The toxicity assessment of 14 biocides for industrial circulating cooling water system by damage/repair pathway profiling analysis.

The toxicity of 14 biocides commonly used in circulating cooling water systems were evaluated. Results showed that biocide exposure can induce complex damage/repair pathways, including DNA, oxidative, protein, general, and membrane stress. All damages enhanced with increasing concentrations. Among them, MTC exhibited toxicity at concentrations as low as 1.00 × 10-17 mg/L, and TELItotal reached 1.60. We derived molecular toxicity endpoints based on dose-response curves to compare the normalized toxicity of biocides. Total-TELI1.5 exhibited that THPS, MTC, and DBNPA have the lowest toxic exposure concentrations, which are 2.180 × 10-27, 1.015 × 10-14, and 3.523 × 10-6 mg/L. TBTC, MTC, and 2,4-DCP had the highest Total-TELImax values, which are 861.70, 526.30, and 248.30. Moreover, there was a high correlation (R2 =0.43-0.97) between biocides' molecular structure and toxicity. And, biocide exposure combinations were found to increase toxicity pathways and enhance toxic effects, with a similar toxicity mechanism observed as in single-component exposure.