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Pool Water Contamination





I will go straight to it. Illnesses spread by water used for recreating are called Recreational Water Illnesses (RWI). RWIs are spread by swallowing, breathing, or having contact with contaminated water from swimming pools, spas, hut tubs, water parks, interactive fountains, and other recreational water.

Water can be contaminated by microscopic organisms such as bacteria, viruses, or protozoa. Microorganisms causing illness in humans are said to be pathogens. These organisms can end up in the water from the environment or from users. RWIs can cause wide variety of symptoms, including gastrotestinal, skin, ear, respiratory, eye, neurologic, and wound infections. The most commonly reported RWI symptom is diarrhea caused by pathogens such as Crypto, Norovirus, Shigella, Escherichia coli 0157:H7, and Giardia. Symptoms associated with gastroenteritis are diarrhea, nausea, vomiting and abdominal cramping. Large outbreaks occur more frequently in the summer. To ensure that most germs are killed proper level of disinfectant and pH must be maintained at all times. Fecal contamination may come from sources other than users. Feces from warm blooded animals can be tracked into the pool area from contaminated soil. Animals that enter the pool can contaminate water. Birds, ducks or geese can contaminate water with their droppings.


Adenovirus most commonly cause respiratory illness; however, they may also cause various other illnesses, such as gastroenteritis, conjunctivitis, skin rashes. Patients with compromised immune system are especially susceptible to severe complications of adenovirus infection. Adenoviruses are unusually resistant to chemical or physical agents and adverse pH conditions, allowing for prolonged survival outside of the body.


Hepatitis A. The word hepatitis means inflammation of the liver. Hepatitis is also the name of a family of viral infections that affect the liver, with three prevalent Hepatitis virus stains: A, B, C. Only Hepatitis A has the potential to contaminate a pool, because it is transmitted through the feces. Hepatitis B and C are transmitted through blood.

Infection with the Hepatitis A virus leads to a contagious liver disease. The most common symptoms are nausea, vomiting, diarrhea, low grade fever, rash, fatigue, jaundice, dark urine, and liver pain. Many people, especially children, have no symptoms. If symptoms occur, they usually appear from two to six weeks after exposure. Symptoms usually last less than two months, although some people can be ill for as long as six months. While Hepatitis A causes liver inflammation, most people's livers can fully recover without any long-term damage. Studies have shown that Hepatitis A can be easily inactivated in a properly maintained pool with free chlorine levels of 1 ppm within 16 minutes.


Germs Inactivation Time (CT Value) for Chlorinated Water level 1ppm

E. coli O157:H7 - Bacterium - less than 1 minute

Hepatitis A - Virus - about 16 minutes

Giardia - Parasite - about 45 minutes

Cryptosporidium - Parasite - about 15,300 minutes (10.6 days)


Crypto inactivation time for Diarrheal incident

Chlorine level 1.0 - 255 hours

Chlorine level 10 - 25.5 hours

Chlorine level 20 - 12.75 Hours


Germ Inactivation Times (CT Values)


To effectively disinfect the pool after some form of pathogen is known to be present, it is required that the pathogen be 99.9% inactivated. To achieve this level of germ inactivation for any pathogen the Contamination Time (CT) value for that pathogen must be achieved. The CT inactivation value is the concertation (C) or free chlorine in ppm (ml/L) multiplied by time (T) in minutes.


CT value = C x T


The CT value for Giardia is 45 and the CT value for Crypto is 15,300: both at about pH 7.5, 77F. If you choose different chlorine concentration or inactivation time, you must ensure that CT values remain the same.

For example, to determine the length of time needed do disinfect a pool after a diarrheal accident at 15ppm (mg/L), use the following formula:

Time=15,300:15ppm (mg/L) = 1,020 Minutes or 17 hours


Vomit and Blood Contamination in Pool Water


The most common germs spread through recreational water are germs that cause diarrheal illnesses and skin rashes. These are spread by swallowing water contaminated with feces or by the user's skin exposure to contaminated water. Pool water is unlikely to spread illness via vomit or blood.

Vomiting while swimming is a common event. Often vomiting is a result of swallowing too much water. In these cases, the vomit is probably not infectious. However, if the full contents of the stomach are vomited, respond to the vomit accident as you would respond to a formed fecal accident, using CDC's recommendations.

Noroviruses are the most likely germs to be spread by vomit. The time and chlorine level combinations needed to kill noroviruses and Giardia are similar. Since killing Giardia is the basis of CDC's formed fecal accident response recommendations, this protocol should be adequate for disinfecting a potentially infectious vomit accident.

Germs (e.g. Hepatitis B virus or HIV) found in blood are spread when infected blood or certain body fluids get into the body and bloodstream. There is no evidence that these germs have ever been transmitted from a blood spill in a pool.


Non-Fecal Illnesses


There are several diseases that can be transmitted or contracted in the recreational water environment that are not associated with feces and do not cause gastrointestinal illness, but can still cause disease.


Pseudomonas aeruginosa


Pseudomonas aeruginosa is the most common bacteria isolated from skin rashes and ear infections. It is commonly found on skin and hair, and is common throughout the environment in soil, water, plants and leaves.

Common infections include dermatitis and folliculitis (infection or hair follicle), which are usually seen in armpits, groin, abdomen, and areas covered by swim suites. Rashes range from itchy small red bumps like flea bites, to larger pus-filled blisters like poison ivy. The rash usually occurs within two to eight days after contact and can last a week.

Pseudomonas grows in warm water and is more commonly associated with rashes from poorly maintained spas that swimming pools. The Spa & Therapy Operators chapter reviews the challenges operators face when maintaining proper water chemistry in a spa. If the concentration of disinfection dips below proper operating levels, the environment becomes perfect for Pseudomonas growth. This is why it is sometimes referred to as hut tub rash. Surrounding damp areas, such as decks, benches, and drains, can also provide optimum growth conditions. Normal disinfectant levels are sufficient to control Pseudomonas.









I'm sharing screenshots of my latest Seminar that I attended, it was about preventing recreational water illnesses.

I barely touched the surface of this topic, but stay tuned, more to come about illnesses like swimmer's ear, plantar warts, athlete's foot... and later about disinfection. Thanks for being here!



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