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Metalworking Fluids - Asthma and Dermatitis

Updated: May 19, 2020

Precision engineering often involves intricate and precise metalworking processes which are carried out using specialist lathes, milling machines and saws. With these processes, the metalworking fluids used to lubricate and cool the workpiece pose a significant risk to health through inhalation and as a result of the fluids coming into contact with the skin.

Essentially, there are three types of metalworking fluids which are used in these types of processes.

  • Mineral Oils - a mix of mineral-based oils of different viscosities and additives used to gain a specific characteristic.

  • Soluble Oils - Soluble water-in-oil cutting fluids (water-mix metalworking fluids) are mineral oils that contain emulsifiers and additives. Some include rust inhibitors and bactericides.

  • Synthetic Fluids - Cutting fluids with solutions of non-petroleum based fluids, additives and water.

Often, the metal particulate generated by precision metalworking would be too large to inhale as these are often shavings opposed to airborne dust particles. Any fugitive emission would be prevented from becoming airborne as the metalworking fluids will act as a dust suppressant. Therefore, the risk of contracting asthma doesn't originate from the inhalation of dust, but the inhalation of the mists generated by the fluids hitting the workpieces or becoming hot and evaporating.

The inhalation of metalworking fluids can cause severe adverse health effects. A single exposure to metalworking fluid mist can cause asthma, chronic bronchitis, impaired pulmonary function and allergic alveolitis. Symptoms include breathing difficulty, wheezing, and dry coughs. Chills, sweating, aching, discomfort and/or fatigue may accompany respiratory problems.

Metalworking fluids are respiratory and dermal sensitisers and can cause severe reactions that can lead to serious occupational illness and even fatalities.

Upon coming into contact with the skin, the metalworking fluids can trigger the body's allergic response which in turn, causes blistering, swelling and cracking. The emulsifiers present in the mixtures can also defat the skin.

Sensitisation is a term used to denote a process by which the body's immune system produces an adverse reaction that can be severe. The immune system attacks the substance causing damage to the skin or even closing up the airways to prevent further exposure. A reaction can occur acutely, or at a later time following exposure.

Used metalworking fluid can become infected with bacteria of which gets circulated through the machinery posing a risk of bacterial exposure. As the mist or vapour is formed, it can be inhaled, contaminating the respiratory system.

Metalworking fluids can also contain Polycyclic Hydrocarbons. According to the Agency for Toxic Substances and Disease Registry (ATSDR), PAHs can be harmful to your health under some circumstances. Several of the PAHs, including benz[a]anthracene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, chrysene, dibenz[a,h]anthracene, and indeno[1,2,3-c,d]pyrene, have caused tumours in laboratory animals when they breathed these substances in the air, when they ate them, or when they had long periods of skin contact with them. Studies of people show that individuals exposed by breathing or skin contact for long periods to mixtures that contain PAHs and other compounds can also develop cancer.

A common condition amongst metalworking operatives is "Scrotal Cancer". This is caused by the fluids coming into contact with the skin around the scrotal area. Operatives have been known to place soaked cloths and rags in their pockets, exposing the skin as the substance soaks through the pocket liners.

To effectively quantify exposures and test the efficiency of the applied control measures, workplace air monitoring can be undertaken. Regarding control systems, through examination and testing of the Local Exhaust Ventilation should be undertaken within a 14-month time frame.

Effective and sufficient control of the substances can be achieved by implementing and undertaking all of the following:

  • If you're an employer, provide suitable information, instruction and training of the specifically designed safe systems of work.

  • If you are an employee, follow the instructions and training given by your employer on safe systems of work when working with metalworking fluids.

  • Utilise splash guards to control splashing and misting.

  • Minimise the production of mist and vapour by controlling the volume and rate of delivery of the fluid to the cutting edge of the tool.

  • Enclose the processes and use any enclosures or ventilation provided to remove or control any mist or vapour produced.

  • Allow a time delay before opening the doors on machine enclosures to ensure that all mist and vapour have been removed by the ventilation.

  • Report any damaged or defective splash guards, ventilation hoods or other control equipment. Carry out routine maintenance and repair any faulty equipment immediately.

  • Open workroom doors and windows to improve natural ventilation.

  • Refrain from using compressed air to remove excess metalworking fluids from machined parts or plant or equipment.

  • Routine health surveillance can be carried out to assess worker health.

Do You Need Support with COSHH?

It is hoped that this article goes some way to providing a brief overview of COSHH. If you wish to know more on this subject or need support with your COSHH assessments, exposure monitoring or the testing of your LEV systems, RPE Fit Testing then please feel free to get in touch with us through social media or our website (, by email at or simply give us a call on 01709 931299.

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