Inability of GSTT1 to activate iodinated halomethanes to mutagens in Salmonella

Comparing the toxicity of iodinated X-ray contrast media on eukaryote- and prokaryote-based quantified microarray assays

This study compared the toxicity mechanisms of four X-ray-based iodinated contrast media (ICM) on Escherichia coli (E. coli) and yeast microarray assays, aiming to determine the diverse toxicity mechanisms among different exposed organisms and the relationship between toxicity and their physical and chemical characteristics. The conventional phenotypic endpoint cytotoxicity and the change in reactive oxygen species (ROS) level were employed in conjunction with toxicogenomics to quantify changes in the gene/protein biomarker level in the regulation of different damage/repair pathways. The results showed that molecular toxicity endpoints, named transcriptional effect level index (TELI) and protein effect level index (PELI) for E. coli and yeast, respectively, correlated well with the phenotypic endpoints. Temporal altered gene/protein expression profiles revealed dynamic and complex damage/toxic mechanisms. In particular, compared with E. coli cells, yeast cells exposed to ICM exhibited significantly higher stress intensity and diverse stress types, resulting in stress or damage to the organism. The toxic mechanisms of ICM are concentration/property-dependent and relevant to the cellular structure and defense systems in prokaryotes and eukaryotes. In particular, the toxicity of ionic ICM is higher than that of non-ionic ICM, and eukaryotes are more susceptible than prokaryotes to ICM exposure.

Disinfection byproducts in chlorinated or brominated swimming pools and spas: Role of brominated DBPs and association with mutagenicity

Although the health benefits of swimming are well-documented, health effects such as asthma and bladder cancer are linked to disinfection by-products (DBPs) in pool water. DBPs are formed from the reaction of disinfectants such as chlorine (Cl) or bromine (Br) with organics in the water. Our previous study (Daiber et al., Environ. Sci. Technol. 50, 6652; 2016) found correlations between the concentrations of classes of DBPs and the mutagenic potencies of waters from chlorinated or brominated swimming pools and spas. We extended this study by identifying significantly different concentrations of 21 individual DBPs in brominated or chlorinated pool and spa waters as well as identifying which DBPs and additional DBP classes were most associated with the mutagenicity of these waters. Using data from our previous study, we found that among 21 DBPs analyzed in 21 pool and spa waters, the concentration of bromoacetic acid was significantly higher in Br-waters versus Cl-waters, whereas the concentration of trichloroacetic acid was significantly higher in Cl-waters. Five Br-DBPs (tribromomethane, dibromochloroacetic acid, dibromoacetonitrile, bromoacetic acid, and tribromoacetic acid) had significantly higher concentrations in Br-spa versus Cl-spa waters. Cl-pools had significantly higher concentrations of Cl-DBPs (trichloroacetaldehyde, trichloromethane, dichloroacetic acid, and chloroacetic acid), whereas Br-pools had significantly higher concentrations of Br-DBPs (tribromomethane, dibromoacetic acid, dibromoacetonitrile, and tribromoacetic acid). The concentrations of the sum of all 4 trihalomethanes, all 11 Br-DBPs, and all 5 nitrogen-containing DBPs were each significantly higher in brominated than in chlorinated pools and spas. The 8 Br-DBPs were the only DBPs whose individual concentrations were significantly correlated with the mutagenic potencies of the pool and spa waters. These results, along with those from our earlier study, highlight the importance of Br-DBPs in the mutagenicity of these recreational waters.