Occupational Exposure to Metalworking Fluid Mist and Sump Fluid Contaminants

Abstract

This paper summarizes the analytical and occupational hygiene findings from a recent survey of occupational exposure to metalworking fluids (MWFs) in the engineering industry. The aim of the survey was to link MWF mist exposure measurements with particular engineering processes and controls, and utilize the data obtained to develop exposure standards. At the same time the opportunity was taken to assess fluid management and control, including bacterial and fines contamination in the machine sumps. In general, occupational exposure to mineral oil MWF mist was controlled to <3 mg/m(3) (8 h time-weighted average) and to <1 mg/m(3) for water-mix MWF mist (in terms of the concentrate). These exposure values do not necessarily represent best practice, but are believed to be achievable and representative of industry as a whole. Gravimetric analysis of the total inhalable particulate was found to be a good predictor of mineral oil MWF mist but not for water-mix MWF mist. Grinding and drilling operations produced higher exposures than turning and milling for water-mix fluids. There were insufficient data to compare machining operations for mineral oil MWFs. On the whole, fluid management was found to be poor, with most sites failing to meet industry good practice or Health & Safety Executive (HSE) standards. Some of the operating procedures utilized were deficient or unsatisfactory. Poor standards of fluid management were found at all sizes of company. High levels of bacteria, endotoxin and fines were found in sumps, and control of other factors, such as water-mix fluid concentration, was often poor. Mineral oils had higher levels of fines than water-mix fluids (medians of 395 and 18 mg/l, respectively), and grinding produced high levels of fines in both types of MWF. Many water-mix sumps contained bacterial levels of >1 x 10(6) CFU/ml, and endotoxin levels of >100 000 EU/ml were not uncommon. The median values were 109 000 CFU/ml and 8039 EU/ml, respectively. Mists could potentially contain extensive contamination from bacteria and endotoxin. Analysis of the data suggests that sumps operating under typical conditions for machining (a temperature of 20 degrees C, a pH of 9 and a fluid strength below 10%), also appear to provide optimum conditions for the proliferation of bacteria. Low levels of benzo[a]pyrene (median 0.03 micro g/g) were found in the mineral oils, and low levels of N-nitrosodiethanolamine (median 0.4 micro g/ml) were found in the water-mix MWFs. The results of this work will contribute to guidance from the HSE, setting out accepted industry good practice, including guide values for MWF mist and sump fluid contaminants, with significant emphasis on sump fluid management (maintenance and monitoring), as well as control issues.

Microorganisms in metalworking fluids: Current issues in research and management

“…An occupational exposure to MWF microorganisms in metal industry occurs mainly by direct contact with skin or by inhalation of the oil mist [6]. In the United States more than a million workers have a daily contact with the coolant during their regular operations [7].…”

“…In the United States more than a million workers have a daily contact with the coolant during their regular operations [7]. The most common complications in the respiratory system are asthma, upper respiratory tract infections, chronic bronchitis and IJOMEH 2013;26(1) 6 the cultural methods underestimate by up to five orders of magnitude the actual number of bacteria in MWFs. When the density of microorganisms was above this value, both approaches, either quantitative PCR (polymerase chain reaction) or plating provided similar results (4.51×10 9 16S rRNA copies/ml with a median value of 9.23×10 7 copies/ml versus 2.36×10 9 CFU/ml with a median value of 3.05×10 7 CFU/ml, N = 44) [13].…”

The Occupational Exposure Limit for Fluid Aerosol Generated in Metalworking Operations: Limitations and Recommendations

“…In addition, in order to control microbial growth, biocides are added (either originally or during use) only to water-soluble MWFs, which provides an excellent environment for microbial growth [3]. Each component of MWF may contribute to health effects, and hence the nature and severity of any health effects depends to some extent on the specific composition of the MWF [11,12] and the specific metalworking operation in which the fluid is applied. The complexity of the MWFs themselves and the various operations in which they are used makes it difficult to differentiate the type and abundance of specific MWF components, not only within a specific fluid but also among the four fluid types.…”

DermaDermal Health of Metal Machinistsetal Machinists

“…Metalworking fluid (MWF) is a complex mixture used during machining of metal objects and usually contains substances including biocides, corrosion inhibitors, metal fines, tramp oils, and biological contamination (1, 2). Water-based MWF causes much more skin disorders than oil-based fluids and irritant contact dermatitis is the main type of skin disorders (3).…”