Although environmental exposure...

to nanomaterials may not be a new phenomenon, the rapid development of commercial applications involving the use of a wide variety of manufactured nanomaterials, may result in the introduction of increasing amounts of nanomaterials into the natural environment, while little information is available on their probable harmful effects.

Potential pathways of nanoparticles into the environment (air, soil and aquatic systems) include point sources such as production facilities, landfills or wastewater treatment plants or diffuse sources such as wear and tear from materials containing nanoparticles. Accidental release during production or transport is also possible.[16]

At present, after more than twenty years of dedicated research, relatively little is known about the environmental and human health impacts of nanoparticles. The general hazard and risk patterns of nanomaterials differ from other chemical substances. For nanomaterials the surface area, size, shape, charge, solubility and persistence are predominant factors, much more than their chemical composition per se, determining their fate and impact.

It is complex to determine the environmental exposure of manufactured nanomaterials as there is little information on their actual use in nano-enabled products and their potential to be released. As a consequence environmental risk assessment has to rely on estimations. Studies on environmental transport (and fate) show that nanoparticles can be highly mobile in the environment, but they have a large tendency to aggregate and attach to mineral surfaces.[17]

Once nanoparticles enter the natural environment they might cause adverse effects to biological organisms. Due to their small size and high surface area, coupled with other physico-chemical features, nanomaterials may well have unpredictable toxic and genotoxic properties.[18]

In general, nanoparticles affect organisms through the disruption of membranes and the formation of reactive oxygen species resulting in oxidation of proteins (including enzymes) and interruption of energy transduction. They may also cause DNA damage directly, by passing through cellular membranes if small enough, or indirectly, by promoting oxidative stress and inflammatory responses.[19] While these responses can be clearly shown in in vitro cell culture studies, measurable responses in organisms (primarily fish and daphnia) are less predictable because of dependencies on temperature, physical/chemical properties of the exposure medium, differences in species, chemical composition of the nanoparticles and their properties.[20]

Although information about the toxic or ecotoxic effects of nanoparticles is still limited and fragmented, scientific literature on nanotoxicology is constantly growing, identifying the harmful effects of some engineered nanoparticles in biological organisms. For example, recent studies showed that exogenous nanoparticles, containing zinc and aluminum, exert toxic effects on germination and growth of roots in the seedlings of plants.[21] Other studies demonstrated that tungsten carbide and tungsten carbide cobalt nanoparticles are able to enter the cells of gills of rainbow trout and exert toxic effect.[22],[23] The toxicity of C60 fullerenes and titanium dioxide was witnessed in an aquatic invertebrate, Daphnia magna.[24]

In conclusion, before introducing nanoparticles into the environment or in consumer products, a comprehensive, valid, scientifically sound, quantitative, evidence-based risk assessment is needed in order to conduct risk evaluation and risk management.

How Nanoparticles with potential toxic and ecotoxic effects enter the environment