PU635 Unit 5 Chemical Hazard Case Study Example

A Butter Smell Each Time the Lid Lifts: A Unit 5 Chemical Hazard Case Study Following Diacetyl From a Heated Flavor Kettle to Three Workers at a Composite Bakery, Where Nothing Has Ever Been Measured

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Purdue University Global

PU635: Survey of Environmental and Occupational Health

Unit 5 Chemical Hazard Case Study

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[Date]

Corliss Street Bakery, its flavor room and its workers are composite; the chemical, the disease history, the exposure limits and the research cited are real.

The Agent

Diacetyl, 2,3-butanedione, is a small ketone that gives butter its smell and is used widely in artificial butter flavorings. It is volatile at room temperature and more so when heated. For decades it was treated as a food ingredient rather than an inhalation hazard, because it is safe to eat in the amounts found in food. Inhalation turned out to be a different matter. In May 2000, eight former workers from a microwave popcorn plant were reported with severe bronchiolitis obliterans, a disease in which the small airways scar and narrow. When the current workforce was evaluated, the 117 workers who answered the questionnaire had 3.3 times the expected rate of airway obstruction, and never-smokers among them had 10.8 times the expected rate. Obstruction rose with cumulative exposure to diacetyl, the main ketone in the plant's air (Kreiss et al., 2002). The airway scarring of bronchiolitis obliterans is largely irreversible, which is why prevention rather than treatment carries the case. The hazard was invisible for years because the agent was a food, and nobody asked what eating and breathing it had in common.

The Source at Corliss Street

The flavor room makes a buttery spread for the plant's dinner rolls. Margarine is melted in a 40-gallon jacketed kettle held at about 140 degrees Fahrenheit, and liquid butter flavoring is poured in from a one-gallon jug, four additions per batch, three batches per shift. The safety data sheet lists diacetyl as a component, with a concentration range rather than a figure, and gives no inhalation warning beyond a general instruction to ensure adequate ventilation. Three features of the process increase release. Heat raises the vapor pressure of diacetyl. The kettle is open whenever the lid is lifted, which happens for every addition and every stir check. And the jug is decanted at the kettle rim, by hand, with the pourer's face directly above the opening. The room is 12 by 16 feet with one ceiling exhaust fan and a door to the make-up area that stays open for carts.

The Exposure, and What the Case Cannot Say

Nobody at Corliss Street has measured diacetyl in air, and this case does not invent a figure. What it can say is how exposure is likely to be patterned. Peaks will occur at each pour and each lid lift, twelve or more times per shift, with a lower background between them. The pourer will have the highest exposure, the two workers who portion the finished spread less. Workers in the make-up area by the open door may also be exposed at low levels, which is a pattern that has been described in other food plants where flavoring rooms were not separated from production. The sampling that would replace this reasoning is straightforward: full-shift personal samples on the three flavor-room workers and one make-up worker by the door, plus short samples during the pour, collected on sorbent tubes and analyzed by an accredited laboratory using a published method for diacetyl and its substitutes. Short samples matter here, because the limit discussed next includes a short-term value.

The Limits

1. OSHA: no permissible exposure limit for diacetyl. Enforcement would have to rely on the general duty clause, which requires proof of a recognized serious hazard and a feasible means of reducing it.

2. NIOSH: a recommended exposure limit of 5 parts per billion as an eight-hour time-weighted average and a short-term limit of 25 parts per billion over fifteen minutes, published in its 2016 criteria document, with recommended limits also set for 2,3-pentanedione (National Institute for Occupational Safety and Health [NIOSH], 2016).

The absence of an OSHA limit is not a finding that the exposure is safe. It reflects the age of most permissible limits and the difficulty of setting new ones. The NIOSH value is low enough that it may be exceeded by tasks that produce only a faint smell, and the case treats it as the benchmark for the sampling.

Controls, Down the Hierarchy

Elimination. Remove butter flavoring from the spread and use real butter or a flavor-free spread. This removes the hazard entirely and is put to the product team first, with the cost and the taste trial it needs. Substitution. The obvious substitute is a diacetyl-free flavoring, and it is where the case is most careful. A common replacement, 2,3-pentanedione, is a closely related compound. In rats exposed to its vapor, it damaged the lining of the airways and produced fibrotic lesions in the airways, findings the authors said raise concern that it may cause bronchiolitis obliterans in people (Morgan et al., 2012). A label reading diacetyl-free is therefore not enough. Any substitute must come with a full composition from the supplier and must contain no alpha-diketones. Engineering. If flavoring stays, the kettle gets a closed lid with a small addition port and a local exhaust hood at the rim, ducted outside rather than into the room. The flavoring is added through the port by a closed transfer from the container, and the batch is cooled before addition where the recipe allows. The flavor room door is fitted with a closer. Administrative. Containers are kept closed, the number of people in the room during additions is limited to the pourer, and the job rotates among trained workers. Protective equipment. Until sampling shows the engineering controls hold exposure below the NIOSH value, the pourer wears a respirator under a written respiratory protection program, chosen for organic vapors.

Surveillance

The three flavor-room workers receive a baseline respiratory questionnaire and spirometry performed to quality standards, repeated at intervals set by the occupational physician, with results compared with each worker's own baseline rather than with population norms alone. A drop in lung function from a worker's own baseline is a signal to investigate, even if the result is still within normal limits. The make-up worker nearest the door is offered the same. The surveillance program has a stopping rule: if sampling after controls is below the NIOSH limit on three occasions, intervals can lengthen.

What the Case Shows About Unregulated Chemicals

Corliss Street's flavor room is legal, unmeasured and probably hazardous. The case demonstrates a sequence that applies to any chemical without a permissible limit: identify the agent, locate the source, reason about the exposure while naming the samples that would measure it, use the best available recommended limit as the benchmark, and choose controls that do not swap one hazard for a related one. The popcorn workers' disease went unrecognized for years for want of exactly that sequence.

References

Kreiss, K., Gomaa, A., Kullman, G., Fedan, K., Simoes, E. J., & Enright, P. L. (2002). Clinical bronchiolitis obliterans in workers at a microwave-popcorn plant. The New England Journal of Medicine, 347(5), 330-338. https://doi.org/10.1056/NEJMoa020300

Morgan, D. L., Jokinen, M. P., Price, H. C., Gwinn, W. M., Palmer, S. M., & Flake, G. P. (2012). Bronchial and bronchiolar fibrosis in rats exposed to 2,3-pentanedione vapors: Implications for bronchiolitis obliterans in humans. Toxicologic Pathology, 40(3), 448-465. https://doi.org/10.1177/0192623311431946

National Institute for Occupational Safety and Health. (2016). Criteria for a recommended standard: Occupational exposure to diacetyl and 2,3-pentanedione (DHHS [NIOSH] Publication No. 2016-111). U.S. Department of Health and Human Services.