Biomonitoring of genotoxic exposure among stainless steel welders.

A biosurvey in the Danish metal industry measured the genotoxic exposure from stainless steel welding. The study comprised measurements of chromosomal aberrations (CA), sister-chromatid exchanges (SCE), unscheduled DNA synthesis (UDS) in peripheral lymphocytes and serum immunoglobulin G. Environmental monitoring of welding fumes and selected metal oxides, biomonitoring of chromium and nickel in serum and urine and mutagenic activity in urine, and evaluation of semen quality were also done. Manual metal arc (MMA) welding and tungsten inert gas (TIG) welding were the dominant welding processes. A higher frequency of chromosomal aberrations, classified as translocations, double minutes, exchanges and rings, was observed in stainless steel welders than in non-welders. SCE was lower in welders working with both MMA and TIG welding than in reference persons. N-Acetoxy-N-acetylaminofluorene (NA-AAF)-induced UDS was lower in 23 never-smoking welders than in 19 unexposed never-smokers. Smoking was a confounding factor resulting in significantly higher CA, SCE, NA-AAF binding to DNA and mutagenic activity in urine. Age was also a confounder: CA, SCE, NA-AAF binding to DNA and UDS increased significantly with age. No significant correlation between SCE and CA or between CA and UDS was found. UDS decreased significantly with increasing lymphocyte count and a higher lymphocyte count was seen in MMA welders than in reference persons and in smokers than in non-smokers. Differences in the composition among lymphocytes in exposed persons compared with non-exposed are suggested. MMA welding gave the highest exposure to chromium, an increased number of chromosomal aberrations and a decrease in SCE when compared with TIG welding. Consequently improvements in the occupational practice of stainless steel welding with MMA is recommended.     

Effect of stainless steel manual metal arc welding fume on free radical production, DNA damage, and apoptosis induction

Questions exist concerning the potential carcinogenic effects after welding fume exposure. Welding processes that use stainless steel (SS) materials can produce fumes that may contain metals (e.g., Cr, Ni) known to be carcinogenic to humans. The objective was to determine the effect of in vitro and in vivo welding fume treatment on free radical generation, DNA damage, cytotoxicity and apoptosis induction, all factors possibly involved with the pathogenesis of lung cancer. SS welding fume was collected during manual metal arc welding (MMA). Elemental analysis indicated that the MMA-SS sample was highly soluble in water, and a majority (87%) of the soluble metal was Cr. Using electron spin resonance (ESR), the SS welding fume had the ability to produce the biologically reactive hydroxyl radical (^•OH), likely as a result of the reduction of Cr(VI) to Cr(V). In vitro treatment with the MMA-SS sample caused a concentration-dependent increase in DNA damage and lung macrophage death. In addition, a time-dependent increase in the number of apoptotic cells in lung tissue was observed after in vivo treatment with the welding fume. In summary, a soluble MMA-SS welding fume was found to generate reactive oxygen species and cause DNA damage, lung macrophage cytotoxicity and in vivo lung cell apoptosis. These responses have been shown to be involved in various toxicological and carcinogenic processes. The effects observed appear to be related to the soluble component of the MMA-SS sample that is predominately Cr. A more comprehensive in vivo animal study is ongoing in the laboratory that is continuing these experiments to try to elucidate the potential mechanisms that may be involved with welding fume-induced lung disease.     

Evidence for the presence of mutagenic compounds other than chromium in particles from mild steel welding

A modified Salmonella/microsome liquid culture assay was used to investigate the mutagenicity of the particulate fraction from mild steel welding. Previous reports have implicated compounds of chromium VI as the mutagenic and toxic agents in welding fumes, since only the particles from welding on stainless steel, which contains 15-25% chromium, were mutagenic, whereas particles from welding on mild steel, which contain less than 0.1% chromium, were not mutagenic or toxic. In this investigation, mild steel particles were shown to contain direct-acting and promutagenic compounds that induced frameshift mutations. The mutagenic agents, which were insoluble in sodium phosphate buffer, did not include chromium VI or organic compounds. Further, the expression of mutation appears to require a cell-particle interaction for the release of the mutagenic species from the particles.     

Exposure of welders and other metal workers to ELF magnetic fields

This study assessed exposure to extremely low frequency (ELF) magnetic fields of welders and other metal workers and compared exposure from different welding processes. Exposure to ELF magnetic fields was measured for 50 workers selected from a nationwide cohort of metal workers and 15 nonrandomly selected full-time welders in a shipyard. The measurements were carried out with personal exposure meters during 3 days of work for the metal workers and 1 day of work for the shipyard welders. To record a large dynamic range of ELF magnetic field values, the measurements were carried out with “high/low” pairs of personal exposure meters. Additional measurements of static magnetic fields at fixed positions close to welding installations were done with a Hall-effect fluxmeter. The total time of measurement was 1273 hours. The metal workers reported welding activity for 5.8% of the time, and the median of the work-period mean exposure to ELF magnetic fields was 0.18 μT. DC metal inert or active gas welding (MIG/MAG) was used 80% of the time for welding, and AC manual metal arc welding (MMA) was used 10% of the time. The shipyard welders reported welding activity for 56% of the time, and the median and maximum of the workday mean exposure to ELF magnetic fields was 4.70 and 27.5 μT, respectively. For full-shift welders the average workday mean was 21.2 μT for MMA welders and 2.3 μT for MIG/MAG welders. The average exposure during the effective time of welding was estimated to be 65 μT for the MMA welding process and 7 μT for the MIG/MAG welding process. The time of exposure above 1 μT was found to be a useful measure of the effective time of welding. Large differences in exposure to ELF magnetic fields were found between different groups of welders, depending on the welding process and effective time of welding. MMA (AC) welding caused roughly 10 times higher exposure to ELF magnetic fields compared with MIG/MAG (DC) welding. The measurements of static fields suggest that the combined exposure to static and ELF fields of MIG/MAG (DC) welders and the exposure to ELF fields of MMA (AC) welders are roughly of the same level. Bioelectromagnetics 18:470–477, 1997. © 1997 Wiley-Liss, Inc.     

Characterization of organic extracts from standard reference materials 1649, ‘urban dust/organics,’ and 1650, ‘diesel particulate matter’, using a microsuspension assay. A WHO/IPCS/CSCM study

Mutagenicity associated with replicate organic extracts from standard reference materials 1649 ‘urban dust/organics’ (air particles), and 1650, ‘diesel particulate matter’ (diesel particles), was determined using a Salmonella microsuspension assay. The results indicate that the mutagenicity of samples such as these can readily be determined using the microsuspension assay with only 5% of the mass required for the standard plate incorporation asssay.In general, 80% of the variation in mutagenic activity was due to the bioassay procedure and 20% to the extraction process. Extracts from both samples had primarily direct-acting mutagenicity as there were no significant differences in responses with and without metabolic activation (S9). The TA98 - S9 mean air particles mutagenic activities (C.V., %) based on mass of extractable organics or particles were 4.4 (4.7%) and 0.29 (3.6%) revertants/μg, respectively, and for the diesel particles were 66 (44%) and 12 (29%) revertants/μg, respectively. More of the observed direct-acting mutagenicity in the diesel particles extracts was due to nitro-substituted compounds because there were significant reductions in activity with TA98NR (45% of TA98 -S9) and TA98-1,8-DNP6 (21% of TA98 -S9). In the air particles extracts, the TA98NR activities were not significantly different from TA98 - S9 but the TA98-1,8-DNP6 levels were.     

Characterization of organic extracts from standard reference materials 1649, 'urban dust/organics,' and 1650, 'diesel particulate matter', using a microsuspension assay. A WHO/IPCS/CSCM study.

Mutagenicity associated with replicate organic extracts from standard reference materials 1649 'urban dust/organics' (air particles), and 1650, 'diesel particulate matter' (diesel particles), was determined using a Salmonella microsuspension assay. The results indicate that the mutagenicity of samples such as these can readily be determined using the microsuspension assay with only 5% of the mass required for the standard plate incorporation assay. In general, 80% of the variation in mutagenic activity was due to the bioassay procedure and 20% to the extraction process. Extracts from both samples had primarily direct-acting mutagenicity as there were no significant differences in responses with and without metabolic activation (S9). The TA98-S9 mean air particles mutagenic activities (C.V., %) based on mass of extractable organics or particles were 4.4 (4.7%) and 0.29 (3.6%) revertants/micrograms, respectively, and for the diesel particles were 66 (44%) and 12 (29%) revertants/microgram, respectively. More of the observed direct-acting mutagenicity in the diesel particles extracts was due to nitro-substituted compounds because there were significant reductions in activity with TA98NR (45% of TA98 -S9) and TA98-1,8-DNP6 (21% of TA98 -S9). In the air particles extracts, the TA98NR activities were not significantly different from TA98 -S9 but the TA98-1,8-DNP6 levels were.     

Mutagenicity of potentially carcinogenic mycotoxins produced byFusarium moniliforme

The mutagenic behaviour of two potentially carcinogenic mycotoxins produced byFusarium moniliforme was investigated in theSalmonella mutagenicity test using tester strains TA97a, TA98, TA100, and TA102. The mutagenic response obtained with fusarin C (1, 5, and 10μg/plate) against tester strains TA98 and TA100 in the presence of microsomal activation confirmed previous observations on the mutagenic behaviour of this mutagen while that obtained against TA97a is reported for the first time. No dose-response relationship could be detected for the concentration levels (0.2, 0.5, 1, 5, 10 mg/plate) tested for FB₁, FB₂, and FB₃ against any of the tester strains used in either the plate incorporation and / or the pre-incubation tests. A cytotoxic effect was obtained at concentration levels of 5 and 10mg/plate in the absence of the microsomal activation mixture. From the studies it became evident thatF moniliforme produces two compounds, a mutagenic compound, fusarin C which has been shown to lack carcinogenic activity in rats and the non-mutagenic fumonisin B mycotoxins of which FB₁ is known to be responsible for the hepatocarcinogenicity of the fungus in rats.     

Mutagenic activities of selected nitrofluoranthene derivatives in Salmonella typhimurium strains TA98, TA98NR and TA98/1,8-DNP6

The mutagenic activities of novel nitrofluoranthene derivatives in Salmonella strains TA98, TA98NR and TA98/1,8-DNP6 (with and without S9 addition) are given. These derivatives were produced from the reactions of fluoranthene (FL) and its directly mutagenic 2- and 3-nitro derivatives with covalent dinitrogen pentoxide (N2O5) in CCl4 solution at ambient temperature. The influence of the addition of a nitro group on the observed activity of the resulting di- and tri-nitrofluoranthenes is discussed.     

Evaluation of new 2,2'-dimethyl-5,5'-dipropoxybenzidine- and 3,3'-dipropoxybenzidine-based direct dye analogs for mutagenic activity by use of the Salmonella/mammalian mutagenicity assay

As part of a continuing study aimed at establishing structure-activity relationships and heuristic principles useful for the design of non-genotoxic azo dyes, a series of new direct dyes based on two non-mutagenic benzidine analogs, 2,2'-dimethyl-5,5'-dipropoxybenzidine and 3,3'-dipropoxybenzidine, were evaluated for mutagenic activity in Salmonella typhimurium strains TA98 and TA100. These strains are widely used for mutagenicity screening and have been shown to detect the mutagenic activity of benzidine analogs. While some toxicity was seen with some dyes at high doses, all of the dyes examined were judged non-mutagenic with and without metabolic activation in the standard Salmonella plate-incorporation assay. The results in the standard test are consistent with the properties of the diamines themselves. However, only one of the dyes was non-mutagenic when a reductive-metabolism pre-incubation assay was used. The results of this study suggest that although benzidine analogs are potential replacements for benzidine, there is a need to understand which mutagenic products are produced when reductive metabolism is present. There is also a need to know whether or not metal complexes of these dyes are mutagenic. Such information will allow the development of new non-mutagenic azo dyes.     

Metal corrosion by aerobic bacteria isolated from stimulated corrosion systems: Effects of additional nitrate sources

Many microorganisms are reported to influence the corrosive behaviour of mild steel and stainless steel in different habitats. In this study, 40 bacterial strains were isolated from corroded mild steel and stainless steel coupons in the nitrate supplemented environments. The corrosion abilities of the isolates against the mild steel and stainless steel coupons were tested with or without additional nitrate sources. The presence of bacterial isolates alone stimulated the corrosion of mild steel coupons. Most of the bio-corrosion processes of mild steel coupons were mitigated by adding nitrate supplement with bacterial isolates. The effects of bacterial isolates and additional nitrogen sources on corrosion of stainless steels were varied. Not all bacterial isolates stimulated the corrosion on stainless steel during the study period. Unlike the effects on mild steel coupons, additional NaNO₃ might stimulate, retard the corrosion rate by the bacterial isolates or have limited effects. Similar results were obtained when NH₄NO₃ was used. Phylogenetic analysis demonstrated that all isolates were closely related. The majority of the bacterial isolates from corroded metal coupons were identified as Bacillus species. Others were identified as Pseudomonas sp., Marinobacter sp., and Halomonas species. The results prove that the isolated aerobic microorganisms do play a role in the corrosion process of stainless and mild steel. Adding additional nitrate sources might be a tool to mitigate corrosion of mild steel which was stimulated by the presence of bacteria. However, to prevent the corrosion of stainless steels, it might need a trial and errors approach in each case.     

Mutagenic compounds in wood-chip drying fumes

The mutagenicity of fumes from the heating of freshly cut spruce and birch chips was measured with Salmonella typhimurium strains TA98, TA100 and TA102. The bacteria were exposed directly and indirectly to the fumes. Wood chips were also extracted with solvents. No mutagenicity was found in wood extracts or the fume samples measured indirectly. The results from the direct exposure experiments indicate, however, that drying spruce and birch at 170 degrees C emits mutagenic compounds, which are short-lived and/or volatile. One of the mutagenic compounds of the fumes is probably 3-carene. These results are consistent with previous epidemiological findings, which suggest that these fumes are carcinogenic.     

Mutagenic activity of furfural in Salmonella typhimurium TA100.

The mutagenic activity of furfural was tested in Salmonella typhimurium strains TA98 and TA100. Furfural produced mutations in the TA100 strain, but not in the TA98 strain. A rat-liver microsomal fraction did not increase the mutagenic activity of furfural in either strain. Mutagenic activity of furfural in the TA100 strain was not increased by benzo[alpha]pyrene in the presence of metabolic activation.     

Mechanism and relevance of glutathione mutagenicity

The ubiquitous tripeptide glutathione (GSH) has previously been shown to be mutagenic to Salmonella typhimurium TA100 when incubated with kidney subcellular fractions at physiological concentrations (Glatt et al., 1983). Here we report that the mutagenic effect of GSH can be inhibited by the use of the gamma-glutamyl-transpeptidase (gamma-GT) inhibitor anthglutin and by the metal chelators bathocuproine, EDTA and diethyldithiocarbamate. As the chelating agents did not inhibit gamma-GT activity this suggested that the mechanism underlying the mutagenic effect of GSH was at least a two-step process, dependent upon the cleavage of GSH by gamma-GT and the presence of either free transition metals or those contained in enzymes such as glutathione oxidase. As gamma-GT is located on the outer surface of kidney tubule cells and is therefore exposed to relatively low concentrations of GSH, and the precise physiological control of levels of transition metals, this mechanism is unlikely to occur in vivo.     

Results of a comparative study on the Salmonella pre-incubation and plate incorporation assays using test samples from the IPCS collaborative study.

Three complex mixtures (air particles, diesel particles and a coal tar fraction) and two pure compounds (benzo[a]pyrene and 1-nitropyrene) were tested in both the pre-incubation and the plate incorporation assay employing Salmonella typhimurium TA98 and TA100. Each experiment was conducted independently 2 or 4 times in duplicate in the presence and absence of metabolic activation. The mutagenic activities were calculated by least squares linear regression from the slope of the linear portion of each dose-response curve. Although slightly higher mutagenic activity was observed in the pre-incubation assay for the two pure compounds and with the plate incorporation assay for the diesel particulate sample, the overall data from both assays gave similar values and good correlations in TA100 and TA98. The results indicate that the pre-incubation assay could be used for these samples instead of the plate incorporation assay.     

Bacterial mutagenicity of some tobacco aromatic nitrogen bases and their mixtures

The first aim was to compare the genotoxicities of two tobacco-specific nitrosamines (TSNA), 4-(methylnitrosamino)-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN) in two types of tests, the Salmonella reverse mutation assay (250-2000 microg per plate) and the Mutatox test (up to 1000 microg/ml) using dark mutant M-169 of Vibrio fischeri. The second aim was to assess the effects of single other tobacco chemicals and metabolites (nicotine (NIC), cotinine (COT), trans-3-hydroxycotinine (3HC), cotinine-N-oxide (CNO) and nicotine-N-oxide (NNO)) on the mutagenic responses at relative concentrations observed physiologically. The Salmonella strains were TA100, TA7004, TA7005, and TA7006, all showing missense backmutations that are characteristic of the TSNA. NNN was a direct mutagen to strains TA100, TA7004, and in the Mutatox test, and was not mutagenic in the presence of rat or hamster S9. NNK was mutagenic only in strain TA7004 with rat and hamster S9, but not in TA100, but was directly mutagenic in the Mutatox test. While all the other tobacco chemicals were not mutagenic alone to strains TA100 and TA7004 in the presence and absence of rat or hamster S9, the Mutatox test produced direct mutagenicity for COT, 3HC, and NNO, but not CNO. The latter was mutagenic in the Mutatox test with rat or hamster S9, but only rat S9 was effective for COT, NNO and 3HC. Inhibitory potentiations of NNN by NIC and COT were observed on strain TA7004, and by NIC on strain TA100. There were no interactions on NNK in the presence of S9 for strain TA7004 or TA100. In contrast, a complex inhibition and enhancement behavior occurred in the Mutatox test for each interaction, but no effects were observed for CNO on NNK without S9, and few for NIC on NNK with hamster S9. Compounds which showed no activity alone modulated the genotoxicity of two potent TSNAs in both types of tests.     

The mutagenicity of electrocautery smoke.

Careful analysis of electrocautery smoke produced during breast surgery has found organic compounds that are unidentifiable with current analytical techniques. The purpose of this study was to determine the potential mutagenicity of the smoke produced by the electrocautery knife during reduction mammaplasty. Multiple air samples were collected in the operating room during two reduction mammaplasty procedures. Airborne smoke particles were tested for mutagenic potential in both tester strains of Salmonella typhimurium (TA98 and TA100) using the standard Salmonella microsomal test (Ames test). All testing was performed by the Hazard Evaluations and Technical Assistance Branch of the National Institute of Occupational Safety and Health. The smoke produced with the electrocautery knife during reduction mammaplasty was found to be mutagenic to the TA98 strain. The Ames test, an established technique for evaluating the mutagenicity of a substance, was convincingly positive for the smoke collected during the breast surgery. Whether the smoke represents a serious health risk to operating room personnel is not known. Development of techniques to limit electrocautery smoke exposure in the operating room appears to be needed, and surgeons should attempt to minimize their exposure.     

Collaborative study using the preincubation Salmonella typhimurium mutation assay for airborne particulate matter in Japan. A trial to minimize interlaboratory variation.

A collaborative study has been performed over a period of 3 years to develop a suitable method for monitoring the mutagenicity of airborne particulate matter. The study was organized with 8 laboratories and performed in the following steps: (1) selection of a suitable technique for each process involved in the mutagenicity monitoring, (2) developing a tentative protocol by combining systematically the selected techniques, (3) evaluation of the protocol by intra- and inter-laboratory studies, (4) modification of the protocol according to the evaluation, and (5) evaluation of the modified protocol by conducting an interlaboratory study. We found a suitable method for mutagenicity monitoring of particles in the atmosphere. Airborne particles were sampled with a high-volume sampler, the samples were stored at -80 degrees C, extracted by sonication using dichloromethane, solvent-exchanged, and assayed by the preincubation method using Salmonella typhimurium TA98 and TA100. The observed mutagenic activity was normalized with that of an internal standard. Round robin tests revealed that the method resulted in excellent reproducibility. The coefficient of variation for mutagenic activities of airborne particulate samples collected in various districts of Japan were in the range of 14.7 +/- 6.6% to 19.6 +/- 4.0% for strains TA98 and TA100 with and without metabolic activation. We also found that the plate incorporation method was equivalent to the preincubation method for airborne particulate extracts.     

Cytotoxic, mutagenic and antimutagenic screening of Arenosclera brasiliensis acetone and ethanol extracts

The marine environment is a rich source of biologically active compounds with pharmacological properties. Marine organisms often produce secondary metabolites with structural features different from those produced by terrestrial ones, and the Phylum Porifera seems to be one of the most productive in this sense. This study was undertaken to provide data on mutagenic and antimutagenic activities from an acetone (Areac) and an ethanol (Areet) extract obtained from Arenosclera brasiliensis, an endemic Brazilian sponge. A qualitative Salmonella reverse mutation test was performed with the TA97, TA98, TA100, and TA102 strains by incubating cells with Areac and Areet in the presence and absence of a known mutagen. A cytotoxic evaluation of the extracts was also performed. A. brasiliensis did not display any mutagenic activity, but Areac showed significant toxicity against test strains. In the antimutagenic assay, a reduction in the number of his+ revertants was observed for the TA97, TA100 and TA102 strains treated with Areac when compared to the positive controls. Areet treatment showed protective activity against DNA lesions only for the TA100. These results are in agreement with those obtained previously with other A. brasiliensis extracts, suggesting an antimutagenic activity.     

Fabrication of a Bionic Needle with both Super-Hydrophobic and Antibacterial Properties

Many biological surfaces possess unusual micro-nano hierarchical structures that could influence their wettability, which provide new methods for the construction of novel materials. In this work, silver nanoparticles were successfully coated on the surface of stainless steel needle by a simple electroless replacement reaction process between the AgNO₃ solution and the activated stainless steel needle. After the replacement reaction, porous micro/nanostructures were formed on the surface of the stainless steel needle. By modifying long chains of thiol molecules, the stainless steel needle exhibited good super-hydrophobic property with a contact angle greater than 150°. Moreover, the silver coated stainless steel needle (bionic needle) showed strong antibacterial activity against the gram-negative bacterium Escherichia coli (E. coli). By calculating the area of the inhibition zone against E. coli formed on agar medium, the antibacterial activity of the bionic needle with the contact angle of 152° is much better than that with the contact angle of 138°. The as-prepared bionic needle with both super-hydrophobic and antibacterial properties has the potential to be applied in modern medical devices.     

Synthesis and mutagenicity of the two stereoisomers of an azide metabolite (azidoalanine)

The L- and D-isomers of azidoalanine (azide metabolite) have been chemically synthesized with 60% yield using corresponding N-(tert-butoxycarbonyl)-serine as starting materials. The mutagenic properties of synthesized L-azidoalanine are very similar to those of azide and in vivo synthesized azidoalanine. Synthetic D-azidoalanine shows very low mutagenic activity on Salmonella typhimurium TA1530 strain compared to that of the L-isomer. Thus a stereoselective process is involved in azidoalanine mutagenicity. The data presented in this study suggest that further biochemical activation is required for L-azidoalanine to produce its mutagenic activity.