HSE Statistics showed that in 2020 approximately 12,000 lung disease deaths each year are linked to past exposures at work and an estimated 17,000 new cases of breathing problems caused or made worse by work each year* demonstrating why the safe use of Metal Working Fluids and the Occupational Health risk is an important priority health topic.

Metal working fluids are neat oils or water-based fluids used during the machining and shaping of metals to provide coolants and lubricants in machine workshop equipment. It can be used on a wide range of equipment including CNC machines, lathes, punches, cutting saws and pillar drills.

Although the exact causations of ill health are not fully understood it is very likely this is caused from:

    Ingredients within the metal working fluids,

    contaminants such as metal and other materials

    microbial and biocides which are added to the fluids.

Water content within the fluid makes it vulnerable to microbial contamination, causing workers to breathe in harmful bacteria, including Legionella, yeasts and fungi – and the toxic biocides. 

Fluids are often inhaled as aerosol or mists which are likely to be generated from higher tool speeds.  They can be inhaled in the breathing zone of the operator where machinery is positioned and particularly where operating enclosures such as CNC’s and were using compressed air lines.

MWFs have also been linked to a catalogue of lung diseases including occupational asthma and hypersensitivity pneumonitis.  Severe skin irritation and dermatitis, a painful type of eczema can also come as a result from prolonged contact with the fine metal particles chemicals and working with the fluids.

The Control of Substances Hazardous to Health Regulations 2002 (COSHH) requires that MWFs be risk assessed and controls suitable and sufficient to protect employees from exposure. There is no Work Exposure Limit (WEL) for MWF, so you must ensure controls bring the risk to As Low As Reasonably Practicable (ALARP). With recent guidance updates, it is important to know some of the important things you may need to consider for the general use of MWF and the controls that can be implemented within the workplace.

    Can operations using MWF be minimised by redesigning operating processes?  You must demonstrate you can reduce mist levels and emissions to as low as reasonably practicable. Engineering controls – Consider high-speed equipment where mists are generated such as CNC, lathes milling equipment particularly where this is enclosed. 

    Assess whether mists are captured fully and is LEV fitted? Does this incorporate a filter mist system or extracted externally?

    Are other controls and best practices such as time delays for enclosures required? Operators can be exposed when the doors to CNC lathes and Milling equipment is opened and the machine comes to a stop. The Delay will allow for the mist to disperse before opening the doors reducing the risk to machinery operators

    Assess the use of airlines for cleaning down equipment. Where compressed air is used as part of the process, such as in a CNC, it is recommended this is completed within the unit, so mist is contained within the machine, the pressure can be reduced and the type of equipment accessed

    Where machines are not enclosed to consider splash guards for machinery to reduce skin contact and use tools such as vacuums, brushes as opposed to just using hands when cleaning.

How to keep things in check?

    There should be regular testing of the MWFs. For water-based fluids bacterial growth is indicated when dip slide results are consistently at or above 10,000 CFU/ml (104 CFU/ml). Dip slide tests should be completed on a weekly basis, however testing frequency can be rolled back once levels are normalised and can be demonstrated through records. Where issues are noted and there is the potential effect on microbial development, this should revert to weekly again. By using fully synthetic solutions this would negate the need for dip-slide testing.

    Implement a renewal programme for all MWFs. MWF dangers increase with use, as fluids become contaminated by tramp oil, soluble metals, metal fines and microbes. It’s good practice to establish a regular schedule of emptying and renewing reservoirs – but how often depends on usage rates, contamination types and temperature. To determine your ideal regime, use a refractometer to gauge oil health and contaminant levels,

    As with all checks, good record keeping is essential to maintain a due diligence defence which you must keep for 5 years.

    In order to identify exposure, air monitoring may be required. This will help measure likely exposure and to ensure you are working within the Where controls leave a residual risk, employers are advised to introduce health surveillance for MWF-linked skin and respiratory conditions. The programme should include lung function checks and regular visual inspection of workers’ hands and exposed skin

    Ensure all staff are trained in controls and risk assessment and they are aware of the hazards. It is essential that staff know how to control the risks, and how PPE correctly such as changing overalls and gloves regularly when they are heavily contaminated

    Dust monitoring lamps can be used to show mist in the atmosphere whilst opening the enclosure as a way to verify controls.

Southalls health and safety consultancy services streamline processes and control hazards across your entire business, helping you stay confidently compliant through sector-specific risk assessments, tailored employee training and expert crisis support. Talk to the team to learn more.

*(Health and Safety at work Summary statistics for Great Britain 2020)