Health Risk of Occupational Exposure in Welding Processes I. Genotoxic Risk

Health Risk of Occupational Exposure in Welding Processes II. Immunological Effects

Many of epidemiological studies have certified the relationship between welding and various forms of health damages. In our study we performed an immunological research within a group of twenty men, working in the risky environment of manufacturing of stainless steel constructions (11 welders and 9 grinders, average age was 31 years, 55 % of smokers, average time period in welding occupational exposure was 8 years). The exposed group of men was compared with a group of healthy blood donors, marked as the control group (people with various types of employment, living in same locality as a people from exposed group). People within the control group were not occupationally exposed to harmful chemical compounds (from 30 to 100 men were chosen for the individual immune parameters, average age of the whole group was 38 years, 40 % of smokers). When compared with the control group, the exposed group of welders and grinders showed higher level of C3 complement (p<0.001), orosomucoid (p<0.05), beta-2–microglobulin (p<0.001), neopterin (p<0.001) and all fagocytic cells (p<0.001). On the contrary, in the group of exposed people decreased values of IgA (p<0.001), IgG (p<0.001), IgM (p<0.001), transferin (p<0.001), alpha-1–antitrypsin (p<0.001), alpha-2–macroglobulin (p<0.001), haptoglobulin (p<0.001) and ceruloplasmin (p<0.05) were found. Some of these changes were characteristic for the exposed group. They could be considered as precursors of biological markers of effect for given type of exposure.

A Bio-assessment of DNA damage by Alkaline Comet Assay in metal workers of Kano metropolis, Nigeria

Metallic work is one of the widespread economic activities in urban Kano. Little or no attention is usually directed at occupational health risk by local or state authorities in Kano. The present work was aimed at the evaluation of DNA damage in metal workers by Alkaline Comet Assay in blood lymphocytes. The results showed that there was significant difference statistically between the level of DNA damage in blood lymphocytes of metal workers and control group (p < 0.05). In addition, the level of damage to DNA in blood of subjects with long term exposure and old age is of serious concern. There is the need to monitor occupational activities that can pose serious health risks. The relative ignorance of the metal workers about the health risks they are exposed to as well as the public should be addressed.

A Field Study on the Respiratory Deposition of the Nano-Sized Fraction of Mild and Stainless Steel Welding Fume Metals

A field study was conducted to estimate the amount of Cr, Mn, and Ni deposited in the respiratory system of 44 welders in two facilities. Each worker wore a nanoparticle respiratory deposition (NRD) sampler during gas metal arc welding (GMAW) of mild and stainless steel and flux-cored arc welding (FCAW) of mild steel. Several welders also wore side-by-side NRD samplers and closed-face filter cassettes for total particulate samples. The NRD sampler estimates the aerosol's nano-fraction deposited in the respiratory system. Mn concentrations for both welding processes ranged 2.8-199 μg/m3; Ni concentrations ranged 10-51 μg/m3; and Cr concentrations ranged 40-105 μg/m3. Cr(VI) concentrations ranged between 0.5-1.3 μg/m3. For the FCAW process the largest concentrations were reported for welders working in pairs. As a consequence this often resulted in workers being exposed to their own welding fumes and to those generated from the welding partner. Overall no correlation was found between air velocity and exposure (R2 = 0.002). The estimated percentage of the nano-fraction of Mn deposited in a mild-steel-welder's respiratory system ranged between 10 and 56%. For stainless steel welding, the NRD samplers collected 59% of the total Mn, 90% of the total Cr, and 64% of the total Ni. These results indicate that most of the Cr and more than half of the Ni and Mn in the fumes were in the fraction smaller than 300 nm.

Heart rate variability and DNA methylation levels are altered after short-term metal fume exposure among occupational welders: a repeated-measures panel study

Background

In occupational settings, boilermakers are exposed to high levels of metallic fine particulate matter (PM_2.5) generated during the welding process. The effect of welding PM_2.5 on heart rate variability (HRV) has been described, but the relationship between PM_2.5, DNA methylation, and HRV is not known.

Methods

In this repeated-measures panel study, we recorded resting HRV and measured DNA methylation levels in transposable elements Alu and long interspersed nuclear element-1 (LINE-1) in peripheral blood leukocytes under ambient conditions (pre-shift) and right after a welding task (post-shift) among 66 welders. We also monitored personal PM_2.5 level in the ambient environment and during the welding procedure.

Results

The concentration of welding PM_2.5 was significantly higher than background levels in the union hall (0.43 mg/m³ vs. 0.11 mg/m³, p < 0.0001). The natural log of transformed power in the high frequency range (ln HF) had a significantly negative association with PM_2.5 exposure (β = -0.76, p = 0.035). pNN10 and pNN20 also had a negative association with PM_2.5 exposure (β = -0.16%, p = 0.006 and β = -0.13%, p = 0.030, respectively). PM_2.5 was positively associated with LINE-1 methylation [β = 0.79%, 5-methylcytosince (%mC), p = 0.013]; adjusted for covariates. LINE-1 methylation did not show an independent association with HRV.

Conclusions

Acute decline of HRV was observed following exposure to welding PM_2.5 and evidence for an epigenetic response of transposable elements to short-term exposure to high-level metal-rich particulates was reported.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2458-14-1279) contains supplementary material, which is available to authorized users.

Physicochemical and toxicological characteristics of welding fume derived particles generated from real time welding processes

Welding fume particles have been well studied in the past; however, most studies have examined welding fumes generated from machine models rather than actual exposures. Furthermore, the link between physicochemical and toxicological properties of welding fume particles has not been well understood. This study aims to investigate the physicochemical properties of particles derived during real time welding processes generated during actual welding processes and to assess the particle size specific toxicological properties. A compact cascade impactor (Harvard CCI) was stationed within the welding booth to sample particles by size. Size fractionated particles were extracted and used for both off-line physicochemical analysis and in vitro cellular toxicological characterization. Each size fraction was analyzed for ions, elemental compositions, and mass concentration. Furthermore, real time optical particle monitors (DustTrak™, TSI Inc., Shoreview, Minn.) were used in the same welding booth to collect real time PM2.5 particle number concentration data. The sampled particles were extracted from the polyurethane foam (PUF) impaction substrates using a previously developed and validated protocol, and used in a cellular assay to assess oxidative stress. By mass, welding aerosols were found to be in coarse (PM 2.5–10), and fine (PM 0.1–2.5) size ranges. Most of the water soluble (WS) metals presented higher concentrations in the coarse size range with some exceptions such as sodium, which presented elevated concentration in the PM 0.1 size range. In vitro data showed size specific dependency, with the fine and ultrafine size ranges having the highest reactive oxygen species (ROS) activity. Additionally, this study suggests a possible correlation between welders' experience, the welding procedure and equipment used and particles generated from welding fumes. Mass concentrations and total metal and water soluble metal concentrations of welding fume particles may be greatly influenced by these factors. Furthermore, the results also confirmed the hypothesis that smaller particles generate more ROS activity and should be evaluated carefully for risk assessment.

Analysis of plasma indices of redox homeostasis in dairy cows reared in polluted areas of Piedmont (northern Italy)

Steel manufacturing is responsible for the emission of pollutants, including dioxins and transition metals, inducing reactive oxygen species generation and DNA damage. Dioxin pollution represents the major cause of milk and dairy product contamination, in Italy, and is associated with oxidative stress-related processes, that may impair health and performance of cows. We evaluated the effect of exposure to different concentrations of pollutants derived from steel manufacturing on blood redox homeostasis of bovine cows. We analyzed two groups of dairy cows (A, B), reared in two different polluted areas, and a control group of cows bred in an industry free area. The extent of exposure to contaminants was defined by measuring dioxin level in bulk milk samples collected from animals of each farm. This level was lower in milk of group A than in group B. Plasma concentrations of retinol, alpha-tocopherol and ascorbate, the total antioxidant capacity, and the activities of superoxide dismutase and glutathione peroxidase were higher in control group than in exposed groups. In particular, retinol and tocopherol levels were higher in the group with lower milk dioxin level. Plasma titers of protein-bound carbonyls (PC), nitro-tyrosine, and hydroperoxides were lower in control group than in A or B. Hydroperoxides and PC plasma concentrations were increased in the group with higher milk concentration of dioxin. Our results demonstrate that, irrespective of the nature of chemicals inducing oxidative modifications, the extent of damage to plasma protein and lipid, is correlated with the concentration of dioxin in milk. So, the characterization of blood redox status might be a useful tool for identifying animals exposed to environmental pollutants. Plasma concentrations of retinol, alpha-tocopherol, PC and hydroperoxides could therefore represent good indices of the extent of animal exposure, as they significantly change in groups with different milk concentrations of dioxin.

A trace metal survey of non-occupationally exposed Gauteng residents

Specific reference values for background levels of body burden of trace metals are not available for South Africa. Currently, laboratories measuring trace metal levels in workers use internationaly established values for comparison. A preliminary cross-sectional survey of 107 non-occupationally exposed volunteers of both genders and all races provided blood and urine samples. The samples were collected with consideration for possible routes of contamination. Seven metals were measured in blood and ten in urine. Reference ranges for a Gauteng population were then calculated using the central 95% of data to provide lower and upper limits, which were then compared to international limits. The trace metal levels described had both lower and higher reference ranges in blood and urine compared to international studies. This reflects the differences in the environments. Statistically significant differences in metal levels were observed by gender. The differences in detected trace metal levels in our sample as compared to other published data demonstrate the need for the establishment of local reference values for laboratories. The establishment of local 95% reference ranges would also allow South Africa to determine its exposure levels compared to those internationally. This would assist with establishing pollution control priorities.

The mutagenicity and carcinogenicity of inorganic manganese compounds: a synthesis of the evidence

Manganese (Mn), a naturally occurring element present in many foodstuffs, is an essential trace element with many biological functions. In industry, inorganic Mn compounds have a range of different applications, although the majority of Mn is used to make alloys and steel. For the general population, the major source of exposure to Mn is dietary, although drinking water may constitute an additional source in some regions. However, in occupationally exposed humans, inhalation of Mn is likely to be an important additional route. In general, Mn and its inorganic compounds are considered to possess low mutagenic or carcinogenic potential compared with some heavy metals. In this review, an up-to-date analysis of the available published studies on the carcinogenic and genotoxic potential of inorganic Mn is provided (organic Mn compounds are not considered). The current literature indicates that Mn may be weakly mutagenic in vitro and possibly clastogenic in vivo, with unknown genotoxic effects in humans; the possible mechanisms underlying these effects are discussed. The experimental evidence on carcinogenicity (quantitative increase in incidence of thyroid tumors in mice but not rats) does not provide any clear evidence, while the available occupational and environmental epidemiological evidence is equivocal as to whether exposure to inorganic Mn is associated with a significant cancer risk. Hence, it is concluded that there is insufficient evidence to indicate that inorganic Mn exposure produces cancer in animals or humans.

DNA strand breakage and lipid peroxidation after exposure to welding fumes in vivo

A remarkable number of complex aerosols are generated from welding processes. The objective of this study was to compare DNA damage and lipid peroxidation in plasma and in lung and in liver tissue of rats exposed to welding fumes in an exposure chamber with those of control animals. Three air samples from the chamber were also collected to assess the exposure dose for each exposure (total samplings = 18). Eight male Sprague-Dawley rats were exposed to welding fumes at a concentration of 1540.76 mg/m(3) for 10 min/day six times on day 1, day 3, day 7, day 15, day 30 and day 40. Lung, liver and kidney injury was measured following exposure, as well as in unexposed control rats (n = 4 at the beginning of the study). DNA strand breakage [tail moment (TMOM)] in exposed animals showed significant differences at day 1, day 4, day 7 and day 15 relative to the levels in control animals. Malondialdehyde (MDA, a lipid peroxidation product) levels increased gradually post-welding to 0.4 microM at 7 days. MDA and TMOM both reached maximum levels 7 days after the first exposure. At the start, an increasing trend in DNA strand breakage was more obvious than increases in MDA levels; MDA seemed to reflect long-term effects of exposure to welding fumes since it increased after 7 days and was sustained to 40 days in vivo. Significant differences in both MDA levels and DNA strand breakage were seen in lung, liver and kidney 40 days after the first fume inhalation. We conclude that acute exposure of rats to welding fumes causes noticeable oxidative damage and lipid peroxidation effects and that DNA damage may recover after long and repeat exposure. More chronic inhalation and low-dose studies are needed in order to further assess the effects of inhalation of welding fumes on DNA and to elucidate the possible causal mechanisms associated with the biologically damaging effects of welding fumes.

Assessment of occupational exposure to welding fumes by inductively coupled plasma-mass spectroscopy and by the alkaline Comet assay

Welding fumes are classified as possibly carcinogenic to humans (Group 2B) by the International Agency for Research on Cancer. In the current study, blood and urine concentrations of aluminum (Al), cadmium (Cd), cobalt (Co), chromium (Cr), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) were monitored by inductively coupled plasma-mass spectrometry (ICP-MS) in 30 welders and in 22 controls. In addition, DNA damage was examined in the lymphocytes of these subjects by the alkaline Comet assay. Two biological samples were taken from the welders at the beginning (BW) and at the end (EW) of a work week. In controls, collection of samples was limited to BW. Blood concentrations of Cd, Co, Cr, Ni, and Pb were higher in the welders than in the control group while higher concentrations of Al, Cd, Co, Cr, Ni, and Pb were detected in welder urines. There was no significant difference in the metal concentrations for the BW and EW welder samples. Increased levels of DNA damage were found in lymphocytes from welders as compared to the controls, and 20/30 welders had higher levels of DNA lesions in the EW than in the BW samples. Age had a significant effect on DNA damage in the control group. Spearman's rank correlation analysis indicated that there were positive correlations between blood concentrations of Al, Co, Ni, and Pb and the levels of DNA damage. A negative correlation was found between DNA damage and Mn in blood, while there was a positive correlation between urinary Mn concentration and DNA damage. These data indicate that occupational exposure to welding fumes increases DNA damage in lymphocytes.

Carcinogenic lead chromate induces DNA double-strand breaks in human lung cells

Hexavalent chromium (Cr(VI)) is a widespread environmental contaminant and a known human carcinogen, generally causing bronchial cancer. Recent studies have shown that the particulate forms of Cr(VI) are the potent carcinogens. Particulate Cr(VI) is known to induce a spectrum of DNA damage such as DNA single strand breaks, Cr-DNA adducts, DNA-protein crosslinks and chromosomal aberrations. However, particulate Cr(VI)-induced DNA double strand breaks (DSBs) have not been reported. Thus, the aim of this study was to determine if particulate Cr(VI)-induces DSBs in human bronchial cells. Using the single cell gel electrophoresis assay (comet assay), showed that lead chromate-induced concentration dependent increases in DSBs with 0.1, 0.5, 1 and 5 microg/cm2 lead chromate inducing a 20, 50, 67 and 109% relative increase in the tail integrated intensity ratio, respectively. Sodium chromate at concentrations of 1, 2.5 and 5 microM induced 38, 78 and 107% relative increase in the tail integrated intensity ratio, respectively. We also show that genotoxic concentrations of lead chromate activate the ataxia telangiectasia mutated (ATM) protein, which is thought to play a central role in the early stages of DSB detection and controls cellular responses to this damage. The H2A.X protein becomes rapidly phosphorylated on residue serine 139 in cells when DSBs are introduced into the DNA by ionizing radiation. By using immunofluorescence, we found that lead chromate-induced concentration-dependent increases in phosphorylated H2A.X (r-H2A.X) foci formation with 0.1, 0.5, 1, 5 and 10 microg/cm2 lead chromate inducing a relative increase in the number of cells with r-H2A.X foci formation of 43, 51, 115 and 129%, respectively.

Intermittent and chronic ultraviolet light exposure and uveal melanoma: a meta-analysis

OBJECTIVE

To examine the association between ultraviolet light exposure and uveal melanoma.

DESIGN

Meta-analysis.

METHODS

A review of 133 published reports on risk factors for uveal melanoma revealed 12 studies that provided sufficient information to calculate odds ratios (ORs) and standard errors for ultraviolet light exposure factors. Data from these studies were extracted and categorized into intermittent ultraviolet exposure factors (welding, outdoor leisure, photokeratitis) and chronic ultraviolet exposure factors (occupational sunlight exposure, birth latitude, lifetime ultraviolet exposure index). Summary statistics were calculated for all risk factors reported by > or =4 independent studies.

MAIN EXPOSURE MEASURES

Welding, outdoor leisure, photokeratitis, occupational sunlight exposure, birth latitude, and lifetime ultraviolet exposure index.

RESULTS

For intermittent ultraviolet exposure, welding was found to be a significant risk factor (5 studies, 1137 cases; OR, 2.05 [95% confidence interval [CI], 1.20-3.51]). Outdoor leisure was found to be nonsignificant (4 studies, 1332 cases; OR, 0.86 [95% CI, 0.71-1.04]). Photokeratitis conferred susceptibility in 3 reports studying this variable, but there were too few studies to validate meta-analyses. For chronic ultraviolet exposure, meta-analysis found occupational sunlight exposure to be a borderline nonsignificant risk factor for development of uveal melanoma (4 studies, 572 cases; OR, 1.37 [95% CI, 0.96-1.96]). Latitude of birth was found to be nonsignificant (5 studies, 1765 cases; OR, 1.08 [95% CI, 0.67-1.74]).

CONCLUSION

This meta-analysis yielded inconsistent results associating ultraviolet light with development of uveal melanoma. There was evidence implicating welding as a possible risk factor for uveal melanoma.