Reduction in welding fume and metal exposure of stainless steel welders: an example from the WELDOX study

Purpose

In a plant where flux-cored arc welding was applied to stainless steel, we investigated changes in airborne and internal metal exposure following improvements of exhaust ventilation and respiratory protection.

Methods

Twelve welders were examined at a time in 2008 and in 2011 after improving health protection. Seven welders were enrolled in both surveys. Exposure measurement was performed by personal sampling of respirable welding fume inside the welding helmets during one work shift. Urine and blood samples were taken after the shift. Chromium (Cr), nickel (Ni), and manganese (Mn) were determined in air and biological samples.

Results

The geometric mean of respirable particles could be reduced from 4.1 mg/m³ in 2008–0.5 mg/m³ in 2011. Exposure to airborne metal compounds was also strongly reduced (Mn: 399 vs. 6.8 μg/m³; Cr: 187 vs. 6.3 μg/m³; Ni: 76 vs. 2.8 μg/m³), with the most striking reduction inside helmets with purified air supply. Area sampling revealed several concentrations above established or proposed exposure limits. Urinary metal concentrations were also reduced, but to a lesser extent (Cr: 14.8 vs. 4.5 μg/L; Ni: 7.9 vs. 3.1 μg/L). Although biologically regulated, the mean Mn concentration in blood declined from 12.8 to 8.9 μg/L.

Conclusion

This intervention study demonstrated a distinct reduction in the exposure of welders using improved exhaust ventilation and welding helmets with purified air supply in the daily routine. Data from area sampling and biomonitoring indicated that the area background level may add considerably to the internal exposure.     

Relation between various chromium compounds and some other elements in fumes from manual metal arc stainless steel welding.

For the years 1987-1990 160 individual samples of manual metal arc stainless steel (MMA/SS) welding fumes from the breathing zone of welders in four industrial plants were collected. Concentrations of soluble and insoluble chromium (Cr) III and Cr VI compounds as well as of some other welding fume elements (Fe, Mn, Ni, F) were determined. Concentration of welding fumes in the breathing zone ranged from 0.2 to 23.4 mg/m3. Total Cr amounted to 0.005-0.991 mg/m3 (including 0.005-0.842 mg/m3 Cr VI). Total Cr content of fumes varied from 0.1 to 7.4%. The distribution of particular Cr compounds was: 52.6% soluble Cr (including 50.7% Cr VI), 65.5% total Cr VI, and 11.4% insoluble Cr VI. The results obtained indicate that MMA/SS welding is a process that could be highly hazardous to human health. Evaluation of occupational exposure has shown that MMA/SS welders may exceed the admissible concentrations of soluble and insoluble Cr VI forms as well as of Mn and Ni. In the plants investigated the sum of the ratios of concentrations of particular welding fumes in the breathing zone of welders exceeded corresponding maximum allowable concentration values by 24 times (including 17 times for total Cr VI). Due to the variety and changeability of particular parameters occurring in the working environment, the composition of MMA/SS welding fumes (in the welder's breathing zone) is so variable that it is not possible to assess the exposure by means of one universal exposure indicator (maximum additive hygienic limit value). The evaluation should be based on the results of measurements of concentrations of particular elements in welding fumes.     

Heavy-Metal Levels in Feathers of Cattle Egret and Their Surrounding Environment: A Case of the Punjab Province, Pakistan

Levels of 10 heavy metals in cattle egret chick feathers, prey, and surrounding soils from three heronries in Punjab Province, Pakistan, were assessed by atomic absorption spectrophotometry. Mean levels of cadmium (Cd), iron (Fe), chromium (Cr), and lithium (Li) in feathers, manganese (Mn), cobalt (Co), and nickel (Ni) in prey, and lead (Pb), iron (Fe), chromium (Cr), zinc (Zn), cobalt (Co), and lithium (Li) in soils were significantly different among Trimun Headworks, Shorkot, and Mailsi heroneries. Mean levels of Pb (43.10 μg/g), Cr (35.77 μg/g), Co (18.34 μg/g), Cu (0.20 μg/g), and Ni (0.22 μg/g) in feathers were significantly greater at Mailsi, and Mn (3.07 μg/g), Zn (18.83 μg/g), and Li (1.5 μg/g) levels were significantly greater at Shorkot. Multivariate analysis identified that some metals, such as Fe, Zn, and Li, in feathers were either associated with natural sources or with human-related activities, whereas Ni, Cr, Pb, Cd, Cu, Co, and Mn were correlated mainly with anthropogenic processes. Alarming levels were recorded for Cr, Pb, and Cd in feathers that were above threshold levels that may affect cattle egret flighting capacity and reproduction, thus leading to their population decline in Punjab Province. The results of this study provide evidence for the potential of feathers of cattle egret to be used as a biomonitor for the local heavy-metal contamination.     

Control of exposure to hexavalent chromium concentration in shielded metal arc welding fumes by nano-coating of electrodes

Background: Cr(VI) is a suspected human carcinogen formed as a by-product of stainless steel welding. Nano-alumina and nano-titania coating of electrodes reduced the welding fume levels.

Objective: To investigate the effect of nano-coating of welding electrodes on Cr(VI) formation rate (Cr(VI) FR) from a shielded metal arc welding process.

Methods: The core welding wires were coated with nano-alumina and nano-titania using the sol-gel dip coating technique. Bead-on plate welds were deposited on SS 316 LN plates kept inside a fume test chamber. Cr(VI) analysis was done using an atomic absorption spectrometer (AAS).

Results: A reduction of 40% and 76%, respectively, in the Cr(VI) FR was observed from nano-alumina and nano-titania coated electrodes. Increase in the fume level decreased the Cr(VI) FR.

Discussion: Increase in fume levels blocked the UV radiation responsible for the formation of ozone thereby preventing the formation of Cr(VI).     

Evaluation of Trace Metals in Tea Samples from Jeddah and Jazan, Saudi Arabia by Atomic Absorption Spectrometry

The Cd, Pb, Mn, Zn, Ni, Co, Fe, Cr and Cu content were determined in various teas available in local markets of Jeddah and Jazan, Saudi Arabia. Concentrations of the trace metals were measured after acid digestion using a flame atomic absorption spectrometer. Validation of the digestion procedure was performed by the analysis of a certified reference material. The cadmium, lead, manganese, zinc, nickel, cobalt, iron, chromium and copper concentrations were found in the range of below the detection limit (BDL)—0.7 μg/g, BDL—8.7 μg/g, 48–859 μg/g, 6.6–120 μg/g, BDL—16.9 μg/g, BDL—3.1 μg/g, 46–348 μg/g, BDL—4.9 μg/g and 5.2–21.6 μg/g respectively. The values found in this study were compared with literature values.     

The Origin of Hexavalent Chromium as a Critical Parameter for Remediation of Contaminated Aquifers

Two different cases of Cr(VI) contaminated ophiolitic aquifers are presented herein. The first is located at Vergina (Northern Greece), where the maximum Cr(VI) concentration measured was 64 μg/L, being one of the highest geogenic concentrations recorded globally in areas with similar geological background. The second case is located at Inofyta (Central Greece), a makeshift industrial area, where the maximum detected Cr(VI) concentration exceeds 10,000 μg/L, indicating clearly anthropogenic activities as the main source. Although for the Vergina aquifer, area-wide institutional measures and in some cases pump and treat systems might be sufficient to ensure a safe water supply for domestic and agricultural use, this is not the case for the contaminated aquifer of Inofyta. There a comprehensive remediation scheme should be properly implemented adopting, however, realistic remediation targets, that should also take into account the geogenic contribution to the high Cr(VI) groundwater concentrations measured.     

Reduction of hexavalent chromium concentration in fumes from metal cored arc welding by addition of reactive metals

Previous work has demonstrated that both the mass and composition of fumes produced during metal arc welding can be influenced by changes in the welding wire composition, the flux or gas shielding used and by changes in the process parameters, including voltage, adopted. The present paper describes modifications directed at reducing the concentration of hexavalent chromium [Cr(VI)] in welding fume by the addition of active metals—zinc, magnesium and aluminium to metal cored arc welding wires containing 10% Cr. There were marked changes in both the Cr(VI) concentration in the fume and the fume formation rate and hence in the Cr(VI) formation rate over the range of voltages used (18–24 V). Fume from wires containing the addition of 1% zinc contained Cr(VI) concentrations in the fume below those in the control and in wires with 1% magnesium and wires with 1% aluminium additions. Also, at 18 V, the Cr(VI) formation rate was at a minimum compared to the other wires. This advantage was not sustained as the voltage was increased and above 21 V the Cr(VI) formation rate for all the three wires containing active metal additions was higher than the control. These results demonstrate that at 18 V a significant reduction of Cr(VI) in welding fume can be produced by the addition of 1% zinc to the welding wire.     

Exposure to respirable dust and manganese and prevalence of airways symptoms,among Swedish mild steel welders in the manufacturing industry

Purpose

Welding fume consists of metal fumes, e.g., manganese (Mn) and gases, e.g., ozone. Particles in the respirable dust (RD) size range dominate. Exposure to welding fume could cause short- and long-term respiratory effects. The prevalence of work-related symptoms among mild steel welders was studied, and the occupational exposure to welding fumes was quantified by repeated measurements of RD, respirable Mn, and ozone. Also the variance components were studied.

Method

A questionnaire concerning airway symptoms and occupational history was answered by 79 % of a cohort of 484 welders. A group of welders (N = 108) were selected and surveyed by personal exposure measurements of RD and ozone three times during 1 year.

Results

The welders had a high frequency of work-related symptoms, e.g., stuffy nose (33 %), ocular symptoms (28 %), and dry cough (24 %). The geometric mean exposure to RD and respirable Mn was 1.3 mg/m³ (min–max 0.1–38.3 mg/m³) and 0.08 mg/m³ (min–max <0.01–2.13 mg/m³), respectively. More than 50 % of the Mn concentrations exceeded the Swedish occupational exposure limit (OEL). Mainly, low concentrations of ozone were measured, but 2 % of the samples exceeded the OEL. Of the total variance for RD, 30 and 33 % can be attributed to within-worker variability and between-company variability, respectively.

Conclusions

Welders had a high prevalence of work-related symptom from the airways and eyes. The welders’ exposure to Mn was unacceptably high. To reduce the exposure further, control measures in the welding workshops are needed. Correct use of general mechanical ventilation and local exhaust ventilation can, for example, efficiently reduce the exposure.     

Airborne exposure to inhalable hexavalent chromium in welders and other occupations: Estimates from the German MEGA database

This study aimed to estimate occupational exposure to inhalable hexavalent chromium (Cr(VI)) using the exposure database MEGA. The database has been compiling Cr(VI) concentrations and ancillary data about measurements at German workplaces. We analysed 3659 personal measurements of inhalable Cr(VI) collected between 1994 and 2009. Cr(VI) was determined spectrophotometrically at 540 nm after reaction with diphenylcarbazide. We assigned the measurements to pre-defined at-risk occupations using the information provided about the workplaces. Two-thirds of the measurements were below the limit of quantification (LOQ) and multiply imputed according to the distribution above LOQ. The 75th percentile value was 5.2 μg/m³ and the 95th percentile was 57.2 μg/m³. We predicted the geometric mean for 2 h sampling in the year 2000, and the time trend of Cr(VI) exposure in these settings with and without adjustment for the duration of measurements. The largest dataset was available for welding (N = 1898), which could be further detailed according to technique. The geometric means were above 5 μg/m³ in the following situations: spray painting, shielded metal arc welding, and flux-cored arc welding if applied to stainless steel. The geometric means were between 1 μg/m³ and 5 μg/m³ for gas metal arc welding of stainless steel, cutting, hard-chromium plating, metal spraying and in the chemical chromium industry. The exposure profiles described here are useful for epidemiologic and industrial health purposes. Exposure to Cr(VI) varies not only between occupations, but also within occupations as shown for welders. In epidemiologic studies, it would be desirable to collect exposure-specific information in addition to the job title.     

Speciation of hexavalent chromium in welding fumes interference by air oxidation of chromium

The determination of various chromium species in welding fume normally involves digestion in a hot alkaline solution. This work confirms that Cr(III) can be oxidized to Cr(VI) during this digestion. However, only dissolved forms of Cr(III), such as the hydroxochromate(III) ion, [Cr(OH)4], are susceptible to oxidation under these conditions. The air oxidation of Cr(III) can be prevented by hydrolytic destabilization of the hydroxochromate(III) complex by the presence of magnesium hydroxide precipitate. The procedure has been used successfully in the determination of insoluble chromium(VI) in welding fumes. Excellent reproducibility is documented for soluble and insoluble chromium(VI) fractions in the analysis of a bulk sample of welding fume.     

Control of occupational exposure to hexavalent chromium and ozone in tubular wire arc-welding processes by replacement of potassium by lithium or by addition of zinc

Hexavalent chromium [Cr(VI)] and ozone are produced in many arc-welding processes. Cr(VI) is formed when welding with chromium-containing alloys and is a suspected carcinogen. Ozone is formed by the action of ultraviolet light from the arc on oxygen and can cause severe irritation to the eyes and mucous membranes. Previous work has demonstrated that reduction of sodium and potassium in manual metal arc-welding electrodes leads to substantial reductions in Cr(VI) concentrations in the fume as well as a reduction in the fume formation rate. In this paper replacement of potassium by lithium in a tubular wire welding electrode (self-shielding flux-cored) is shown to give reductions in Cr(VI) concentrations and fume formation rates. Previous work has also demonstrated that use of a tubular wire (metal cored) containing 1% zinc can, under certain conditions, result in a reduction in Cr(VI) formation rate and in ozone concentration near the arc but with a rise in the total fume formation rate. The effects of different shield gases and different levels of zinc are examined. An experimental chromium-containing tubular wire with 1% zinc was used with the following shield gases: argon, Argoshield 5, Argoshield 20, Helishield 101, Ar + 2% CO2, Ar + 5% CO2, Ar + 1% O2 and Ar + 2% O2. The wire gave > 98% reduction in Cr(VI) formation rate compared to the control wire provided the shield gas contained no oxygen. When the shield gas did contain oxygen, 1% zinc enhanced Cr(VI) formation rate, resulting in more than double the rates measured when welding with the control wire. Experiments with zinc concentrations, from 0.018 to 0.9% using Helishield 101, gave results indicating that there is an optimum zinc concentration from the point of view of Cr(VI) reduction. Implications of the use of lithium or zinc on the overall exposure risk are discussed.     

Assessing Arsenic Exposure from Consumption of Seafood from Vieques-Puerto Rico: A Pilot Biomonitoring Study Using Different Biomarkers

The various toxic effects associated with inorganic arsenic (iAs) warrants that exposure sources be identified. This pilot study evaluated if greater seafood consumption from Vieques-Puerto Rico is associated with increased exposure to iAs. Nail, hair, and urine samples were used as biomarkers of iAs exposure in adult women and men from Vieques classified as high (n = 31) and low (n = 21) seafood consumers, who reported eating fish and/or shellfish ≥1 time per week and once per month or less, respectively. The sum of urinary iAs (As III + As V), monomethylarsonic acid (MA[V]), and dimethylarsinic acid (DMA[V]), denoted as SumAs, fluctuated from 3.3 µg/g Cr (1.2 μg/L) to 42.7 μg/g Cr (42 μg/L) (n = 52). Levels of As in nail samples (n = 49) varied from 0.04 to 0.82 μg/g dry weight (dw), whereas in hair (n = 49) As was only detected in 49 % of the samples with a maximum value of 0.95 μg/g dw. None of the biomarkers of exposure to As exceeded exposure reference values for urine (50 μg/g Cr or 50 μg/L), nails (1 μg/g), or hair (1 μg/g). However, median (10.0 μg/g Cr; 10.6 μg/L) and 95th percentile (31.9 μg/g Cr; 40.4 μg/L) of urinary SumAs were higher in Vieques samples than in the those from the general population of other countries. Among the three biomarkers of exposure, nail samples reflected better the exposure to iAs from seafood consumption with significantly higher average As concentrations in high (0.24 μg/g) than low (0.12 μg/g) seafood consumers. Multivariate results for As in nail samples (R ² = 0.55, p < 0.0001) showed a positive association with fish consumption, particularly for men, with levels increasing with years of residency in Vieques.     

Nonwoven textile for use in a nanoparticle respiratory deposition sampler

The nanoparticle respiratory deposition (NRD) sampler is a personal sampler that combines a cyclone, impactor, and a nylon mesh diffusion stage to measure a worker's exposure to nanoparticles. The concentration of titanium in the nylon mesh of the diffusion stage complicates the application of the NRD sampler for assessing exposures to titanium dioxide nanoparticles. This study evaluated commercially available nonwoven textiles for use as an alternative media in the diffusion stage of the NRD sampler. Three textiles were selected as containing little titanium from an initial screening of 11 textiles by field portable x-ray fluorescence (FPXRF). Further evaluation on these three textiles was conducted to determine the concentration of titanium and other metals by inductively coupled plasma–optical emission spectroscopy (ICP-OES), the number of layers required to achieve desired collection characteristics for use as the diffusion stage in the NRD sampler (i.e., the nanoparticulate matter, NPM, criterion), and the pressure drop associated with that number of layers.

?Only three (two composed of cotton fibers, C1 and C2; and one of viscose bamboo and cotton fibers, BC) of 11 textiles screened had titanium concentrations below the limit of detection the XRF device (0.15 µg/cm²). Multiple metals, including small amounts of titanium, were found in each of the three nonwoven textiles using ICP-OES. The number of 25-mm-diameter layers required to achieve the collection efficiency by size required for the NRD sampler was three for C1 (R² = 0.95 with reference to the NPM criterion), two for C2 (R² = 0.79), and three for BC (R² = 0.87). All measured pressure drops were less than theoretical and even the greatest pressure drop of 65.4 Pa indicated that a typical personal sampling pump could accommodate any of the three nonwoven textiles in the NRD sampler. The titanium concentration, collection efficiency, and measured pressure drops show there is a potential for nonwoven textiles to be used as the diffusion stage of the NRD sampler.     

Seasonal Variations in Toxic Metal Levels of Two Fish Species,Mugil cephalus and Mullus barbatus and Estimation of Risk for Children

Concentrations of five toxic metals were determined in two fish species namely, Mugil cephalus and Mullus barbatus consumed in two neighboring Turkish cities during 2010–2011. Lead concentrations (mean 900 μg kg^?1) for M. cephalus were found to be higher than the maximum allowances concentration (MAC) of 300 μg kg^?1. Similarly, Cr (mean 410 μg kg^?1), Ni (mean 331 μg kg^?1) and Cu (mean 834 μg kg^?1) concentrations in M. cephalus were significantly higher than in M. barbatus (mean 341 μg Cr kg^?1, 256 μg Ni kg^?1 and 568 μg Cu kg^?1). Although concentrations of some metals exceed the limits set by the authorities, the estimated non-carcinogenic and carcinogenic health risks by the Target Hazard Quotient and target carcinogenic risk indicate that there is no carcinogenic risk for humans, and the risk of developing cancer over a human lifetime is between 2 and 12 in 1,000,000.     

Systematic review and quantification of respiratory cancer risk for occupational exposure to hexavalent chromium

Aim

To investigate the exposure-risk relationship for occupational chromium (VI) exposure and lung cancer in order to establish exposure limits.

Methods

We systematically searched for studies reporting on occupational Cr(VI) exposure and cancers of the respiratory tract. To be included, studies needed to provide data for more than one level of occupational Cr(VI) exposure, adequately consider the confounder smoking and be of adequate methodological quality. Because direct genotoxicity was considered the predominant mechanism of carcinogenesis of Cr(VI), linear models were applied in order to fit risk data. Relative risks were calculated based on these linear regression models and then used to estimate excess absolute risks.

Results

Five studies of two cohorts of chromium production workers in Baltimore, Maryland, and Painesville, Ohio, were included. Based on different estimates for the exposure effect, the absolute excess risk was found to be “acceptable” (less than 4 per 10,000 according to the German Committee on Hazardous Substances, “AGS”) at a Cr(VI) concentration of 0.1 μg/m³, and became “intolerable” (more than 4 per 1,000) beyond a Cr(VI) concentration of 1 μg/m³.

Conclusion

Occupational exposure limits for Cr(VI) based on excess absolute risks can be derived from published data identified by a systematic literature review.     

Profiling stainless steel welding processes to reduce fume emissions,hexavalent chromium emissions and operating costs in the workplace

Nine gas metal arc welding (GMAW) processes for stainless steel were assessed for fume generation rates, fume generation rates per g of electrode consumed, and emission rates for hexavalent chromium (Cr⁶⁺). Elemental manganese, nickel, chromium, iron emissions per unit length of weld, and labor plus consumables costs were similarly measured. Flux-cored arc welding and shielded metal arc (SMAW) processes were also studied. The objective was to identify the best welding processes for reducing workplace exposures, and estimate costs for all processes. Using a conical chamber, fumes were collected, weighed, recovered, and analyzed by inductively coupled atomic emission spectroscopy for metals, and by ion chromatography for Cr⁶⁺. GMAW processes used were Surface Tension Transfer, Regulated Metal Deposition, Cold Metal Transfer, short-circuit, axial spray, and pulsed spray modes. Flux-cored welding used gas shielding; SMAW used E308 rods. Costs were estimated as dollars per m length of a ¼ in (6.3 mm) thick horizontal butt weld; equipment costs were estimated as ratios of new equipment costs to a 250 ampere capacity SMAW welding machine. Results indicate a broad range of fume emission factors for the processes studied. Fume emission rates per g of electrode were lowest for GMAW processes such as pulsed-spray mode (0.2 mg/g), and highest for SMAW (8 mg fume/g electrode). Emission rates of Cr⁶⁺ ranged from 50–7800 µg/min, and Cr⁶⁺ generation rates per g electrode ranged from 1–270 µg/g. Elemental Cr generation rates spanned 13–330 µg/g. Manganese emission rates ranged from 50–300 µg/g. Nickel emission rates ranged from 4–140 µg/g.

Labor and consumables costs ranged from $3.15 (GMAW pulsed spray) to $7.40 (SMAW) per meter of finished weld, and were measured or estimated for all 11 processes tested. Equipment costs for some processes may be as much as five times the cost of a typical SMAW welding machine.

The results show that all of the GMAW processes in this study can substantially reduce fume, Cr⁶⁺, manganese and costs relative to SMAW, the most commonly used welding process, and several have exceptional capabilities for reducing emissions.     

Chromium Removal with Environmentally Friendly Iron Nanoparticles in a Pilot Scale Study

Nano zero valent iron (nZVI) is highly reactive, targets a wide range of contaminants and is considered as a promising material for the in situ remediation of contaminated aquifers. Injection of nZVI suspension is a remedial option for the in-situ reduction and immobilization of pollutants in aquifers. The goal of the present study was to evaluate the efficiency of iron nanoparticles (GT-nZVI), synthesised by a green synthesis route, for Cr(VI) removal in a pilot scale application. A tank with dimensions 2.5 m (width)?×?3.75 m (length)?×?1.5 m (height) was constructed and filled with 24 tons of soil. Firstly 3 m³ GT-nZVI suspension was injected and then the supply of contaminated water containing 5 mg/L Cr(VI) was initiated. Samples were analysed for pH, redox potential and electric conductivity, as well as Fe_tot and Cr(VI). The reactive zone operated efficiently for the treatment of contaminated water for 1 year.     

Respiratory deposition and health risk of inhalation of particle-bound heavy metals in the carbon black feeding area of a tire manufacturer

The health effects of metal-containing carbon black (CB) particles obtained from the CB feeding area of a tire manufacturing plant were investigated. Atmospheric samples were collected over 24 h for 20 working days in 2016 using the 12 impaction stages of micro-orifice uniform deposit impactor, and metal-containing particles were analyzed using an inductively coupled plasma optical emission spectrometer. The concentration of total particulate matter in the CB feeding area was 944.8 ± 456.4 μg/m³, and the most abundant elements in the samples include Zn (8622.0 ± 5679.0 ng/m³), Al (3113.3 ± 2017.1 ng/m³), and Fe (1519.1 ± 875.0 ng/m³). Carcinogenic metals (Cd, Co, Cr, and Ni) with the mass median diameter were incorporated in submicron particles. The mean total deposition flux in the head airway (HA) region was approximately 16–30 times higher than that in the tracheobronchial (TB) region and alveolar region (AR). The most abundant deposition flux of heavy metals in the AR and TB region was distributed in particles of less than 3.2 μm. The cancer risk presented by carcinogenic metals (Cd, Co, Cr, and Ni) in total particles to CB feeding workers ranged from 5.52 × 10^?4 to 5.65 × 10^?2, which is substantially higher than the acceptable cancer risk range 10^?6–10^?4. In particular, the cancer risk presented by these four metals in ultrafine particles (UFPs) exceeded the 10^?6 benchmark level. These results demonstrate the high health risk presented by particle-bound heavy metals to workers in a CB feeding area via inhalation exposure.     

Evaluation of occupational exposure to toxic metals released in the process of aluminum welding

The objective of this study was to evaluate occupational exposure to welding fumes and its elements on aluminum welders in Polish industry. The study included 52 MIG/Al fume samples and 18 TIG/Al samples in 3 plants. Air samples were collected in the breathing zone of welders (total and respirable dust). Dust concentration was determined gravimetrically, and the elements in the collected dust were determined by AAS. Mean time-weighted average (TWA) concentrations of the welding dusts/fumes and their components in the breathing zone obtained for different welding processes were, in mg/m3: MIG/Al fumes mean 6.0 (0.8-17.8), Al 2.1 (0.1-7.7), Mg 0.2 (< 0.1-0.9), Mn 0.014 (0.002-0.049), Cu 0.011 (0.002-0.092), Zn 0.016 (0.002-0.14), Pb 0.009 (0.005-0.025), Cr 0.003 (0.002-0.007), and TIG/Al fumes 0.7 (0.3-1.4), Al 0.17 (0.07-0.50). A correlation has been found between the concentration of the main components and the fume/dust concentrations in MIG/Al and TIG/Al fumes. Mean percentages of the individual components in MIG/Al fumes/dusts were Al: 30 (9-56) percent; Mg: 3 (1-5.6) percent; Mn: 0.2 (0.1-0.3) percent; Cu: 0.2 (< 0.1-1.8) percent; Zn: 0.2 (< 0.1-0.8) percent; Pb: 0.2 (< 0.1-1) percent; Cr: < 0.1 percent. The proportion of the respirable fraction in the fumes and their constituents varied between 10 percent and 100 percent. The results showed that MIG/Al fumes concentration was 1.2 times higher than the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV), and the index of the combined exposure to the determined agents was 2.3 (0.4-8.0), mostly because of high Al2O3 contribution. The background concentrations of the components (ca. 5-10 times lower than those in the breathing zone of the welders) did not exceed the Polish MAC value. The elemental composition of total and respirable fume/dust may differ considerably depending on welding methods, the nature of welding-related operations, and work environment conditions.     

Inhalation exposure to welding fumes of arc welders in processing Cr-Ni steel in large chemical industry

For clearing up the inhalative load by welding fumes and gases of arc welders in industrial workshops mainly working on Cr-Ni-steels the following welding processes were studied: tungsten inert-gas (TIG), electrode-by-hand (EH), metal inert-gas (MIG), and plasma cutting (plasma). From the total load by welding fumes follows the rank TIG less than EH less than plasma less than MIG. Observing the maximum allowable concentration (MACD) for the total welding fume, no MACD for Cr and Ni was found exceeded. Regarding the welding gases ozone and CO no limit values were exceeded. From the results conclusions were made.