Occupational exposure to mineral oil metalworking fluid (MWFs) mist: Development of new methodologies for mist sampling and analysis. Results from an inter-laboratory comparison

Metalworking Fluids (MWFs) are largely used in the sector of undercutting, a large professional activity in Switzerland, in particular in the fine mechanic and watch making industry. France proposes a Permissible Exposure Limit (PEL) of 1 mg.m-3 of aerosol. The American Conference of Governmental Industrial Hygienists (ACGIH) sets its value at 5 mg.m-3 but a proposal to lower the standard (intended changes) to 0.2 mg.m-3 of aerosol is pending since 2001. However, it has not become a recognized threshold limit value for exposure. Since 2003, the new Swiss PEL (MAK) recommendations would be 0.2 mg.m-3 of aerosol (oil with boiling point > 350?C without additives) and/or 20 mg.m-3 of oil aerosol + vapour for medium or light oil. To evaluate evaporative losses of sampled oil, the German Berufsgenossenschaftliches Institut f?r Arbeitssicherheit (BGIA) recommends the use of a XAD-2 cartridge behind the filter. The method seems to work perfectly for MWFs in a clean occupational atmosphere free from interference of light vapour cleaning solvent such as White Spirit. But, in real situation, machine shop atmosphere contaminated with traces of White Spirit, the BGIA method failed to estimate the MWFs levels (over-estimation). In this paper, we propose a new approach meant to measure both oil vapours and aerosols. Five inter-laboratory comparisons are discussed, based on the production of oil mist in an experimental chamber under controlled conditions.