Effect of water hardness on peracetic acid toxicity to zebrafish, Danio rerio, embryos

The use of peracetic acid (PAA) in aquaculture has been suggested as an alternative therapeutic agent. Few data are available concerning fish toxicity by PAA or factors that modify this toxicity. The aim of this study was to investigate the influence of water hardness on the acute toxicity of PAA products to embryos of zebrafish (Danio rerio). Embryos were exposed to PAA ranging from 0 to 9 mg/L in low-hardness (1.4 A degrees dH or 25 mg/L hardness as CaCO3), medium-hardness (14 A degrees dH or 250 mg/L hardness as CaCO3) and high-hardness (140 A degrees dH or 2,500 mg/L hardness as CaCO3) waters. The lowest LC50 value was 2.24 mg/L PAA in the low-hardness water, and the highest LC50 value was 7.14 mg/L PAA in the high-hardness water. Toxicity of PAA to embryos was found to be negatively correlated with water hardness. The pH decreased with increasing concentrations of PAA, and the test waters were observed to become more acidic in low hardness. In conclusion, aquaculturists using PAA should pay attention to water hardness to avoid acidosis.