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.

Automated headspace solid-phase microextraction-gas chromatography-mass spectrometry of trihalomethane and typical nitrogenous disinfection by-products in water.

Disinfection by-products (DBPs) are detrimental to public health owing to their carcinogenicity and mutagenesis. Fast and reliable determination of DBPs is essential for ascertaining their formation, characteristics, and occurrence. This study reported an automated headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) method for quantifying typical nitrogenous-DBPs, including haloacetonitriles (HANs), trichloronitromethane, and trihalomethanes (THMs). The analysis was further optimized by selecting SPME fiber coatings, extraction/desorption time and temperature, and salt addition. The optimized method examined the occurrence and stability of the selected DBPs in aqueous samples under different preservation conditions and showed good sensitivity (limit of detection: 0.010-0.320 µg/L) and precision. Most THMs and HANs with high recovery were preserved in ultrapure water under dark and low-temperature conditions. However, real samples exhibited greater analytical biases due to comprehensive effects of photochemistry, biochemistry, and physiochemistry. Based on the findings of this study, we recommend that tested samples should be preserved in a frozen state and analyzed within three days.

Acute impact of Hg2+, Cu2+, and Ag+ on the formation of biopolymers and nitrogenous soluble microbiological products in activated sludge for wastewater treatment.

In the present work, acute impact of heavy metals on activated sludge was investigated, specifically the release of biopolymers and nitrogenous soluble microbiological products (N-SMP) that significantly impact tertiary effluent quality. Based on the previously reported studies, Hg2+ and Ag+ were selected as representative "non-essential" heavy metals, while Cu2+ was selected as the "essential" heavy metal. Stress tests show that under the present experimental conditions, adding a higher concentration of heavy metals to the activated sludge increases the concentration of biopolymers and SMP in the supernatant; N-SMP increased more significantly than carbonaceous products, implying a greater risk of formation of toxic nitrogenous disinfection by-products or membrane fouling in relevant tertiary treatment processes. The severity of the release of SMP into the supernatant depended on the heavy metal, with an order of Hg2+ > Ag+ > Cu2+ ("non-essential" > "essential") under identical molar concentrations. The mass balance of typical organics (e.g., biopolymers) in SMP and extracellular polymeric substances (EPS) in activated sludge was analyzed, and a negative correlation between the organics in the SMP and tightly bound EPS was observed, implying that a significant fraction of the SMP could be quickly released from the tightly bound EPS under heavy metal shock conditions and could be related to cell response or damage.