Risk Assessment for Metalworking Fluids and Respiratory Outcomes

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.

The influence of ventilation modes on oil mist particles diffusion in a machining workshop

Mechanical processing and operations are widely involved in modern industry. Large amount of oil mist is tended to be produced and will diffuse in the processing workshop when metalworking fluids are applied on the high temperature workpiece. The ventilation modes and air distributions can influence the air pollutants dilution in machining workshops. Therefore, this paper presents both experimental investigation and simulation study on the oil mist particles diffusion under different ventilation modes. The results identified PM2.5 as the primary component among different oil mist particles generated during a typical machining process. The distribution of oil mist particles in a full-scale machining workshop laboratory was investigated under two ventilation modes: high-sidewall nozzle air supply and low-sidewall air supply. Results revealed obvious influences of both air supply modes on the distribution of oil mist particles. Under the high-sidewall-nozzle air supply mode, the airflow and the oil mist distribution in the workshop was relatively uniform; while the low-sidewall-vent air supply mode led to an uneven distribution of oil mist particles, and the maximum oil mist concentration appeared at the height of 3 m. Under both modes, the attempts to increase the airflow rate are not always successful. Compared with low-sidewall-vent air supply mode, the high-sidewall-nozzle air supply mode presents better performance in achieving lower overall particle concentration level. Overall, the results of this study give useful reference to improve the air quality of industrial plant by properly designing the ventilation mode of machining workshop.

Prediction of size-selective permitted daily exposures for mineral oil mist based on an in vitro study in different scenarios

The incidence of DNA damage from exposure to specific types of metalworking fluids has been reported. In this research, size-selective permissible limits to prevent genotoxic damage in A549 cell lines exposed to two types of mineral oil were estimated for the first time using a benchmark dose approach and extrapolated to workers. The comet assay was performed based on Olive and Banath protocol to determine DNA damage. Then, the Benchmark Dose, the 95% lower bound confidence limit BMD, and the 95% upper-bound confidence limit BMD were determined using continuous response data. Finally, the four Benchmark Dose levels reported in the A549 cell line were extrapolated to the human population in occupational settings in two phases. This study showed when determining the permissible limits, the type used or unused, the type of injury, the organ affected in the body and the size of the particles should also be considered.

Machine operator's lung outbreak due to Eikenella corrodens

BACKGROUND

Outbreaks of hypersensitivity pneumonitis (HP) are not uncommon in workplaces where metalworking fluids (MWFs) are used. The recirculation of MWFs leads to microbiological contamination, which is responsible for outbreaks. Most outbreak reports come from USA and the UK; however, no similar reports have been published from Central Europe.

AIMS

To describe an outbreak of MWF-associated HP in workers from a compressor assembly manufacturing facility in Slovak Republic and to identify the potential antigens responsible for the outbreak.

METHODS

We investigated the history of worker's symptoms, physical examinations, lung function tests, radiographic scans and lung biopsies. The MWF samples were analysed for different strains of bacteria and fungi. Antigen extracts were produced from the microorganisms isolated from MWFs, and positive precipitin reactions were evaluated.

RESULTS

MWF-associated HP was diagnosed in 21 men and 6 women. All workers had work-related dyspnoea and cough with abnormal pulmonary diffusing capacity. Twenty-four cases had evidence of interstitial lung disease. Four cases were classified as having fibrotic HP. Nineteen microbial isolates (12 bacteria and 7 fungi) were cultured from the MWFs. Twenty-five cases had a positive response to at least one isolate. Eikenella corrodens and Bacillus subtilis were the most frequently reacting antigens (in 15 and 12 workers, respectively).

CONCLUSIONS

Despite decreasing reports of MWF-associated HP outbreaks over the past several decades, we describe one of the largest outbreaks in Europe. While the bacterium E. corrodens was found in the MWF samples, its relationship to the disease should be further investigated.

Analysis of a Vegetable Oil Performance in a Milling Process by MQL Lubrication

In this work, we carried out a comparison between the dry machining of an aluminum block with conventional cutting oil and a block with vegetable oil. The two oils had different flow rates. Using the Taguchi method, it was possible to determine the matrices for optimizing the best parameters for each group of tests. Then, we studied the utility of using vegetable oil as a cutting lubricant. We found that the vegetable oil studied in this work had good properties in terms of reducing cutting temperatures but was less effective than conventional cutting oil in reducing the surface roughness of the machined part. Tribological tests were carried out to understand the influence of the selected lubricants in reducing friction and wear. After the sliding experiments, which were performed without lubrication in the presence of the same lubricants that were used in the machining tests and in the presence of distilled water, we concluded that vegetable oil has satisfactory lubricating properties that are similar to those of the conventional cutting fluid, indicating a potential for consideration as an effective alternative to the conventional cutting fluid, with economic, environmental, and health advantages.

Release of Interleukin-1β evaluation among mineral oil mist–exposed workers

Exposure to aerosols has been found to be linked to respiratory impairment. Although the effects of both indoor and outdoor exposures to particulates have been extensively reported, exposures to mists are less studied. Herein, we reported a survey of mineral oil mist toxicity in an occupational exposure scenario. For the purpose of this study, 65 lathe workers of the metal processing industry, as mineral oil mist–exposed population, were studied. Thereafter, the participants’ age, smoking habits and work experience were matched with those of the control workers ( n = 65) who were not occupationally exposed to mist. Thereafter, air samples were evaluated from the breathing zone of the workers using NIOSH method 5026. Plasma Interleukin-1β as a pro-inflammatory indicator was assessed in all the studied subjects. Mean ± standard deviation of mineral oil mist time-weighted average exposure in lathe workers was 7.10± 3.49 mg/m3. IL-1β cytokine levels were significantly higher in the lathe groups compared to the control group. The mean level of Interleukin-1β in the control subjects (2922 pg/L) was selected as the cut-off point of the inflammation effect. Based on this pro-inflammatory point, the results of monitoring showed that 60% of the exposed were affected. A Spearman correlation was also found between mineral oil mist exposure and inflammation in the affected subjects. Our findings highlighted the immunological potential of mineral oil mist in occupational exposure. Overall, the results of this study suggested that Interleukin-1β evaluation in mineral oil mist exposure could be considered as both an acute and chronic inflammation marker.

Accelerated apoptosis, oxidative stress, and cholinergic inflammation in blood of metalworkers

Metalworkers are exposed to numerous chemicals in their workplace environment, such as solvents, heavy metals, and metalworking fluids, that have a negative impact on their health. Furthermore, there is an increase in the prevalence of chronic diseases among metalworkers; however, the molecular mechanisms involved in this increased predisposition to chronic diseases are unclear. Considering that occupational exposure represents a potential risk for metalworkers, the aim of this study was to measure biomarkers of oxidative stress, inflammation, and cytotoxicity in the peripheral blood of metalworkers from Southern Brazil. The study included 40 metalworkers and 20 individuals who did not perform activities with any recognized exposure to chemical substances, such as those working in administration, commerce, and education, as controls. Cellular and molecular biomarkers as leukocyte viability, intracellular production of reactive species, mitochondrial mass and membrane potential and plasma lipid peroxidation, sulfhydryl groups, total antioxidant capacity, and butyrylcholinesterase activity were evaluated in the blood of metalworkers and controls. Metalworkers were found to have higher rates of apoptosis, increased production of reactive species, and increased mitochondrial potential and mass in leukocytes associated with decreased antioxidant defenses and increased activity of the butyrylcholinesterase enzyme in their plasma. It can be concluded that cytotoxicity, oxidative stress, and inflammation are involved in the multiplicity of health outcomes related to chemical exposure in the metalworking industry.

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 (OP^FOX). Considering the particulate fraction, the water-based MWF presented the greatest OP^FOX. 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 OP^FOX. The OP^FOX measurement is thus integrative of multiple parameters, and bring complementary information when assessing MWF exposures. Our results highlight that OP^FOX account for MWF type and could be an interesting parameter to characterize such exposure.

Occupational respiratory and skin diseases among workers exposed to metalworking fluids

PURPOSE OF REVIEW

To examine respiratory and skin diseases that occur among workers exposed to metalworking fluids (MWFs) used during machining processes.

RECENT FINDINGS

Five cases of a severe and previously unrecognized lung disease characterized by B-cell bronchiolitis and alveolar ductitis with emphysema (BADE) were identified among workers at a machining facility that used MWFs, although MWF exposure could not be confirmed as the etiology. In the United Kingdom, MWF is now the predominant cause of occupational hypersensitivity pneumonitis (HP). Under continuous conditions associated with respiratory disease outbreaks, over a working lifetime of 45 years, workers exposed to MWF at 0.1 mg/m3 are estimated to have a 45.3% risk of acquiring HP or occupational asthma under outbreak conditions and a 3.0% risk assuming outbreak conditions exist in 5% of MWF environments. In addition to respiratory outcomes, skin diseases such as allergic and irritant contact dermatitis persist as frequent causes of occupational disease following MWF exposure.

SUMMARY

Healthcare providers need to consider MWF exposure as a potential cause for work-related respiratory and skin diseases. Additional work is necessary to more definitively characterize any potential association between MWF exposures and BADE. Medical surveillance should be implemented for workers regularly exposed to MWF.