Trends, risks and opportunities in environmental nanotechnologies

Environmental applications of nanomaterials include pollution control, clean water production, and detection and monitoring. Despite the considerable potential environmental benefits of nanotechnologies, the large-scale manufacturing requirements, cost limitations and potential health and environmental risks of engineered nanomaterials (ENMs) are common barriers to their widespread use.

In this review, we assess the benefits of using ENMs in environmental applications against their potential risks to public health and the environment, focusing on water treatment and reuse, and identify strategies for their responsible use.

Life cycle analyses indicate that the highest potential environmental and health impacts of ENMs used in commercial products are associated with their production rather than their release during use. In general, the concentrations of ENMs detected or predicted are 1 to 4 orders of magnitude lower than the concentrations at which effects are observed. The environmental and health risks of ENMs are therefore relatively low, given the low concentrations and passivating transformations (such as oxidation) that occur in the environment. However, the potential impacts on human health and ecosystems of long-term exposure (from several months to several years) to low concentrations of ENMs (for example, a level of less than a microgram per litre in water) remain largely unexplored.

The adoption of green chemistry and immobilisation strategies (in or on substrates such as electrodes and membranes) can further limit the release of ENMs and mitigate exposure, thereby minimising their potential release into the environment. Such 'sustainable and safer by design' strategies to reduce toxicity and exposure enable sustainable use of ENMs, so that the environmental benefits could outweigh the risks if managed correctly.