Embryotoxicity and HSP70 gene expression in Zebrafish (Danio rerio) embryo after exposure to treated wastewater effluents from a wastewater treatment plant (WWTP)

Abstract

Wastewater treatment plants (WWTP) are highly important in the treatment of wastewater as its effluents are discharged in the environment. However, the effects of the treated wastewater effluents in the environment are not yet well-established, especially in the Philippines. In line with this, this study aims to determine the chemical constituents of both treated and untreated wastewater sample from a WWTP in Manila, and whether exposure to varying dilutions of treated wastewater effluents induce heat shock protein 70 (HSP70) gene expression and malformations in zebrafish embryos. The chemical components of both treated and untreated wastewater samples were determined via liquid chromatography-mass spectrometry. Zebrafish embryotoxicity test (ZFET) was performed as well as HSP70 gene expression via RT-qPCR. Both the wastewater samples were found to be composed mainly of aliphatic amines, from personal care products, and minute amounts of pharmaceuticals. The HSP70 gene was found to be induced in the embryos exposed to various dilutions of treated wastewater and is found to be directly proportional to the concentration of the wastewater effluent. The embryos also presented embryotoxicity in terms of malformation occurrence, hatch rate, and mortality.