Human health risks from direct consumption of toxic nanoplastics are already scary, but researchers have confirmed that nanoplastics in water give rise to an additional threat: They strengthen bacteria.
In a recent study published in Water Research , Virginia Tech's Jingqiu Liao and a group of international researchers found that nanoplastics' interactions with environmental microbes may pose indirect dangers to people, specifically by way of water systems.
"It is very important to better understand the adverse effects of the nanoplastics on human health, and not just in humans but also in the environment, which indirectly influences human health," said Liao, assistant professor of civil and environmental engineering . "The nanoplastics can make the antimicrobial-resistant pathogens better survive, which could be harmful to the environment and would have public health implications."
In the study, the authors note this resistance to disinfectants has the potential to create great challenges for water treatment and distribution systems.
"When the nanoplastics interact with the biofilm and the bacteria inside them, they can strengthen the biofilm and make it more resistant to any kind of measures that are going to keep the water clean," said Liao, who is also an affiliate with Fralin Life Sciences Institute 's Global Change Center.
Jingqiu Liao is an assistant professor of civil and environmental engineering. Photo by Peter Means for Virginia Tech.
Nanoplastics are a subset of microplastics and include particles ranging in size from roughly one to 1,000 nanometers, all of which are too small to be seen by the naked eye. The researchers looked at the effects nanoplastics have on the biofilm formation in drinking water systems.
Biofilms are communities of different bacteria that attach to surfaces, such as water pipes, and form a protective matrix that shields them from environmental stress. In some locations, biofilms can be beneficial, removing potentially harmful elements, but in drinking water distribution systems, they can be hazardous to humans.
According to Liao, this is rooted in the pathogenic nature of certain bacteria within biofilms as well as the fact that bacteria are also hosts to bacteriophages, which are viruses. How these potentially problematic microorganisms interact with nanoplastics was largely unknown prior to the study.
"The primary process that we were particularly interested in is how the bacteria and the bacteriophages interact with each other during the process when the nanoplastics influence the biofilm as a whole," said Liao, also an affiliate with the Fralin Life Sciences Institute's Center for Emerging, Zoonotic, and Arthropod-borne Pathogens .
Liao's expertise with microbial ecology and metagenomic analysis made her ideal for the study. She's published studies on the role of soil in the spread of antibiotic resistance and recently won a Scaling Scholarship Award through the College of Engineering's Major Grants Initiative related to her work on the Nature Communications publication, "Differential roles of deterministic and stochastic processes in structuring soil bacterial ecotypes across terrestrial ecosystems."
Liao said the researchers discovered that when the biofilm composed of E. coli and Pseudomonas aeruginosa is exposed to nanoplastics, several responses from the bacteria are triggered:
- Different bacteria "talk" with each other and secrete substances that make the biofilm thicker, heavier, and more protective.
- Prophages — phages that integrate their own genomes (DNA) into their bacterial hosts' genomes — are activated, destroying the bacterial cells they live in and creating many new virus particles.
- Bacteria fight the prophages using clustered regularly interspaced short palindromic repeats (CRISPR) of DNA or RNA cells to target them as an antiviral defense system.
An illustration of the three responses from the bacteria when the nanoplastics come into contact with the biofilm. Image courtesy of Jingqiu Liao.
In the study, the authors conclude that "the increased mechanical strength of the biofilm and its resistance to the disinfectants highlight a potential challenge for water treatment and distribution systems, as nanoplastics may increase the formation of difficult-to-eradicate biofilms on the surface of some water treatment and distribution systems."
Liao believes more research is needed to better understand the molecular mechanisms underlying the ecological responses of complex multispecies biofilms to nanoplastics. She also suggests that the size of the plastics matters. She points out that microplastics, which are larger than the nanoplastics, may have different effects on the bacteria-phage interactions within the biofilm.
"Overall, our findings provide novel insights into the interplay between nanoplastics and bacterium-phage dynamics, highlighting increased microbial risks associated with waterborne nanoplastics," Liao said.
Other researchers in the study include the following:
- Haibo Wang, associate professor, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
- Hui Chen, associate research fellow, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
- Chujin Ruan, postdoctoral fellow, environmental microbiology, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland
- Cory Schwarz, postdoctoral fellow, civil and environmental engineering and Rice WaTER Institute, Rice University, Texas
- Baoyou Shi, professor, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China
- Pedro J.J. Alvarez, professor, civil and environmental engineering and Rice WaTER Institute, Rice University, Texas
- Pingfeng Yu, postdoctoral fellow, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China
Original study : doi.org/10.1016/j.watres.2025.124712
