Controlling the microbial pollution of water-mixable cooling lubricants

Status:

completed 09/1996

Aims:

Health risks from cooling lubricants can also occur through the increasing colonisation with pathogenic micro-organisms during use, in spite of the addition of biocides. The level of knowledge is insufficient for effective methods of prevention, in particular for risk assessment. Goal: information concerning germ formation and multiplication depending on material and process parameters; validation of different analytical procedures.

Activities/Methods:

Simulation of cooling lubricant plants; bacteriological investigations of 250 cooling lubricant samples from metal works (identification and quantification of pathogenic and other germs)

Results:

65 % of the working samples were contaminated with bacteria and 25 % with fungi; 20 % contained pathogenic germs. 56 % of the tests with aerobic bacteria showed concentrations over 1 million colony forming units (cfu) per ml. A dependency of type/type composition and quantity of germs on microbiological parameters could not be shown. Different strains can develop under identical conditions; even the type composition changes during operation. This last phenomenon rules out the approach of evaluating the microbiological states of the cooling lubricants on the basis of test/indicator organisms. The rapid diagnosis processes which were tested are inappropriate due to the system itself lacking validity. Dip-slide method results correlate with laboratory results but with a wide spread. Conclusions: Determining the operational risk with regard to pathogenic micro-organisms in cooling lubricants is unrealisable both in respect of the lack of a suitable measuring technique as well as in principle.

Publications:

Warfolomeow, I.: Keimbelastung wassergemischter Kühlschmierstoffe. Die BG (1998) Nr. 5, S. 274-281

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