Metalworking fluids (MWFs) are used as coolants and lubricants in machine workshop equipment including CNC machines, lathes, punches, cutting saws and pillar drills. Typically a mixture of oil and water, MWFs can boost tool performance and extend the working life of costly kit – but they also pose a range of health hazards to employees. 

Prolonged contact with the fine metal particles and anti-corrosion chemicals within MWFs can lead to severe skin irritation and dermatitis, a painful type of eczema. Because fluids are often inhaled as aerosol mists, MWFs have also been linked to a catalogue of lung diseases including occupational asthma and hypersensitivity pneumonitis. 

The Control of Substances Hazardous to Health Regulations 2002 (COSHH) requires that MWFs be risk assessed – and businesses face serious penalties if they fail to protect their people. Following HSE prosecution in 2020, a Rickmansworth-based metalworking premises was fined more than £24,000 for neglecting their legal duties.  

To prevent claims and safeguard staff, it’s wise to put precautions in place across three key areas:  

Stop risks at their source 

  • Implement a renewal programme. 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, and dip slides to register the bacterial load. As with all checks, good record keeping is essential to maintain a due diligence defence.
  • Keep bacterial growth in check. MWFs’ water content makes them vulnerable to microbial contamination, causing workers to breathe in harmful bacteria (including Legionella), yeasts and fungi – and the toxic biocides often used to kill them off. Include biofilm build-up checks in your renewal programme and clean or flush through susceptible areas such as dead legs in tanks and filters on a weekly basis, testing the liquid for organisms using a dip slide. Bacterial growth is indicated when dip slide results are consistently at or above 10,000 CFU/ml (104 CFU/ml). Testing frequency can be rolled back once levels are normalised but keep a watchful eye on ambient temperature and its potential effect on microbial development. You can also sidestep the issue of contamination by sourcing fully synthetic MWFs that aren’t mixed with water.

Reduce skin contact 

  • Skin contact can be minimised by redesigning operating processes to cut MWF mist levels and emissions to as low as reasonably practicable. Complementary control measures include local exhaust ventilation (LEV), respiratory protective equipment and personal protective equipment such as gloves and overalls. 

Set up ongoing health surveillance 

  • 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.

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.