Nanoplastics in Drinking Water May Be Making Dangerous Bacteria Stronger, Study Warns

A study published July 17 in the journal Water Research found that nanoplastics, tiny plastic particles invisible to the naked eye, can increase the mechanical strength of bacterial biofilms and make them more resistant to disinfectants. The research, conducted by Virginia Tech and an international team, examined how these particles affect microbial communities inside drinking water systems and what that means for public health.

What did the researchers find?

The study focused on biofilms containing E. coli and Pseudomonas aeruginosa, two bacteria commonly associated with waterborne infections. When exposed to nanoplastics, the bacteria activated multiple defense mechanisms, resulting in thicker, heavier biofilms. Jingqiu Liao, assistant professor of civil and environmental engineering at Virginia Tech and lead author of the study, said the findings indicate indirect public health risks through water systems.

“The nanoplastics can make the antimicrobial-resistant pathogens better survive, which could be harmful to the environment and would have public health implications,” Liao said, according to a Virginia Tech press release carried by ScienceDaily.

How did the bacteria respond to nanoplastics?

The researchers exposed biofilms consisting of E. coli and Pseudomonas aeruginosa to nanoplastics and observed three primary responses:

Quorum sensing: chemical signaling among bacteria that coordinates group behavior.
Prophage activation: dormant viruses within bacteria become active, destroying host cells and releasing new virus particles.
CRISPR antiviral defense: bacteria used CRISPR systems to defend against the prophages.

According to the study, these responses led to a biofilm that was thicker, heavier, and more protective than untreated biofilms.

What are nanoplastics and where are they found?

Nanoplastics are a subset of microplastics, ranging from one to 1,000 nanometers in size. They have been detected in drinking water, bottled water, food, and human tissues. A Columbia University-led study cited in the reporting found that an average liter of bottled water contains nearly 240,000 plastic particles, with 90 percent classified as nanoplastics. These particles are small enough to penetrate cells and organs, raising concerns about potential health effects.

A separate French government study found that glass bottles can contain five to 50 times more microplastics than plastic bottles, with contamination often originating from painted caps. The Environmental Protection Agency has placed microplastics on its “Sixth Contaminant Candidate List,” a step toward potential regulation.

Why do tougher biofilms matter for water treatment?

Biofilms are communities of bacteria that attach to surfaces, such as the interior walls of water pipes, and produce a protective matrix that shields them from environmental threats, including disinfectants. While some biofilms are beneficial, those formed by pathogenic bacteria can pose risks inside drinking water distribution systems.

The authors wrote 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.” Tougher biofilms could become more difficult to remove from pipes and treatment equipment, potentially allowing harmful bacteria to persist even after standard disinfection.

What do the researchers recommend next?

Liao noted that further research is needed to identify the molecular mechanisms driving these responses and to understand how particle size affects the interaction. Microplastics, which are larger than nanoplastics, may influence bacterium-phage dynamics differently, she said. Prior to this study, scientists had limited understanding of how nanoplastics might influence the interactions between bacteria, biofilms, and bacteriophages, the viruses that infect bacteria.

“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.

The authors call for additional investigations into how these particles affect complex, multi-species biofilms and emphasize the need for research on larger microplastics as well. The study adds urgency to existing monitoring efforts, according to the researchers.

FAQ

What did the new study find about nanoplastics in drinking water?

A study published July 17 in the journal Water Research, led by Virginia Tech, found that nanoplastics can increase the mechanical strength of bacterial biofilms in drinking water systems and make them more resistant to disinfectants.

Which bacteria were studied?

The researchers focused on biofilms containing E. coli and Pseudomonas aeruginosa, two bacteria commonly associated with waterborne infections.

How can nanoplastics affect water treatment?

Nanoplastics can cause bacteria to form thicker, heavier biofilms that are more resistant to disinfectants, making them harder to remove from pipes and treatment equipment and potentially allowing harmful bacteria to persist after standard disinfection.