Legionella bacteria are commonly found in water supplies at low concentrations and if conditions (eg temperature and nutrients) are right, these microorganisms will grow. Water mix metal working fluids (MWFs) are mostly water and their industrial use may produce aerosols. Inhaling an aerosol contaminated with Legionella bacteria can cause Legionnaires’ disease. HSE guidance L8 “Legionnaires' disease. The control of legionella bacteria in water systems” recommends that the MWF storage and distribution system of lathe and machine tool coolant systems should be cleaned and disinfected every six months or more frequently if recommended by machine tool or fluid suppliers.
However, the Health and Safety Laboratory has carried out research, Survival of Legionella pneumophila in metalworking fluids, which shows there is a minimal risk of Legionella bacteria contaminating such a system, if the system is properly managed.
HSE’s guidance on managing bacterial contamination of metalworking fluids suggests a risk-based approach, based on monitoring fluid condition and bacterial contamination.
If you can demonstrate that metalworking fluids are managed in accordance with the COSHH essentials sheet Managing sumps and bacterial contamination and HSE’s guidance on managing bacterial contamination in metalworking fluids an additional assessment of the risk of Legionnaires’ disease is normally unnecessary. However, further assessment and precautions will be necessary to cover any special circumstances, such as deep cleaning of sumps and machinery with jet washers, where the potential for exposure to airborne hazardous bacteria is much greater. This is due to the disturbance of microbial slime known as biofilm – where Legionella may survive. Avoid water jetting where possible, as it tends to create fine water droplets or mists.
If water jetting is necessary carry out a risk assessment, to include respiratory and other risks such as those arising from the use of high pressure and electricity, see,
For more information on controlling the risk of Legionnaires’ disease, see Legionella and Legionnaires' disease