Challenges in assessing release, exposure and fate of silver nanoparticles within the UK environment

There are significant challenges in assessing the fate and exposure of nanoparticles (NPs) in the environment owing to the lack of information on their use, potential pathways and sinks in the environment. In order to better understand the environmental exposure of silver nanoparticles (AgNPs), we reviewed the uses and potential exposure sources of both Ag and AgNPs. The approach taken was to identify the range of products that utilise its properties, identify potential environmental release pathways and subsequent fate once released into the environment. We then compared measured environmental concentrations with modelled concentrations from our work and others. We estimate that within the United Kingdom (UK) a total quantity of 8.8 tonnes per year of AgNPs is released from products containing AgNPs and enters UK waste water systems. Sewage sludge was identified as an important receiving compartment. Agricultural land with sludge applied was estimated to have a yearly increase in AgNP concentration of 36 μg per kg per year. Available ecotoxicity data for soil and the predicted environmental concentrations are used to perform a risk characterisation. This work highlights the on-going challenges faced when undertaking a risk assessment of AgNPs in the environment.