People could be increasingly at risk of swallowing bacteria from sewage in coastal waters and rivers - and it's probably due to climate change, an academic has warned.

Bangor University researchers believe climate change is leading to more freak weather like storms - which can cause sewers to overflow into the sea - just as warming water temperatures are tempting bathers to go for a dip.

There are numerous sewage discharges into the sea and rivers of North Wales every year - including at three beaches on Anglesey - Benllech, Rhosneigr and Aberffraw - in July. There were concerns too about potential sewage in the River Conwy last week although that turned out to be algae blooms.

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One disease people can catch is norovirus, says Dr Kata Farkas, an environmental biologist at Bangor University. She and fellow researcher Dr Jess Kevill are taking water samples from Anglesey to Wrexham to learn how bad the situation is around North Wales - and how to reduce the health risk.

Dr Farkas said even if sewage is treated viruses can survive. "People bathe in the water or consume the water. It can get into their mouths and throat and there is a chance that they can get sick.

"Pathogens including viruses can also accumulate in shellfish, like oysters. But if you cook them properly the virus would decay and wouldn't pose any risk."

Researcher Dr Kata Farkas, of Bangor University, is studying water quality around North Wales
Researcher Dr Kata Farkas, of Bangor University, is studying water quality around North Wales

Dr Farkas said the researchers are probing the impact of climate change. "The temperatures are rising which means the water temperature is rising. That also means that more people would be in the water for recreation so there are more people at risk. So we want to explore how bad the situation can get because of climate change and how the pathogens will behave in a changed environment.

"Will it be a higher risk or a lower risk? We try to assess the risk and come up with ideas on how to make sure people are safe."

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Dr Farkas and Dr Kevill are collecting data on how long viruses like norovirus and E. coli survive at different temperatures. Dr Farkas added: "It can be dangerous to do these (recreation) activities but we don't want to discourage people from doing so. So we are looking at active management.

"If we can find when and where it is safe to harvest shellfish or bathe in the water (then) we could say 'After a storm event you can go back in this many days and enjoy contact with water' or 'This beach is polluted but that beach down the road is much safer' then that would be good for everyone.

Researcher Dr Jessica Kevill of Bangor University is studying water quality around North Wales
Researcher Dr Jessica Kevill of Bangor University is studying water quality around North Wales

"It's the (fecal) poop that contains the majority of the virus (not urine) which then goes into the base water and is discharged into the environment. It's very hard to know if you've got a water-born infection because it can take days to get sick.

"It's a concern and it should be addressed in a timely manner." Dr Farkas's work is on the PATHSAFE Project which investigates norovirus and antimicrobial resistant microbes in wastewater and their spread into rivers and the coast.

She also oversees wastewater surveillance for the Welsh Government.

Her colleague Dr Kevill works on the "BlueAdapt" European research project, funded by Horizon Europe and UKRI, on the climate-based health risks of pathogens and antimicrobial drug resistant bacteria in coastal waters.

Dr Kevill, who takes water samples from the Menai Strait, River Conwy, Conwy estuary and the coast up to Kinmel Bay, said: "My work focuses on human viruses in coastal waters, their viability (infectivity), and the human health risk.

"Both of our research overlaps and the data we generate is fed into a computer simulation model, which shows the spread of the viruses throughout the environment. The model focuses on the Conwy River and coast at Conwy."

The work to collect data is ongoing and results and solutions will be suggested in due course.