For this blog entry, we discuss the occurrence of "Popcorn workers lung" attributed to diacetyl inhalation, following the recent legal proceedings of a Bronchiolitis obliterans (BO) sufferer who contracted the respiratory disease following exposure to diacetyl from Popcorn. BO is an obstructive respiratory disease, whereby the bronchioles are obstructed by tissue damage and aberrant epithelial repair. The result is a narrowing of the bronchioles, restricting normal respiratory function. This should be of concern to managers and safety officals of manufacturing plants producing diacetyl and whose employees or consumer base may be at risk from exposure.


Popcorn workers lung, also known as Bronchiolitis obliterans (BO), is a condition of the bronchioles causing a reduction in normal respiratory function. Bronchiolitis obliterans is triggered by the inhalation of a chemical reagent called diacetyl. Diacetyl is a naturally occurring by product of the fermentation process and is found in foods such as butter and cheese. It is artificially synthesised by food manufacturing companies as a flavouring in microwaveable Popcorn and savouries. Despite its known causal role in BO, it is approved for used by the Federal Drug Authority. Its use however is strictly regulated. Despite this, workers at microwave Popcorn manufacturing plants were reported to develop BO. Establishing a cause-effect relationship between diacetyl exposure and BO in the work place is difficult to prove, as exposure of workers to diacetyl is variable between different industries and even within an industry. Detection methods are adversely affected by regional environmental conditions such as humidity, resulting in an underestimation of diacetyl levels.

The release of diacetyl into the environment is thought to occur upon heating of the diacetyl, where it readily enters a vapour phase, facilitating inhalation and dissemination through the respiratory tract. Should the amount of diacetyl released as a vapour exceed a certain concentration, diacetyl would pose a serious health risk. This has been illustrated by dose –response studies, in which concentrations of diacetyl in a gaseous phase led to an increase in respiratory damage. Studies examining the state of the cells lining the lung of animal models as well as workers exposed to diacetyl show significant epithial cell injury after diacetyl exposure, which escalated with duration of exposure. Mice exposed to diacetyl for up to 7 days had elevated neutrophil levels, while the level of alveolar macrophages greatly exceeded the numbers present in the control. Following diacetyl induced epithial cell damage and neutrophil recruitment, aberrant airway epithelial regeneration has been reported to occur due to a loss of intracellular control factors. Aberrant regeneration of the lining of the bronchioles causes narrowing and reduced airflow. This observation is consistent with the inflammation and tissue scaring reported by clinicians. It is expected that damage to the airway in this way would reduce lung function and VO2 capacity.

Bronchiolitis obliterans is difficult to reverse once established. Measures taken once a case has been identified involve limiting any further exposure of the patient to diacetyl. Once diagnosed, patients may be given a trial of steroids or immunosuppressant therapy. In some cases a lung transplant may be required. In a case reported in 2002, 5 out of 9 workers suffering from Bronchiolitis obliterans arising out of diacetyl exposure required lung transplantation. Given the seemingly irreversible nature of this condition, and the limited success of medical intervention, a preventive approach should be employed to reduce the risk of occurrence.

Preventative approaches to limit the exposure of workers to compounds such as diacetyl include:

• Substitution of diacetyl with a flavouring of less toxicity

• Utilisation of effective engineering controls to minimise the release of diacetyl into the environment;

o Use of a closed system for transfer of diacetyl

o Use of a separate diacetyl mixing room kept under negative air pressure with appropriate personal protection

o An appropriate and working ventilation system

Preventive measures to reduce the risk of diacetyl exposure should also encompass administrative and educational controls. Such measures should seek to educate workers and administrative staff on the importance of quality systems in the work place. This should focus on inventory management, health and safety programs and the provision of information on hazard warnings through postings and labelling's.

It is imperative for manufactures utlising diacetyl or any hazardous chemical to routinely carry out independent environmental risk assessments of their plants. An industrial hygienist may carry out an environmental risk assessment and can sample an area for the presence of harmful chemicals. The data collected by an industrial hygienist can be compared to acceptable levels deemed safe by regulatory bodies for occupational exposure. Should the levels of hazardous material in the environment be deemed a risk for workers, steps should be taken to reduce such levels and remediate the environment. With the recent legal action of an exposed confectionary consumer to diacetyl, this should be an immediate concern to the producers of confectionary. The case serves to illustrate the occupational hazards of working with diacetyl, but also the risk posed to the consumer base that buy such products. This highlights the need for routine environmental testing during the manufacturing process.


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Diacetyl and Food Flavorings (Centers for Disease Control and Prevention accessed 23-Sept-12

Respiratory toxicity of diacetyl in C57BL/6 mice accessed 23-Sept-12

Diacetyl - Occupation Safety & Health Administration accessed 23-Sept-12

Evaluation of Flavorings-Related Lung Disease Risk at Six Microwave Popcorn Plants accessed 23-Sept-12

Popcorn worker's lung: in vitro exposure to diacetyl, an ingredient in microwave popcorn butter flavoring, increases reactivity to methacholine (pdf) accessed 23-Sept-12


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