Nanoscale plastic pollution: sources, identification and potential mitigation

The amount of global plastic waste has been increasing steadily since synthetic polymers were introduced over a century ago and plastic products have become ubiquitous in modern societies. A significant portion of this waste can accumulate and persist for many decades as plastic particulate pollution that can interact with natural ecosystems, and in urban and rural environments. The size of these plastic particles can vary widely, from millimetres to micrometre and nanometre scales, depending on several factors including material properties, production, application, age and environmental exposure. Importantly, the properties and potential impact of plastic pollution can depend strongly on particle size, particularly for nanoscale dimensions, or nanoplastics. Nanoplastics, and slightly larger microplastics, are more difficult to detect, can spread more easily, and potentially interact more directly with biological organisms and ecosystems. This review provides a detailed synopsis of nanoscale plastic pollution. After an overview of plastic particle pollution in general, the sources and impact of nanoplastics, both environmental and biological are discussed. Methods for identifying and characterising nanoplastics via microscopy, spectroscopy, spectrometry and related techniques are then covered along with practical challenges that can often hinder detection. Potential solutions for mitigating nanoplastics waste and pollution, both at the source and after production, and lastly, future directions and outlook round out the review.