has worked with its partners to advance research on the occupational health and safety aspects of diacetyl and has published numerous studies, recommendations, and scientific methods in this pioneering area. The NIOSH web page at provides a portal to these and other resources.

NIOSH is the Federal agency that conducts research and makes recommendations for preventing work-related injuries and illnesses. It was created under the Occupational Safety and Health Act of 1970 and is part of the U.S. Centers for Disease Control and Prevention. More information about NIOSH can be found at