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Bathing Water

Essentials

  • Notice that this article has been written from the viewpoint of bathing waters in Finland. Potential differences in relevant pathogens and health hazards existing in other locations should be taken into account.
  • Sources of bathing water pollution include cyanobacteria, or blue-green algae, waste water discharge into bathing water, intestinal microbes from swimmers, faeces of wild animals, birds or cattle grazing close to the beach, storm water from densely populated areas or impurities flushed into bathing water by flooding.
  • Skin infections and gastroenteritis are the most significant diseases caused by dirty bathing water.
  • Water containing cyanobacteria, or blue-green algae, may cause allergic skin symptoms, nausea, abdominal complaints, eye and ear infections, rhinitis, fever and headache.
  • Swallowing bathing water which has intestinal pathogens may cause a disease involving vomiting or diarrhoea.
  • In Finland, norovirus have been the most common cause of waterborne epidemics.
  • When the weather is hot, bacteria of the genus Vibrio may multiply in coastal brackish waters and cause wound infections, otitis, diarrhoea and abdominal pain in swimmers.
  • Schistosome flatworms are parasites of waterfowl that may cause cercarial dermatitis, or swimmer's itch.

Bathing water pollutants

  • The quality of bathing water may become temporarily worse for various reasons. Bathing water pollutants include
    • cyanobacteria, or blue-green algae
    • waste water discharge into bathing water
    • intestinal microbes from swimmers
    • faeces of birds or other wild animals or of cattle grazing close to the beach
    • storm water from densely populated areas
    • impurities flushed into bathing water by abundant rain or floods
    • chemical pollution, such as oil release.
  • The most significant surface water pollutant is waste water from densely and sparsely populated areas, carrying pathogenic microbes, nutrients and chemical impurities into surface water.
    • Even though waste water is normally released far from beach areas, malfunction or breakdown of the waste water system or overflow or spill of waste water from a treatment plant may allow waste water to flow near to a beach. Should this happen, the numbers of microbes in bathing water may increase to far beyond the normal level. Downpours which get heavier with the climate change may make the spills of waste water more common.
  • Storm water may carry impurities from densely populated areas to the beach.
    • Rain may flush animal droppings and other environmental impurities into bathing water.
    • Nesting of waterfowl, such as sea gulls, barnacle geese or cormorants, on beaches may pollute beach environments and bathing water.
    • With climate change, increasingly common extreme weather conditions, such as storms and heavy rain, increase the amount of storm water and may thus increasingly often make bathing water quality worse.
  • Cyanobacteria sometimes occur both in surface water and in bathing water.
    • Warm, calm weather and good nutritional conditions promote the proliferation and occurrence of cyanobacteria.
    • Cyanobacteria may stain water green and in multitudes form thick masses called blooms on the water surface; these are hard to predict and to control.
    • Since wind and currents may move cyanobacteria masses, the presence of cyanobacteria in water may vary even within the same day.
    • With the climate change, the presence of cyanobacteria in surface waters may increase if hot periods become more common and if nutrient washout into surface waters caused by downpour increase.
    • When the weather is hot, bacteria of the genus Vibrio may multiply in low-salinity brackish waters. Vibrio species present in the Baltic Sea are V. cholerae (non-toxigenic strains), V. vulnificus, V. parahaemolyticus and V. alganolyticus http://wwwnc.cdc.gov/eid/article/22/7/15-1996.
  • Bathing water may also be polluted through the action of swimmers themselves if their intestinal microbes end up in bathing water or in the beach environment.
    • Swimming should therefore be avoided if the swimmer has a disease involving vomiting or diarrhoea, and on the beach, appropriate hygiene should always be observed.
    • Baby nappies should be changed and the baby washed in other than bathing water.

Health hazards associated with bathing water

  • Bathing water is not potable. However, a swimmer may accidentally swallow some water and thus be exposed to any pathogens or other impurities in the bathing water.
  • Bathing water may also have adverse health effects on swimmers through skin contact. Pseudomonas and staphylococci, for example, may cause skin infections, and Pseudomonas bacteria are also known to cause external otitis in swimmers.
  • Noroviruses (formerly called caliciviruses) that cause vomiting and diarrhoea have made many swimmers ill 6.
  • In addition to noroviruses, E. coli O157:H7 bacteria causing diarrhoea have been linked to a bathing-water-mediated epidemic 7.
  • Pathogens such as campylobacteria, Giardia and Cryptosporidium protozoa 3 5, which have been found in surface water, may also cause intestinal infections through bathing water.
  • Vibrios have been found to proliferate in brackish water with sufficient cyanobacterial dissolved organic matter and a sufficiently high temperature 2.
    • Vibrios may cause diseases such as diarrhoea, wound infections and systemic infections.
    • In the summer of 2014, there were more vibrio infections than normal in Northern Europe - Finland and Sweden, in particular - suspected of being due to swimming in warm coastal water 1. Even though most of the infections were caused by V. cholerae, no choleragen (cholera toxin) was observed, and these were therefore not actual cholera infections.
    • In the future, the number of bathing-water-mediated vibrio infections may increase if climate change renders bathing water favourable for the proliferation of vibrios.
  • The waterfowl parasite Schistosoma cercariae can cause swimmer's itch Schistosomal Dermatitis, an allergic reaction appearing as red papules on the skin.
    • The parasite most commonly occurs in shallow water with reeds.
    • Swimmers should avoid wading in reeds and start swimming from a bathing platform.
    • Swimmer's itch may be prevented by washing with clean water after swimming, and drying with a rough towel.
  • It should always be kept in mind that water with blue-green algae may cause health hazards.
    • Swimming should be avoided if cyanobacteria are visible in the water.
    • Water containing cyanobacteria must not be used as the water thrown on the heated stones in sauna nor as people's or animals' drinking water even if it is boiled.
    • Cyanobacteria may produce compounds irritating the skin. Water containing cyanobacteria may cause allergic skin symptoms, nausea, abdominal complaints, eye and ear infections, rhinitis, fever and headache. Some cyanobacteria produce hepatotoxins or neurotoxins.
    • If a person suspects they have been swimming in water containing cyanobacteria, they should wash themselves with clean water after swimming.
  • Local regulations and instructions may apply regarding the investigation and reporting of waterborne epidemics.

References

  • Baker-Austin C, Trinanes JA, Salmenlinna S et al. Heat Wave-Associated Vibriosis, Sweden and Finland, 2014. Emerg Infect Dis 2016;22(7):1216-20. [PubMed]http://wwwnc.cdc.gov/eid/article/22/7/15-1996_article
  • Eiler A, Gonzalez-Rey C, Allen S et al. Growth response of Vibrio cholerae and other Vibrio spp. to cyanobacterial dissolved organic matter and temperature in brackish water. FEMS Microbiol Ecol 2007;60(3):411-8. [PubMed]http://www.ncbi.nlm.nih.gov/pubmed/17386033
  • Hokajärvi AM, Pitkänen T, Siljanen HM et al. Occurrence of thermotolerant Campylobacter spp. and adenoviruses in Finnish bathing waters and purified sewage effluents. J Water Health 2013;11(1):120-34. http://urn.fi/URN:978-951-740-716-8
  • Hörman A, Rimhanen-Finne R, Maunula L et al. Campylobacter spp., Giardia spp., Cryptosporidium spp., noroviruses, and indicator organisms in surface water in southwestern Finland, 2000-2001. Appl Environ Microbiol 2004;70(1):87-95. [PubMed]
  • Kauppinen A, Al-Hello H, Zacheus O et al. Increase in outbreaks of gastroenteritis linked to bathing water in Finland in summer 2014. Euro Surveill 2017;22(8):. [PubMed]http://www.ncbi.nlm.nih.gov/pubmed/28251888
  • Paunio M, Pebody R, Keskimäki M et al. Swimming-associated outbreak of Escherichia coli O157:H7. Epidemiol Infect 1999;122(1):1-5. [PubMed]http://www.ncbi.nlm.nih.gov/pubmed/10098778