Comprehensive Diacetyl Safety Guide: Identifying exposure risks, monitoring workplace safety, and implementing critical control measures.
What is Diacetyl?
Diacetyl (butanedione or butane-2,3-dione) is an organic compound prized for its intense, buttery flavour. While it occurs naturally through fermentation in alcoholic beverages and is safe for ingestion in food, inhaling its vapours poses a severe health risk.
Occupational exposure, notably in microwave popcorn plants, coffee roasteries, and flavour manufacturing, has been linked to Bronchiolitis Obliterans, more commonly known as “Popcorn Lung.”
This is a rare, irreversible, and life-threatening obstructive lung disease where the small airways (bronchioles) become scarred and narrowed.
Sources of Exposure
Diacetyl risk is not limited to synthetic additives; it can also be a natural byproduct of industrial food processes:
- Coffee Production: Diacetyl vapour is generated during the roasting and grinding of coffee beans. Levels are significantly higher if beans are ground while warm (approx. 40°C) rather than cooled to room temperature (16–20°C).
- Brewing: It is present during the fermentation of certain beers, including English ales, stouts, and bitters.
- Flavour Manufacturing: Synthetic diacetyl is highly concentrated and classified as a hazardous substance. It is toxic if inhaled, corrosive to the eyes, and irritating to the skin.
High-Risk Activities
The Health and Safety Executive (HSE) warns that heating mixtures containing even low concentrations of diacetyl (below 5%) significantly increase the risk of exceeding safe limits. Dangerous exposure points include:
- Opening, decanting, and weighing flavouring containers.
- Mixing and spray-drying powdered flavourings.
- Packaging and vessel cleaning.
- Adding flavourings to hot processes.
Legal Requirements and Exposure Limits
Under the COSHH Regulations 2002, employers are legally required to assess, prevent, or adequately control diacetyl exposure. The Workplace Exposure Limits (WELs) for diacetyl are strictly defined:
Exposure Duration
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Limit in ppb
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Limit in ppm
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8-hour Time Weighted Average (TWA)
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20 ppb
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0.02 ppm
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15-minute Short-Term Limit (STEL)
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100 ppb
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0.10 ppm
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Controlling the Risk
To ensure a safe working environment, companies must follow a hierarchy of control:
- Risk Assessment: Identify where diacetyl is used or generated. Determine who is at risk and how vapours are being released.
- Safety Data Sheets (SDS): Regularly review SDS for all flavourings and chemicals. Suppliers are legally required to provide these.
- Substitution: Whenever possible, replace diacetyl with a less harmful flavouring alternative.
- Engineering Controls: If diacetyl cannot be eliminated, install Local Exhaust Ventilation (LEV) to capture vapours at the source.
- PPE/RPE: Use Respiratory Protective Equipment (RPE) where engineering controls are insufficient.
- Health Surveillance: If your risk assessment suggests a likelihood of harm, you must implement a health surveillance program in consultation with an occupational health provider.
Case Study: Masteroast, Peterborough
The necessity of these controls was highlighted by a recent HSE inspection at Masteroast, a coffee roastery producing 4,000 tonnes annually. The firm was issued an official improvement notice for failing to meet COSHH standards.
Key Failings Included:
- Poor Maintenance: Ventilation systems had not been thoroughly evaluated for over 14 months.
- Inadequate Vapour Control: Systems failed to protect workers from coffee dust and diacetyl vapours.
- Neglected Health Monitoring: The company failed to act on employee health surveys or review the effectiveness of existing protective measures.
This case serves as a critical reminder that compliance is not just a legal hurdle, but a vital necessity for protecting employee respiratory health.
Understanding Your Rights: Employer Duties
Under UK law, your employer has a “duty of care” to ensure you are not put at foreseeable risk. Key statutory duties include:
Health and Safety at Work Act 1974
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Ensure the general safety and welfare of all employees.
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COSHH 2002
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Prevent or adequately control exposure to hazardous substances (like diacetyl).
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Management Regulations 1999
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Conduct regular risk assessments and provide health surveillance.
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PPE Regulations 1992
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Provide and assess suitable personal protective equipment.
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Frequently asked questions:
Industrial Disease Claims: A Guide for Workers
If you have developed a respiratory condition, such as occupational asthma, due to workplace exposure, you may be entitled to compensation. Claims are split into two categories:
- General Damages
This covers pain, suffering, and loss of amenity. It compensates you for the physical injury and the impact it has on your quality of life (e.g., being unable to enjoy hobbies or exercise).
Estimated Award for Occupational Asthma: Typically ranges between £3,000 and £12,000, depending on the medical evidence.
- Special Damages
This covers financial losses resulting from the illness. This includes:
- Loss of earnings (past and future).
- Medication and treatment costs.
- Care costs (even if provided by family).
- Paid services for tasks you can no longer do, such as gardening or dog walking.
While some diseases, such as asbestosis, take decades to appear, symptoms of occupational asthma usually manifest shortly after exposure. However, if you have recently been diagnosed after leaving a company, you may still be able to bring a claim.
How did I contract an industrial disease?
Sufferers of industrial diseases often contract them due to their working environments, with symptoms potentially manifesting long after they have left employment.
This situation necessitates tracing back to previous employers to pursue claims, which may involve multiple liable parties if the individual worked for several similar companies. Even if a former employer is no longer in operation, claims can still be filed by conducting an Employers’ Liability Tracing Office (ELTO) search to identify the insurance provider from the time of employment.
Given that exposure often dates back decades, individuals may struggle to remember all their past positions or the exact employment years, leading to challenges in establishing liability.
To address this, employment schedules can be obtained from HMRC to compile a comprehensive list of all past employers. Following discussions with the claimant, legal actions can then be initiated against all identified defendants and their insurers.
What are the symptoms of respiratory diseases?
The main problems to look out for are the following:
- Difficulty breathing: While shortness of breath during exercise is normal, if it does not go away or is present when you are resting, it could be a sign of respiratory illness.
- Breathing noisily: If you find yourself wheezing or breathing noisily, it is a good indicator that something more serious may be wrong.
- Lingering Chest Pain: If you have a chest pain that seems to linger constantly and seems to get worse / aggravated when coughing, then this could be a sign of respiratory illness.
- Coughing up Blood: If you find yourself coughing up blood, this is a clear sign that something could be wrong. It could be coming from your lungs or respiratory tract. Whatever the cause, this is serious and should be investigated further.
What types of jobs put you most at risk?
There is no finite list of jobs that may expose you to chemicals that could cause respiratory diseases, but the following types of jobs are considered the riskiest:
- Construction: Workers who inhale dust in demolition zones can be at risk.
- Manufacturing: Factory workers are exposed to dust, chemicals, and gases that could lead to respiratory diseases.
- Textiles: Textile workers who make upholstery, towels, socks, bed linens, and clothes are at risk of exposure. They may inhale particles released from cotton and other materials.
- Cleaning: Many commonly used disinfectants can cause or worsen respiratory disease.
I have been diagnosed with an industrial disease, but I left the company a while ago. Can I still file a claim?
If you have only recently become aware of a problem and have only just noticed the issues, then your action should be taken in time for limitation purposes. However, this is something that is solely evidence-based for each action, so it is strongly recommended that you speak with a solicitor to take further advice.
Although a number of illnesses such as occupational cancer, noise-induced hearing loss (NIHL) and asbestos-related illness latency periods can be a number of decades, for other diseases such as occupational asthma, repetitive strain injury (RSI) and vibration white finger, you would expect these symptoms to manifest at the time of (or very shortly after) exposure.
Further information:
Respiratory Disease Claims.
Coffee roaster Masteroast in Peterborough was served with a health and safety improvement notice.
WHAT TO DO NEXT?
If you work in the coffee production industry and are experiencing respiratory issues or are concerned about the safety standards at your workplace, it is vital to seek professional advice.
Call 0113 200 9720 or get in contact for a free initial consultation regarding your options enquiries@oakwoodsolicitors.co.uk.
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Natasha Hardy is a Solicitor and Head of the Industrial Disease Department, specialising in Industrial Disease matters and has experience in handling a wide range of cases including claims for Noise-I…
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