Portland, Ore. - New research suggests that plants may suffer adverse reactions to tiny nanoparticles.
While the possibility of detrimental health effects from nanotechnology has been investigated in relation to animals and humans, researchers at the New Jersey Institute of Technology have now demonstrated that plants too can be hurt by nanoparticles.
A toxicology expert, professor Daniel Watts, reports that aluminum-oxide nanoparticles in groundwater inhibit the growth of all five species tested-corn, cucumber, cabbage, carrot and soybean. Watts warned that care must be taken to prevent these nanoparticles from dispersing in the air, where they will be carried by rain into groundwater systems and stunt plant growth.
These concerns underscore the already accumulating evidence of possible harm to human health (see www.eet.com/ news/latest/ showArticle.jhtml?articleID=172900608) posed by nanotechnology.
"It is difficult to take results from a lab experiment and conclude what will happen in the real world," Watts said. "But we speculate that air deposits of nanoparticles or water transport of them are ways in which nanoparticles could mix with plant life."
Watts, who is executive director of the York Center for Environmental Engineering and Science at the New Jersey Institute of Technology (Newark, N.J.), performed the research along with Ling Yang, a postdoctoral researcher at the institute.
Nanoparticles in general may not be a problem. In Watts' tests on plants, most of the nanoparticles studied had no effect on health. In particular, silicon dioxide-a common nanoparticle-had no detrimental effect on plants. But aluminum-oxide nanoparticles slowed the growth of roots in all five vegetables tested.
"There was an assumption that nanoparticles had no effects on plants," said Watts. "But we have shown that seedlings can interact with nanoparticles such as aluminum oxide, and that they can have a harmful effect on seedlings and perhaps stunt the growth of plants."
The researchers grew seedlings of each vegetable in Petri dishes-feeding plain water to control plants and feeding nanoparticle-laced water to the test plants. After seven days they could detect statistically measurable differences in the growth of the plants' root systems, with root growth stunted in the nanoparticle-fed vegetables.
So far, the researchers have not determined the exact growth mechanism that the nanoparticles are adversely affecting, but they did note that the smaller the nanoparticle, the more pronounced was the adverse effect. The researchers said the nanoparticles tended to clump, creating aggregates that effectively changed the size of the nanoparticles-depending on how many clumped together. They also speculated that the key was the increased surface area exhibited by nanoparticles.
"We don't know as yet the mechanism of the interaction between the particle and the root," said Watts. "But we suppose that the surface characteristics of the nanoparticles played an important role in slowing the growth of the roots-the smaller the particle, the larger is the total amount of surface area per unit weight, which we suspect is what contributes to the growth-slowing interaction between the seeds and the nanoparticles."
Today, semiconductor research is using only small quantities of nanoparticles, but if the prototypes get to the level of mass production, pollution issues may arise. Mass quantities of nanoparticles are already being manufactured for scratch-resistant coatings, for sunscreen lotions that are transparent yet completely block ultraviolet light, as well as for use as environmental catalysts aimed at remediating polluted soil. Nanoparticles from any of these sources could be dispersed in the air by exhaust systems, chimneys or smoke stacks and could also mix with rainwater and snow to gradually and irreversibly pollute groundwater and soil.