US scientists have shown that plants can absorb nanoparticles from their environment - meaning that the particles could find their way into the human food chain, the researchers claim. 

Pumpkin plants can take up iron oxide particles through their roots and accumulate them in their leaves

Yan Jin and colleagues at the University of Delaware, in Newark, found that pumpkin plants can take up nanoparticles through their roots and that the particles are transported around the plant. The study is part of an effort to assess nanoparticles' environmental and biological fate if they are released into soil or groundwater, says Jin. 

Jin and her team grew their pumpkin plants in a medium containing magnetite - magnetic iron oxide - nanoparticles. They then used a vibrating sample magnetometer, which detects weak magnetic signals, to measure the magnetite content in samples from different plant parts. Their studies showed that the plants had taken up significant amounts of particles which accumulated mainly in the roots and the leaves.  

Jin points out that despite rapid developments in nanotechnology in recent years, investigations into the environmental and health impacts of nanomaterials are still in their infancy. While researchers have looked increasingly at nanoparticle toxicity to human cells, bacteria and rodents, until now very few have examined the particles' effects on ecological species such as plants. Since nanoparticles can be highly toxic 'it is imperative that we conduct more comprehensive studies to evaluate the potential risk of nanoparticle accumulation in the food chain by plant uptake of nanoparticles from soil, sediments, and water bodies,' explains Jin.

'I am very impressed,' comments Chuanyi Wang, a nanomaterials researcher at the University of Missouri, in Kansas City, US. 'The researchers give a clear picture of the particles' transportation pathway and distribution in pumpkin plants. Since human or animal tissues are generally the focus when evaluating the potential risk of nanomaterials, this work opens a new window in the field.'  

Sarah Dixon