Feasibility study to derive occupational exposure limits (OELs) for metalworking fluids (MWF) based on toxicological criteria and on criteria from occupational medicine: data documentation and quality assessment

Status:

completed 01/2021

Aims:

This study analyses the feasibility of deriving occupational limit values (OELs) for exposure to metalworking fluids (MWFs) based on toxicological assessment and occupational medicine criteria. The report includes three major parts. In part I, epidemiological and experimental animal study results for MWF exposure and effects were analysed with respect to homogeneity and respiratory effect potency. Part II of this feasibility study analyses indications of carcinogenic effects of occupational MWF exposure, where suggested by the results of epidemiology or experimental animal tests. Part III comprises an updated comprehensive data compilation with respect to toxicological and occupational medicine information concerning dermal exposure to MWFs. This includes skin damage, dermal contact sensitisation and percutaneous penetration by MWFs. Respective data on discrete ingredients of MWFs were compiled.

Activities/Methods:

Part I: Exposure to MWF mixtures is characterised by the respective inhalable aerosol concentration. This aerosol contains both MWF ingredients and reaction products and contaminants of the MWFs and was assessed for straight oil MWFs and water-based (soluble, semi-synthetic and synthetic) MWF product types. Part II: Data on MWF preparations from discrete carcinogenic ingredients or from reaction products or contaminants were compiled. In addition, potential indications resulting from a mode of action, such as genotoxic mechanisms, were discussed.

Results:

Part I: It is demonstrated that the various MWF exposures exert similar effects and similar effect potency in the upper and lower respiratory tract, regardless of their specific composition and use conditions. It is therefore concluded that it is feasible to establish an OEL for exposure to MWFs, even though some significant uncertainties are to be acknowledged. A well-defined analytical procedure for aerosol measurements must be established in connection with this OEL to ensure comparable exposure quantification. As a supportive strategy, some additional OELs – for example for metal or microbiological contaminants – should be derived in the future to provide control for more specific aspects of the respective MWF exposure scenario. Part II: It is concluded that sufficient evidence does not currently exist that exposure to MWF generally equates to an elevated risk of occupational cancer. However, MWF exposure should be regarded as a suspected risk factor for carcinogenicity. Owing to the heterogeneous and conflicting study results, it is proposed that further knowledge be gained on this issue, for example by the monitoring of studies into the genotoxicity of MWFs under conditions in use and by the initiation of epidemiological studies on carcinogenicity of MWFs under actual exposure conditions in Germany. Part III: Dermatological effects are identified as a key health problem of occupational exposure scenarios linked to MWFs. Reported information should be considered during formulation of MWF products.

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