1、Effects of Welding on Health VI American Welding Society o /- - AWS EWH-6 87 W 078Lt265 0005182 2 W Keywords-Welding, health, cancer, disease, exposure, fumes, gases, literature review, noise, radiation, toxicology Effects of Welding on Health-VI Research performed by Tracor Jitco, Rockville, Maryla
2、nd, under contract with the American Welding Society and supported by industry contributions. An updated (July 1984-December 1985) literature survey and evaluation of the data recorded since the publication of the first report (1979). This series of reports is intended to aid in the understanding of
3、 the health effects of welding. Performed by: Winifred Palmer May, 1987 Abstract This literature review with 172 citations has been prepared for the Safety and Health Committee of the American Welding Society to provide an assessment of current knowledge of the effects of welding on health, as well
4、as to aid in the formation of research projects in this area, as part, of an ongoing program sponsored by the Society. Previous work has included studies of the fumes, gases, radiation, and noise generated during various arc welding processes. Referenced materials are available from Tracor Jitco. Pr
5、epared for Safety and Health Committee American Welding Society 550 N.W. LeJeune Road, P.O. Box 351040 Miami, FL 33135 AWS EWH-6 87 m 078L1265 0005383 4 m International Standard Book Number: 0-87171-298-9 American Welding Society, 550 N.W. LeJeune Road, P. O. Box 351040, Miami, Florida 33135 O 1989
6、by American Welding Society. All rights reserved Printed in the United States of America This report is published as a service and convenience to the welding industry and is the product of an indepen- dent contractor (Tracor Jitco) which is solely responsible for its contents. The materials in this
7、report have not been independently reviewed or verified and are only offered as information. AWS assumes no responsibility for any claims that may arise from the use of this information. Users must make independent investigations to determine the applicability of this information for their purposes.
8、 AWS EWH-b 9 m 0742b5 0005L4 b m Personnel AWS Safety and Health Research Committee J.F. Hinrichs, Chairman K.L. Brown, Vice Chairman M.E. Kennebeck, Jr., Secretary M. K Anticoli W. T. Delong* W. S. Ho wes * E. Mastromatteo * Dr. M.T Neu R. J. Simonton D. W. Walsh A.O. Smith Corporation Lincoln Elec
9、tric Company American Welding Society General Motors Corporation Teled yne-McKay NEMA Consultant Caterpillar Tractor Company INCO Alloys International California Polytechnic State University *Advisor iii AWS EWH-6 87 = 07q2b5 0005385 the first covered data published before 1978, while the latter fou
10、r covered time periods between 1978 and June, 1984. The current report includes information published between July, 1984 and December, 1985. It should be read in conjunction with the previous volumes for a comprehensive treatment of the literature on the Effects of Welding on Health. Included in thi
11、s volume are studies of the characteristics of welding emissions that may have an impact on the control technologies necessary to protect the welder (Section 1). In keeping with previous volumes, the health studies are organized according to the affected organ system. The respiratory tract, the prim
12、ary route of exposure to welding emissions, is also a major target organ of a number of components of these emissions. Acute (e.g., metal fume fever, cadmium poisoning) as well as potential chronic respiratory effects (e.g.,emphysema, cancer) of welding emissions are of concern. However, chronic eff
13、ects are not as well defined or understood and whether there is an excess risk of cancer from these exposures has not been established. Continued research in the form of epidemiologic studies, investigations with laboratory animals, and in vitro genotoxicity studies will help to resolve this questio
14、n. Executive Summary Research on the health effects of welding continues to focus on the effects of chronic exposures to weld- ing fumes on the respiratory tract. A problem inher- ent in much of this research is the difficulty in con- ducting studies on homogeneous populations due to the variability
15、 in welding processes and in working conditions. With time, this problem has become bet- ter understood, and today many investigators are attempting to relate their research results to expo- sures during specific welding processes. The Respiratory Tract Abnormal shadows are often seen in chest X-ray
16、s of welders. These shadows represent deposits of par- ticles from welding fumes in the lungs (referred to as arc welders pneumoconiosis). Normally these shadows are not associated with loss of lung function or diseases of the respiratory tract and, in some cases, they disappear after affected welde
17、rs are removed from further exposure to the fumes. Several studies performed during this report period indicate that welders exhibit a reduction in the vol- ume of air that can be inhaled or expelled from the lungs (as measured by lung function tests). Other studies found no changes in lung capacity
18、 and attrib- uted the absence of effects on lung function among welders so good ventilation in the work area or to the use of gas tungsten arc welding (GTAW) which gen- erates little fume compared with most other com- monly used welding methods. The association of welding with bronchitis remains unc
19、lear. An excess of bronchitis was observed in welders in nine studies published during this report period. In three studies, the incidence of bronchitis could not be separated from the use of tobacco. One investigator suggested that smoking and welding may act synergistically in the induction of bro
20、nchitis. Bronchitis was observed more frequently in shielded metal arc welders than in gas metal arc welders, which supports the supposition that bronchitis may be related to the intensity of welding exposure. The question of whether welders have an increased risk of lung cancer remains unresolved.
21、In the past, results of cancer epidemiology studies of welders have been inconsistent, with several studies suggest- ing that the incidence of lung cancer may be elevated among welders. Nickel and hexavalent chromium, potential human carcinogens, may be present in sig- nificant quantities in stainle
22、ss steel welding fumes. Past studies neither refuted nor supported the hypothesis that the lung cancer risk is elevated among stainless steel welders. Investigations currently in progress are focusing on populations exposed to welding fumes with known or suspected carcinogens. The results of these s
23、tudies should begin to provide a much needed answer to the question of whether can- cer in welders is associated with exposures to specific welding processes. Severe acute respiratory distress can result from highly toxic chemicals, such as phosgene, that arise from interactions of degreasing agents
24、 such as l,l,l- trichloroethane and ultra-violet light. Because of this, vapors from degreasing agents or paints can present a hazard in welding shops. Two incidents were described in which welders may have suffered respiratory distress from gas metal arc welding (GMAW) in an area where degreasing a
25、gents were used. Biological Monitoring of Exposure to Welding Emissions Industrial hygiene measurements of airborne con- centrations of contaminants are exceedingly impor- tant for controlling exposures to welding emissions. However, they do not take into account variations in physiology and persona
26、l habits among workers and thus, do not reflect the amount of material actually taken up by the body from the work environment. In conjunction with determination of airborne exposure levels, biological monitoring, or the measurement of chemicals or their metabolites in the body fluids, may provide a
27、 means for estimating the actual dose of contaminants taken up by the body. As in past years, considerable effort was expended during the current report period to identify sub- stances that can be monitored in this way. The feasi- bility of applying biological monitoring techniques to elements such
28、as chromium, nickel, lead, cadmium and manganese was examined. Blood and urine chro- mium levels, but not nickel levels, were found to be useful for estimating exposure to fumes generated by welding of stainless steel. 3 Tech n cal The Exposure Fumes The concentration of solids in welding aerosols v
29、aries with the welding process, electrode, base metal, current, voltage, and base metal coatings. Shielded metal arc welding (SMAW) and flux cored arc welding (FCAW) produce more fumes, while GTAW produces much less fumes than other welding and allied processes. Because of its potential carcino- gen
30、icity to humans, the concentration of hexavalent chromium in fumes is important and has received a great deal of attention. The ratio of hexavalent to total chromium is much higher in fumes generated by SMAW and FCAW than in those generated by GMAW and GTAW. Standardized methods for fume sample coll
31、ection in laboratory settings and in the work place are important for providing realistic appraisals of risk and enabling comparison of results between labora- tories. New standards for collecting samples of air- borne particulates in the breathing zone and work area (Ref. 6) and for determination o
32、f fume genera- tion rates and total fume emissions (Ref. 5) have been published by the American Welding Society. The Swedish fume box for measuring fume emis- sion rates (FER) generated by SMAW electrodes was modified by the British Welding Institute to enable determination of FERS from other weldin
33、g processes (Refs. 94 and 99). FERS of carbon arc gouging, FCAW, GMAW, and GTAW, determined by the modified fume box, were generally within ranges found by other techniques (Ref. 94). Based on data obtained from fume box determinations, the British Welding Institute has established a computerized da
34、ta base for storage and retrieval of data applicable to emissions from all arc welding processes (Ref. 100). Using an aerosol photometer to obtain rapid mea- surements of welding fume concentrations at one sec- ond intervals, Glinsmann and Rosenthal (Ref. 46) showed that fume generation during weldi
35、ng is not uniform and continuous but rather there are wide and instantaneous fhctuations in fume concentra- Summary tion. Such fluctuations did not occur during oxyace- tylene cutting. The chemical composition of fumes may vary with fume generation rate as well as with the formulation of the electro
36、de. Tandon et al. (Ref. 151) showed that the iron content of the fumes was directly propor- tional, and the fluoride content was inversely propor- tional, to fume generation rates. A strong correlation between the ratio of water-soluble hexavalent chro- mium to total chromium in the fume and the con
37、cen- tration of sodium and potassium in the flux was observed. Substitution of sodium silicate for potassium sili- cate in basic electrode coatings reduced fume produc- tion by twenty five percent (Ref. 86). Limpe1 et al. (Ref. 81) found that the quantity of water-soluble, but not total fluorine, wa
38、s considerably greater in fumes generated by electrodes containing potassium silicate than in those with sodium silicate. Other experiments showed that quantities of hydrogen flu- oride (HF) and silicon tetrafluoride (SiF4) increased with the concentration of silica (Si02) in the elec- trode coating
39、, but only HF increased with the mois- ture content (Ref. 165). The levels of hexavalent chromium in the fumes were directly dependent on the quantities of sodium silicate, potassium and cal- cium levels in the electrode coating (Ref. 86). Thorne and Hewitt (Ref. 157) showed that fume formation duri
40、ng brazing Ag-Zn-Cd-Cu alloys is related to the amount of bubbling in molten brazing flux. They concluded that exposures to cadmium fumes can be reduced by raising the pH of the fluoro- borate flux to reduce hydrogen gas formation and by lowering the concentrations of compounds (boric acid and potas
41、sium hydrogen fluoride) in the flux that are largely responsible for bubble formation. The issue of which technique is best for measuring hexavalent and total chromium in fumes remains controversial. Dare et al. (Ref. 29) criticized the interlaboratory round robin validation study of the Blakely and
42、 Zatka method for hexavalent chromium determination (Ref. 22) for not taking into account the short-lived hexavalent chromium species detected in fresh GMAW fumes collected by water impinge- ment (Refs. 53 and 156). Zatka (Ref. 166) suggested that this hexavalent chromium species derives from a - 5
43、AWS EWH-6 87 0784265 0005373 7 . 6 chemical reaction within the impingement collector fluid rather than by reactions within the fume solids. Zatka also modified his initial method (Ref. 22) for hexavalent chromium determination to suppress the small amount of hexavalent chromium that can form during
44、 digestion of trivalent chromium in hot alka- line solutions. need for new standards which would allow realistic appraisal of the hazards associated with welding and cutting of primed materials was stressed (Ref. 97). Degreasing Agents Gases Ozone, carbon monoxide, carbon dioxide and nitrogen oxides
45、 are the principal gases generated by welding. The quantities of nitrogen oxides, carbon monoxide, carbon dioxide and methane released dur- ing SMAW varies considerably with the electrode (Ref, 158). Nemcova (Refs. 108 and 109) reported finding high concentrations of nitrogen oxides and ozone during
46、 plasma arc cutting of steel, aluminum, and copper. Nitrogen oxide levels were relatively high during argon-shielded GTAW of copper and aluminum. Radiation Eriksen (Ref. 37) demonstrated that a short burst of high levels of ultraviolet (UV) radiation occurs during the initial phase of arc ignition d
47、uring GMAW of aluminum. The intensity of this UV overshoot was more than ten times that of the UV light emitted when the arc was burning “smoothlyy. Because of the intensity of the UV overshoot, the unprotected eye at a distance of 0.5 meters may suffer welders flash after exposure to radiation from
48、 only one ignition. Production Coatings Organic compounds, metal oxides, and toxic gases may be released when welding metals coated with paints or primers. Moreton (Ref. 98) and McMillan (Ref. 91) reviewed the hazards of welding coated or contaminated surfaces. Moreton described and eval- uated stan
49、dard procedures recommended by repre- sentatives of the welding and paint industries in 1964 and 1968 for assessing the toxicity of fumes released from flame cutting or welding of primed metals, The Fumes from degreasing agents or paints can present a major hazard in welding (Refs. 9 and 91). Chlorinated hydrocarbons such as trichloroethylene, perchloroethylene and 1 , 1 , l-trichloroethane can decompose in the presence of ultraviolet radiation into highly toxic compounds such as phosgene and dichloroacetyl chloride. Two incidents were described in which photochem- ical decompositi
