Nanomaterial Contamination of Agricultural Crop Species

Nanomaterials (NMs) impacts on agricultural is unknown and this lack of understanding is disconcerting given that food crop contamination is a pathway to human exposure. Previous investigations from our laboratory have shown that commonly employed phytotoxicity assays such as seed germination and root elongation are inappropriate when evaluating NMs phytotoxicity. The effects of NMs (Ag, Cu, Si, Au, fullerenes, single/multiwalled carbon nanotubes [S/MWCNT) and their corresponding bulk/ions counterpart on biomass and transpiration of Cucurbita pepo (zucchini) were determined under hydroponic conditions. Nanoparticle Ag, Si, Cu and MWCNTs reduced plant biomass and transpiration by 30-91% compared to control or to plants exposed to equivalent bulk materials.  The element accumulation was inversely related to particle size.  Fullerenes, Au, and SWCNTs had no impact on plant growth.  Current investigations are focused on a screening study assessing the acute toxicity of 12 different nanoparticles to 12 agricultural crops under hydroponic and soil conditions.  The results so far have shown numerous instances of particle size-specific phytotoxicity, as well as concentration-dependent and species-specific response to NMs exposure. Moreover, the effect of fullerenes on the accumulation of secondary organic pollutants (p,p’-DDE) by zucchini, tomato, pumpkin, and soybean was determined. For select species, fullerenes promoted p,p’-DDE accumulation in the roots and shoots, suggesting enhanced uptake through a fullerene-pollutant complex. The implications of these findings for accurately determining the fate and transport of nanomaterials in agricultural systems, as well as for exposure and risk posed to humans, will be discussed.