Widely used pandemic pharmaceuticals harm marine aquatic ecosystems

A new study published in New Contaminants suggests that several drugs widely used during the COVID-19 pandemic can be toxic to marine organisms, even at relatively low concentrations. The research tested five pharmaceuticals, hydroxychloroquine, ivermectin, nitazoxanide, loratadine, and betamethasone, on nauplii of the brine shrimp Artemia salina, a small crustacean commonly used in marine ecotoxicology.

The pandemic changed not only public health systems, but also the chemical pressure placed on aquatic environments. Our results show that some drugs used or promoted during COVID-19 may affect marine organisms and deserve closer environmental monitoring."

Denis Moledo de Souza Abessa, corresponding author, São Paulo State University

During the pandemic, the use of several pharmaceuticals increased worldwide. After use, these compounds can enter rivers, coastal waters, and the ocean through wastewater, sewage discharge, stormwater runoff, and other pathways. Yet the effects of many COVID-19 related drugs on marine life remain poorly understood.

In 48-hour acute toxicity tests, hydroxychloroquine showed no toxic effect on A. salina at the tested concentrations. In contrast, ivermectin, betamethasone, loratadine, and nitazoxanide caused significant mortality. The lowest observed effect concentrations were 1.0 μg/L for ivermectin, 4 μg/L for betamethasone, 0.02 mg/L for loratadine, and 0.05 mg/L for nitazoxanide.

Based on toxicity thresholds, the study ranked the drugs as follows: ivermectin > betamethasone > loratadine > nitazoxanide > hydroxychloroquine. Ivermectin was the most toxic compound tested, with mortality exceeding 50% at all tested concentrations.

The authors emphasize that these findings do not address drug safety for patients. Instead, they highlight an environmental concern: pharmaceuticals designed for human or veterinary use may continue their journey after disposal or excretion, eventually reaching aquatic ecosystems.

The study calls for more research on the occurrence, persistence, bioaccumulation, and chronic toxicity of COVID-19 related drugs in marine environments, as well as improved wastewater treatment and public awareness to reduce pharmaceutical pollution.