Swimming in the sea increases the risk of developing a variety of ailments, according to a new study.
Published on Monday in the International Journal of Epidemiology, the study found that spending time in the sea – whether swimming, bathing or engaging in another recreational activity – increases the risk of illnesses including earaches and stomach bugs.
The research was led by the University of Exeter Medical School with the Centre for Ecology and Hydrology and funded by the European Regional Development Fund.
Researchers reviewed more than 6,000 studies, ultimately selecting 19 that met their criteria. Their work analysed results from over 120,000 people and covered waters in a range of high-income countries including Denmark, Norway, the UK, the US, Australia and New Zealand.
Results indicated that individuals who go in the sea are 77% more likely to experience an earache and 29% more likely to experience a gastrointestinal illness than those who do not.
“In high-income countries like the UK, there is a perception that there is little risk to health of spending time in the sea,” said study co-author Dr Anne Leonard. “However, our paper shows that spending time in the sea does increase the probability of developing illnesses, such as ear ailments and problems involving the digestive system, such as stomach ache and diarrhoea.”
“We think that this indicates that pollution is still an issue affecting swimmers in some of the world’s richest countries,” Dr Leonard added.
The study also examined whether immersing one’s head in seawater affects the risk of developing an illness. Although World Health Organisation guidelines suggested that people who partake in “high-exposure activities” like surfing or paddling could face higher risk of illness, the review found only minor differences in the chance of reporting an illness. The study notes these differences “did not alter the interpretation of the results.”
Although efforts to improve water quality have increased recently, researchers noted that pollutants such as sewage, industrial waste and agricultural run-off still contaminate seawater.
“We have come a long way in terms of cleaning up our waters, but our evidence shows there is still work to be done,” said Dr Will Gaze, who supervised the research. He said he and the team hope their work “will contribute to further efforts to clean up our coastal waters.”
Even water that is considered to be of “good quality,” defined in the paper as having low levels of faecal indicator organisms, puts swimmers at an increased risk of experiencing gastrointestinal issues, respiratory infections and ear and eye illnesses.
Nevertheless, researchers cautioned that the study’s findings should not stop people from swimming or engaging in other recreational activities in the sea.
“We don’t want to deter people from going into the sea, which has many health benefits such as improving physical fitness, wellbeing and connecting with nature,” said Dr Gaze. “However, it is important that people are aware of the risks so they can make informed decisions.”