Assessment of exposure to manganese in welding operations during the assembly of heavy excavation machinery accessories.

Welder exposure to metals in various industrial sectors is poorly characterized. We had the opportunity to carry out an exploratory study to characterize manganese exposure in welding operations in a recently established Quebec factory that assembled accessories for heavy excavation machinery. Ten workers were sampled for total manganese for at least two consecutive days out of three followed by two consecutive days for respirable manganese (with a size selective sampler with a median cut-off of 4 microns), during a typical week in the summer of 1998. Parts being welded were characterized as large or small. Small parts were those being welded on tables during subassembly. Workers were divided into two groups according to the parts they were welding. Seventy-eight percent of the total manganese exposure levels of welding operations during the assembly of large accessories of heavy excavation machinery exceeded the manganese American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) of 0.20 mg/m3 (GM 0.24 mg/m3, n = 14) while none exceeded the TLV during the assembly of small pieces (GM 0.06 mg/m3, n = 8). Welding operations during the assembly of large heavy excavation machinery accessories may pose a significant health hazard. Considering the importance of task-related variables affecting exposure among workers, further studies are needed to better characterize exposure determinants of welding operations during the assembly of heavy excavation machinery accessories.

Mutagenicity and chemical analysis of sequential organic extracts of airborne particulates.

To obtain insight into the identity of chemicals associated with the mutagenicity of United States National Institute of Standards and Technology (NIST) Standard Reference Materials SRM 1649 (urban dust) and SRM 1650 (diesel particulate), parallel mutagenicity tests and chemical analyses were performed on dichloromethane and sequential organic extracts of these samples. SRM 1649 and 1650 were sequentially extracted with five organic solvents of increasing polarity, in order to partition mutagenic components into discrete fractions. The solvents (with associated polarity index) were as follows: (1) hexane (0.0); (2) hexane:diethyl ether 9:1 (0.29); (3) hexane:diethyl ether 1:1 (1.45); (4) diethyl ether (2.9); (5) methanol (6.6). 0.9270 g of SRM 1649, and 0.0510 g of SRM 1650 were each extracted three times with 8 ml of each of the solvents, the three aliquots were pooled, and analysed for target organics or solvent-exchanged into DMSO for mutagenicity testing in Salmonella typhimurium strains TA98 and TA100. The dichloromethane extracts of SRM 1649 and SRM 1650 contained direct-acting mutagens in Salmonella strains TA98 and TA100; SRM 1650 was significantly more potent than SRM 1649 in either strain. Addition of S9 caused a large decrease in mutagenicity of each extract, although SRM 1650 remained more potent. An interesting pattern of mutagenicity was observed for the sequential extracts of SRM 1649 and SRM 1650: the mutagenic potency of SRM 1649 extracts increased with increasing polarity of the extraction solvent while the response of the SRM 1650 extracts was the opposite. This suggests that the direct-acting mutagens in SRM 1650 are unlike those in SRM 1649. The response, though diminished, was largely unchanged when S9 was included in the test mixture. Chemical analyses on the various extracts were performed using a Hewlett-Packard model 5890 gas chromatograph equipped with a model 5970B mass selective detector (GC-MSD), and a 0.3 microns film thickness cross-linked methyl silicone capillary column (HP 1909A-101). Selected ion monitoring (SIM) methods were used to analyze for 105 target compounds including PAHs and nitro-PAHs. Chemical analysis of the dichloromethane extracts of SRM 1649 and SRM 1650 identified three main classes of compounds: polyaromatic hydrocarbons (PAH), nitro-polyaromatic hydrocarbons (NO2-PAHs) and heterocyclics. The concentration of target compounds and the proportion of nitro-PAHs and heterocyclic compounds were considerably greater in SRM 1650 than in SRM 1649, consistent with the observed differences in their mutagenic potency. However, the different responses of the dichloromethane extracts in TA98 and TA100 suggest the presence of different (unidentified) compounds.(ABSTRACT TRUNCATED AT 400 WORDS)

Synthesis and mutagenicity of 3-halogenated and 3,3',5,5'-tetrahalogenated benzidines.

3-Fluorobenzidine (FBz), 3-chlorobenzidine (ClBz), 3-bromobenzidine (BrBz), 3,3',5,5'-tetrafluorobenzidine (F4Bz), and 3,3',5,5'-tetrachlorobenzidine (Cl4Bz) were synthesized and tested for their ability to revert Salmonella typhimurium. F4Bz was the only compound to show direct-acting mutagenicity and was equally potent in strain TA98 and the acetylase-deficient strain TA98/1,8-DNP6. In the presence of hamster liver S9, all compounds except Cl4Bz were mutagenic. The relative mutagenicities in TA98 were FBz greater than ClBz greater than BrBz greater than F4Bz greater than Bz greater than Cl4Bz = 0. In TA98/1,8-DNP6 the trend was F4Bz approximately BrBz approximately ClBz greater than FBz greater than Bz greater than Cl4Bz = 0.

Synthesis and mutagenicity of 3,3'-dihalogenated benzidines.

3,3'-Difluorobenzidine (F2Bz), and 3,3'-dibromobenzidine (Br2Bz) were synthesized and compared with 3,3'-dichlorobenzidine (Cl2Bz) for ability to revert Salmonella typhimurium. The relative mutagenicities in all systems are Cl2Bz approximately equal to Br2Bz greater than F2Bz greater than Bz. F2Bz, Cl2Bz, and Br2Bz are direct-acting mutagens towards S. typhimurium strain TA98. The acetylase-deficient derivative TA98/1,8-DNP6 displays no resistance to induction of mutagenesis by these compounds, in the absence of mammalian activation. With addition of hamster hepatic S-9 activation the mutagenicity of these compounds increases greatly. TA98/1,8-DNP6 shows some resistance to this mutagenicity. Multiple mechanisms must exist for the genotoxicity of 3,3'-dihalogenated benzidines.