While some impacts of nanoparticles have been widely studied, there is concern over "trickle-down" into the environment with widespread nanoparticle use, where the effects are less well known. In a study published today (August 21) in Proceedings of the National Academy of Sciences, two common nanomaterials have been found to have negative impacts on soybean crops.
Zinc oxide, a common nanomaterial used in cosmetics, escapes sewage treatment and ends up as a component of solid waste, which is widely used as organic fertiliser. Growing soybean in the presence of zinc oxide nanoparticles initially improved crop growth over a control group, but zinc accumulated in the leaves and beans of the plant. There is some evidence zinc oxide particles may be toxic to mammalian cells in culture, but it is unknown whether the nanomaterial is harmful to humans.
A second common nanoparticle, cerium oxide, used to improve combustion and reduce particulate emissions in diesel fuels, affected soybean crops more dramatically. Growth was significantly stunted, and the actions of nitrogen-fixing bacteria associated with the soybean root system appeared to be completely inhibited.
Nanosafety expert Vicki Stone of Heriot-Watt University in Scotland, who was not involved in the study, told BBC News that this study is part of a larger picture of trying to understand the hazards of nanoparticles. "Effects seem to depend upon their physical and chemical characteristics," she said. "This is what scientists are aiming at better understanding, so that in future they can predict toxicity or safety based on these characteristics."