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PubMed1998

Laser welding of a cobalt-chromium removable partial denture alloy.

STATEMENT OF PROBLEM: The electric alloy brazed joints of removable partial denture alloys have failed frequently after routine usage. PURPOSE: A technique providing higher joint strengths was investigated. This investigation compared the tensile strengths of electric-brazed and laser-welded joints for a cobalt-chromium removable partial denture alloy. MATERIAL AND METHODS: Twenty-four cobalt-chromium standard tensile testing rods were prepared and divided into three groups of eight. All specimens in the control group (group 1) were left in the as-cast condition. Groups 2 and 3 were the test specimens, which were sectioned at the center of the rod. Eight specimens were joined by using electric brazing, and the remaining specimens were joined by using laser welding. After joining, each joint was ground to a uniform diameter, then tested to tensile failure on an Instron universal testing machine. Failure loads were recorded and fracture stress calculated. Statistical analysis was applied. RESULTS: The student-Newman-Keuls test showed a highly significant difference between the joint strengths of the as-cast control specimens, the electric-brazed and laser-welded joints. CONCLUSIONS: The tensile strengths of the as-cast joints were higher than those for the laser-welded joints, and both were higher than the electric-brazed joint strengths.

Analysis of Variance↗
PubMedDate not supplied

Semen quality and sex hormones with reference to metal welding.

Welding may involve hazards to the male reproductive system, but previous studies of semen quality have produced inconsistent results. We studied the effects of welding on markers of semen quality in a Danish nationwide sample of 430 first-time pregnancy planners without earlier reproductive experience. Couples were recruited among members of the union of metal workers and three other trade unions and were followed from termination of birth control until pregnancy for a maximum of six menstrual cycles. The males provided semen samples in each cycle. Median sperm density for welders was 56 x 10(6)/mL (52.5 x 10(6)/mL and 50.0 x 10(6)/mL in two reference groups). No statistically significant differences attributable to welding were found in proportions of morphologically normal sperm, sperm motility assessed by computer-aided sperm analysis, or sex hormones (testosterone, follicle-stimulating hormone, and luteinizing hormone). These negative findings may not apply to populations with high-level exposure to welding fume or to welders exposed to other putative hazards, e.g., heat.

Adult↗
PubMed2000

Occupational health concerns in the welding industry.

The Workplace Safety and Health Branch initiated a proactive study in the welding industry in Manitoba. Eight welding companies participated in this study. Health concerns raised by welders were welders' flash, sore/red/teary eyes, headaches, nosebleeds, and a black mucous discharge from their nasal membrane. Most welders expressed concern regarding excessive smoke levels in the workplace and inadequate ventilation. Types of welding identified were MIG mild steel, MIG stainless steel, and TIG aluminum. Monitoring involved an assessment of noise levels, fume composition, and carbon monoxide and ozone concentrations. Metal analyses were according to National Institute for Occupational Safety and Health (NIOSH) Method 7300. Noise dosimeters used were the Quest model 100 and Micro 14 & 15. Carbon monoxide was monitored using the Gastech Model 4700 and ozone using the AID Portable Ozone Meter Model 560. In Manitoba, a hearing conservation program is required when the equivalent sound exposure level (normalized Lex 8-hr) exceeds 80 dBA-weighted. The American Conference of Governmental Industrial Hygienists' threshold limit value-time weighted average (ACGIH TLV-TWA) for iron is 5.0 mg/m3, manganese is 0.2 mg/m3, carbon monoxide is 25 ppm, and ozone is 0.05 ppm (heavy work), 0.08 ppm (moderate work), and 0.1 ppm (light work). Welders' personal exposures to manganese ranged from 0.01-4.93 mg/m3 (N = 42; AM = 0.5; GM = 0.2; SD +/- 0.9; GSD +/- 3.2) and to iron ranged from 0.04-16.29 mg/m3 (N = 42; AM = 3.0; GM = 1.4; SD +/- 3.5; GSD +/- 2.5). Noise exposures ranged from 79-98 dBA (N = 44; AM = 88.9; GM = 88.8; SD +/- 4.2; GSD +/- 1.0). Carbon monoxide levels were less than 5.0 ppm (at source) and ozone levels varied from 0.4-0.6 ppm (at source). Ventilation upgrades in the workplace were required in most welding shops. Only 7 percent of the welders wore respiratory protection. A hearing conservation program and hearing protection were required at all monitored workplaces.

Adult↗
PubMed1985

Evaluation of an aerosol photometer for monitoring welding fume levels in a shipyard.

A direct reading aerosol photometer (Sibata P-5 Digital Dust Indicator) was used to assess fume levels from welding and burning operations in a shipyard. The photometer was calibrated with gravimetric analysis of filter samples collected simultaneously with instrument readings. A six-fold difference between calibration factors for personal and area samples was found. This difference can be explained by expected changes in particle size distributions in welding fume. Monitoring of various work situations was performed in order to assess the value of the photometer for the measurement of fume. Measurements categorized by enclosure of space and quality of ventilation indicated the presence of high fume levels in semi-enclosed and enclosed spaces. The build up of welding fume in an enclosed space occurred over several minutes after the arc was struck. Decay likewise required several minutes. During welding, wide fluctuations of fume concentrations were found. Thus a single reading was not adequate to characterize average fume levels. Although this type of instrument is useful for locating areas with high fume levels and monitoring the effectiveness of ventilation, the uncertainty in calibration factors makes accurate determinations of fume levels difficult.

Aerosols↗
PubMed1995

Welding helmet airborne fume concentrations compared to personal breathing zone sampling.

Metal fume concentrations inside the welding helmet and in the personal breathing zone in 23 experimental welding exposures were studied to explore whether welding helmet use substantially attenuates exposure to airborne metal fume. Observations produced a mean ratio of inside to outside metal fume concentrations of 0.9 +/- S.D. 0.2 with a highly variable effect. Iron fume concentration was inversely correlated with this ratio, representing greater helmet-associated attenuation with heavier exposure (r = -0.70, p < 0.001). In contrast to previous reports, these data suggest that welding helmet use provides marginal and highly variable reductions in fume exposure and cannot substitute for standard respiratory protection.

Adult↗
PubMed1995

The particle size distribution, density, and specific surface area of welding fumes from SMAW and GMAW mild and stainless steel consumables.

Particle size distributions were measured for fumes from mild steel (MS) and stainless steel (SS); shielded metal arc welding (SMAW) and gas metal arc welding (GMAW) consumables. Up to six samples of each type of fume were collected in a test chamber using a micro-orifice uniform deposit (cascade) impactor. Bulk samples were collected for bulk fume density and specific surface area analysis. Additional impactor samples were collected using polycarbonate substrates and analyzed for elemental content. The parameters of the underlying mass distributions were estimated using a nonlinear least squares analysis method that fits a smooth curve to the mass fraction distribution histograms of all samples for each type of fume. The mass distributions for all four consumables were unimodal and well described by a lognormal distribution; with the exception of the GMAW-MS and GMAW-SS comparison, they were statistically different. The estimated mass distribution geometric means for the SMAW-MS and SMAW-SS consumables were 0.59 and 0.46 micron aerodynamic equivalent diameter (AED), respectively, and 0.25 micron AED for both the GMAW-MS and GMAW-SS consumables. The bulk fume densities and specific surface areas were similar for the SMAW-MS and SMAW-SS consumables and for the GMAW-MS and GMAW-SS consumables, but differed between SMAW and GMAW. The distribution of metals was similar to the mass distributions. Particle size distributions and physical properties of the fumes were considerably different when categorized by welding method. Within each welding method there was little difference between MS and SS fumes.

Aerosols↗
PubMed1997

Angles of entry of ultraviolet radiation into welding helmets.

To investigate the angles of entry of ultraviolet (UV) radiation into welding helmets, a UV detector was placed in the eye socket of a head form that was then fitted with a range of welding helmets. The head form was exposed to a collimated beam of UV radiation from various orientations, and the amount of infiltration was measured. Radiation was found to be reflected from the filter plate and into the detector (eye) after entering through (1) an opening between the edge of the shield and the side of the face, and (2) an opening between the top edge of the shield and the top of the head. These results have significance for UV exposure when welding is performed in highly reflective and enclosed situations, and for the design of welding helmets.

Environmental Monitoring↗
PubMed2001

A model for prediction of fume formation rate in gas metal arc welding (GMAW), globular and spray modes, DC electrode positive.

Prediction of fume formation rate during metal arc welding and the composition of the fume are of interest to occupational hygienists concerned with risk assessment and to manufacturers of welding consumables. A model for GMAW (DC electrode positive) is described based on the welder determined process parameters (current, wire feed rate and wire composition), on the surface area of molten metal in the arc and on the partial vapour pressures of the component metals of the alloy wire. The model is applicable to globular and spray welding transfer modes but not to dip mode. Metal evaporation from a droplet is evaluated for short time increments and total evaporation obtained by summation over the life of the droplet. The contribution of fume derived from the weld pool and spatter (particles of metal ejected from the arc) is discussed, as are limitations of the model. Calculated droplet temperatures are similar to values determined by other workers. A degree of relationship between predicted and measured fume formation rates is demonstrated but the model does not at this stage provide a reliable predictive tool.

Air Pollutants, Occupational↗
PubMed1989

Respiratory symptoms and functional impairment from acute (cross-shift) exposure to welding gases and fumes.

One hundred forty-five male welders from a West Coast shipyard were studied cross-sectionally and across a Monday work shift by pulmonary function tests and a questionnaire. Ten years of welding was associated with chronic bronchitis in 23.3% of nonsmokers compared to 3.3% in male controls, shortness of breath in 31.5% of nonsmokers compared to 1.5% in controls, and chest pain or heaviness in 38.4% compared to 4.4% in controls. Men who welded aluminum but had never smoked had more frequent wheezing, chest tightness, phlegm, feverishness and fatigue than those welding mild (black) or stainless steel. There were no significant cross-shift effects from welding exposure on measurements of pulmonary function. Although baseline expiratory flows were reduced slightly when compared to Caucasian-predicted values, ethnic specific comparisons for the largest subgroup showed only that FEF25-75 was reduced to 92.9 percentage of predicted values. Diffusing capacities for carbon monoxide were significantly reduced as compared to referents. The pulmonary function values of 25 current smokers were indistinguishable from the 41 who had never smoked, which probably reflects their low consumption of cigarettes.

Acute Disease↗
PubMed1996

Ocular hazards of industrial spot welding.

Any welding process is perceived to be a radiation hazard to the eye. Site visits were made to an automotive assembly plant to assess the levels of optical radiation and other hazards on the production line. Measurements were taken with a scanning spectro-radiometer and optical power and energy meters at operating working distances at spot welding stations where nonrobotic procedures were performed. Ultraviolet (UV) irradiance levels produced while spot welding with electrodes operating at 10 to 15 kA and 10 to 20 V were several orders of magnitude below recommended safety limits for industrial exposure. Flashes were rich in visible light and infrared (IR) radiation, but not at hazardous levels. The principal hazards in manual spot welding with high-current electrodes are high-speed droplets of molten metal produced by the process. These are easily defended against by wraparound polycarbonate eye shields.

Eye↗
PubMed1996

Evaluation of the utility of spirometry in a regional public health screening program for workers exposed to welding fumes.

The objective of this study was to determine the usefulness of spirometry in the screening of chronic pulmonary problems related to exposure to welding fumes, in a regional public health-based screening program. Pulmonary questionnaires and spirometric tests were administered twice at 5-year intervals on 229 welders/cutters (mean age, 39.9 years from 31 metal manufacturing plants. The baseline mean value at the first test for the forced expiratory volume in one second (FEV1) was 102% of predicted, the forced vital capacity (FVC) was 107%, and the FEV1/FVC ratio was 79%. The mean annual changes in the three spirometric indicators were -47 mL, -46 mL, and -0.3%, respectively. The usefulness of spirometry was assessed by looking at the relationship between exposure to welding fumes and changes in spirometric indices, in multivariate linear regression analysis, accounting for age, height, and smoking. A high lifetime exposure to welding fumes was associated with better lung functions in the cross-sectional approach (healthy worker effect) but not in the longitudinal approach, where no association was found. We concluded that the public health regional application of this screening program generated too many sources of variation for spirometry to fulfill the objective of early detection of pulmonary function decline related to exposure to welding fumes. Based on these observations, we recommend that maintaining questionnaire screening, with spirometry reserved as a second-line diagnostic intervention.

Adult↗
PubMed2006

Clinical experiences with laser-welded titanium frameworks supported by implants in the edentulous mandible: a 10-year follow-up study.

BACKGROUND: Long-term follow-up studies for more than 5 years are not available on laser-welded titanium frameworks. PURPOSE: To report and compare 10-year data on implant-supported prostheses in the edentulous mandible provided with laser-welded titanium frameworks and conventional gold alloy frameworks. MATERIALS AND METHODS: Altogether, 155 patients were consecutively treated with prostheses at abutment level with two generations of fixed laser-welded titanium frameworks (test groups). A control group of 53 randomly selected patients with conventional gold alloy castings was used for comparison. Clinical and radiographic 10-year data were collected for the three groups. RESULTS: All patients followed-up for 10 years (n=112) still had fixed prostheses in the mandible (cumulative success rate [CSR] 100%). The overall 10-year cumulative success rate (CSR) was 92.8 and 100.0% for titanium and gold alloy frameworks, respectively. Ten-year implant cumulative survival rate (CSR) was 99.4 and 99.6% for the test and control groups, respectively. Average 10-year bone loss was 0.56 (SD 0.45) mm for the titanium group and 0.77 (SD 0.36) mm for the control group (p < 0.05). The most common complications for titanium frameworks were resin or veneer fractures, soft tissue inflammation, and fractures (12.9%) of the metal frame. Loose and fractured implant screw components were below 3%. CONCLUSION: Excellent overall long-term results with 100% CSR could be achieved with the present treatment modality. Fractures of the metal frames and remade prostheses were more common for the laser-welded titanium frameworks, and the first generation of titanium frameworks worked poorly when compared with gold alloy frameworks during 10 years (p < 0.05). However, on average more bone loss was observed for implants supporting gold alloy frameworks during 10 years. The reasons for this difference are not clear.

Adult↗
PubMed2005

Welding related occupational eye injuries: a narrative analysis.

OBJECTIVE: To determine the activities and circumstances proximal to a welding related occupational eye injury, a hybrid narrative coding approach derived from two well developed classification systems was developed to categorize and describe the activity, initiating process, mechanism of injury, object and/or substance, and the use of protective eyewear from the narrative text data reported for each injury. METHODS: Routinely collected workers' compensation claims over a one year period (2000) were analyzed from a large US insurance provider. An index term search algorithm of occupation, incident, and injury description fields identified 2209 potential welding related eye injury claims. After detailed review of these claims, 1353 welders and 822 non-welders were analyzed. RESULTS: During 2000, eye(s) as the primary injured body part accounted for 5% (n = 26 413) of all compensation claims. Eye injuries accounted for 25% of all claims for welders. Subjects were mainly male (97.1%) and from manufacturing (70.4%), service (11.8%), or construction (8.4%) related industries. Most injuries were foreign body (71.7%) or burn (22.2%) and 17.6% were bilateral. Common activities include welding (31.9%) and/or grinding (22.5%). Being struck by an airborne object occurred in 56.3% of cases. Non-welders showed similar patterns except that burns (43.8%) were more frequent and more often initiated by another worker (13.9%). CONCLUSIONS: Narrative injury text provides valuable data to supplement traditional epidemiologic analyses. Workers performing welding tasks or working nearby welders should be trained to recognize potential hazards and the effective use of proper safety equipment to prevent ocular injury.

Accidents, Occupational↗
PubMed1983

Stainless steel manual metal arc welding fumes in rats.

Forty two male Wistar rats were exposed to manual metal arc (MMA) stainless steel (SS) welding fumes generated by an automatic welding device for "nose-only" exposure. The exposure simulated an actual MMA/SS welding environment as closely as possible. For the retention study, the duration of exposure was one hour per workday for one, two, three, of four weeks and for the clearance study four weeks. The retention and clearance of the chromium, nickel, and iron found in MMA/SS welding fumes in the rats' lungs were studied as was the distribution of the metals to other organs. Instrumental neutron activation analysis (INAA) was used for the multi-element chemical activation analyses. The concentrations of chromium and nickel in the blood and the urine were determined by atomic absorption method (AAS). The retention of exogenous iron was determined by a magnetic measuring method. The results indicated that the lungs were the target organs of soluble hexavalent chromates. The half times of lung clearance for Cr, Ni, and Fe were 40 +/- 4 d, 20 +/- d, and 50 +/- 10 d. When the lung clearance curves are compared, the half times of Cr and Fe lung clearance are similar but nickel disappears faster. The distribution and clearance patterns of chromium to other organs differ from those obtained after single intravenous or intratracheal injections of alkaline chromates.

Animals↗
PubMed2006

Occupational asthma caused by stainless steel welding fumes: a clinical study.

The aim of the present study was to describe the cases of occupational asthma (OA) due to stainless steel welding fumes diagnosed at the Finnish Institute of Occupational Health during the period 1994-2003. OA was diagnosed according to patient history, lung function examinations and welding challenge tests with measurements of the forced expiratory volume in one second (FEV(1)) and peak expiratory flow (PEF) values. The present series comprised 34 patients, all male, with a mean age of 44.7 yrs (range 22-57), mainly working as welders. The mean duration of exposure was 22.4 yrs, and the mean duration of exposure before the onset of respiratory symptoms was 18 yrs. Dyspnoea was the most frequently reported work-related respiratory symptom. During the inhalation challenge tests, the mode of the asthmatic FEV(1)/PEF reaction was delayed in 16 (47%) patients, immediate in nine (26%) patients and dual (both immediate and delayed) in nine (26%) patients. In the follow-up assessment 6 months later, only six patients were considered able to continue performing welding tasks, whereas occupational injury pension was recommended for seven, and measures of vocational rehabilitation for 14 patients. In most cases, after the diagnosis of occupational asthma, the continuation of welding work was not possible.

Adult↗
PubMed2001

Welding-related parkinsonism: clinical features, treatment, and pathophysiology.

OBJECTIVE: To determine whether welding-related parkinsonism differs from idiopathic PD. BACKGROUND: Welding is considered a cause of parkinsonism, but little information is available about the clinical features exhibited by patients or whether this is a distinct disorder. METHODS: The authors performed a case-control study that compared the clinical features of 15 career welders, who were ascertained through an academic movement disorders center and compared to two control groups with idiopathic PD. One control group was ascertained sequentially to compare the frequency of clinical features, and the second control group was sex- and age-matched to compare the frequency of motor fluctuations. RESULTS: Welders were exposed to a mean of 47,144 welding hours. Welders had a younger age at onset (46 years) of PD compared with sequentially ascertained controls (63 years; p < 0.0001). There was no difference in frequency of tremor, bradykinesia, rigidity, asymmetric onset, postural instability, family history, clinical depression, dementia, or drug-induced psychosis between the welders and the two control groups. All treated welders responded to levodopa. Motor fluctuations and dyskinesias occurred at a similar frequency in welders and the two control groups. PET with 6-[18F]fluorodopa obtained in two of the welders showed findings typical of idiopathic PD, with greatest loss in posterior putamen. CONCLUSIONS: Parkinsonism in welders is distinguished clinically only by age at onset, suggesting welding may be a risk factor for PD. These preliminary data cannot exclude a genetic contribution to susceptibility in these exposed individuals.

Adult↗
PubMedDate not supplied

Optical radiation hazards of welding arcs.

Welding, a widely used industrial process, is one of the most intense artificial sources of optical radiation. Each type of welding process emits a different spectrum and intensity of optical radiation. For most processes, ultraviolet and visible radiation are the main components of the emission. Such factors as arc current, shielding gas, and base metal influence the emission spectrum. Adverse effects are confined to the skin and eyes, with welders suffering from a higher proportion of optical radiation associated eye conditions than do non-welders. Erythema is a common skin condition among welders, but conditions like skin cancer are rare. An evaluation of optical radiation from welding consists of determining an effective irradiance and a maximum permissible exposure duration, which can be very short (from seconds to minutes). Control measures include the use of screens to localize the hazards, and the use of personal protective equipment, such as protective clothing, safety spectacles, and welding helmets. Recent studies indicate that optical radiation can infiltrate into helmets and workers may be exposed to excessive levels. Overall, further investigation into adverse health effects and safety equipment design is warranted.

Eye↗
PubMed2000

Laboratory measurement of hazardous fumes and gases at a point corresponding to breathing zone of welder during a CO2 arc welding.

Concentrations of fumes, ozone (O3), carbon monoxide (CO), nitric oxide (NO), manganese (Mn) and total and hexavalent chromium (Cr) as well as size distribution of fumes were measured at a point corresponding to the welder's breathing zone during CO2-arc welding, using a welding robot and three kinds of wires. Concentrations of fumes, O3, CO, Mn and total-Cr were found to exceed their corresponding occupational exposure limit (OEL) values, while the concentrations of NO and Cr(VI) were below those OEL levels. Airborne concentration of Mn exceeded its OEL value, and the Mn content was 8 times higher in welding fumes than in the wire. Using an additive equation of OEL and exposure concentration of each hazardous component, health risk in welders with combined exposure to welding fumes and gases was assessed as 18.6 to 46.0 times of OEL, which exceeded the unity. This finding suggests that effective protection of welders from the exposure can be attained by use of the supplied-air respirator or combined use of a dust respirator and a local exhaust system.

Air Pollutants, Occupational↗