There is currently no Workplace Exposure Limit (WEL) for oil mist particles – the previous TWA (time weighted average) limit of 5mg/m3 was withdrawn in 2005 following an outbreak of respiratory illness at an automotive plant with airborne oil mist under this limit. Employers are required to minimise oil mist levels to ‘as low as reasonably practicable’ (ALARP) through the use of effective control measures.

This HSE research report provides more information on the monitoring of water-miscible metalworking fluid (MWF) mists: