Published: 16/03/2011

A long union push for workplace regulation of the highly toxic food flavoring diacetyl has resulted in the introduction of a strict new workplace standard in the state of California. California’s initiative has not generated an equivalent binding standard at federal level, but federal authorities have expanded their limited, voluntary guidelines to now include diacetyl substitutes which are equally lethal. In the EU, by contrast, it’s still business as usual, with not even a safety review in sight for this potentially fatal workplace hazard.

Diacetyl (also known as Butanedione and 2,3-Butanedione) is a chemical which is used, singly or in combination with other chemicals, to produce artificial flavors. These are mainly dairy flavors (e.g., butter, cheese, etc.), brown flavors” (e.g., caramel, butterscotch, brown sugar, maple, coffee flavors) and some fruit flavors. It is also used in vanilla, tea, and other flavorings

Diacetyl has been definitively linked to the rare crippling lung disease bronchiolitis obliterans, now widely known in the US as “popcorn workers lung” after a rash of cases developed among workers making butter-flavored microwave popcorn, which uses diacetyl in relatively high concentrations. While often (mis)diagnosed as asthma or emphysema, bronchiolitis obliterans differs from these diseases in the rapidity with which it destroys the bronchioles, the lungs’ tiny airways, leading to diminished respiratory capacity.

Diacetyl has been used for many decades as a food flavoring ingredient, but is generally indicated on the product label only as ‘artificial flavor’ or ‘artificial butter flavor’, if it is identified at all. Due to insufficient regulatory and labeling requirements, the full extent of global worker exposure is therefore not known.

Diacetyl is used in a wide variety of food flavorings 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, pet food and other processed foods and beverages. US scientists have estimated that diacetyl is used in the manufacture of some 6,000 commercial products.

Workers in restaurants or commercial kitchens are also at risk, since diacetyl is a common ingredient in margarines, shortenings and cooking oils and sprays. Heated for cooking, these ingredients release toxic vapors.

In the United States, with growing numbers of food industry workers succumbing to ‘popcorn lung’, IUF-affiliated food unions pushed legislation which would have required the federal occupational safety and health agency OSHA to set mandatory exposure limits for diacetyl and regulate exposure, controls and monitoring procedures.

The bill stalled in Congress, but the UFCW in California – a state with some 20 food flavoring plants plus a large food processing industry – petitioned the state authorities to immediately issue an Emergency Temporary Standard for diacetyl. At the close of 2010, Cal/OSHA responded with a legally-binding standard which requires employers to create a regulated area for each process using diacetyl, unless the process is enclosed. The standard mandates detailed safety measures including a written diacetyl control program, strict labeling requirements and periodic monitoring of exposure levels. Personal protective equipment is mandatory and various types of respirators are required according to concentration levels. Training and medical surveillance are to be provided by the employer at no cost to employees.

In response to the growing number of “popcorn lung” lawsuits, some major companies loudly announced a shift to “diacetyl free” manufacture, including “no diacetyl” microwave popcorn. The problem is that the more common diacetyl substitutes are chemically related to diacetyl and potentially have a similarly toxic impact on the lungs. These include the chemicals 2,3-pentanedione, 2,3-hexanedione, 2,3-heptanedione, acetoin and diacetyl trimer.

In January 2011, US OSHA expanded its “National Emphasis Program” setting safety guidelines for microwave popcorn plants to include these diacetyl substitutes. However, neither this program, nor regulations pertaining to food flavorings, specify permissible exposure levels (PELs) or are legally binding standards.

Under the National Emphasis Program the government at least maintains a registry of microwave popcorn plants where workers are potentially at risk. In the EU, regulatory, safety and trade bodies acknowledge extensive use of diacetyl in food processing and flavor manufacturing but have never made public information on where or how the chemical is used, the size of the exposed population or any details of health surveillance or research into diacetyl exposure as a workplace health and safety issue.

EU Occupational Safety and Health Directives currently set no exposure limits for diacetyl, which has never been evaluated with regard to inhalation and other forms of exposure in manufacturing. EU legislation on food flavorings does not specify use levels or define categories of foodstuffs that are permitted to contain flavorings. In recent correspondence with the European Food Safety Authority, the agency has stated that diacetyl has been declared safe, that no new evaluation was carried out, that it has no plans to do so, and that evaluation falls outside its mandate, which is limited to oral exposure rather than inhalation.

This regulatory inaction in the face of a known workplace killer stands in sharp contrast with the introduction of a binding standard in California. Click here for the latest IUF diacetyl health and safety alert (in English), which provides full background information and proposals for regulatory action.