Control of exposure to hexavalent chromium and ozone in gas metal arc welding of stainless steels by use of a secondary shield gas.
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Previous work has demonstrated that the shield gas composition in gas metal arc welding can have a considerable effect on hexavalent chromium [Cr(VI)] concentration in the fume and on ozone concentrations near the arc. Normally a single shield gas is used. This paper describes a double shroud torch that allows used of concentric shield gases of different compositions. A solid stainless steel wire was used for welding. The double shroud torch used secondary shield gases containing small amounts of the reducing agents NO and C2H4. The Cr(VI) concentration in the fume and ozone concentration at a fixed point relative to the arc were measured and compared with results when using a single shield gas. Use of the reducing agents in secondary shielding using the double shroud torch was found to offer advantages for ozone concentration reduction compared with use in a conventional torch, but this was not found to be an advantage for reducing Cr(VI) concentrations. (+info)
Photoretinitis: an underestimated occupational injury?
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Non-ionizing radiation, which is produced in large amounts by welding arcs, may induce photophthalmia, keratoconjunctivitis and cataracts. Retinal injuries resulting from exposure to electric welding arcs have been reported, but such injuries are not commonly seen and may be misdiagnosed. A case is described of bilateral maculopathy in a millwright exposed to metal arc inert gas-shielded welding and oxygen lance light. Insurance adjudicators denied his claim, as they did not acknowledge the cause-and-effect relationship between welding and retinopathy. Welding emits a wide spectrum of radiation, ranging from IR to UV and beyond. UV and far-IR radiation are adsorbed by the cornea and the lens, whereas visible light and near-IR radiation penetrate to the retina. According to the intensity and time of exposure, they may cause thermal or photochemical retinal damage, which may be permanent and sight-threatening. Workers covered by compulsory collective insurance should be eligible for compensation in every case of welding light-induced retinal damage. (+info)
Cancer incidence and magnetic field exposure in industries using resistance welding in Sweden.
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AIMS: To investigate cancer incidence in workers exposed to high levels of extremely low frequency magnetic fields (ELF-MF). METHODS: A cohort based on the engineering industry was established. Industries assumed to use resistance welding in production were chosen in order to increase the prevalence of high exposed subjects and to reduce the influence of confounding factors. All men and women employed in these branches during 1985-94 were selected, 537 692 men and 180 529 women. Occupation, based on census information from 1980, 1985, and 1990, was linked to a job exposure matrix on ELF-MF. Four exposure groups were used by stratifying on mean workday ELF-MF exposure, using the lowest exposure group as reference. Cancer incidence was obtained by linkage to the Swedish Cancer Registry. RESULTS: Men in the very high exposure group showed an increased incidence of tumours of the kidney, pituitary gland, and biliary passages and liver; for these cancer sites an exposure-response relation was indicated. Women in the very high exposure group showed an increased incidence of astrocytoma I-IV, with a clear exposure-response pattern. An association was suggested in the high exposure group only, for cancer of the corpus uteri and multiple myeloma. Decreased risks in the very high exposure group among men were found for cancer of the colon and connective tissue/muscle. CONCLUSIONS: The results on cancer of the liver, kidney, and pituitary gland among men are in accordance with previous observations. Regarding brain tumours and leukaemia, the outcome for women provided further support of an association. The hypothesis of a biological mechanism involving the endocrine system was partly supported. (+info)
Ten-year update on mortality among mild-steel welders.
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OBJECTIVES: This study is an update on the lung cancer risk of mild-steel welders with no asbestos exposure using a cohort of nonwelders for comparison. METHODS: The subjects came from three United States (US) plants that manufactured heavy equipment. The follow-up was extended from 1988 to 1998. The welders were not exposed to asbestos (typical of shipyard welders) or to chromium or nickel (present in stainless steel). RESULTS: There were 108 lung cancer deaths among the welders and 128 such deaths among the nonwelders (double the previous number of lung cancer deaths). The standardized mortality ratio (SMR) for lung cancer was 1.46 [95% confidence interval (95% CI 1.20-1.76] for the welders and 1.18 (95% CI 0.98-1.40) for the nonwelders, both in comparison with the US general population. Direct comparison between the welders and nonwelders yielded a rate ratio of 1.22 (95% CI 0.93-1.59). Analyses using a 15-year lag time did not differ greatly from those of an unlagged analysis. There were no marked trends for lung cancer risk by duration of exposure or latency. Evidence from cross-sectional data from a sample of the cohort indicated that the welders smoked somewhat more than the US population and more than the nonwelders. An approximate adjustment of the rate ratios for possible confounding by smoking suggested that smoking may have accounted for about half of the excess lung cancer observed among the welders versus that of either reference population. CONCLUSIONS These data provide suggestive but not conclusive evidence of a modest lung cancer risk from mild-steel welding. (+info)
Nasal septum perforation of welders.
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During the periodic physical checkups in 1997-2000, the authors have found eleven cases of nasal septum perforation among 2,869 welders in Ulsan, Korea. They have not suffered from diseases and conditions that could cause septum perforation such as tuberculosis, syphilis, and long-term use of topical corticosteroids. And also they did not have trauma history and surgical experiences on their nasal septum. To investigate the cause of septum perforation we reviewed the past history of pre-employment, the results of annual working environment survey and the material safety data sheets of welding rods and steels with which they have dealt. We also analyzed the concentration of several metals of welding fume and the concentration of blood and urinary chromium. In the result, we assumed that the nasal septum perforation of welders was due to chronic exposure to low-level hexavalent chromium. (+info)
Effects of a welding helmet and dust respirators on respiration at rest and during exercise.
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The influence of welders' protective devices on respiration at rest and during exercise was studied under laboratory conditions. During exercise the devices caused increased ventilation and increased arterial carbon dioxide tension. In the case of the welding helmet the increase was probably a consequence of increased dead space. It is concluded that the physiological affects on respiration are of minor importance in themselves, but they should be taken into account when the degree of exposure to welding fumes is evaluated. (+info)
Failure after 5 years of self-regulation: a health and safety audit of New Zealand engineering companies carrying out welding.
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The aim of this study was to audit the degree of compliance with new health and safety legislation 5 years after enactment in a typical cross-section of New Zealand manufacturing industries. To this end, 299 randomly selected enterprises using a welding process were visited by Occupational Safety and Health Officers of the Department of Labour. An interviewer-administered questionnaire concerning the nature of the hazards encountered in that enterprise and the chosen control measures employed to protect the health of their employees was undertaken and analysed. Only 40% of New Zealand businesses in this sample undertaking welding had adopted the most basic of regulatory requirements to control health and safety risks. This percentage seemed independent of employer size. Fundamental safety issues (e.g. welding in confined spaces) were ignored by >50% of enterprises. In conclusion, self-management of health and safety risks had not occurred in over half the enterprises surveyed. (+info)
Elevated levels of DNA-protein crosslinks and micronuclei in peripheral lymphocytes of tannery workers exposed to trivalent chromium.
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DNA-protein crosslinks (DPC) are a promising biomarker of exposure to hexavalent chromium, a known human carcinogen. Although trivalent chromium is considered to have much lower toxicity, the risk involved in chronic exposure is uncertain. DPC may be a useful tool in clarifying this risk, by signaling an exposure of body tissues to biologically active forms of chromium. DPC quantification was carried out in lymphocytes of a group of tannery workers exposed to trivalent chromium, a small group of manual metal arc stainless steel welders exposed to hexavalent chromium and a control group. This biomarker was compared with the frequency of micronuclei in cytokinesis blocked peripheral lymphocytes as a biomarker of cytogenetic lesions and total plasma and urine chromium levels as an index of exposure. The results indicate a significant increase in the formation of DPC in tannery workers compared with controls (0.88 +/- 0.19 versus 0.57 +/- 0.21%, P < 0.001, Mann-Whitney test) and an even higher level of DPC in welders (2.22 +/- 1.12%, P = 0.03). Tanners showed a significant increase in micronucleated cells compared with controls (6.35 +/- 2.94 versus 3.58 +/- 1.69 per thousand, P < 0.01), whereas in welders this increase was not significant (5.40 +/- 1.67 per thousand ). Urinary chromium was increased in both groups, with a greater increase observed in tanners compared with controls (2.63 +/- 1.62 versus 0.70 +/- 0.38 microg/g creatinine, P < 0.001) than in welders (1.90 +/- 0.37 microg/g creatinine, P < 0.005). Plasma chromium was also increased in both groups (tanners 2.43 +/- 2.11 microg/l, P < 0.001, welders 1.55 +/- 0.67 microg/l, P < 0.005 versus controls 0.41 +/- 0.11 microg/l). In summary, chronic occupational exposure to trivalent chromium can lead to a detectable increase in lymphocyte DNA damage which correlates with a significant exposure of the cells to the metal. (+info)