Human Health

From vomiting and sickness to a case of Leptospirosis, our sickness reports expose a worrying trend of illness after swimming.

In this section:

Sickness reports

What’s in our water?

Millions of infectious microorganisms are present in every cubic metre of untreated wastewater dumped into the sea.2 And although getting sick after a dip is a sadly common occurrence for water users, little research is available on the extent to which sewage pollution and poor water quality are making us sick. Our consumer survey undertaken in May 2022, showed more than half of people who have tried wild swimming or water sports in the UK have experienced sickness after swimming.

For the last three years, we’ve been collating sickness reports through our Safer Seas and Rivers Service (SSRS) app and webpage to unearth the impact of sewage discharges on people’s health and well-being. This year we’ve had more reports submitted to us than ever before. These reports give us a glimpse of the threats faced by water users across the country.

Spewing from sewage

Between 1st October 2021 and 30th September 2022, 720 water users reported getting ill after entering the water.

That’s more than double the amount of reports we received in 2020/21.

Swimming in contaminated recreational waters is known to increase the risk of gastroenteritis as well as sinus infections, skin rashes, and conjunctivitis. Figure 1 shows that the most common illness reported was Gastroenteritis, with 2 in 3 people reporting sickness experiencing it. Alarmingly, we found that many people have suffered from multiple illnesses, with 1 in every 15 cases reporting a combination of illnesses, from nasty rashes to bladder infections.

Figure 1

Types of sickness

About this chart

This pie chart shows the different types of sickness people experienced after entering the water.

Source: SAS Health Reports Oct 21 – Sept 22


Swimming in polluted waters is estimated to cause 120 million cases of gastrointestinal diseases globally and studies have shown open-water swimmers face a considerable risk of gastrointestinal illness from entering the water, regardless of whether it has bathing water status.2,3,4

It harms the economy, it harms ecosystems, it harms health…there are health impacts being seen and sometimes you see GPs reporting on those every year.”
Jim McManus, President of the Association of Directors of Public Health, Radio 4 18th August

Even more worryingly, exposure to contaminated water can lead to potentially life-threatening cases of Leptospirosis. This is a condition that when left untreated can cause kidney failure, acute bleeding from the lungs and disrupt the flow of blood around the body.5 One such case reported to us this year was by Sam who went kayaking on the River Trent in October 2021. Sam reported that their doctor attributed the disease to their time in the river.

“I was hospitalised for four days with kidney and liver failure from Weil’s disease.”
Sam, The River Trent
The evidence is stacking up

Of all the people that told us they had visited a doctor, two-thirds said the doctor attributed the illness to exposure to contaminated water.

Analysis of our data has enabled us to link sickness reports submitted to us through the SSRS app with sewage discharges. Shockingly, we found that 39% of sicknesses reported via the app happened at a time of a confirmed sewage discharge notification.

Figure 2

Number of sickness reports linked to a sewage discharge notification as a proportion of total discharges

About this chart

This chart shows how many times there was a pollution risk due to a confirmed sewage discharge at the same location and on the same day as a sickness report, for each month between October 2021 – September 2022.

Source: Safer Seas and Rivers Service Health Reports Oct 21 – Sept 22


It should be noted that in Figure 2 we’ve used health reports submitted via the app exclusively which accounts for 80% of sickness reports submitted to us, as we aren’t able to link reports submitted online to discharge notifications.

Health risk focus

Polio found in London’s water

In February 2022, waste from sewage treatment works in Newham, London tested positive for the Polio virus. The pathogen, known to have mutated from the live vaccine taken abroad, can pose a serious risk to human health and cause paralysis.

Since the Polio vaccine, the virus has been all but eradicated across the world (except for a few countries in Asia).

But between February and August 2022 the mutated virus has been found in London waste-water 116 times.6

Are wild swimmers around London being exposed to potentially dangerous variants of the Polio virus? We didn’t receive any sickness reports of polio after swimming in our rivers or seas but it’s possible to contract polio from ingesting water where the virus is present, and poliovirus can survive in seawater.7 However, more research is needed to determine how long polio discharged in untreated sewage could survive in seawater or rivers or whether it could be transmitted. The NHS says the risk of getting polio in the UK remains extremely low.8

Bathing Water Classifications

why your swim might not be so “Excellent”

In the UK Designated Bathing Waters are given a water quality rating from “excellent” down to “poor” on an annual basis. This is informed by water quality samples taken during the previous bathing season which are tested for faecal matter (specifically testing for E. coli and intestinal enterococci).

During the last winter period, the SSRS app issued 7,163 discharge notifications and we received 181 reports from water users that got sick during this time.

However, in England and Wales, samples are only taken weekly over the summer months and don’t consider water quality in the winter when many of us are still surfing and swimming. This means lots of discharges will be missed.

Samples are only taken at one point along the designated beach or river and often away from any sources of pollution e.g. a sewage pipe! Shockingly, up to 15% of samples taken can be discounted when there has been an ‘unusual event’ which includes a sewage discharge9. On top of this, no consideration is given to emerging threats such as microplastics and antibiotic resistance. Alarmingly, antibiotic resistance has been shown to be three times more prevalent in the guts of surfers than in the background population.10 With global deaths from antibiotic resistance set to exceed those from cancer by 2025, this is extremely concerning.

This all adds up to a rather murky view of water quality at designated bathing waters, particularly if you want real-time water quality information for your weekly dips. To help this, the regulators in England and Wales supply “Pollution Risk Forecasts” warnings when they suspect the water quality is too poor to enter the water safely. But these are only provided for 222 locations, only issued during the bathing season and are based on historic water quality samples taken during the summer.
Worryingly, this year we received more reports of sickness from ‘excellent’ bathing spots (424 reports) than any other classification, that’s equivalent to one report of sickness at every ‘excellent’ bathing spot in the UK (Figure 3). Meaning, if you just use bathing water ratings you can’t be sure that your swim will be as ‘excellent’ as you might hope.

Figure 3

Sickness reports by bathing water classification

About this chart

This bar chart shows how many reports of sickness we received at excellent, good, sufficient and poor bathing waters.

*It should be noted that there are more ‘excellent’ Bathing Water locations in England than any other category but we shouldn’t be expected to get sick from these location at all.

Source: SAS Health Reports Oct 21 – Sept 22


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