Posted: 5 April 2018
Outbreaks of ill-health have occurred across the world in operators of plant using water-based metalworking fluids (MWFs).
One such outbreak took place in 2005 at the Powertrain engineering plant in Birmingham where workers developed occupational asthma and extrinsic allergic alveolitis. This incident lead to the withdrawal of all formal and guidance exposure limits for MWFs in the UK as the fundamental question of “What exposure level is regarded as safe?” could not be answered. Despite extensive research since that time the answer to this is still not known. So where does that leave us?
The research has shown that the respiratory issues are caused, at least in part, by airborne endotoxins produced by bacteria in the sump. Blood tests carried out on operators have shown that their immune systems are regularly challenged, although ill health is generally avoided. It is therefore essential that MWFs are correctly managed and monitored for microbial growth, which may include legionella.
For correct management and monitoring for microbial growth, dip slides should:
Plotting the data graphically is the best option as trends can be identified more easily. Results of less than 103 CFU/ml (colony-forming units per ml of fluid) are acceptable. If the dip slides show 103 – 106 CFU/ml improvements are needed. This may involve changing the biocide regime or cleaning the sump for example. Results over 106 require immediate action - usually drain down, sump cleaning and fluid replacement. Sumps should be cleaned regularly – at least often enough to maintain control as shown by dip slides.
Whilst these is no formal exposure limit for exposure to MWFs in the UK there is still a need to reduce exposures so far as is reasonably practicable. Good practice should usually allow exposures to be kept below 0.5 mg/m3, a limit still in place in the USA. Your assessment should consider if this is being achieved.
If you require further advice, or assistance, contact Dr Graham Newport at SML.