Characterization of occupational inhalation exposures to particulate and gaseous straight and water-based metalworking fluids.

Exposure assessments to metalworking fluids (MWF) is difficult considering the complex nature of MWF. This study describes a comprehensive exposure assessment to straight and water-based MWFs among workers from 20 workshops. Metal and organic carbon (OC) content in new and used MWF were determined. Full-shift air samples of inhalable particulate and gaseous fraction were collected and analysed gravimetrically and for metals, OC, and aldehydes. Exposure determinants were ascertained through observations and interviews with workers. Determinants associated with personal inhalable particulate and gaseous fractions were systematically identified using mixed models. Similar inhalable particle exposure was observed for straight and water-based MWFs (64-386 µg/m3). The gaseous fraction was the most important contributor to the total mass fraction for both straight (322-2362 µg/m3) and water-based MWFs (101-699 µg/m3). The aerosolized particles exhibited low metal content irrespective of the MWF type; however, notable concentrations were observed in the sumps potentially reaching hazardous concentrations. Job activity clusters were important determinants for both exposure to particulate and gaseous fractions from straight MWF. Current machine enclosures remain an efficient determinant to reduce particulate MWF but were inefficient for the gaseous fraction. Properly managed water-based MWF meaning no recycling and no contamination from hydraulic fluids minimizes gaseous exposure. Workshop temperature also influenced the mass fractions. These findings suggest that exposures may be improved with control measures that reduce the gaseous fraction and proper management of MWF.

Oxidative potential of aerosolized metalworking fluids in occupational settings.

The oxidative potential (OP) measures the ability of pollutants to oxidize a chemical/biological probe. Such assays are starting to gain acceptance as integrative exposure metrics associated with inflammatory-based pathologies. Diseases such as asthma, rhinitis or cancers are reported for workers exposed to oil mist, which are aerosols of metal working fluids (MWF) emitted during the machining of metals. Measuring oil mist in the air is challenging, and exposures are often quantified as the mass fraction, which does not account for exposures to the gaseous fraction. Consequently, exposures are underestimated and furthermore, the hazardous property of oil mist is not assessed. We postulate that it is more relevant to assess occupational exposures to the hazardous fractions of oil mist by measuring OP than by simply measuring mass. We characterized exposures to straight and water-based MWF among workers in the French and Swiss mechanical industry using standard methods for oil mist and the ferrous orange xylenol assay for OP assessment (OPFOX). Considering the particulate fraction, the water-based MWF presented the greatest OPFOX. The OP was associated with organic carbon and iron content. The gaseous fraction of the oil mist presented also an important redox activity, particularly in workshops where straight oils were used. The hexanal concentration was associated with this OPFOX. The OPFOX measurement is thus integrative of multiple parameters, and bring complementary information when assessing MWF exposures. Our results highlight that OPFOX account for MWF type and could be an interesting parameter to characterize such exposure.

Early Effect Markers and Exposure Determinants of Metalworking Fluids Among Metal Industry Workers: Protocol for a Field Study.

BACKGROUND: Exposure to aerosols from metalworking fluids (MWF) has previously been related to a series of adverse health outcomes (eg, cancer, respiratory diseases). Our present epidemiological study focuses on occupational exposures to MWF and a panel of exposure and effect biomarkers. We hypothesize that these health outcomes are caused by particle exposure that generates oxidative stress, leading to airway inflammation and ultimately to chronic respiratory diseases. We aimed to assess whether MWF exposure, in particular as characterized by its oxidative potential, is associated with biomarkers of oxidative stress and inflammation as well as genotoxic effects. OBJECTIVE: The ultimate goal is to develop exposure reduction strategies based on exposure determinants that best predict MWF-related health outcomes. The following relationships will be explored: (1) exposure determinants and measured exposure; (2) occupational exposure and preclinical and clinical effect markers; (3) exposure biomarkers and biomarkers of effect in both exhaled breath condensate and urine; and (4) biomarkers of effect, genotoxic effects and respiratory symptoms. METHODS: At least 90 workers from France and Switzerland (30 controls, 30 exposed to straight MWF and 30 to aqueous MWF) were followed over three consecutive days after a nonexposed period of at least two days. The exposure assessment is based on MWF, metal, aldehyde, and ultrafine particle number concentrations, as well as the intrinsic oxidative potential of aerosols. Furthermore, exposure biomarkers such as metals, metabolites of polycyclic aromatic hydrocarbons and nitrosamine are measured in exhaled breath condensate and urine. Oxidative stress biomarkers (malondialdehyde, 8-isoprostane, 8-hydroxy-2'-deoxyguanosine, nitrates, and nitrites) and exhaled nitric oxide, an airway inflammation marker, are repeatedly measured in exhaled breath condensate and urine. Genotoxic effects are assessed using the buccal micronucleus cytome assay. The statistical analyses will include modelling exposure as a function of exposure determinants, modelling the evolution of the biomarkers of exposure and effect as a function of the measured exposure, and modelling respiratory symptoms and genotoxic effects as a function of the assessed long-term exposure. RESULTS: Data collection, which occurred from January 2018 until June 2019, included 20 companies. At the date of writing, the study included 100 subjects and 29 nonoccupationally exposed controls. CONCLUSIONS: This study is unique as it comprises human biological samples, questionnaires, and MWF exposure measurement. The biomarkers collected in our study are all noninvasive and are useful in monitoring MWF exposed workers. The aim is to develop preventative strategies based on exposure determinants related to health outcomes. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/13744.