The most widespread germs spread via recreational water are those that result in diarrheal illnesses and skin rashes. These germs are distributed by swallowing or by skin exposure to water that has been polluted with germs
Both swimmers and the environment can introduce contaminants to a pool. Primarily a concern for outdoor pools, wind and weather can contribute many contaminating elements, including dirt, plant debris, unsanitary flood water, algae spores from rain drops. Even bird droppings are a concern because of the pathogens they may contain. The risk of environmental contaminants is far lower for indoor pools.
However, both indoor and outdoor pools are at risk for contaminants introduced by swimmers, which can dramatically impact pool operation. The list of contaminants that can be introduced by swimmers is long. They can include body oils, sweat, traces of urine or fecal matter, saliva, chemicals from cosmetics or suntan lotion, and even micro-organisms from infections. Some researchers estimate that the average urine content for a swimming pool is 30 to 80 mL per person. Further, when these contaminants interact with disinfectants and other pool chemicals, by-products like chloramines can be produced. As an example, the research journal Environmental Science and Technology reports that when urine or sweat come into contact with chlorine, two chemicals known to be dangerous for humans are produced: trichloramine and cyanogen chloride. Another dangerous by-product, nitrosamine, is caused by reactions with common pool disinfectants.
"Urine content in pools is measured by tracking the content of acesulfame potassium, a common ingredient in the diet of most people, excreted by the kidneys. Researchers estimate a 220,000 gallon pool, which is normal commercial size, will contain as much as 20 gallons or urine. This would equate to about two gallons of urine in a residential pool," said a spokesperson for a Minneapolis swimming pool company.
Contaminants in swimming pools have been associated with recreational water illnesses (RWIs), which can present a great concern to public health. Pathogens like protozoa, bacteria, viruses, and fungi can lead to diarrhea, Giardiasis, and Cryptosporidiosis. Contaminants can also cause swimmer's ear (otitis externa), respiratory infections, and skin rashes.