Metalworking Fluid Exposure Monitoring

Metalworking fluid exposure monitoring of your staff will help to ensure that your control measures are working.

Exposure to Metalworking Fluid

Processes involving the machining of metal use Metalworking fluid (MWF) as a lubricant or coolant.

Generally, these are drilling, cutting, milling and CNC machining of metals. Workers often also use it for washing down workpieces. Metalworking fluid is present in one of two ways, water-mixed metalworking fluid and mineral oil. Exposure to the mists from either type can be a health hazard. It can affect the lungs of the workers using metalworking machines. While the oils in the mists present a threat, there is also a hazard from bacterial growth. Bacterial growth can occur in the sump of the machine. As a result, the fluids need dip testing to ensure the safety of workers. Our consultants can measure the exposure of your staff to metalworking fluids.

Airborne MWF mists have the potential to cause occupational asthma and occupational hypersensitivity pneumonitis. The HSE refers to these substances as sensitizers. A sensitizer is a substance which can cause an individual to have severe reactions to even small concentrations in the air. This reaction is permanent, occurring whenever the individual is in the presence of the substance. As a result, the person can no longer be present around MWF. Sensitivity can occur at any time and any exposure, but greater exposure increases the likelihood.

Measuring exposure to Metalworking Fluids

HSE document MDHS 84/2 ‘Measurement of oil mist from mineral oil-based metalworking fluids’, specifies the method of workplace air monitoring measuring mineral oil mist in the air. This method is similar to the one described in MDHS 14/4.

The HSE specifies a different method for measuring water-mix fluid mist in the air. This document is called MDHS 95/3. ‘Measurement of personal exposure of metalworking machine operators to airborne water-mix metalworking fluid’.

When measuring either type of MWF, the consultant will use an IOM sampling head. The consultant positions the sampling head, which contains a filter in the breathing zone of the operative. That is to say, within 300mm of the mouth and nose. They also attach a pump to the worker’s belt. Our occupational hygiene consultants can also take background (static) samples. This method is similar, but they put it in a stationary position. The laboratory analyses the filter using MDHS 95/3.

The consultant also takes a sample of the metalworking fluid in addition to the air sample. They submit this fluid to the laboratory who analyse it for marker elements. These are usually boron, potassium or sodium. The laboratory finds the dominant component in the sump fluid and analyses the filter for that metal.

Airborne Exposure Limits

Neither type of metalworking fluid has a UK Workplace Exposure Limit (WEL). Oil mist historically had a limit within EH40, but this has now been removed. Water-mixed metalworking fluid has never had a limit. The reason that neither substance now has a WEL is that the HSE does not consider any level of exposure ‘safe’.

Because MWF is a sensitizer, the HSE requires employers to control it to a level as low as reasonably practicable (ALARP). Even if exposure is below the limit, employers must use further measures if they are available. This caution is because there is no safe exposure to carcinogens and sensitizers.

Exposure to Skin

Controlling Exposure

Controlling Exposure to Metalworking Fluids

Where sites handle MWF, the HSE expect employers to use local exhaust ventilation (LEV) to control MWF mists. Employers have a legal obligation to test and maintain systems in line with HSE guidance HSG258 ‘Controlling airborne contaminants at work’. While employers enclose many processes using MWF, mists may still escape if they are not under negative pressure during use. Synergy Occupational Hygiene Ltd can test if this is the case. We recommend combining this LEV testing with exposure monitoring for metalworking fluids whenever possible.