As part of a recent study, British researchers asserted that wild swimming in freshwater carries heightened health risks. This may also apply to areas that meet current European standards. What are these risks?
Gastroenteritis and skin problems
With the new school year already underway, the temperatures still feel fairly summer-like, prompting some people to swim in lakes and rivers. However, a recent study published in the International Journal of Hygiene and Environmental Health urges caution. Researchers from the University of East Anglia (United Kingdom) stated that plunging into these freshwater waters posed increased health risks.
The authors analyzed the health of 2,368 individuals invited to swim in lakes and rivers in Hungary. Participants were asked to immerse themselves for about ten minutes and to submerge their head underwater on three occasions. According to the results, 2.1% of swimmers contracted gastroenteritis compared with 1.9% of non-swimmers who remained on the shore. Additionally, 2.7% developed skin problems – redness, itching, skin ulcers – versus 1.3% among non-swimmers.
“These findings provide to date one of the most compelling pieces of evidence that contamination of freshwater recreation sites can translate into illness among bathers.”, reads the press release describing the study.
Bacteria revealing fecal pollution
In practice, the study and the monitoring of bathing waters highlighted several invisible biological factors. For instance, there were high concentrations of bacteria such as Escherichia coli, along with enterococci originating from soils, manure, or wastewater. These are directly linked to rising cases of gastroenteritis. Regarding skin issues—particularly cercarial dermatitis—the authors suspect cercaria, a parasitic larva capable of penetrating human skin and causing strong irritations.
“We also found that the risk of gastroenteritis increased with the concentration of E. coli and viruses that infect human intestinal bacteria in the water, which points to fecal contamination.” explained the researchers.
Let us also mention cyanobacteria. Although absent from the study, it should be noted that these organisms proliferate in warm, stagnant waters during summer. They release dangerous toxins that can trigger headaches and cause liver or neurological damage.
Tests not frequent enough?
In general, authorities carry out sampling at regular intervals. However, a sudden storm can cause sewage overflows or manure runoff from fields; while a rapid rise in temperature can accelerate the growth of microorganisms. The four Hungarian sites tested in the study adhered strictly to European Union standards at the time of the experiment. Thus, the work shows that EU criteria, while useful, can offer a sense of safety that is sometimes misleading for freshwater waters, which are logically more unstable than seawater.
Finally, the study’s authors offered a few recommendations, notably favor monitored zones, where water quality is checked very regularly by health authorities. It is also advised not to submerge the head underwater and to rinse off after swimming. Lastly, monitoring the water temperature may be prudent, since any water that is too warm and stagnant promotes the development of bacteria.
