Nanoparticles in Sewage Sludge May End Up in the Food Chain
Plants and microbes can absorb nano-sized synthetic particles that magnify in concentration within predators up the food chain, according to two new studies.
Nanoparticles can be made of countless different materials, and their safety isn’t well-understood. Yet the minuscule specks are infused into hundreds of consumer products ranging from transparent suncreens to odor-eating socks.
From there, they can wash down drains, ultimately ending up in the sewage sludge of wastewater treatment plants. About 3 million tons of dried-out sludge is subsequently mixed into agricultural soil each year.
“We wanted to look into the possibility of nanoparticles getting into the food chain in this way,” said environmental toxicologist Paul Bertsch of the University of Kentucky. “What we found really surprised us.”
Synthetic nanoparticles are about 1 to 100 nanometers in size (as small as some viruses) and made of silver, titanium dioxide, zinc oxide and other substances. By virtue of their small size and stability, they can nullify odors, prevent food spoilage and absorb harmful ultraviolet radiation, among other feats.
But knowledge about their impacts to the environment is still in a state of infancy, Bertsch said.
To explore nanoparticle absorption in the food chain, Bertsch’s team raised tobacco plants in a hydroponic greenhouse. While the plants grew, the team added super-stable gold nanoparticles to the water to mimic consumer nanoparticles in wastewater sludge.