Behavior, Fate, and Toxicity of Engineered Nanoparticles in Estuarine and Coastal Environments

The aquatic environment, encompassing freshwater, brackish, and marine waters, is a sensitive and important component of the biosphere. Due to the enormous diversity of life that these environmental compartments support, any input from anthropogenic activities represents a threat that may disrupt the delicate balance in these ecosystems. With the ever-increasing production and use of nanomaterials, the potential for such materials to enter the aquatic environment is continuously growing. It has become increasingly clear that their complex physico-chemical behavior in natural waters forms the foundation for their subsequent impact on biota. In particular, aspects such as size, elemental content, and surface chemistry play key roles, as well as their interaction with natural organic matter which modulates a range of processes including nanoparticle ion release and dissolution, agglomeration, and aggregation. Increasing the complexity of the system further, an array of abiotic parameters such as temperature, salinity, pH, and light intensity also influence the behavior and persistence time of nanomaterials in natural waters. Such materials, for example metal, metal oxide, and polymer nanoparticles, are already being shown to give rise to a broad variety of harmful impacts in biota, ranging from disruption to genetic and metabolic processes at the cellular level to embryonal developmental defects or swimming and feeding behavior at the whole organism level. In broader terms, it is clear that such effects may eventually lead to wider impacts in ecosystems. Ultimately, while much has already been learned, there are still enormous gaps in knowledge, for example the potential for bioaccumulation and biomagnification of nanomaterials in food webs through trophic transfer, or sub-lethal chronic exposure to materials such as nanoplastics. Moreover, their toxicological profile in biota must be resolved, enabling grouping of nanomaterials and read-across. This will form the foundation for developing realistic risk assessments and informing policy so as to suitably adapt the regulatory landscape to ensure the future safe use of nanomaterials.