A new study in the journal Chemosphere studies the effects of polystyrene beads on three freshwater species.

The study expands the knowledge on the acute, chronic, and subchronic effects of MP polystyrene beads (PS-MP, size 1.0 µm) on three species of the freshwater chain. These species are the green alga Raphidocelis subcapitata, the rotifer Brachionus calyciflorus, the cladoceran crustacean Ceriodaphnia dubia, and the benthic ostracod Heterocypris incongruens. Researchers also studied the genotoxicity and ROS production in C. dubia. Next, using light microscopy, scientists also explored the presence of PS-MP in the gut of daphnids and also calculated the risk quotient (RQ) to estimate the risk posed by PS-MPs in the freshwater environment.

Key Findings

Researchers observed that the organisms acutely affected by 24 hour – PS-MP exposure were the rotifer and the cladoceran crustacean. In addition, an independent study found the median immobilization of Daphnia pulex to be around 76.69 mg/L, and this number was well within the confidence interval obtained by the authors of the present study.

The crustacean C. dubia was the organism most affected by the PS-MP. Its EC50, after 7 days exposure, was in the order of units of µg/L (10⁶ p/L) and it also reported a lowest observed effect concentration (LOEC) value in the order of tenths of µg/L (10⁵ p/L). These values signify operating very close to what could be considered to be an environmental concern. Further, researchers also observed that the gut of C. dubia was filled with PS-MP after 24 hours exposure, at concentrations ranging from 8.5 µg/L through 85 mg/L. The former concentration corresponds to 50% mortality while the latter is 100% mortality.

Scientists stated that the exposure of aquatic organisms to PS-MP could lead to long-term toxicity and also have adverse effects, including DNA damage. By exposing C. dubia neonates to PS-MP for 24 hours, they demonstrated the alterations in genetic material and production of ROS. Previous studies have also shown that exposure to PS-microparticles or PS- nanoparticles could increase the amount of ROS, causing the breakage of DNA strands.

More on this story can be read here and the published journal article in Chemosphere can be found here.