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Exposure to Diacetyl Vapour in Food and Drink Manufacture

Credit seventyfour
Credit seventyfour

The Health and Safety Executive have issued a Safety alert targeting Employers, and the self-employed, in food and drink manufacture who use diacetyl.


Exposure to vapour from diacetyl, often used as a flavouring and a by-product of coffee roasting, can lead to severe and irreversible lung disease. Even if diacetyl is present at low concentrations within mixtures or flavourings, exposure to its vapour may be above safe workplace exposure limits (WELs).

Outline of the problem

HSE scientific studies show that heating diacetyl above certain temperatures significantly increases airborne concentrations and the potential for exposures above safe workplace limits.

Risk in coffee manufacture

Exposure levels during bean roasting and grinding can exceed WELs. The amount of diacetyl generated naturally during bean grinding is temperature dependent.  Concentrations are significantly greater if the roasted beans are ground when still warm (around 40°C) and reduced if the beans are cooled between roasting and grinding down to room temp (around 16-20°C).

Risk in flavour manufacture 

Airborne concentrations and the potential for exposures above safe workplace limits is significantly increased if flavour mixtures containing diacetyl, even at low concentrations (below 5%) are heated, added to hot processes or spray dried.

Risk of exposure can occur during

  • opening of diacetyl or flavouring containers
  • decanting and weighing
  • mixing
  • spray drying to produce powdered mixtures 
  • packaging
  • cleaning of vessels or spillages        

Hazardous substance workplace exposure limit (WEL)   

Diacetyl (CAS: 431-03-8), also known as 2,3-butanedione, is a naturally occurring organic compound but is also manufactured synthetically. Diacetyl vapour can be generated as a by-product during the roasting and grinding of coffee beans and may also be present during brewing of some beers. Synthetic diacetyl is classified as a hazardous substance. It is toxic if inhaled, can cause skin irritation and eye damage by contact and harmful if swallowed.

WELs for diacetyl were published in EH40/2005 Workplace Exposure Limits. Limits are at 20 parts per billion (ppb) or 0.02 parts per million (ppm) over an 8-hr time weighted average (TWA) and 100 ppb or 0.10 ppm over a 15-min TWA period. Suppliers’ safety data sheets for diacetyl or for mixtures containing diacetyl should list these WELs.  the Control of Substances Hazardous to Health (COSHH) Regulations 2002 (as amended) require employers to ensure work-related exposure is assessed, prevented or adequately controlled so that it is below the WELs.

Action required

Assess the risk

If your processes include the use of diacetyl, food flavourings that contain diacetyl, or are likely to produce diacetyl, then you must carry-out a risk assessment. Your risk assessment will help you to identify the hazards associated with the potential for exposure, understand who might be harmed and how, evaluate the risks and decide on precautions.

Check the safety data sheet

If diacetyl is not mentioned on a safety data sheet for food flavourings (which are likely to contain it) you should contact the supplier to confirm if it is present or not


If there is a potential for diacetyl exposure use sampling and analysis to verify whether exposure is likely to be above the WEL.


Substitute to a safer alternative product.  Substitutes should not contain compounds similar to diacetyl such as 2,3-pentanedione. 

Control risk of exposure

If substitution is not a viable option (for example if diacetyl is a natural by-product), then strict controls must be implemented:

  1. Keep the flavouring at a low temperature (below 4°C) as this will significantly reduce vaporisation
  2. Enclose the process and use extraction, to control diacetyl vapour emissions at source
  3. For coffee manufacture, cool the coffee beans (to at least below 20ºC) pre-grind.
  4. For diacetyl flavouring manufacture and use, add the flavouring at the last stage of production and via an enclosed or automated system
  5. Where the above controls do not reduce exposure below the WEL, you should consider providing suitable personal protective equipment (PPE), including suitable respiratory protection equipment (RPE).

Health surveillance

If there is a reasonable likelihood that workers may be harmed by diacetyl you must introduce a health surveillance programme. Your risk assessment will help you decide if this is required. A health surveillance programme should be devised in consultation with an occupational health provider.

Carbon Monoxide (CO)

Carbon monoxide is also known to be a by-product in coffee processing. Control of diacetyl through enclosure and extraction will also help control CO emission. HSE recommends that as part of a risk assessment process, you carry out sampling to establish whether any further controls for CO might be necessary.

Engineering company fined after worker diagnosed with occupational asthma

High precision CNC machining center working, operator machining automotive sample part process in industrial factory

An Engineering Company has been sentenced for health breaches after workers were exposed to metal working fluid (MWF).

MWF is hazardous to health, and exposure can cause health conditions including irritation of the skin/dermatitis, occupational asthma, bronchitis and irritation of the upper respiratory tract.

Sheffield Magistrates’ Court heard that, in February 2016 a visit was conducted by the HSE and enforcement taken requiring the company to provide health surveillance and manage MWF. In September 2016 an employee was diagnosed with occupational asthma. Further enforcement was taken in December 2016 with an Improvement Notice issued to develop a system for managing MWF.

An investigation by HSE found that a water mix MWF was in use in the majority of machines including saws, machine centres and milling machines. None of these machines had local exhaust ventilation (LEV) and some door seals were observed to be in poor condition.  The MWF sumps to some machines were in visibly poor condition, with fines, swarf and/or tramp oil being present.

Lantern Engineering Ltd of Globe Court, Denby, Doncaster South Yorkshire pleaded guilty to breaching Section 2 (1) of the Health & Safety at Work etc Act 1974. The company has been fined £15,000 and ordered to pay £7,500 in costs.

After the hearing, HSE Inspector Laura Hunter commented: “The company’s failure to manage MWF exposed employees to risk.

“Companies should be aware that HSE will not hesitate to take appropriate enforcement action against those that fall below the required standards”.

SHP October 2021

Dakar Here We Come

Just wanted to share news that our Occhnet Sponsored Rider Simon Hewitt was in action again at the weekend in the Dawn to Dusk Enduro, competing in the 6 hour Marathon Clubman category. He had a solid race, at ‘a day in Dakar’ pace and completed 8 laps of the Walters Arena course at a consistent 43 minutes a lap pace….. awesome job!

If you’d like to know more and become a sponsor pop over to his website

In a world profoundly affected by the COVID-19 pandemic, and the role of OSH professionals pushed centre stage, continuing professional development (CPD) is essential. In response Occhnet has certified CPD courses available to keep you up to date….. but here’s some practical advice about how to keep that all important balance.


  1. Professional development is about taking time out and evaluating where you are, where you want to be, and making appropriate changes to gain control in stressful overwork situations. But CPD is not all about courses and qualifications – it is also about extracting learning from the working day and using that to make the subsequent activities more effective.
  2. To avoid feeling stressed and overwhelmed, make a clear distinction between working, studying and enjoying your own time.
  3. Incorporate one learning activity into each day – and enjoy it. You can also combine this activity with day-to-day work.
  4. Take time to think about what you are doing and learning. Evaluating outcomes will show how you have used your abilities and that you have a ‘valued role’.
  5. Separate activities into different spaces if possible – sit in an armchair with a book, or use a pen not a computer.
  6. Plan your time carefully to learn when you are not tired – for example after lunch or first thing in the morning. Don’t try to learn when you are tired, or on a Friday.
  7. Set your own pace.
  8. Take frequent rests, and eat and sleep well. Use exercise to work out difficult problems – just let the thoughts float around your head while exercising (or sleeping) and you may find what comes out of it is interesting.

Source: Dr Angela Carter, occupational psychologist at Just Development via IOSH Magazine Jan 2021

Social Distancing Rule at Work

The UK’s Health and Safety Executive (HSE) has warned employers it will hand out enforcement notices to those who do not comply with the two-metre social distancing rule in workplaces that remain open during the coronavirus outbreak.

The regulator said it is ‘constantly reviewing’ the situation and will consider taking action against those who flout the rules.

‘In these extraordinary times, HSE is constantly reviewing the fast-moving situation with our partners across government to support the national effort to tackle Covid-19. 

‘Where HSE identifies employers who are not taking action to comply with the relevant [Public Health England] guidance to control public health risks, for example employers not taking appropriate action to socially distance or ensure workers in the shielded category can follow the NHS advice to self-isolate for the period specified, we will consider taking a range of actions to improve control of workplace risks. These actions include the provision of specific advice to employers through to issuing enforcement notices to help secure improvements with the PHE guidance.’

IOSH Magazine, July 2020

HSE receives more than 4,500 COVID-19 complaints

More than 4,500 complaints have been made to the Health and Safety Executive (HSE) since the first UK case of coronavirus was confirmed, it has been revealed.

Last month the HSE issued a warning to employers that it would hand out enforcement notices to those who do not comply with the two-metre social distancing rule in workplaces that remain open during the outbreak.

The workplace safety regulator said it was now working through the reports, received since March, with a ‘range of actions’.

Talking to IOSH magazine, it said: “Between 9 March and 3 May 2020, we have received more than 4,500 workplace concerns relating to COVID-19 in some form. We are listening to these concerns and working through these with a range of actions. Further updates on these outcomes will be made available as soon as possible.”

IOSH Magazine
May 2020


Fire safety warning as millions work from home

Firefighters issued urgent #StayHomeStaySafe advice as millions of people started their first full week of working from home amidst the Coronavirus pandemic.

The majority of city office workers have now stopped commuting following Government advice to avoid all but essential travel in a bid to try and contain the spread of Covid-19.

With the increased numbers of people at home during the day, London Fire Brigade is warning of the potential for more fires as people adapt their daily routines and others are in isolation, and calling for people to think, take action and avoid becoming a further casualty for the NHS.

Firefighters are usually called to a larger number of domestic fires between 6pm and 8pm and there has traditionally been an increase in cooking fires during the weekend when people are at home for longer periods of time.

However in 2020 we are seeing an increase in weekday fires and fires earlier in the day so firefighters are warning that common causes of fires in the home such as cooking, smoking, electrical items and heating sources could become even more prevalent as people are spending more time indoors than usual.

The Brigade’s Assistant Commissioner for Fire Safety, Dan Daly, said: “It’s absolutely vital that in these uncertain and unprecedented times people don’t forget about basic fire safety in the home.

“We are not trying to scaremonger, but clearly with increased numbers of people indoors for much longer periods of time, there is a heightened risk of fire.

“This is about keeping you and your loved ones safe and we must all do what we can to not inadvertently add pressure to our already challenged NHS.

“There are such simple things we can all do to ensure we are keeping safe while we are all spending more time at home. The first thing you can do is test that your smoke alarms are working.”

Cooking fires are a major concern as people are expected to cook more during the day and with schools shut and children at home, parents could get distracted.

An increase in smoking-related fires, which are the most common cause of fire deaths, is also thought to be a possibility as smokers may start smoking inside more as people are continually advised not to go out unnecessarily. While it may not be possible to visit vulnerable friends and family members at the moment, please speak to them and remind them about the dangers of smoking.

As people who don’t usually work from home set up temporary offices, there is also a risk of an increase in electrical fires.

Hazards include overloading plug sockets, using counterfeit or incorrect chargers for tablets, laptops and mobile phones and “daisy-chaining” – plugging multiple extension leads together or plugging many multi-socket adaptors into a single socket.

Another concern around people spending more time at home is that it could lead to higher heating bills, which in turn may tempt people to heat their home unsafely.

Assistant Commissioner Daly added: “This is all about basic fire safety awareness and the checks we are advising will take just a few minutes to carry out to keep you and your family safe.”

London Fire Brigade
March 2020

Must know: Suicide Prevention

Suicide is a major issue for society and a leading cause of years of life lost. There were 5,021 deaths from suicide registered in England in 2018 and for every person who dies at least ten people are affected.

The Local Government Association (LGA) points out that councils are well placed to prevent suicide because their work on public health addresses many of the risk factors, such as alcohol and drug misuse, and spans efforts to address wider determinants of health such as employment and housing. There are also important opportunities to reach local people who are not in contact with health services through online initiatives or working with the voluntary and community sector.

However, it also points out that this needs to be a joint approach from various stakeholders. A local suicide prevention plan combines actions by local authorities, mental health and health care services, primary care, community-based organisations and voluntary agencies, employers, schools, colleges and universities, the police, transport services, prisons and others.

Councils have been active on suicide prevention work in recent years. Significant progress has been made in getting plans for suicide prevention into place. Attention is now focused on ensuring action is taken to reduce suicides.

The delivery of a comprehensive strategy is effective in reducing deaths by suicide through interventions that build community resilience and target groups of people at heightened risk of suicide, says the LGA. Councillors, directors of public health and health and wellbeing boards have a central role. Their involvement is crucial in coordinating local suicide prevention efforts and ensuring every area’s strategy is turning into action.

March 2020

Health and work – infographics

Public Health England (PHE) and The Work Foundation have collaborated to produce 13 infographics intended to help raise awareness and understanding of the relationship between health and work.

These infographics are intended to help public health practitioners, local authorities and policy makers to make the case and inform planning on embedding health, work and worklessness within and across these issues.

The infographic covering ‘Spotlight on alcohol, drugs and tobacco’ to Health and work has been updated. This, together with the other infographics, is available here

  1. The other infographics cover the following:
  2. spotlight on mental health
  3. cost of ill health
  4. health of the working age population
  5. health of UK employees
  6. spotlight on musculoskeletal conditions (MSK)
  7. managing health at work for employers
  8. spotlight on small medium enterprises (SME)
  9. unemployment and economic inactivity
  10. welfare
  11. the local picture
  12. supporting older workers with health problems
  13. young people and health at work.
Public Health England