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Flavouring Ingredient Diacetyl Linked to Deadly Lung Disease

Posted to the IUF website 23-Nov-2007

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On November 6 the IUF issued a press release calling for government regulatory authorities around the world to take urgent action to control the use of the food flavouring chemical diacetyl. Evidence has linked diacetyl to the crippling lung disease bronchiolitis obliterans, which has affected workers exposed to diacetyl in the food processing industry.

This IUF briefing outlines the evidence linking diacetyl to bronchiolitis obliterans and concludes with a call for action. The IUF is also surveying its members on the use of diacetyl in their workplaces.and a questionnaire to survey members' experience with diacetyl.

What is diacetyl?

Diacetyl is a chemical with the molecular structure C4H6O2, designated Butanedione or 2,3-butanedione according to the standardized nomenclature of the International Union of Pure and Applied Chemistry (IUPAC). Diacetyl occurs naturally as a result of certain fermentation processes and therefore is present in certain beers, wines and dairy products.

It is the use of diacetyl as a synthetic food flavouring, rather than naturally occurring diacetyl, which has given rise to serious health concerns. Artificially synthesized diacetyl has been used for many decades as a food flavouring ingredient, but is rarely if ever specifically identified. Used singly or in combination with other chemical ingredients to produce an artificial butter flavour, it generally identified on the product label as 'artificial flavour' or 'artificial butter flavour', if it is identified at all. Manufacturing workers will generally handle diacetyl as a yellowish liquid in various mixing stages of production, through the risks of inhaling the vapours are not confined to mixing (see below).

In which products is diacetyl used?

Manufactured diacetyl is used in a wide variety of food flavourings employed in the manufacture of frozen and snack foods (including microwave popcorn and potato/corn chips), confectionery, baked goods, dairy products including processed cheese, sour cream and cottage cheese, commercial baking mixes, icings, salad dressings, sauces, marinades and other processed foods and beverages.

Diacetyl and 'popcorn workers' lung'

Evidence has increasingly linked diacetyl to the crippling lung disease bronchiolitis obliterans, now widely known in the US as 'popcorn workers lung.' The disease can quickly destroy the bronchioles, the lung's smallest airways, resulting in the radical restriction of respiratory capacity. It is debilitating, progressive, untreatable and potentially fatal. The only remedy is a lung transplant. Food workers risk exposure to diacetyl as vapours, droplets or dust in the manufacturing process.

The evidence

While diacetyl has in recent years been identified as a serious workplace hazard in connection with the manufacture of microwave butter-flavoured popcorn, which uses diacetyl in high concentrations relative to other applications, a possible link with the potentially fatal lung disease bronchiolitis obliterans was first suggested by the US National Institute of Occupational Safety and Health (NIOSH) in 1985. Workers in the mixing room of a company supplying food and flavouring materials to bakeries developed "insidious" obstructive lung disease within a short time of beginning work (the study is available at http://www.defendingscience.org/case_studies/upload/NIOSH_1985_Intl_Bakers.pdf)

A 1993 study by the German chemical manufacturer BASF in 1993 testing laboratory rats for of inhalation exposure to diacetyl vapors showed effects to be fatal after a single 4-hour exposure above a certain level. The study was not published at the time, but the results are available at http://www.defendingscience.org/case_studies/upload/BASF-Study.pdf

NIOSH achieved broadly similar results in a 2006 study.

In 2000, NIOSH (http://www.cdc.gov/niosh/) studied a group of 135 workers at a microwave popcorn production plant, finding that "workers had 2.6 times the expected rates of chronic cough and shortness of breath, according to comparisons with the national data, and twice the expected rates of physician-diagnosed asthma and chronic bronchitis. Overall, the workers had 3.3 times the expected rate of airway obstruction; those who had never smoked had 10.8 times the expected rate. Workers directly involved in the production of microwave popcorn had higher rates of shortness of breath on exertion and skin problems that had developed since they started work than workers in other parts of the plant. There was a strong relation between the quartile of estimated cumulative exposure to diacetyl and the frequency and extent of airway obstruction.

"Conclusions: The excess rates of lung disease and lung-function abnormalities and the relation between exposure and outcomes in this working population indicate that they probably had occupational bronchiolitis obliterans caused by the inhalation of volatile butter-flavoring ingredients." (The results were published in the New England Journal of Medicine and are available here: http://defendingscience.org/case_studies/upload/Kreiss-et-al-Study.pdf). Four workers from the popcorn plant in this study were placed on the list of recipients for lung transplants.

Further studies carried out in the US involving workers in microwave-popcorn plants have found a high incidence of occupational lung disease among workers exposed to vapours from artificial butter flavourings (including diacetyl) in both mixing and packing operations. Studies have also detected high concentrations of airborne diacetyl at testing stations for quality control.

As research has widened, more victims of bronchiolitis obliterans have been identified in flavour-manufacturing facilities, including one worker employed at a plant making flavouring ingredients for dog food. Since 2006, the California Division of Occupational Safety and Health (Cal/OSHA http://www.dir.ca.gov/dosh/dosh1.html) has found eight flavouring plant workers with fixed obstructive lung disease, most of those with bronchiolitis obliterans. Twenty-two more have below-normal lung capacity, possibly indicating the beginning of the disease

New research has further pinpointed diacetyl as the specific ingredient in butter flavourings which causes bronchiolitis obliterans, while alerting health and safety specialists to other potentially hazardous artificial ingredients. The results of a recent Dutch study (http://ajrccm.atsjournals.org/cgi/content/abstract/176/5/498?etoc) of workers in an (unnamed) chemical plant producing diacetyl concluded that "Exposure to an agent during diacetyl production appears to be responsible for causing bronchiolitis obliterans syndrome in chemical process operators, consistent with the suspected role of diacetyl in downstream food production."

The ongoing study into diacetyl in California has identified at least 30 manufacturing sites using diacetyl as an ingredient. There is, however, no national database, nor is there a comprehensive list of the food companies and their product brands which use diacetyl. When contacted recently by the IUF, the European Flavour and Fragrance Association (EFFA) refused to disclose the names or locations of specific manufacturers which use diacetyl or the product brands containing diacetyl.

Because diacetyl has never been evaluated from the standpoint of worker exposure and because there are no diacetyl-specific labeling, use and handling requirements, the full extent of diacetyl-related lung disease is not known. What is known is that over 150 lawsuits have been filed against manufacturers using diacetyl by workers in the United States, and that researchers continue to uncover new cases of bronchiolitis obliterans linked to diacetyl exposure.

Diagnosing the symptoms

The symptoms of bronchiolitis obliterans are frequently misdiagnosed as asthma or Chronic Obstructive Pulmonary Disease (COPD) for example, bronchitis or emphysema). Because there are sometimes no symptoms indicating the onset of the disease, and because the progress of the disease is extremely rapid, it is vitally important that workers with potential diacetyl exposure at any level receive comprehensive medical examinations and regular followup surveillance. The respiratory symptoms of potential bronchiolitis obliterans include wheezing, shortness of breath, and coughing, usually a dry cough. Diacetyl can also cause irritation (and even chemical burns) to the eyes and skin.

Union action on diacetyl in the workplace

The fact that three major US manufacturers of microwave popcorn have dropped diacetyl as an ingredient in that product indicates that safer substitutes are currently available. The IUF proposes an immediate ban on diacetyl in food flavouring until safe exposure levels - if such there are - can be reliably established. There should be no use of diacetyl where safer alternatives are available.

Airborne levels must be monitored and regular health surveillance of potentially exposed workers undertaken. This should include all stages from handling of raw materials through all relevant stages of processing and packaging. The results of medical screening and occupational hygiene surveillance should be provided to union representatives, on a strictly confidential basis where required.

As interim safety measures, unions must demand that all manufacturing processes use closed production methods, eliminating handling/exposure to open containers of diacetyl, full ventilation of all workplace areas using exhaust ventilation (rather than compressed air) and the use of approved respirators. Full protection of the skin and eyes is also a necessity.

However, it must be emphasized that no personal protective equipment can be considered adequate in the absence of exposure standards based on rigorous workplace hazard analysis and further medical research.

What you can do

The IUF urges all unions with membership in food processing to take action to: