In recent years, micro- and nanoplastic (MNPs) have been detected in increasing numbers in the environment from the tropics to the poles, and also within tissues of animals and plants. The environmental and human health effects of these materials have become a major concern to the public and to regulatory bodies.
Assessment of environmental risk generally involves identifying the hazard of the substance of concern, identifying the likely affected organisms, establishing routes of exposure and quantities or concentrations of substances involved, and from these, making an assessment of the degree of risk.
For MNPs, however, assessing the risk to the environment is proving a challenge because of the wide range of factors that must be considered. The toxicity of environmental MNPs is affected by the types of plastic, their sizes, and their content of plasticisers, pigments, or associated environmental contaminants. There are also multiple routes of exposure, and the range of effects observed in organisms can vary from physical disruption (blocking the alimentary canal or abrading gill filaments) to causing oxidative stress, immune dysfunction, inflammation and cellular damage.
Much of the toxicity data available is based on simple systems with commercial uniform MNPs that do not reflect environmental reality. Even the measures of concentration, by particle number, volume or weight are not consistent between methods, making comparison between studies difficult.
To try to overcome these challenges and improve the quality of environmental risk of MNPs, new approaches have become available recently. These include new software for calculating Species Sensitivity Distributions; methods for harmonising data that use different concentration measurements and different ranges of particle sizes; updated databases of research results; and new frameworks for assessment.