Mitigating phthalate toxicity: The protective role of humic acid and clay in zebrafish larvae

Abstract

This research study aimed to explore the mitigating effects of humic acid and clay on the toxicity induced by three different phthalates (DBP, DEP, DEHP) on zebrafish larvae growth. Prolonged exposure to DBP resulted in a concerning 87.33% mortality rate, significantly reduced to 7.3% when co-administered with humic acid. A similar reduction in mortality was observed for the other two phthalates (DEP and DEHP). Additionally, the introduction of phthalates with humic acid, clay, or their combination led to a significant decrease in the malformation rate in larvae. High-Performance Liquid Chromatography (HPLC) analysis of phthalates in treatments revealed a noteworthy decline in their concentration when combined with humic acid and clay. This suggests a reduced bioavailability of phthalates to larvae, aligning with diminished toxicity, lower mortality, fewer malformations, and improved organ development, as well as less oxidative stress. Furthermore, measurements of larval length and morphological scoring affirmed the protective role of humic acid and clay in promoting the normal growth of zebrafish. This study underscores the potential of environment modulators, such as humic acid and clay, as effective bioremediation agents against phthalate toxicity. The generation of reactive oxygen species (ROS), indicative of oxidative stress, was markedly higher in larvae treated solely with phthalates compared to the control. Conversely, larvae treated with a combination of phthalates and humic acid or clay exhibited a significant decrease in ROS generation, signaling a decline in oxidative stress. Histopathological analysis of adult fish subjected to various treatments revealed significant damage to vital organs like the liver and intestine when treated with phthalates alone. However, when phthalates were introduced with humic acid, clay, or both, the morphology closely resembled that of the control, reinforcing the protective role of humic acid and clay in zebrafish development against administered phthalates.

Keywords: Bioavailability; Malformations; Mortality; Organ development; Oxidative stress.