Little is known about how the tiny engineered objects known as nanoparticles affect the environment when they escape. A stream of new commercial applications for the diverse, super-tiny particles — in everything from paint and dental implants to sunscreen and scratch-proof eyeglasses — have far outstripped the environmental science.
New research from the University of Minnesota shows why that could be a problem.
Researchers found that a bacterium commonly found in soil and water adapts rapidly when exposed to certain nanoparticles that are used in lithium ion batteries, so that the bacterium that would have died on exposure became permanently resistant.
The bacteria mutated and continued to grow even when exposed to nanoparticles in twice the concentration that was previously lethal.
The researchers don't know if the mutation is dangerous, but the point is that the battery nanoparticles are doing something unintended, said U chemist Erin E. Carlson, lead author of the study.
"Just because we designed them as batteries doesn't mean that they don't do all kinds of other things," Carlson said in an interview. "My greatest concern is that we are putting things out in the environment without any data."
The finding was especially noteworthy given that the type of nanoparticle they studied wasn't developed to have any special antibacterial properties. It was designed for use in a lithium-ion battery for a Nissan LEAF electric vehicle. The bacteria used in the study, called Shewanella oneidensis MR-1, is often used in environmental studies.
The findings were published online in August in the journal Chemical Science.
According to the study, each electric vehicle contains about 50 kilograms, or about 110 pounds, of nanoscale cathode materials.
The study notes that bacteria and microbial communities are central to the functioning of natural ecosystems, and underscores the danger of contamination.
"There's a very real possibility that there are parts of ecosystems that are severely damaged," Carlson said.
Carlson did the research in conjunction with the National Science Foundation Center for Sustainable Nanotechnology, a collaboration with more than a dozen universities and labs.
She said the researchers don't know how the bacteria adapted to the nanoparticles, but they are studying the question, with results expected in 2020.
Nanoparticles, so small that hundreds of thousands of them could fit on the head of a pin, have been the subject of intense research and development for several decades. They're now in more than 1,000 consumer products. In medicine, for example, they are being developed as an alternative to antibiotics to fight infectious diseases that show resistance to traditional antibiotics. Some see potential in copper nanoparticles as an alternative to conventional chemical pesticides such as glyphosate, the active ingredient in the weedkiller Roundup.
But nanoparticles escape into the environment through industrial processing and many other pathways such as landfills and waste water treatment plants. Some degrade into contaminants and can have a range of human health impacts.
The U.S. Environmental Protection Agency has been trying to understand the toxicity of diverse nanoparticles. It considers many nanoparticles as chemical substances subject to the Toxic Substances Control Act, and has required manufacturers to report information, such as the chemical identity, how much they are producing and any research they have on environmental and health effects.