Engineered nanomaterials in water and soils: a risk quantification based on probabilistic exposure and effect modeling

Abstract

The production and use of engineered nanomaterials (ENMs) are increasing rapidly, and therefore, the need to assess their environmental exposure and associated risks has become increasingly important. Only a handful of studies have quantified the release and environmental concentrations of ENMs, but much work has been done to investigate the effects of these materials on organisms. The aim of the present study was to quantify probabilistically the environmental risks of ENMs, producing species sensitivity distributions that were then compared with probability distributions of predicted environmental concentrations. Five nanomaterials (nano-Ag, nano-TiO2 , nano-ZnO, carbon nanotubes [CNTs], and fullerenes) and 4 environmental compartments (surface water, sewage treatment plant effluents, soils, and sludge-treated soils) were considered. From 60 ecotoxicological studies, the authors extracted 112 single values to work with (25 values in 13 studies for nano-Ag, 17 values in 10 studies for CNTs, 7 values in 7 studies for fullerenes, 34 values in 23 studies for nano-TiO2 , and 29 values in 17 studies for nano-ZnO). The results indicate there is only a marginal risk for these metal-based nanomaterials in surface water (0.7% risk for nano-Ag and <0.1% for nano-TiO2 ) and some risk in sewage treatment plant effluents (nano-Ag 39.7%, nano-TiO2 18.7%, and nano-ZnO 1.1%). Apart from a marginal value of <0.1% for nano-TiO2 in sludge-treated soils, no risk from the other evaluated ENMs in terrestrial compartments is currently predicted. The discussion of the results considers the influence of the effects of different forms of 1 ENM (coating, agglomeration state, and mineralogy), the test conditions (dissolution and agglomeration), and transformation reactions.