|Rodent Study Finds Artificial Butter Chemical
Harmful to Lungs
A new study shows that exposure to a chemical called diacetyl,
a component of artificial butter flavoring, can be harmful to the
nose and airways of mice. Scientists at the National Institute
of Environmental Health Sciences (NIEHS), part of the National
Institutes of Health, conducted the study because diacetyl has
been implicated in causing obliterative bronchiolitis (OB) in humans.
OB is a debilitating but rare lung disease, which has been detected
recently in workers who inhale significant concentrations of the
flavoring in microwave popcorn packaging plants.
When laboratory mice inhaled diacetyl vapors for three months,
they developed lymphocytic bronchiolitis — a potential precursor
of OB. None of the mice, however, were diagnosed with OB.
"This is one of the first studies to evaluate the respiratory
toxicity of diacetyl at levels relevant to human health. Mice were
exposed to diacetyl at concentrations and durations comparable
to what may be inhaled at some microwave popcorn packaging plants," said
Daniel L. Morgan, Ph.D., head of the Respiratory Toxicology Group
at the NIEHS and co-author on the paper that appears online in
the journal, Toxicological Sciences. The study was done
in collaboration with Duke University researchers.
The authors conclude that these findings suggest that workplace
exposure to diacetyl contributes to the development of OB in humans,
but more research is needed.
Although exposure of laboratory animals by inhalation closely
duplicates the way humans are exposed to airborne toxicants, the
study points out that some anatomical differences between the mice
and humans may account for why the nasal cavity of mice is more
susceptible to reactive vapors than that of humans. Another reason
may be that mice breathe exclusively through their noses.
The researchers also speculate that the extensive reaction of
diacetyl vapors in the nose and upper airways of mice may have
prevented toxic concentrations from penetrating deeper in the lung
to the bronchioles or tiny airways where obstruction occurs in
When the mice were exposed to high concentrations of diacetyl
using a method that bypasses the nose, the researchers found lesions
partially obstructing the small airways. More studies are under
way to determine if these lesions progress to OB in mice.
The National Toxicology Program, headquartered at the NIEHS, plans
to do a larger set of studies to provide inhalation toxicity data
on artificial butter flavoring and the two major components, diacetyl
and another compound called acetoin. The NTP studies will help
pinpoint more definitively the toxic components of artificial butter
flavoring and potentially help identify biomarkers for early detection.
The NTP data will then be shared with public health and regulatory
agencies so they can set safe exposure levels for these compounds
and develop guidance to protect the health of workers in occupations
where these chemicals are used.
The National Toxicology Program is an interagency program established
in 1978 by the Secretary of Health, Education and Welfare, which
today is known as the U.S. Department of Health and Human Services.
The program was created as a cooperative effort to coordinate toxicology
testing programs within the federal government, strengthen the
science base in toxicology, develop and validate improved testing
methods, and provide information about potentially toxic chemicals
to health, regulatory, and research agencies, scientific and medical
communities, and the public. The NTP is headquartered at the NIEHS,
for additional information visit http://ntp.niehs.nih.gov/.
The primary mission of the National
Institute of Environmental Health Sciences (http://www.niehs.nih.gov/)
(NIEHS), one of 27 Institutes and Centers at the National Institutes
of Health, is to reduce the burden of human illness and disability
by understanding how the environment influences the development
and progression of human disease. For additional information,
visit the NIEHS Web site at http://www.niehs.nih.gov/.
The National Institutes of Health (NIH) — The Nation's
Medical Research Agency — includes 27 Institutes and
Centers and is a component of the U.S. Department of Health and
Human Services. It is the primary federal agency for conducting
and supporting basic, clinical and translational medical research,
and it investigates the causes, treatments, and cures for both
common and rare diseases. For more information about NIH and
its programs, visit www.nih.gov.
Morgan DL, Flake GP, Kirby PJ, Palmer, SM. Respiratory Toxicity of
Diacetyl in C57Bl/6 Mice Toxicological Sciences. Advance
Access published on January 27, 2008. doi:10.1093/toxsci/kfn016.