1-Mansori

JRHS 2008; 8(2): 1-8

Copyright © Journal of Research in Health Sciences

Gravimetric and Analytical Evaluation of Welding Fume in an Automobile Part Manufacturing Factory

Mansouri N (PhD)a*, Atbi F (PhD)a, Moharamnezhad N (PhD)a, Rahbaran DA (MSc)a, Alahiari M (MSc)a

a Department of Environment Engineering, Graduate School of  Environment & Energy, Science & Research Campus, Islamic Azad University, Tehran, Iran

*Corresponding Author: Dr Mansouri, E-mail: nmansourin@ gmail.com

Received: 7 July 2008; Accepted :12 November 2008

Abstract

Background: Welding is one of the most exercised industrial processes which welders are exposed to chemi­cal and physical Hazardous agents. This study was conducted to evaluate occupational and environ­mental exposures to aerosols generated by welding processes in a factory.

Methods: A total of 28 samples of aerosols were collected at 4 different locations including indoor, out­door, source of welding and the stacks using a high volume pump with a volumetric flow rate of 112 lit/min calibrated with a dry gas meter. The samples were collected on round 110 mm fiber glass fil­ters, measured gravimetrically, extracted using nitric acid and analyzed with atomic absorption spectros­copy method for heavy metals including Fe, Mn, Ni, Cr3+, Cr+6, Co, and Zn.

Results: Gravimetric measuring has shown the mean values of indoor air: 1.33 mg/m3, breathing zone of the welders using coated electrodes and CO2: 7.25 mg/m3 and 6.45 mg/m3 respectively and in ventila­tion exhausts: 95.07 mg/m3. The mean values of Fe, Mn, and Ni were 0.8, 0.041, and 0.00 mg/m3 in indoor air, 2.7, 0.18, and 0.15 mg/m3 in breathing zone of welders used coated electrodes, and 1.75, 0.08, and 0.22 mg/m3 in breathing zone of welders used CO2 welding respectively. The concentra­tions of Cr3+, Cr+6, Co, and Zn were too low to be detected.   

Conclusion: The welders were exposed to high concentration of metallic fumes, which raise the risk of pul­monary dysfunction and other health disorders. Using suitable respiratory masks and Appling the ef­fective local ventilation system may improve the working condition.

Keywords: Particulate maters, Heavy metal, Welder exposure, Aerosol

Introduction

Welding is one of the most important and in­dustrial expertise known to man and one can­not imagine all the industrial develop­ments with­out it. Unfortunately welding prac­tices in­volves a lot of chemical and physi­cal dan­gers which threatens techni­cians' and experi­enced experts' health that is the most valu­able resource of an industry. It is believed that wel­d­ing fumes would eventu­ally lead to can­cer and other serious lung deceases such as occupa­tional asthma but enough proof and experi­men­-

tal tests on animals which proving welding fu­mes alone being responsible for the symp­toms above, are not available (1). Fumes, which are a mix­ture of metal oxide compounds, Sili­cates and fluorides, are produced when metals are heated to their boiling point temperature and this process is achieved continuously in weld­ing. In other words, they are solid parti­cles, which are generated following com­pre­s­sion of metallic vapors in the air af­ter va­po­rization or sublimation of melted mat­ters. These particles are so small with a di­ameter of 0.2 to 0.3 micron that, they would be able to get to the ending parts of the respiratory organs thus causing a wide range of respiratory prob­lems (2).

Generally, welding fumes are oxides of welded material and used electrodes and in case of coated or painted materials, addi­tional sub­stances means more toxicity and in this case more protecting considerations should be taken into account concerning the technicians' and pos­sibly exposed people. All kinds of weld­ing processes produce fumes but the concen­trations would vary for different processes. In different studies, main sources of fume in welding processes are the metal being welded, electrode, flux material, coatings, oils, greases, rust, solution paints, and the lining on the origi­nal metal respec­tively (3).

Pires have revealed in his studies that arc weld­ing in CO2 produces more fumes com­pared to that in Argon and generated fumes contain more iron, Manganese, silica, tita­nium and so­dium oxide (4). The results of studies on full time welding technicians showed that they have suffered more from bronchitis, respiratory ir­ritation, lung disor­ders, and cancer (5). Simi­lar studies also have shown that generated fumes using arc welding in CO2, contains more iron and man­ganese (6). Analysing of gener­ated fumes from arc welding in an automo­tive in­dustry indicated higher concentrations of zinc, iron, manganese and chromium as more notable compounds (7). Research on acute sym­ptoms of welding fumes on lung, in­dicated a 6 day period of onset in mice and contrary to the past belief, solubility of fumes in water is not an effective parameter in its toxicity and the more important factor would be the abil­ity to release free radicals in lung tissues (8).

Methods

Location of the study

The present study was carried out in a weld­ing workplace of an automobile part manu­fac­turing industry, producing a vehicle axles and located 10 kilometers away from west of the Tehran. This factory included 7 en­closed halls with an area of approximately 77000 m2 and its welding department had 26 welding technicians and the same number of other work­ers. Welding operations on automo­bile axel shells have been done in two separate ways using coated electrodes and uncoated ones in CO2. There were 14 op­erational stations with a cluttered layout which resulted in difficult movement of per­sonnel and also intensified emission of pollu­tions in the workplace.

Sampling and measuring total particulate concentrations:

To determine total concentration of particu­lates, NIOSH 7200 gravimetric method based on taking samples using filters and weight­ing them was employed. Samples were taken us­ing fiber glass filters with a di­ameter of 110 mm and high volume sampler pump with a flow rate of 112 lit/min (9). A laboratory balance made by Sartorius Com­pany, Germany, with a resolution of 0.0001 grams was used for weighting the samples. Even though the fil­ters were placed in a desic­cator before and af­ter sampling and be­fore weighting for 24 h, but in order to control weighting related errors, for every three sampling filters, one was con­sidered as a blank.

Totally 28 samples of four categories includ­ing welders' breathing zone, hall, exhaust sha­ft of the ventilation system and outside air were taken. The height of sampling in the hall and outside was 170 cm equivalent to peo­ple's stan­d­ing breathing height. Sampling points in the hall have been chosen accord­ing to the num­ber of workers and busyness and in the out­side air, according to the wind blow at the up­side and downside during the sampling period. Duration of the sampling was 20 min for each sample and sam­pling process were carried out during weld­ing technicians' normal activity.

Sample analysis using atomic absorption

Measuring concentration of heavy elements is usually done using atomic absorption spec­troscopy in most studies so the atomic ab­sorp­tion spectroscopy method based on ASTMD 4185 has been used in this study (10). Accord­ing to similar researches, heavy metals like iron, zinc, cobalt, nickel, manga­nese, +3 and +6 val­ance chromium (Cr3+, Cr6+, Mn, Ni, Co, Zn, Fe) have the high­est probability of being pre­sent in welding fume (4, 6, 7). In the men­tioned method, first the samples are laid out in a suitable beaker and 2 ml of nitric acid is added and the beaker is placed in a hot water bath in or­der to dissolve and digest con­tai­ned material. The filter is rinsed with acid and is sepa­rated. 2 ml of hydrogen peroxide is added to the resulted acidic solution and is heated for elucidation until a couple of drops remains. Eventually the sample will get up to volume in a 50 ml volumetric flask. Acquir­ing stan­dard solutions in different concentra­tions con­taining mentioned elements, the amo­unt of absorption compared to unknown sam­ples using atomic absorption spectroscope is meas­ured. Comparison of the amount of ab­sorp­tion of the samples compared to stan­dard solution will result in concentrations of the ele­ments (10).

Results

Figure 1 shows the average concentration of to­tal suspended solids in the hall and breathing zone of the welders through two processes of electric welding using coated electrodes in Manual Metal Arc (MMA) welding and un­coated electrodes with CO2 in Metal Inert Gas (MIG) welding methods. As the mean of the data indicates, the concentration of par­ticu­late matter released at the source of weld­ing using coated and uncoated elec­trodes in CO2 was higher than the standard limits of TLVs proposed by American Confer­ence of Governmental Industrial Hy­gienists (ACGIH) (11) and also that of Ira­nian Technical Com­mittee of Occupational Health (ITCOH) (12). In contrast the indoor concentrations in the halls were lower than those limits.

Figure 1: The concentration of particulate matter in evaluated locations

Figure 2 Shows iron concentration in evaluated locations. It is noticeable that the Fe concen­tra­tion at the indoor environment was low but at the sources of MIG and MMA has ex­ceeded from the proposed standard limit of ACGIH, 1mg/m3, and also and also that of ITCOH. The interesting trend was the higher concentration of both Fe fumes and particu­late matters in electric welding using coated electrodes compared to that of CO2 tech­nique. It seems that using CO2 in welding point not only improves the quality and dura­bility of welding, but decreases the emis­sion of pollutants. This is an appropriate reason for substitution of this method of weld­ing instead of other electric arc welding techniques in in­dustries. This improvement can be referred to the fact that using CO2 welding, this gas will aggregate around the melted point and will hinder oxygen from reaching to the poi­nt which will result in oxi­dation of iron atoms. Basically carbon will be the product of the reaction which is resis­tant to the high tem­peratures experienced dur­ing the welding proc­ess and will remain in­tact. The only problem would be inhalation of CO2 itself which will result in dilution of oxygen in breathing air, increasing red blood cells and hemoglobin or polycythemia in the workers and combating this issue requires lo­cal ventilation and creat­ing a flow pattern from the worker to the weld­ing  point.

Figure 2: The concentration of iron in evaluated locations

One of the heavy metals which can be found in welding electrode compounds and also in the metal pieces going through the welding proc­ess and possibly in their coatings is man­ga­nese. This metal is considered highly toxic, with an allowable concentration of 0.2 mg/m3 ac­cording to ACGIH. The measured manganese concentrations in the samples were lower than allowable limits in all three groups of samples including MIG, MMA and indoor halls. Off course the mean concen­tration for using coated electrodes was more than 2 times as big as that for weld­ing processes of MIC in CO2 which can be related to the electrodes being coated in this method which may lead to production of other (Figure 3).

Figure 3: The concentration of manganese in evaluated locations

Figure 4 shows the nickel concentrations in eva­lu­ated locations. As the graph is shown, the concentration of nickel in the hall, indoor air, has been undetectable. For the source of MIG and MMA welding methods it was de­tected but of very low order. Analyzing of welding fu­mes taken from all locations has shown that there were no reasonable amount Cr+3, Cr+6, Zn, and Co.

Figure 4: Nickel concentrations in evaluated locations

The concentrations of environmental emis­sions of particulate matters through the stacks were also measured (Figure 5). As the fig­ure has shown, the particulate emissions for 2 stacks were lower and the third one was higher than 100 mg/m3 that ped as emis­sion standard for this kind of industrial activ­ity by Iranian Depart­ment of Environment (IDE) (13). The sig­nifi­cant emission rate of particulate matter from the stacks can affect the outside environ­ment. In order to evaluate this effect, concentra­tions of particulate mat­ter in the ambient air at upward and down­ward of the halls stacks  according to the di­rection of the wind blow have been meas­ured (Figure 6). Fortunately mea­s­ured concentra­tions were lower compared to the ex­posure standard level of 150 µg/m3 pro­posed by EPA (14) and also IDE. Comparing downward and upward concentrations indi­cates the effects of stacks' emissions from the welding hall in increasing outside particu­late concentrations to a level of about 10%.


Figure 5: Particulate concentrations measured at the stacks of  the welding hall

Figure 6: Outside air particulate concentrations (µg/m3)

Discussion

The results of this study have showed that the welding technique which used CO2 is safer than that use coated electrode. The sec­ond one produce more heavy metals oxides so can damage the welder to their toxic ef­fects. Off course there is some new welding technique such as that is done in argon gas which is safer the CO2 technique too. Pires in his studies, in 2006, has revealed that the arc welding in argon gas produces less fumes compared to arc welding in CO2 that gener­ate fumes contain more iron, manga­nese, sil­ica, titanium and sodium oxide (4). Also ac­cording to studies done by Korczyn­ski in 2000, generated fumes using arc weld­ing in CO2, contains more iron and manga­nese compar­ing with welding in argon gas (6). Although the work related diseases his­tory of welders werent searched in this study but many of them have complained from their respiratory problems in conven­tional interview during the sampling period. This is well according with James M. An­tonini and Hunnu et al. results in their re­searches which demonstrated the fact those full time welding technicians have suffered more from asthma, bronchitis, respi­ratory irri­tation, lung problems, and cancer (5, 15). The fig. 1 shows the higher particles emitted from sources of welding and this can endan­ger the welders to many disorders such as pneumonia and lung cancer. As research on acute symptoms of welding fumes on lung has indicated, the results of a 6 day period of exposure in mice to welding fumes showed that, contrary to the past belief, solubility of fumes in water is not an effective parameter in its toxicity and the more important factor would be the ability to release free radicals in lung tissues (8).

Generally, it can be stated that the concentra­tions of particulate matter at welders' breath­ing zone is hazardous. The majority of par­ticu­lates in the factory consist of fumes gen­erated during melting of metals which have diameters less than 0.5 micrometers and are able to penetrate to the most vulner­able ending parts of the respiratory system or the alveoli.  the welders usually used the per­sonal mouth dust mask, but because of high toxic heavy metal such as nickel, chromium and manga­nese in the welding fumes which have a risk of producing cancer, changing the welding technique to less emission ones may be noted. Also due to higher price of good quality dust masks in the market, the fac­tories owners pre­fer to buy cheaper ones which dont have eno­ugh efficiency to pre­vent fine particle to in­hale with welders, so controlling the emis­sion of pollutants in or­der to prevent related sy­mptoms in the work­ers would be necessary. Also the analysis of heavy metal fume con­cen­trations including iron, manganese and nickel in the samples in the region of weld­ers' breath­ing zone, indi­cated that electric welding using coated elec­trodes generate more pollutants com­pared to uncoated electrode welding in CO2 So substi­tuting of welding process with coated electrode with welding using inert gas such as argon or CO2 is recommended. Con­sider­ing lower standard limits of present heavy met­als in welding fumes reveal their high tox­icity which makes development of safer weld­ing procedures by industries and super­vising bodies unavoidable. Even though work­ers were not exposed to high concentra­tions of pollut­ants, using qualified masks, peri­odic physical examination and implemen­tation of an effi­cient local ventila­tion system is recom­men­ded. As the factory is located at the near dis­tance from the west of Tehran that usually suffer from air pollu­tion related to rising levels of particulate mat­ter, the industries in this area have addi­tional responsibilities to control their air emis­sions so considering the high content of pollutants in the ventilation exhaust system, de­signing a filtering device such as a wet sc­rubber in order to eliminate the particulate mat­ter of exhaust air suggested.

Acknowledgements

The authors wish to appreciate the Manage­ment Board of Mehvarsazan Irankhodro Com­pany for their sincere assistance.

Conflict of interest statement

The authors declare that they have no con­flict of interests.

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