Modelling of exposure to respirable and inhalable welding fumes at German workplaces

Biomonitoring of exposure to multiple metal components in urine, hair and nails of apprentice welders performing shielded metal arc welding (SMAW)

Welding fumes are associated with various diseases. Increased air levels of metals were reported during welding. However, few multielement biomonitoring studies were conducted to assess the actual dose of metal components absorbed in apprentice welders in a learning environment. This research aimed to establish the nature and level of exposure to welding fumes and their metallic components in apprentice welders performing 'Shielded Metal Arc Welding' (SMAW), based on multi-element and multi-matrix analyses. A total of 86 apprentice welders were recruited in three different schools in Montreal, Québec, Canada. Twenty-one elements were measured in urine, hair, fingernail, and toenail samples collected at the beginning of the program and at the end of SMAW practical training. Concentrations of welding fumes and 12 metals were also determined in personal respirable air samples collected over a typical workday in a subgroup of 19 apprentices. Levels of manganese (Mn), iron (Fe) and nickel (Ni) in urine and Mn in hair were higher in samples taken at the end of the SMAW module compared to the beginning of training, while there was no significant difference for the other elements or for nail concentrations. Geometric mean concentrations [5th-95th percentiles] reached 0.31 [0.032-2.84], 9.4 [3.1-51] and 0.87 [0.35-3.1] μg/g creat. in post-shift urine, respectively, for Mn, Fe and Ni, and 0.37 [0.46-6.4] μg Mn/g hair at the end of SWAW. Median concentrations [5th-95th percentiles] were 29 [4.6-1200], 120 [27-3100] and 0.31 [ Collapse

Key Words

• Biomonitoring
• Metalloids
• Metals
• Occupational exposure
• Shielded metal arc welding
• Welding fume exposure

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MESH Headings

• Humans
• Nails/chemistry
• Air Pollutants, Occupational/analysis
• Biological Monitoring
• Welding
• Metal Workers
• Metals/analysis
• Occupational Exposure/analysis
• Manganese/analysis
• Nickel
• Gases

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Affiliation(s)

Jairo Buitrago Cortes Department of Environmental and Occupational Health, Chair in Toxicological Risk Assessment and Management, and Public Health Research Center (CReSP), University of Montreal, Roger-Gaudry Building, U436, P.O. Box 6128, Main Station, Montreal, Quebec, H3C 3J7, Canada
Philippe Sarazin Chemical and Biological Hazards Prevention, Institut de recherche Robert-Sauvé en santé et en sécurité du travail, 505 Boulevard de Maisonneuve O, Montréal, Québec, H3A 3C2, Canada
Denis Dieme Department of Environmental and Occupational Health, Chair in Toxicological Risk Assessment and Management, and Public Health Research Center (CReSP), University of Montreal, Roger-Gaudry Building, U436, P.O. Box 6128, Main Station, Montreal, Quebec, H3C 3J7, Canada
Jonathan Côté Department of Environmental and Occupational Health, Chair in Toxicological Risk Assessment and Management, and Public Health Research Center (CReSP), University of Montreal, Roger-Gaudry Building, U436, P.O. Box 6128, Main Station, Montreal, Quebec, H3C 3J7, Canada
Capucine Ouellet Chemical and Biological Hazards Prevention, Institut de recherche Robert-Sauvé en santé et en sécurité du travail, 505 Boulevard de Maisonneuve O, Montréal, Québec, H3A 3C2, Canada
Naïma El Majidi Department of Environmental and Occupational Health, Chair in Toxicological Risk Assessment and Management, and Public Health Research Center (CReSP), University of Montreal, Roger-Gaudry Building, U436, P.O. Box 6128, Main Station, Montreal, Quebec, H3C 3J7, Canada
Michèle Bouchard Department of Environmental and Occupational Health, Chair in Toxicological Risk Assessment and Management, and Public Health Research Center (CReSP), University of Montreal, Roger-Gaudry Building, U436, P.O. Box 6128, Main Station, Montreal, Quebec, H3C 3J7, Canada.

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Prerequisite for Imputing Non-detects among Airborne Samples in OSHA's IMIS Databank: Prediction of Sample's Volume

INTRODUCTION

The US Integrated Management Information System (IMIS) contains workplace measurements collected by Occupational Safety and Health Administration (OSHA) inspectors. Its use for research is limited by the lack of record of a value for the limit of detection (LOD) associated with non-detected measurements, which should be used to set censoring point in statistical analysis. We aimed to remedy this by developing a predictive model of the volume of air sampled (V) for the non-detected results of airborne measurements, to then estimate the LOD using the instrument detection limit (IDL), as IDL/V.

METHODS

We obtained the Chemical Exposure Health Data from OSHA's central laboratory in Salt Lake City that partially overlaps IMIS and contains information on V. We used classification and regression trees (CART) to develop a predictive model of V for all measurements where the two datasets overlapped. The analysis was restricted to 69 chemical agents with at least 100 non-detected measurements, and calculated sampling air flow rates consistent with workplace measurement practices; undefined types of inspections were excluded, leaving 412,201/413,515 records. CART models were fitted on randomly selected 70% of the data using 10-fold cross-validation and validated on the remaining data. A separate CART model was fitted to styrene data.

RESULTS

Sampled air volume had a right-skewed distribution with a mean of 357 l, a median (M) of 318, and ranged from 0.040 to 1868 l. There were 173,131 measurements described as non-detects (42% of the data). For the non-detects, the V tended to be greater (M = 378 l) than measurements characterized as either 'short-term' (M = 218 l) or 'long-term' (M = 297 l). The CART models were complex and not easy to interpret, but substance, industry, and year were among the top three most important classifiers. They predicted V well overall (Pearson correlation (r) = 0.73, P < 0.0001; Lin's concordance correlation (rc) = 0.69) and among records captured as non-detects in IMIS (r = 0.66, P < 0.0001l; rc = 0.60). For styrene, CART built on measurements for all agents predicted V among 569 non-detects poorly (r = 0.15; rc = 0.04), but styrene-specific CART predicted it well (r = 0.87, P < 0.0001; rc = 0.86).

DISCUSSION

Among the limitations of our work is the fact that samples may have been collected on different workers and processes within each inspection, each with its own V. Furthermore, we lack measurement-level predictors because classifiers were captured at the inspection level. We did not study all substances that may be of interest and did not use the information that substances measured on the same sampling media should have the same V. We must note that CART models tend to over-fit data and their predictions depend on the selected data, as illustrated by contrasting predictions created using all data vs. limited to styrene.

CONCLUSIONS

We developed predictive models of sampled air volume that should enable the calculation of LOD for non-detects in IMIS. Our predictions may guide future work on handling non-detects in IMIS, although it is advisable to develop separate predictive models for each substance, industry, and year of interest, while also considering other factors, such as whether the measurement evaluated long-term or short-term exposure.

Assessment of welding fume impacts in a confined workplace by two extraction patterns - a case study of small-scale manufacturing industries

Welding fume exposure at work is recognized as a known concern for public health. This study aims to assess the welding fumes produced during welding using two different extraction patterns and to compare their influences. A thorough assessment of domestic arc welders in the erode district of India was done to assess their exposure to welding gases. The survey results chose the gas metal arc welding (GMAW) process for future investigation. The stainless-steel grade SS 316 L was used in this study. To weld 3-mm, 5-mm, and 6-mm-thick stainless-steel specimens, ER316 L filler wire and four shielding gas compositions were used. Two distinct, cost-effective welding hoods with a square duct section and a conical duct section were constructed to examine welding gases. The produced fume was collected on a 240 mm glass fibre filter and re-weighted during welding. Gas flow rates of 5, 10, and 15 LPM were investigated, with current intensities of 150A, 200A, and 275A. A novel attempt has been made to compare fume formation rates (FFR) obtained using two extraction patterns. According to this investigation, weld fume hoods with conical duct sections extract more welding gases than square duct sections. The extraction rate using two extraction patterns was compared. Furthermore, the addition of CO₂ to any shielding gas mixture results in a higher fume formation rate. The experimental FFR values were quite close to the American Welding Society (AWS) specifications. This finding also revealed that welders' socio-demographic characteristics, such as age, marital status, level of education, and work experience, influenced their awareness of occupational hazards and personal protection equipment (PPEs). As a result, there should be a strong emphasis on hazard identification education and strict enforcement of proper PPEs use among small-scale welders in and around the erode district to protect welders from a variety of hazards.

Lifetime Exposure to Welding Fumes and Risk of Some Rare Cancers

We investigated the association between exposure to welding fumes and the risk of biliary tract, male breast, bone, and thymus cancer, as well as cancer of the small intestine, eye melanoma, and mycosis fungoides, among men in a European, multicenter case-control study. From 1995-1997, 644 cases and 1,959 control subjects from 7 countries were studied with respect to information on welding and potential confounders. We linked the welding histories of the participants with a measurement-based exposure matrix to calculate lifetime exposure to welding fumes. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression models, conditional on country and 5-year age groups, and adjusted for education and relevant confounders. Regular welding was associated with an increased risk of cancer of the small intestine (OR = 2.30, 95% CI: 1.17, 4.50). Lifetime exposure to welding fumes above the median of exposed controls was associated with an increased risk of cancer of the small intestine (OR = 2.00, 95% CI: 1.07, 3.72) and male breast (OR = 2.07, 95% CI: 1.14, 3.77), and some elevation in risk was apparent for bone cancer (OR = 1.92, 95% CI: 0.85, 4.34) with increasing lifetime exposure to welding fumes. Welding fumes could contribute to an increased risk of some rare cancers.

Investigating the field effectiveness of respirators against metal particle exposure in various workplaces: a systematic review

Welders are exposed to high levels of metal fumes, which could be resulting in various health impairments. Respirators became a practical protective option in workplaces, as they are lightweight and easy to use. This systematic review attempts to explore the field effectiveness of using respirators to reduce metal particle exposure in workplaces. We reviewed papers published from 1900 to April 2019 in five major bibliographic databases, including Embase, Web of Science, Medline, Scopus, and CINAHL, along with organizational websites to cover gray literature. In total, 983 references were identified from the databases, out of which, 520 duplicates were removed from the EndNote database. The remaining 463 references were screened for their title and abstract. Out of 463, 70 references went through the full-text screening. Finally, eight papers, including 19 workplace respirator studies, satisfied all the inclusion criteria and were reviewed in this report. The geometric means for metal levels in workers' breathing zone with and without respirators were 9.4 and 1,777 µg/m³ for iron, 1.1 and 139 µg/m³ for lead, 2.1 and 242 µg/m³ for zinc, and 27 and 1,398 µg/m³ for manganese oxide, respectively. Most reviewed studies reported significant differences between measured metal particle levels among workers who worn respirators and who did not. In addition, results showed that N95 provided significantly less protection than elastomeric half facepieces, full-face respirators, and powered air-purifying respirators (p<0.001). More field studies are recommended to investigate Workplace Protection Factor (WPF) and fit factor (FF) of different respirators to understand the actual protection levels that they could be provided to control welding fume exposure among welders in various workplaces.

Assessment of the Oxidative Potential and Oxidative Burden from Occupational Exposures to Particulate Matter

Oxidative potential (OP) is a toxicologically relevant metric that integrates features like mass concentration and chemical composition of particulate matter (PM). Although it has been extensively explored as a metric for the characterization of environmental particles, this is still an underexplored application in the occupational field. This study aimed to estimate the OP of particles in two occupational settings from a construction trades school. This characterization also includes the comparison between activities, sampling strategies, and size fractions. Particulate mass concentrations (PM4-Personal, PM4-Area, and PM2.5-Area) and number concentrations were measured during three weeks of welding and construction/bricklaying activities. The OP was assessed by the ascorbate assay (OPAA) using a synthetic respiratory tract lining fluid (RTLF), while the oxidative burden (OBAA) was determined by multiplying the OPAA values with PM concentrations. Median (25th-75th percentiles) of PM mass and number concentrations were 900 (672-1730) µg m-3 and 128 000 (78 000-169 000) particles cm-3 for welding, and 432 (345-530) µg m-3 and 2800 (1700-4400) particles cm-3 for construction. Welding particles, especially from the first week of activities, were also associated with higher redox activity (OPAA: 3.3 (2.3-4.6) ρmol min-1 µg-1; OBAA: 1750 (893-4560) ρmol min-1 m-3) compared to the construction site (OPAA: 1.4 (1.0-1.8) ρmol min-1 µg-1; OBAA: 486 (341-695) ρmol min-1 m-3). The OPAA was independent of the sampling strategy or size fraction. However, driven by the higher PM concentrations, the OBAA from personal samples was higher compared to area samples in the welding shop, suggesting an influence of the sampling strategy on PM concentrations and OBAA. These results demonstrate that important levels of OPAA can be found in occupational settings, especially during welding activities. Furthermore, the OBAA found in both workplaces largely exceeded the levels found in environmental studies. Therefore, measures of OP and OB could be further explored as metrics for exposure assessment to occupational PM, as well as for associations with cardiorespiratory outcomes in future occupational epidemiological studies.

How to Reduce the Exposure of Welders to an Acceptable Level: Results of the InterWeld Study

OBJECTIVES

Workplace measurements in the past have shown that the applicable occupational exposure limits (OELs) are regularly exceeded in practice when high-emission welding processes are applied. The InterWeld pilot study was planned as part of an intervention study to show under which conditions compliance with the OEL is achievable in gas metal arc welding (GMAW) with solid wire. The investigation focussed on local exhaust ventilation, i.e. captor hoods and welding torches with integrated fume extraction.

METHODS

Forty tests with hand-guided GMAW were configured by experts with regard to all technical parameters and carried out by a professional welder. Effects of protective measures and process parameters on the exposure to respirable welding fumes and airborne manganese (Mn), chromium, nickel, and hexavalent chromium were investigated. Personal sampling was carried out in the welder's breathing zone outside the face shield at high flow rates (10 l min-1) in order to achieve sufficient filter loading. Particle masses and welding fume concentrations were determined by weighing the sampling filters. Metal concentrations were analysed by inductive coupled plasma mass spectrometry. In order to evaluate the effects on exposure, the measurements were performed under similar conditions. The data were analysed descriptively and with mixed linear models. For measurements below the limit of detection, the exposure level was estimated using multiple imputation.

RESULTS

Two to five times higher exposures to respirable welding fumes and airborne metals were observed during welding of 10 mm sheets than during welding of 2- or 3-mm sheets. Welding fume and Mn exposure were reduced by 70 and 90% when on-torch extraction or a captor hood was applied. Other airborne metals were reduced to a similar extent. Modifications on welding parameters led to a reduction of exposure against respirable particles by 51 up to 54%.

CONCLUSIONS

Although proper extraction at the point of origin and lower-emitting process variants ensure a drastic reduction in exposure, compliance with current OELs is not guaranteed. In order to ensure adequate health protection, especially at workplaces where thick sheets with long relative arc times are processed, there is a need for technical development.

Construction and Calibration of an Exposure Matrix for the Welding Trades

OBJECTIVES

This study aimed to construct, validate, and calibrate an exposure matrix that would be used to estimate personal airborne exposures to total dust, manganese, nickel, chromium, and aluminum for welders in the WHAT-ME cohort. The Workers' Health in Apprenticeship Trades: metal and electrical (WHAT-ME) study established a cohort of women and men welders to investigate pregnancy and other birth outcomes along with health issues related to welding. To construct the matrix, data were extracted and assembled from the literature and analyzed to produce exposure models. Final models derived in this first step were then compared with external data gathered under controlled conditions and later combined to form calibrated models.

METHODS

A systematic literature search was conducted to identify and extract all relevant data from published journal articles appearing in selected databases. Summary data were extracted that represented airborne personal exposures to total, inhalable and respirable dusts along with metal concentrations for manganese, nickel, chromium, and aluminum. Mathematical exposure models were derived and a validation of the models undertaken in the second part of this study. The most common welding combinations of welding process, base metal, and consumable (welding scenarios) for welders taking part in the WHAT-ME study were identified through detailed welding questionnaires completed by WHAT-ME participants. These were replicated under controlled conditions with a welder equipped with a personal air sampling pump to gather samples. A gravimetric analysis was performed to determine total dust exposures followed by a metals analysis using ICP-MS. Predictions were made for these welding scenarios replicated in the laboratory, using the exposure models derived in the literature and the predictions correlated against the results from the welding laboratory replications.

RESULTS

The systematic review yielded 92 published articles from which 737 summary statistics were extracted representing 4620 personal samples of total dust, 4762 of manganese, 4679 of nickel, 3972 of chromium, and 676 of aluminum. The highest total dust exposures were for flux-core arc welding (FCAW) while the highest manganese producing base metal was mild steel. For nickel, the highest emissions were from high alloyed steel using gas metal arc welding while chromium emissions were most abundant in manual metal arc welding on stainless steel. Aluminum exposures were highest in FCAW welding and on aluminum as a base metal. The replication of 21 scenarios covered more than 90% of the scenarios in the WHAT-ME study. Sixty-one laboratory welding sessions took place with a minimum of two replications per scenario. Spearman rank correlations between predicted exposures and mean measured exposures yielded a rho of 0.93 (P < 0.001) for total dust, 0.87 (P < 0.001) for manganese, 0.54 (P < 0.024) for nickel, 0.43 (P = 0.055) for chromium, and 0.29 (P = 0.210) for aluminum.

CONCLUSIONS

This study produced the first welding exposure matrix composed of process, base metal, and consumable. This model was able to predict exposures observed under controlled conditions and could be used by any researcher to estimate welding exposures in a wide range of occupational contexts.

Direct Exposure of Welders to Welding Fumes and Effect of Fume Extraction Systems Under Controlled Conditions

INTRODUCTION

Welding fume exposure of welders occurs either directly from the welding process and sputters or from the fume background within the workshop. In this study the contribution of fume originating directly from the welding process was assessed.

METHODS

Exposure was quantified by measuring the time integral of fume mass concentration using a tapered element oscillating micro balance connected to a welder dummy.

RESULTS

Direct fume exposure was highest for welding processes with low fume emission rates and lowest for processes with high fume emission rates.

CONCLUSIONS

This finding is supposed to be due to the higher energy input of high emitting processes which stabilizes the thermic column and therefore eliminates fume particles from the welder's breathing zone. Exposure can be minimized by additionally optimizing workshop ventilation.

Microscopic Characteristics and Properties of Fe-Based Amorphous Alloy Compound Reinforced WC-Co-Based Coating via Plasma Spray Welding

Plasma spray welding, as one of the material surface strengthening techniques, has the advantages of low alloy material consumption, high mechanical properties and good coating compactness. Here, the Co alloy, WC and Fe-based amorphous alloy composite coating is prepared by the plasma spray welding method, and the coating characteristics are investigated. The results indicate that the coatings have a full metallurgical bond in the coating/substrate interface, and the powder composition influences the microstructures and properties of the coating. The hardness of coatings increases with the mass fraction of the Fe-based amorphous alloy. The spray welding layer has a much higher wear resistance compared with the carbon steel, and the Fe-20 exhibits a superior wear resistance when compared to others. The results indicate that the amorphous alloy powders are an effective additive to prepare the coating by plasma spray welding for improving the wear resistance of the coating.

Exposure to Welding Fumes, Hexavalent Chromium, or Nickel and Risk of Lung Cancer

To investigate the risk of lung cancer after exposure to welding fumes, hexavalent chromium (Cr(VI)), and nickel, we analyzed 3,418 lung cancer cases and 3,488 controls among men from 2 German case-control studies (1988-1996). We developed a welding-process exposure matrix from measurements of these agents, and this was linked with welding histories from a job-specific questionnaire to calculate cumulative exposure variables. Logistic regression models were fitted to estimate odds ratios with confidence intervals conditional on study, and they adjusted for age, smoking, and working in other at-risk occupations. Additionally, we mutually adjusted for the other exposure variables under study. Overall, 800 cases and 645 controls ever worked as regular or occasional welders. Odds ratios for lung cancer with high exposure were 1.55 (95% confidence interval (CI): 1.17, 2.05; median, 1.8 mg/m3 × years) for welding fumes, 1.85 (95% CI: 1.35, 2.54; median, 1.4 μg/m3 × years) for Cr(VI), and 1.60 (95% CI: 1.21, 2.12; median, 9 μg/m3 × years) for nickel. Risk estimates increased with increasing cumulative exposure to welding fumes and with increasing exposure duration for Cr(VI) and nickel. Our results showed that welding fumes, Cr(VI), and nickel might contribute independently to the excess lung cancer risk associated with welding. However, quantitative exposure assessment remains challenging.