Researchers found 10 ‘target’ PFAS (perfluoroalkyl substances) — chemicals which do not break down in nature — in tap and bottled water available for consumption in major cities in the UK and China. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) were detected in over 99% of samples of bottled water sourced from 15 countries around the world.

They observed significant differences in PFAS concentrations between tap water samples from Birmingham, UK, and Shenzhen, China, with Chinese tap water found to have higher concentrations of PFAS compared to UK tap water.

However, the study demonstrates that measures such as boiling and/or activated carbon filtration — typically using a ‘jug’ water filter — can substantially reduce PFAS concentrations in drinking water, with removal rates ranging from 50% to 90% depending on the PFAS and treatment type.

Publishing their findings today (17 October) in ACS ES&T Water, researchers from the University of Birmingham, Southern University of Science and Technology, Shenzhen, and Hainan University, Haikou, reveal a wide range of PFAS contamination for target PFAS, starting at 63% of bottled waters tested.

Co-author Professor Stuart Harrad, from the University of Birmingham, commented: “Our findings highlight the widespread presence of PFAS in drinking water and the effectiveness of simple treatment methods to reduce their levels. Either using a simple water filtration jug or boiling the water removes a substantial proportion of these substances.

“While current PFAS levels in most water samples are not a major health concern, ongoing monitoring and regulation are crucial to protect public health. We provide valuable data on the presence of PFAS in drinking water alongside practical solutions to mitigate consumer exposure via drinking water. This is a significant step towards ensuring safer drinking water for communities worldwide.”

Bottled water from various countries showed varying levels of PFAS, with natural mineral water containing higher concentrations than purified water, but the concentrations were generally below health advisory levels set by regulatory agencies.

Co-author Professor Yi Zheng, from Southern University of Science and Technology, commented: “Increased awareness about the presence of PFAS in both tap and bottled water can lead to more informed choices by consumers, encouraging the use of water purification methods.

Our findings also suggest that the potential health risks of PFAS in drinking water may be influenced by lifestyle and economic conditions, highlighting the need for future research to further explore these factors from a socio-economic perspective.”

Except for comparisons between natural mineral and purified water, the researchers observed no significant difference in target PFAS concentrations between glass and plastic or still and sparkling bottled water.

While concentrations of most individual PFAS were well below corresponding health-based reference values, average PFOS concentrations in tap water samples from Shenzhen, China exceeded the maximum contaminant level (MCL) of 4 ng/L newly promulgated by the US Environmental Protection Agency (USEPA) in 2024.

Researchers purchased 112 bottled water samples from local shops and online supermarkets in the UK and China including 89 still and 23 sparkling waters in either plastic or glass bottles. The samples covered 87 brands with water sources originating from 15 countries in Asia, Europe, North America, and Oceania

They collected 41 tap water samples from homes in Birmingham and the nearby cities of Worcester, Coventry, and Derby — provided by two suppliers: South Staffordshire Water and Seven Trent Water, with a further 14 tap water samples collected from homes in Shenzhen, China.

PFAS are used widely in industry, in fire-fighting foams, and consumer products from waterproof clothing and school uniforms to personal care products because of their water and stain repellent properties. While some have been banned by government regulation, others are still widely used and their toxic effects not yet fully investigated.

The chemicals are already known to enter the body in different ways, for example being breathed in, ingested via food or drinking water, or absorbed through the skin. They are known to cause adverse health effects such as a lowered immune response to vaccination, impaired liver function, decreased birth weight, and increased risk of some cancers.

The scientists were investigating the hippocampus, a brain area that plays a key role in memory in humans and mice. Specifically, they focused on the CA2 region, which is significant for social memory, the ability to remember other individuals, and the CA1 region, which is important for remembering places.

In this new study, the researchers for the first time reveal that CA1 and CA2 respectively encode the locations and individuals linked with a threatening experience. The results show that, beyond simply recognizing individuals, CA2 helps record more complex aspects of social memory: in this case, whether another individual is safe or risky. The scientists published their findings on October 15 in the journal Nature Neuroscience.

“It’s vital to all species that live in social communities, including mice and humans, to have social memories that can help one avoid future experiences with others that might prove harmful while keeping ourselves open to individuals who may be beneficial,” saidPegah Kassraian, PhD, a postdoctoral research fellow in the Siegelbaum lab and lead author of the new study. “Fearful memories are important for survival and help to keep us safe.”

To investigate where fearful social memories originate in the brain, Dr. Kassraian and her colleagues gave individual mice a choice. They could scamper to one place, meet another mouse that was unknown to them, and receive a mild foot shock (much like a static electricity zap people might get after walking on a carpet and touching a doorknob). Scurrying in the opposite direction to meet a different stranger was safe. Normally, the mice quickly learned to avoid the strangers and locations that were associated with the shocks, and these memories lasted for at least 24 hours.

To determine where in the hippocampus these memories were stored, the researchers genetically altered the mice to enable them to selectively suppress the CA1 or CA2 regions. Surprisingly, turning off each region had very different effects. When the scientists silenced CA1, the mice could no longer remember where they were zapped, but they could still remember which stranger was associated with the threat. When they silenced CA2, the mice remembered where they were shocked, but became indiscriminately afraid of both strangers they met.

These new findings reveal that CA2 helps mice remember whether past encounters with others were threatening or safe. The results also are consistent with prior research detailing how CA1 is home to place cells, which encode locations.

Previous research has implicated CA2 in various neuropsychiatric conditions such as schizophrenia and autism. The new study suggests that further investigating CA2 might help scientists better understand social anxiety, post-traumatic stress disorder and other conditions that can lead to social withdrawal.

“It’s possible that social withdrawal symptoms are related to an inability to discriminate between who is a threat and who is not,” said Dr. Siegelbaum, who is also a professor and chair of the department of neuroscience at Columbia’s Vagelos College of Physicians and Surgeons. “Targeting CA2 could be a useful way of diagnosing or treating disorders linked with a fear of others.”

The paper, “The hippocampal CA2 region discriminates social threat from social safety,” was published online in Nature Neuroscience on October 15, 2024.

The full list of authors includes Pegah Kassraian, Shivani K. Bigler, Diana M. Gilly, Neilesh Shrotri, Anastasia Barnett, Heon-Jin Lee, W. Scott Young, and Steven A. Siegelbaum.

The authors report no conflicts of interest.