The ecotoxicology and chemistry of manufactured nanoparticles

Abstract

The emerging literature on the ecotoxicity of nanoparticles and nanomaterials is summarised, then the fundamental physico-chemistry that governs particle behaviour is explained in an ecotoxicological context. Techniques for measuring nanoparticles in various biological and chemical matrices are also outlined. The emerging ecotoxicological literature shows toxic effects on fish and invertebrates, often at low mg l(-1) concentrations of nanoparticles. However, data on bacteria, plants, and terrestrial species are particularly lacking at present. Initial data suggest that at least some manufactured nanoparticles may interact with other contaminants, influencing their ecotoxicity. Particle behaviour is influenced by particle size, shape, surface charge, and the presence of other materials in the environment. Nanoparticles tend to aggregate in hard water and seawater, and are greatly influenced by the specific type of organic matter or other natural particles (colloids) present in freshwater. The state of dispersion will alter ecotoxicity, but many abiotic factors that influence this, such as pH, salinity, and the presence of organic matter remain to be systematically investigated as part of ecotoxicological studies. Concentrations of manufactured nanoparticles have rarely been measured in the environment to date. Various techniques are available to characterise nanoparticles for exposure and dosimetry, although each of these methods has advantages and disadvantages for the ecotoxicologist. We conclude with a consideration of implications for environmental risk assessment of manufactured nanoparticles.

Potential scenarios for nanomaterial release and subsequent alteration in the environment

“…Dissolution (process 4a) refers specifically to the release of individual ions or molecules that are soluble in water [4,[22][23][24]. The dissolution process can involve reaction of the surface molecules and ultimate release of the ionic form [21] or direct dissolution of the constituent materials, followed by a diffusional transport of the dissolved compounds [25].…”

“…These processes will determine exposure levels and toxicity of ENM [1][2][3][4]. The specific processes that must be considered are not unique to nanomaterials, but the responses of ENM to these processes are likely to differ considerably from those of chemical contaminants historically considered in risk assessments.…”

Ecotoxicity test methods for engineered nanomaterials: Practical experiences and recommendations from the bench

“…For example, the term aqueous may be inappropriate. One is not dealing with aqueous solution chemistry, but instead, with a colloidal dispersion [1]. The term solvent control as currently used in testing protocols is also therefore inaccurate; indeed, perhaps a better technical term would be dispersing agent control.…”

“…The ecotoxicity of engineered nanomaterials (ENMs) has been the subject of several extensive reviews [1][2][3][4]. These reviews highlight the importance of understanding particle chemistry in the context of the bioavailability and ecotoxicity of ENMs.…”

“…These reviews highlight the importance of understanding particle chemistry in the context of the bioavailability and ecotoxicity of ENMs. Some environmental factors that may alter the toxicity of ENMs, such as pH, salinity, divalent ions, and the presence of natural organic matter, also have been discussed [1,2]. Much of the research has focused on fundamental aspects of ecotoxicity, such as estimates of lethal concentrations, documenting sublethal effects on organisms, identifying potential mechanisms of toxicity, as well as describing the fate and behavior of ENMs.…”