Ecotoxicity testing of micro- and nano-plastics

Plastic pollution has become a significant environmental and human health issue at a global scale. Yet, despite increasing concern over the harmful effects of micro- and nano-plastics (MNPs), no harmonized guidelines or protocols for their ecotoxicity testing have been available to date. Current ecotoxicity studies often use commercial spherical particles as models for MNPs, but in nature, MNPs occur in variable shapes, sizes and chemical compositions. Moreover, protocols developed for chemicals that dissolve or form stable dispersions are currently used for assessing the ecotoxicity of MNPs, but these protocols are not optimal for studying MNPs, as plastic particles do not dissolve and also show dynamic behaviour in the exposure medium, depending on, for example, MNP physicochemical properties and the medium's ionic strength.

The new exposure protocol considers the particle-specific properties of MNPs and their dynamic behaviour in exposure systems. The protocol enables, e.g., the production of more realistic MNPs that resemble those occurring in nature. The protocol also describes exposure system development for short- and long-term toxicity tests for soil and water organisms.

The researchers provide examples of using the protocol to test, for example, MNP toxicity in marine rotifers, freshwater mussels, daphnids and earthworms. The present protocol takes between 24 h and 2 months, depending on the test of interest, and can be applied by students, academics, environmental risk assessors and industries.