Joint action of pollutant combinations (pesticides and metals) on survival (LC50 values) and acetylcholinesterase activity of <i>Tigriopus brevicornis</i> (Copepoda, Harpacticoida)

TLDR

Acetylcholinesterase is used as a biomarker in marine coastal environments to assess exposure to neurotoxic pollutants such as organophosphorous and carbamate insecticides and most metals. The study determined the joint toxicity of nine binary mixtures of a metal (arsenic, copper, or cadmium) and a pesticide (carbofuran, dichlorvos, or malathion) in the marine microcrustacean *Tigriopus brevicornis* using 96‑h LC50 tests and acetylcholinesterase inhibition, applying a toxic‑unit approach to evaluate the response‑addition model for chemicals with different modes of action. All mixtures produced synergistic lethal effects, with the strongest acute toxicity observed for copper‑malathion, cadmium‑malathion, dichlorvos‑malathion, and cadmium‑dichlorvos, and at sublethal levels the metals enhanced the acetylcholinesterase inhibition of certain organophosphorous and carbamate insecticides.

Abstract

Abstract The joint toxicity of nine binary mixtures of a metal (arsenic, copper, or cadmium) and a pesticide (carbofuran, dichlorvos, or malathion) was determined in the marine microcrustacean Tigriopus brevicornis (Müller) (Copepoda) by 96-h LC50 tests and measurement of acetylcholinesterase (AChE) inhibition. Acetylcholinesterase is used in the marine coastal environment as a biomarker to evaluate exposure to neurotoxic pollutants, including organophosphorous (OP) and carbamate (C) insecticides and most metals. A toxic unit (TU) approach was used to test the response addition model for mixtures of chemicals with different action modes. Studies of mixtures showed synergistic lethal effects in all cases (the strongest acute effects being observed in coppermalathion, cadmium-malathion, dichlorvos-malathion, and cadmium-dichlorvos combinations). At the sublethal level, the presence of the three metals tested seemed to enhance the inhibitory effects of certain OP and C insecticides.