Coarse, fine and ultrafine particles arising during welding - Analysis of occupational exposure

Accepted Manuscript Coarse, fine and ultrafine particles arising during welding Analysis of occupational exposure

Magdalena Stanislawska, Tadeusz Halatek, Malgorzata Cieslak, Irena Kaminska, Renata Kuras, Beata Janasik, Wojciech Wasowicz PII: DOI: Reference:

S0026-265X(17)30251-5 doi: 10.1016/j.microc.2017.06.021 MICROC 2862

To appear in:

Microchemical Journal

Received date: Revised date: Accepted date:

14 March 2017 22 June 2017 22 June 2017

Please cite this article as: Magdalena Stanislawska, Tadeusz Halatek, Malgorzata Cieslak, Irena Kaminska, Renata Kuras, Beata Janasik, Wojciech Wasowicz , Coarse, fine and ultrafine particles arising during welding - Analysis of occupational exposure, Microchemical Journal (2017), doi: 10.1016/j.microc.2017.06.021

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ACCEPTED MANUSCRIPT Coarse, fine and ultrafine particles arising during welding - Analysis of occupational exposure.

Magdalena Stanislawskaa, Tadeusz Halateka, Malgorzata Cieslakb, Irena Kaminskab, Renata Kurasa, Beata Janasika, Wojciech Wasowicza. a

Department of Environmental and Biological Monitoring, Nofer Institute of Occupational Medicine, Lodz, Poland b

Scientific Department of Unconventional Technologies and Textiles, Textile Research Institute, Lodz, Poland

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Tadeusz Halatek a, e-mail: [email protected]

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Postal address: Nofer Institute of Occupational Medicine

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Saint Teresy Street 8, 91-348 Lodz, Poland.

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telephone: +48 42 63 314 620

Malgorzata Cieslak b, e-mail: [email protected]

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Postal address: Textile Research Institute Gdanska Street 118, Lodz, Poland

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telephone: +48 42 25 34 405

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Irena Kaminska b,

e-mail: [email protected]

Postal address: Textile Research Institute

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Gdanska Street 118, Lodz, Poland

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telephone: +48 42 25 34 405

Renata Kuras a,

e-mail: [email protected] Postal address: Nofer Institute of Occupational Medicine Saint Teresy Street 8, 91-348 Lodz, Poland. telephone: +48 42 63 314 814

Beata Janasik a, e-mail: [email protected] Postal address: Nofer Institute of Occupational Medicine

ACCEPTED MANUSCRIPT Saint Teresy Street 8, 91-348 Lodz, Poland. telephone: +48 42 63 314 806

Wojciech Wasowicz a, e-mail: [email protected] Postal address: Nofer Institute of Occupational Medicine Saint Teresy Street 8, 91-348 Lodz, Poland.

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telephone: +48 42 63 314 626

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Corresponding author: Magdalena Stanislawska

Postal address: Nofer Institute of Occupational Medicine Saint Teresy Street 8, 91-348 Lodz, Poland.

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telephone: +48 42 63 314 818

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fax number: +48 42 63 314 813

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e-mail: [email protected]

ACCEPTED MANUSCRIPT Abstract Analysis of occupational exposure to welding fumes is based on determination of inhalable and respirable fractions of dust and its chemical components. Such measurement does not reflect the actual exposure because it does not include significant parameters related to particle sizes, especially the ultrafine. The study was aimed at investigating exposure to welding fumes containing metals and fine and ultrafine particles. The studies were carried out at two metal industry plants during stainless steel and mild steel welding. Stationary samples of

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welding fumes were collected for evaluation of morphology and structure of fluids, using scanning electron

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microscope (SEM) and energy dispersive spectrometry (EDS). Individual samples were collected from welders inhalable breathing zones to determine the concentration of iron (Fe), manganese (Mn), nickel (Ni), chromium +6

and Cr

+3

) and their compounds in inhalable and respirable fractions, using flame absorption atomic

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(Cr

spectrometry (FAAS) and inductively coupled plasma mass spectrometry (ICP-MS) techniques. The results

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indicate that stainless steel welders were capable of producing fumes containing carcinogenic and neurotoxic

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metals with concentrations exceeding Limit Values (LV).

Keywords: Scanning electron microscope (SEM) and energy dispersive spectrometry (EDS); Inductively

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coupled plasma mass spectrometry (ICP-MS); Carcinogenic metals; Particles; welding fumes.

ACCEPTED MANUSCRIPT 1.

Introduction

Welding is a process which due to high temperature and radiation of welding arc from the welded material, electrodes, shield gases and ambient air gives rise to welding fumes (WF), i.e. a mixture of fine-dispersive solid particles – welding dust and gases constituting a dispersive medium [1]. Welding fume arising from the arc plasma effects on the welded material consists of simple and complex oxides, silicates, fluosilicates, fluorides,

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chromates, dichromates, and metal carbonates. In the welding arc the welded materials are melting, the metal vapours are oxidated, and then a condensation process occurs in lower temperature atmosphere, which results in

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the formation of solid particles. These particles, mostly fine and ultrafine (below 100 nanometres), having a

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three-dimensional structure, are characterized by a very diversified chemical composition and morphology, which determines their toxicity [2, 3]. Studies on health effects of exposure to welding fumes containing

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nanoparticles are usually confined exclusively to experimental research conducted on animals [4] and cellular lines [5, 6]. A significant factor which affects the extent of exposure is the way through which nanoparticles get

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into the human organism. In welders’ exposure it is usually the inhalatory way. Nanoparticles in the respiratory tract may cause quite different health effects than those of bigger particles, and their penetration skills make them easily get from the lungs into circulatory system and through vessels to distant organs and systems,

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including the brain, which may cause such health effects as Parkinson’s disease [7]. The research conducted in

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vitro [8] and in vivo [9] demonstrated that the toxicity of welding fumes is determined by several factors, including particles solubility in biological fluids, size of particles or aggregates which they form, as well as their

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chemical composition. Toxicologists’ studies are focused on the mechanisms of the effects of nanoparticles inhaled with the welding dust. However, still missing is any detailed information on the impact of those particles

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on particular organs and cellular structures. Scientific experiments conducted on cellular lines indicate that nanoparticles may easily bind with cellular structures and components, thereby inducing their damage-related processes [10]. The components of welding fumes, mainly metals, also contribute to induction of oxidative stress reaction. Investigations have shown an increase in reactive oxygen species (ROS) production after welding fume generation [11]. ROS and reactive nitrogen species (RNS) arising from those processes play a key role in initiating of cancerogenetic processes through damaging of cellular DNA [12]. Considering that we do not know what contributes more to the development of health effects in people exposed to nanoparticles: their concentration, mass or perhaps chemical composition, the use of merely one technique for analysis of welding fumes does not satisfy our needs in this

ACCEPTED MANUSCRIPT respect. Besides, dispersion of nanoparticles in welders’ breathing zone and time-variable concentrations of hazardous agents within the fumes inhibit the measurement and may cause erroneous interpretation of results if we use one analytical technique. Taking into account the size of nanoparticles in relation to their precise measurement, they may be measured precisely only by techniques which enable reaching a subnanometric resolution [13]. However, such analysis is confined merely to investigating the structure and size of dust particles but is does not give any information about its chemical composition. A sine qua non for a complete

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evaluation of exposure to fumes arising from welding is a physico-chemical analysis of dust, taking into account the size of particles of inhalable and respirable fraction and analysis of its chemical composition. The latter is

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possible due to the use of the latest spectrometric techniques applied for identification and determination of the

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concentrations of metals and their compounds. A qualitative analysis of chemical composition of dusts on the surface of filters is possible with the use of EDS X-ray radiation microanalysis. The results of analysis obtained

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with simultaneous use of several analytical techniques, such as scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), flame absorption atomic spectrometry (FAAS), inductively coupled plasma mass

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spectrometry (ICP-MS), combined high-performance liquid chromatography – inductively coupled plasma mass spectrometry (HPLC-ICP-MS) enable a complex identification and evaluation of exposures. Most of the studies carried out so far are related to the structure, size of particles, and composition of dusts

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coming from welding of chromium-nickel steels [14], but information about the structure and size of particles

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arising from welding of low-alloy steels is scarce.

The aim of the study was to determine the exposure to welding dusts containing metals and their compounds

2.

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steels (MS).

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and coarse, fine and ultrafine particles typically found in the welding processes of stainless steels (SS) and mild

Material and methods

2.1. Plant and workers The studies were carried out in two metal industry plants. In one plant (P1) the steel structures made of highalloy steel designed for the production of buses were welded, while the second plant (P2) welded low-alloy steel designed for the production of heavy wheeled vehicles. The welding methods used in the plants were: MIG (Metal Inert Gas) welding with consumable electrode in the shield of protective gases: argon (Ar) and carbon dioxide (CO2). Welding by this method consists in the fusion of the welded metal and consumable electrode

ACCEPTED MANUSCRIPT material with the heat of electrical arc glowing between the electrode and the welded steel. The consumable electrode has the form of a solid wire which often in its chemical composition is similar to the welded steel. This method may be used to perform high quality bonds of MS and SS resistant to corrosion. The wire used in the P1 at SS steel welding contained: C – 0.01%; Mn – 1.8 %; Si – 0.8 %; Cr – 23.3 %; Ni – 13.8 %; Mo – 0.14 %. In P2 a wire containing: C – 0.09 %; Si – 0.90 %; Mn – 1 % was used to weld MS steel. Workstations had general ventilation, supply and exhaust ventilation, and local ventilation extraction nozzle.

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Workers included into the studies were equipped with special (welders) helmets. The number of workers involved in the study for P1 and P2 was 21 and 10, respectively. In the P1, 21 workers were included into the

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studies, in the P2, 10 workers. Welders work the day shift in both plants. Day shift is 6:00 a.m. to 2:00 p.m. with

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one hour lunch break, five days a week. Each participant completed a comprehensive questionnaire on individual welding history and intensity applied during the previous one week and the previous year. They were asked in

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detail about their duration of SS and MS welding in their careers and intensity of smoking. The mean age of the SS welders was 50 years, range (34 – 63). The mean age of the MS welders was 44 years, range (31 – 58). The

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mean years of work in exposure of the SS welders was 22 years, range (7 – 40). The mean years of work in exposure of the MS welders was 15 years, range (5 – 38).

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2.2. Sample collection

Stationary air samples were collected at workstations to evaluate the structure, morphology, and diameter of welding fume particles and individual air samples for evaluation of the composition of welding fume and its

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components. Individual samples were collected by individual dosimetry in workers’ breathing zone

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continuously, during 6–7 hrs [15, 16]. Stationary samples were collected at the same time according to sampling strategy. Sampling was done by individual dust-meters (Personal Air Samples, Gilian GilAir 3 Gilian Manufactured by Sensidyne, St Petersburg FL USA), collecting a fraction of inhalable dust at 2 l/min flow onto membrane filters made of cellulose nitrate (Sartorius 11304, filter diameter 25 mm) and glass fibre filters (Wathman GF/A, filter diameter 37 mm), and respirable dust fraction at 2.2 l/min, on membrane filters made of cellulose nitrate (Sartorius 11304, filter diameter 37 mm). The fraction of inhalable and respirable dust was sampled by simultaneous placing of three filters in the worker’s breathing zone. Stationary samples were collected at the same time; inhalable and respirable fractions of dust were sampled at the same time by collecting the inhalable and respirable fraction of dust at a distance of approx. one meter

ACCEPTED MANUSCRIPT from the welders’ workstation. Summary of welding fume airborne samples showed in Table 1a, b. Subsequently, the samples at approx. 20°C were transported to the laboratory. Having been transported to the laboratory the samples were dried at 105°C and then conditioned in exsiccator for 24 hrs. Analysis of the samples was carried out within one month. The size and structure of dusts were tested by SEM equipped with EDS X-ray radiation microanalyser. Chemical analysis of dust and its components was

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conducted using ICP-MS and FAAS and combined technique HPLC-ICP-MS.

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Table 1. Summary of welding fume (a) stationary airborne samples and (b) individual airborne samples

Preparation and analysis of samples using the SEM/EDS technique

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2.3.1.

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2.3. Sample preparation

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The surface of the samples was sputtered with conductive material – gold (layer of 15 nm), using a vacuum sputter Quorum Technologies Ltd. Analysis of the dimensions and structure of welding dust particles and

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elemental composition of particles on the membrane filters surface was carried out using a scanning electron

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microscope (SEM) VEGA3 produced by TESCAN, equipped with X-ray microanalyser EDS INCA Energy produced by Oxford Instruments. The EDS analysis was carried out under 20 Pa pressure, using the energy probing electron beams 20keV, without sputtering with a conductive substance. The qualitative and quantitative

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analysis of the elemental composition of the surface of tested samples was carried out in microareas of 46656 µm2. Percentage calculations of the content of elements in the analyzed micro-regions of samples were made

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using the INCA software with the ZAF corrective procedure. The SEM microscope analysis was carried out under high vacuum conditions. The magnifications used were 5000, 20000, and 50000x. The magnifications of 5000x, 20000x, 50000x were used.

ACCEPTED MANUSCRIPT 2.3.2.

Preparation and analysis of samples by a gravimetric method

Having been dried and cooled in exsiccator, the welding dust samples were analyzed by gravimetric method, using scales (Sartorius RD-200, USA), with 0.01 mg measurement accuracy. In this way the welding dust concentration was determined.

Preparation and analysis of samples using the ICP-MS and FAAS technique

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2.3.3.

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Filters with sampled dusts, following determination of dust concentration by gravimetric method were

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subjected to wet mineralization with concentrated nitric acid (J.T. Baker® Instra-analyzed 69-70% for trace metal analysis). Mineralized samples were transferred to measuring flasks of 10 ml volume and filled with 1 %

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nitric acid. If it was necessary, the solutions were diluted respectively with 1% HNO3. In samples solutions the following metals were analyzed: iron (Fe), manganese (Mn), total chromium (Cr) and nickel (Ni).

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Concentrations of respective metals were read on standard curve prepared from standard solution of 10 mg/l concentration (Multi- Element Calibration Standard 3 ICP-MS, PerkinElmer Pure Plus). Analysis of metals: compounds of chromium and nickel as components of welding dusts was carried out using

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mass spectrometer with inductively coupled plasma (ICP-MS, Elan DRC-e, made by Perkin Elmer, SCIEX,

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Waltham, MA., USA) with DRC-e reaction cell to eliminate both spectral interferences and those coming from the sample matrix. Analysis of metals: compounds of iron and manganese was carried out using flame atomic

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absorption spectrometer in air-acetylene flame (FAAS made by Varian, SpectrAA 250 Plus) equipped with

2.3.4.

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lamps with hollow cathode to determine a given metal.

Preparation and analysis of samples using the HPLC-ICP-MS technique

The glass fiber filters were subjected to washing out with alkaline solution (2% NaOH - 3% Na2CO3), then diluted with mobile phase (50 mM, ammonium acetate CH 3COONH4 and 10 mM sodium perchlorate NaClO4) and injected on chromatographic column (Hamilton PRP-X100 - 150 x 4.6 mm, 5µm) to separate form Cr (VI) [17].

ACCEPTED MANUSCRIPT 3.

Results and discussion

According to SEM/EDS analysis of dusts coming from welding of SS and MS steels the elemental composition of dusts was determined on the surface of filters and the particle size of dusts containing metals and their compounds was determined. Dust particles have different shapes and may be divided depending on their dimensions lower than 270 nm and large ones with a sizes up to 47 µm. into lower to 270 nm and large ones

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sized up to 47 µm. The mean size of the particles of dusts emitted at welding of SS and MS in inhalable fraction is bigger than in the respirable fraction and is characterized by a high dispersion of measurement results. Dust

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particles in respirable fraction have similar sizes. Nanoparticles, which are defined as particles <100 nm were

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3.1. Size of particles within welding fumes

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found in the samples of dusts emitted both during welding of SS and MS.

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The inhalable dust fraction consisted of single particles and differently shaped and sized agglomerates. The dimensions of particles of dust coming from welding of SS ranged from 27 nm to 344 nm in the case of fine

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particles, and from 2 µm to 46 µm in the case of coarse particles. Instead in welding of MS the diameter of fine

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and ultrafine particles was half that value, ranging from 18 nm to 137 nm. Similar results were obtained in the case of bigger particles the diameter of which was also lower and reached from 2µm to 32µm (Fig. 1a, 1b).

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Fig. 1. Comparison size of fine, ultrafine particles (a) and coarse particles (b) in inhalable dust from stainless steel welding - SS and mild steel welding – MS

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The fraction of respirable dust, sampled in cyclones, was assumed to consist of particles with diameter below 4 µm, for 50% of sampled dust [18]. This fraction, emitted at welding of SS, consisted of fine and ultrafine particles having diameter from 23 nm to 193 nm and of coarse particles with diameter from 0.4 µm to 10 µm. Similarly as in the case of respirable fraction, the diameter of dust particles at welding of MS steel was smaller: from 28 nm to 107 nm of fine particles and from 0.5 µm to 4 µm of coarse particles (Fig. 2a, 2b). The obtained results, determining the sizes of dust particles, indicate that welding fumes emitted during MS steel welding are characterized by a smaller diameter of particles, as compared to the fumes emitted during SS welding. For both types of welding, both inhalable and respirable fraction, most of the fine particles were those below 100 nm, i. e.

ACCEPTED MANUSCRIPT ultrafine, considered as the most hazardous to employees’ health [19]. Comparing the size of particles emitted during welding of MS and SS we obtained the results related to inhalable and respirable fractions. In the respirable fraction the dust grains diameter was much smaller, as compared to the studies carried out by Leonard et al. (2010) [11]. According to Leonard et al., the diameter of most of the particles, calculated by mass, within the fumes emitted during MS and SS welding ranged from 0.56 to 0.1 µm. The results obtained by them indicate that the welding fumes in both types of welding are toxic, however the fumes arising from SS welding exhibit

welders may be exposed to particles of different sizes, usually below 1 µm.

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much higher reactivity due to the presence of Cr and Ni. It was concluded that throughout the working day

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Presently there are no standardized methods of air sampling in the working environment to evaluate the

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exposure to particles of different sizes, i.e. fine and ultrafine particles, and nanoparticles. The efficacy of certain methods may be very low. We should also remember that apart from identification of fine and ultrafine particles

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the information about their amount and surface is also important. To evaluate correctly the occupational risk connected with exposure to ultrafine particles, such parameters should be tested which may be compared with

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allowable values. Presently there are no commonly accepted allowable values for fine and ultrafine particles emitted during welding. Therefore, we can only evaluate their potential exposure to fine and ultrafine particles emitted during welding. Therefore we can only evaluate the potential exposure to fine and ultrafine particles

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occurring in the work environment. Presently, in the EU the evaluation of occupational risk resulting from

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exposure to nano-objects may adapt the existing methods developed for substances of a higher size of particles [20]. For welding fumes no highest allowable concentration value was established. The essence of evaluation of

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exposure in this case is evaluation of the concentration of particular components of welding fumes and their comparison with mandatory values of the highest allowable concentrations.

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Fig. 2. Comparison size of fine, ultrafine particles (a) and coarse particles (b) in respirable dust from stainless steel welding - SS and mild steel welding – MS

3.2. Morphology and chemical composition of superficial layer of welding fumes

SEM images of welding dusts showed not only sizes but also morphology of particles. Combining of SEM research with EDS analysis enabled determination of certain relations between the structure and elemental composition of the tested samples.

ACCEPTED MANUSCRIPT According to the obtained results the welding fumes contain spherical, irregular particles and agglomerates. Particles of dusts of inhalable and respirable fractions, coming from SS welding, were characterized by differentiated shapes; they often had a porous form with sharp edges or irregular curves resembling crystals (Fig. 3a, 3b). While the fumes coming from MS welding adopted mainly spherical shapes called spherules, their surface was smooth or undulatory. Deposits of ultrafine particles, sometimes forming agglomerates, were visible

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on their surface (Fig. 3c, 3d).

Fig. 3 SEM images of the welding dust particles; inhalable fraction SS (a1,a2), respirable fraction SS (b1, b2),

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inhalable fraction MS (c1, c2), respirable fraction MS (d).

SEM/EDS technique enabled determining of the dusts chemical composition on the surface of filters. EDS

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analysis demonstrated that the welding fumes structure depended on its elemental composition which differed, especially in the content of Fe, Mn, Cr, Ni iron, manganese, chromium, nickel and silicon (Si) (Table 2, Fig. 4 a,

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b). Due to the majority of iron, occurring in form of iron oxides in WF emitted during MS welding, and a low content of other elements such as Cr and Ni, the fume particles take spherical forms – spherules. These forms assume magnetic nature, they probably arise from the presence of Fe and manganese oxides [21]. The fumes

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coming from SS welding were characterized by more differentiated chemical composition, as compared to the

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fumes coming from MS welding (Table 2 and Fig. 5). Apart from Fe and Mn, they contained Cr and Ni. Toxic properties of Cr, Ni and Mn are well known and described [19, 22, 23], whereas Fe is an element whose toxic

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properties are still disputable [24]. Furthermore, they contained a higher concentration of Mn, calcium (Ca), sodium (Na), Si and zinc (Zn). Zn, perhaps in the presence of other metals, may induce an inflammatory state in

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lungs. Metals, especially their soluble forms: Zn (II), Ca (II), Mg (II) and Fe (II) and Mn (II) may enhance toxic effects of Ni [25].

Analysis of the morphology of SS dust showed that the elemental composition significantly affected the shape of particles. Increased content of carbon (C) and Si could give rise to crystalline particles of irregular, sharp edges [26]. The presence of magnetic and crystalline particles present in welding dust emitted during welding of chromium-nickel steels was described by Moroni and Viti [14]. Comparing the analysis of the chemical composition of dusts arising from welding of SS and MS in relation to the size of particles occurring in them we observed that a higher content of such elements as Na, K, S, and F resulted in bigger particles of dust.

ACCEPTED MANUSCRIPT Similar observations were also reported by Berlinger et al. [27] who concluded that the presence of light metals caused an increase in the size of particles and a tendency to form agglomerates.

Table 2. Chemical composition of the stainless steel (SS) and mild steel (MS) samples obtained by EDS

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Fig. 4. Example of EDS spectra for SS (a) and (b) MS welding dust samples.

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analysis – the reported values correspond to the mean obtained from five measurements

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Fig. 5. Comparison of elemental composition of samples for SS and MS welding

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3.3. Concentration of fumes and their components arising from SS and MS welding

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Analysis of chemical composition of welding dust samples, performed by the SEM-EDS technique, provided information on identification and content of metals on filters surface. However, that information was insufficient for analysis of welders exposure to fumes and their components. Complete information came from

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analyses made on mineralized samples, using spectrometric techniques FAAS and ICP-MS. The obtained results

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made it possible to analyze the chemical composition of welding fumes samples collected in the breathing zone. The results of determination of fumes and their components in the work environment air during welding of MS

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and SS are presented in Table 3.

welders

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Table 3. Concentrations of welding fume and its elements at workplace of the stainless steel and mild steel

Higher concentrations of fumes occurred in P1 - MS welding. They ranged from 1.92 to 4.25 mg/m3 for inhalable fraction and from 0.81 to 2.37 mg/m3 for respirable fraction; those were twice higher values, as compared to P1 where SS were welded. In P1, concentrations of fumes during SS welding reached respectively from 0.12 to 3.50 mg/m3 for inhalable fraction and from 0.12 to 1.65 mg/m3 for respirable fraction. Arithmetic mean (AM) concentration of dusts in inhalable fraction was twice higher than that in respirable fraction. Such tendency occurred in two plants. For welding fumes the American Conference of Governmental Industrial

ACCEPTED MANUSCRIPT Hygienists ACGIH did not establish any threshold limit value (TLV ®). In Germany, according to the Federal Ministry of Labor and Social Affairs the value of occupational exposure limit (OEL) for inhalable dust fraction reaches 10 mg/m3 and for respirable fraction 3 mg/m3. In Poland no value of the maximum admissible concentration (MAC) for welding fumes was established. Evaluation of welders’ exposure is based on analysis of the concentration of metals which are components of welding fumes, and their comparison with mandatory values. However, the gravimetric method enabling the measurement of dust concentration does not reflect the

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employees’ actual exposure. A consecutive stage of the research was the analysis and determination of metals and their compounds which are components of welding fumes.

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In the case of MS welding, the AM values of the concentration of compounds of Fe and Mn were found to

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be at least twice as high as those in SS welding. This refers to both inhalable and respirable fraction. The AM concentration of Fe in inhalable fraction in P2 was almost five times higher, as compared to P1; such relation of

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the concentrations values differed from the values obtained by the EDS technique (table 3) which refer only to Fe content on the surface of filters. Measurements made by the FAAS technique confirmed the difference in

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concentration of Fe and its compounds in the tested samples coming from welding of SS and MS. A higher concentration of Fe and its compounds, especially in form of oxides, may account for a characteristic structure of dust with predominance of spherical forms exhibiting magnetic properties.

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Interesting were the results of tests of Mn concentrations in SS welders. In inhalable and respirable fraction

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the Mn concentration was almost the same, i.e. total Mn constituted a the respirable fraction of dust. AM concentrations of Mn in SS welding fumes reached 42.2 µg/m3 in inhalable fraction and 43.4 µg/m3 in respirable fraction. On the other hand, in MS welding the AM values in inhalable fraction amounted to 96.5 µg/m 3 and 85.7

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µg/m3 in respirable fraction. AM concentrations of Mn were higher than those obtained in researach conducted by Lenhert et al. [28] and comparable with the results obtained in the research carried out by Hoet et al. [29].

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Considering the proposed value of the threshold limit value (TLV ®) for Mn amounting to 200 µg/m3 in inhalable fraction and 20 µg/m3 in respirable fraction [30], those values in workers of P1 and P2 were exceeded in respirable fraction. In Poland the value of the MAC for Mn in inhalable fraction is the same as the value established by the ACGIH. On the other hand in respirable fraction it amounts to 50µg/m³ and is over twice as high [31]. As the effects of exposure to Mn may have severe consequences for employees’ health and the conducted studies continue to provide us with new evidence of Mn effects on health, this value may change in the future. In Poland in result of the welders’ proved exposure to Mn the workers are more and more frequently subjected to

ACCEPTED MANUSCRIPT biological monitoring research. These studies consist of the measurement of Mn concentration in blood and the comparison of the obtained value with the reference value for occupationally exposed people [32]. Such a solution seems to be appropriate, because only the combination of the studies within work environment monitoring and biological monitoring enables a complete evaluation of welders’ exposure. AM concentrations of Cr and its compounds in fume samples collected in P1 were fourteen times higher than those collected in P2. Similar results were obtained in the case of Ni and its compounds, however in this

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case the differences in concentrations between the plants were much lower; at MS welding the AM concentration of Ni reached 10.9 µg/m3 and was four times lower than the AM concentration of Ni which is a component of

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fumes emitted at SS welding. The studies indicate that in none of the tested welders the value of allowable

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concentration of Ni compounds was exceeded, as compared to the values recommended by ACGIH, reaching: TLV® for metallic Ni 1.5 mg/m3 and its insoluble compounds 0.2 mg/m3 [29]. In Poland the value of the MAC

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for Ni both for soluble and insoluble compounds amounts to 0.25 mg/m³ [31]. Instead, exceeded were the values of allowable concentrations of Cr

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in SS welding, referring to

occupational exposure limits (OEL) for Cr

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recommendations of US Occupational Health and Safety Administration (OSHA) – the established value of +6

was at the level of 5 µg/m3 [33]. In Poland, the MAC for

occupational exposure to total (both soluble and insoluble) Cr +3

compounds in dust and aerosols amounts to 0.1

compounds to 0.5 mg/m3 of air [31]. The research on the chemical composition of

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mg/m3 of air and for Cr

+6

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welding fumes demonstrated that exposure of this group of workers constitutes a topical problem from the point of view of health effects. Exceeded allowable values, especially of metals of cancerogenic effects, such as Cr

+6

,

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and metals of neurotoxic effects such as Mn, indicates that welders continue to be exposed to occupational diseases. The presence of toxic and cancerogenic metals and their compounds contributes to enhanced risk of the

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occurrence of neoplastic and civilization diseases in this group [34]. In welding processes the composition and concentration of emitted fumes depend on such elements as the type of the welded steel and welding method and parameters. The latter may sometimes be more important than we could expect. Sriram et al. (2015) in their study showed that by specifically modulated welding voltage, keeping the current and shielding gas constant, the fume composition WF can be altered significantly [35]. Unfortunately in practice the workers, unaware of risks, increase the welding voltage. The plants where the welding parameters are controlled by the computer process are still scarce, and the workers cannot affect their adjustment. The key role is played here by the knowledge and increasing the employer’s and workers’ awareness. Therefore, all studies conducted at the workplaces in actual conditions may be an important source of

ACCEPTED MANUSCRIPT information about the existing exposure. Furthermore, such information constitutes a basis for developing the guidelines aimed at an improvement of work conditions, e.g. by the use of effective personal protective measures.

4.

Conclusion

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The research on the chemical composition of welding fumes is one of the elements of evaluation of

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exposure. As the hazardous effects of chemical agents on human organism are determined not only by chemical but also by physical factors, a question arises if evaluation of exposure based on chemical analysis of welding

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fumes is sufficient. The studies demonstrate that although welders of SS were exposed to cancerogenic and neurotoxic metals, the welders of MS were exposed to particles of smaller sizes exhibiting potentially stronger

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toxic effects. The results obtained by the SEM/EDS technique give information about form and size of particles and topography and elemental composition of particles surface. Over twenty years ago Sjorgen et al. (1994)

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summing up their studies concluded that the welding fumes arising from SS welding increase the risk of lung cancer [36]. On the other hand, analyses of the exposure to fumes arising from MS welding, containing low

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concentrations of Cr and Ni, constitute a separate problem which may be discussed in the future, involving other

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issues. Nowadays, over 20 years later, this statement has a new meaning. Increased analytical possibilities which enable testing of the size and structure of welding fumes significantly extend the knowledge about their hazardous effects. The results presented in the study demonstrate that the much lower diameter of grains in the

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fumes emitted during MS welding may determine their toxicity. Continuation of studies based on other techniques enabling extending of the knowledge on the

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physicochemical properties of dusts gives high cognitive possibilities. We should assume that evaluation of exposure to welding fumes should be conducted in a complex way to comprise both analysis of chemical agents concentrations and a comprehensive physical analysis of fumes, using suitable complementary analytical techniques. Only in this way we can identify risks and prevent them efficiently.

Acknowledgments Thanks to our colleagues, Malgorzata Kałuża, Elzbieta Hiler and Wieslaw Kuszka, who cooperated in the sampling, sample preparation and analytical measurements.

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Funding This work was supported by the National Center of Sciences in Poland [Grant numbers 2013/09/B/NZ7/04092];

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and the Nofer Institute of Occupational Medicine in Lodz, Poland [internal grant numbers IMP 1.27].

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ACCEPTED MANUSCRIPT Fig. 1. Comparison size of fine, ultrafine particles (a) and coarse particles (b) in inhalable dust from stainless steel welding - SS and mild steel welding – MS a.

180 160

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100 80 60

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Mean value [nm]

140

40

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20 0 SS-2

SS-3 SS-4 SS-5 Number of samples

MS-1

SS-2 SS-3 SS-4 SS-5 MS-1 MS-2

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15 10 5

SS-1 SS-2

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SS-3 SS-4

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Mean value [µm]

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SS-5 MS-1 MS-2

0 SS-1

SS-2

SS-3 SS-4 SS-5 Number of samples

MS-1

MS-2

ACCEPTED MANUSCRIPT Fig. 2. Comparison size of fine, ultrafine particles (a) and coarse particles (b) in respirable dust from stainless steel welding - SS and mild steel welding – MS a.

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Mean value [nm]

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SS-3 SS-4 SS-5 Number of samples

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SS-2 SS-3 SS-4 SS-5 MS-1 MS-2

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SS-5 MS-1 MS-2

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SS-4

Number of samples

SS-5

MS-1

MS-2

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Fig. 4. Example of EDS spectra for SS (a) and (b) MS welding dust samples a.

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ACCEPTED MANUSCRIPT Fig. 5. Comparison of elemental composition of samples for SS and MS welding 30

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ACCEPTED MANUSCRIPT Table 1. Summary of welding fume (a) stationary airborne samples and (b) individual airborne samples a. Welding steel / Welding Sampled Mass concentration Plant The Number of samples method volume (l) (mg/m3)

P1

Stainless steel / MIG

650

1.7

SS-1 w

650

-

SS-1 respirable

715

0.8

680

1.3

SS-2 w

680

-

SS-2 respirable

748

SS-2 inhalable

Stainless steel / MIG

SS-3 inhalable

Stainless steel / MIG

P1

SS-4 inhalable

Stainless steel / MIG

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SS-4 w SS-4 respirable SS-5 inhalable

Stainless steel / MIG

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P1

SS-5 w SS-5 respirable MS-1 inhalable

Mild steel / MIG

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P2

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MS-1 w MS-1 respirable P2

MS-2 inhalable

Mild steel / MIG

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MS-2 w

720

-

792

0.5

720

1.5

720

-

792

0.6

720

1.6

720

-

792

0.7

720

1.7

720

-

792

0.9

700

1.5

700

-

770

0.8

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SS-3 w SS-3 respirable

720

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P1

SS-1 inhalable

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P1

MS-2 respirable

0.7 1.3

b. Plant

P1

P2

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w – glass filter for analysis Cr(VI)

Welding steel / Welding

No of samples / No

Sampled volume (l)

Mass concentration

method

of workers

range

(mg/m3) range

Stainless steel / MIG

21 inhalable

730-790

0.13-3.5

21 w

730-790

-

21 respirable / n=21

803-869

0.12-1.7

10 inhalable

660-750

1.92-4.25

10 w

660-750

-

10 respirable /n=10

726-825

0.81-2.37

Mild steel / MIG

w – glass filter for analysis Cr(VI)

ACCEPTED MANUSCRIPT Table 2. Chemical composition of the stainless steel (SS) and mild steel (MS) samples obtained by EDS analysis – the reported values correspond to the mean obtained from five measurements EDS chemical compositions of the stainless steel (SS) and mild steel (MS) samples – the mean values obtained from five EDS spectra. SS

MS

Element

40.23

21.65

O

26.33

32.76

F

4.33

2.48

Na

1.02

0.63

Mg

2.21

1.33

Al

0.81

1.10

Si

3.86

2.40

P

0.46

-*

S

0.17

0.28

Cl

0.11

0.34

K

0.19

0.54

Ca

1.49

0.99

Ti

0.22

0.14

Cr

2.64

0.26

Mn

0.61

Fe

12.72

Ni

0.73

0.23

Cu

0.14

0.28

Zn

1.75

0.49

Total

100.00

100.00

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32.32

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*below detection

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Weight %

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Respirable particles

(mg/m3)

(mg/m3)

P1, welding

1.28 ± 0.95

SS

Plant

Fe inhalable

Fe respirable

Mn inhalable

Mn respirable

Cr

Cr respirable

Cr (VI)

Cr (III)

inhalable

Ni inhalable

Ni respirable

(µg/m3)

(µg/m3)

(µg/m3)

(µg/m3)

(µg/m3)

(µg/m3)

(µg/m3)

(µg/m3)

(µg/m3)

(µg/m3)

0.74 ± 0.39

264.0 ± 279.8

154,9 ± 91.9

42.2 ± 24.1

43.4 ± 23.5

83.3 ± 6.0

68.1 ± 48.5

45.8 ± 7.8

37.5 ± 5.1

40.4 ± 24.4

39.1± 22.8

(0.12–3.50)

(0.12–1.65)

(30.2-590.7)

(20.8-300.0)

(5.5-89.7)

(5.6-88.8)

(6.0-229.1)

(4.5-149.3)

(41.0-82.5)

(9.2-51.0)

(3.8-85.5)

(3.5-74.5)

P2, welding MS

3.06 ± 0.82

1.49 ± 0.42

1173.8 ± 387.4

647,6 ± 286.5

96.5 ± 51.6

85.7 ± 33.4

10.9 ± 3.0

3.8 ± 1.2

< LOQ

< LOQ (7.6-14.9)

(2.6-6.5)

(1.92-4.25)

(0.81-2.37)

(751.6-1851.6)

(317.2-1152.8)

(14.5-176.2)

(n = 10)

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(LOQ) Limit of quantification for Cr +6 and Cr +3 1 µg/m *Arithmetic mean

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**Standard deviation

A

C C

N A

(41.7-153.5)

M

I R

C S U

(n = 21)

5.7 ± 3.0

(2.5-11.4)

T P

1.2 ± 0.7 (0.5-3.0)

ACCEPTED MANUSCRIPT Highlights

Determination of welding fumes and its chemical components in welders’ breathing zone

The size and structure of dusts were tested by SEM with EDS X-ray microanalyser

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Metals of welding fumes was conducted using ICP-MS, FAAS, HPLC-ICP-MS techniques

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Size and structure of particles in welding fumes depend on their chemical composition