Pool Water Contamination
Swimming pools present no special infection risk, provided they are properly managed and disinfected.
Pool users are the primary cause of contamination. Therefore, management of their numbers, according to maintenance capabilities, is necessary. Overcrowding in the pool, in change rooms and at the poolside is to be avoided. Sensible hygiene rules, such as nappy changing in change rooms rather than at poolside, should be encouraged.
‘Contamination’ is defined as any addition to the water that makes it dirty or impure. If pollution is present there is a risk of bather contamination. This has legal, ethical and health implications. Effective maintenance of water chemistry, balance and quality associated with adequate hygiene standards will counteract most pollutants.
The following principles need to be fully understood by pool maintenance staff.
Sources of Contamination
Contamination is introduced predominantly via pool users, but also via the environment, including source water.
Environmental contamination is especially relevant to outdoor pools where there is dust, soil, sand, leaves and grass constantly around and in the pool.
Pool users contaminate the pool in three different ways:
– From bodily fluids, solids and wastes— urine, mucus from the nose and chest, saliva, sweat, hair, scales from skin and faecal matter. These are pollutants in themselves, but may also contain harmful microorganisms which could cause illness in other pool users.
– From dirt—collected on the body before bathing, for example, on the feet from the pool concourse, on skin from clothes.
– From cosmetics—perfumes, oils, hairspray, lotions, sunscreen and creams.
Transmission of Infection
Many microorganisms are harmless and normally present in healthy people. However, if they are swallowed in large numbers by a bather who is unwell or has altered immunity (which may be the case during pregnancy or illness), then infection and sickness can result. For this reason the entire pool environment—that is, the change rooms, toilets, concourse, as well as pool water—should be adequately cleaned and managed at all times.
Minimum hygiene standards should be met for all change rooms, toilets and showers. The pool concourse should be cleaned at least daily. Pool users should be encouraged to shower prior to entering the pool to rinse off dust and body oils.
Some infections can be transmitted through the pool water from one bather to another if there is inadequate disinfectant. Other potential infections are through contamination with spilt blood, vomit or faecal matter. In these cases immediate action is necessary and all pools should have emergency response procedures documented.
Infections and Conditions Associated with Pool Use
Gastro-Intestinal Infections, Including Cryptosporidium
Generally speaking, most microorganisms responsible for gastrointestinal infections will be inactivated by the disinfectant residual and removed by the filtration system. Therefore, correct maintenance levels of disinfectant and filtration are necessary. However, two problem organisms—Cryptosporidium and Giardia—remain. These cause watery diarrhoea and abdominal cramping, associated with symptoms of fatigue, fever, loss of appetite, nausea and vomiting. In the healthy individual these symptoms are usually mild, but they can cause severe, chronic, debilitating illness if the recipient is unwell or has a reduced immune system.
Cryptosporidium is resistant to the usual maintenance levels of disinfectant and can remain in the pool system for several months. Normal filtration processes may be ineffective in removing Cryptosporidium parasites due to their tiny size. Because normal disinfectant residuals and filtering processes are not effective in eliminating Cryptosporidium, special care is needed in cases of suspected contamination. Disinfection levels need to be raised to 14 ppm and kept at that level for 12 hours. The addition of coagulant and frequent backwashing of filters is also advisable.
Pool users suspected of being infected with either Cryptosporidium or Giardia are advised to avoid attending a pool for one month after symptoms cease. As the recommended maintenance level for disinfectant is less than 8 ppm, the pool must remain closed until water samples prove no evidence of the microorganism. If a pool is closed due to suspected contamination by Cryptosporidium, signage is advisable to warn infected persons not to visit or potentially contaminate other pools.
Patrons who have suffered a gastrointestinal illness or diarrhoea should be advised not to use the pool until at least one week after symptoms cease.
Usual maintenance levels of disinfection in the pool water will kill fungi or bacteria associated with foot infections. However, two common conditions can be caught from the damp environment of pool surrounds, change rooms or showers.
Tinea Pedis (Athlete’s Foot)
Tinea pedis is a fungal infection causing an itchy scaling between the toes. This is hard to distinguish from soggy skin caused by inadequate drying between the toes. Tinea is spread by contact on damp floor surfaces, such as showers or poolside, where there are infected fragments of skin. Adequate floor cleaning reduces the number of infective particles. Wearing pool shoes or thongs in showers and at the poolside reduces skin contact with a potentially contaminated floor. Exclusion from the pool is not necessary.
Plantar Warts (Verrucae)
Plantar warts are caused by a virus, and may be picked up from contact with contaminated fragments of skin on the surrounds of the pool. As with tinea, adequate cleaning of pool surrounds is necessary and users should wear pool shoes or thongs around the pool. Carriers are advised to cover warts to prevent contamination of pool surround surfaces but exclusion from the pool is not necessary.
Viruses are not spread in the pool if adequate sanitiser levels are present. Human immunodeficiency virus (HIV) and hepatitis are viruses carried in the blood and other body fluids. They are inactivated by the disinfectant residual at normal maintenance levels. Blood, vomit or faecal spills from swimmers with these viruses are treated as above.
Ear and Sinus Problems
Wetting, de-waxing and degreasing of the outer ear may cause swimmer’s ear (otitis externa). This may result in skin drying and damage, with or without infection caused by the usual bacteria found on normal, healthy skin. It is most common in endurance and competitive swimmers. High numbers of Pseudomonas aeruginosa present in the water may cause an unusually high incidence of this condition (as well as skin infections). Normal sanitation levels should eliminate the presence of Pseudomonas.
Infection of the middle ear (otitis media) and sinusitis following swimming are usually caused by infected mucus forced into the nose and throat while swimming. People are encouraged not to swim if they have an upper respiratory tract infection, but need not be excluded.
Meningitis associated with swimming is extremely rare and has not been detected in pools that are properly treated and maintained. The free-living amoeba naegleria fowleri causes it. In each case associated with swimming, the pool has been found to be receiving polluted, warm spring water—and to be inadequately disinfected. Normal disinfection levels are necessary. Pool make-up water must be clean and come from secure sources. Circulation systems, including balance tanks, should be designed to avoid prolonged periods of stagnation. Any debris should be removed regularly.
Legionella pneumophila bacteria cause a severe form of pneumonia known as legionnaire’s disease. For it to be spread there must be an infected spray, such as with spray humidifiers or cooling towers. Legionnaire’s disease has not been associated with conventional swimming pools. However, it is easily spread in poorly maintained and disinfected spa pools due to the fine spray (aerosols) generated at the turbulent water surface. Careful maintenance, frequent filter backwashing and close attention to disinfectant levels are critical.
Skin Irritations and Rashes
Skin irritation and rashes can be associated with pool use. Good water management and adequate dilution will keep these to a minimum. Skin rashes associated with pool use are usually due to one of the following factors:
– Drying of the skin due to a reduction in natural body oils—common with prolonged immersion and warm water in hydrotherapy pools and spas.
– Residual disinfectant left on the skin.
– Infection (more common in spas due to higher bather loads) skin abrasion from the aerated water jets and higher water temperature.
These factors contribute to common skin conditions, such as pool rash, bromine itch and folliculitis.
Pool rash is essentially a mild dermatitis caused by prolonged immersion and the effect of the disinfectant creating a dry, irritated skin. It responds well to unperfumed moisturising creams and/or reduced exposure to the pool.
‘Bromine itch’ is another form of dermatitis caused by sensitisation to bromine and its by-products used to disinfect the pool. Incidence increases with age and exposure, particularly with prolonged immersion. It is intensely itchy and occurs within 12 hours of exposure. It often recurs with repeated exposure to brominated pools.
Folliculitis is an infection of the hair follicle caused by the bacteria Pseudomonas aeruginosa. A combination of intense skin wetting and high levels of the bacteria is necessary for the infection to occur. It is most common in spas, where there are higher temperatures (over 35˚C), longer exposure times (one to two hours) and inadequate disinfection. Unlike bromine rash, it tends not to be itchy.
Generally speaking, the warm, humid air around a pool assists respiration. High levels of chloramines, the by-product of chlorine disinfection, may trigger asthma attacks. These levels can be high because the pool is poorly designed, overloaded or poorly maintained. Chloramines themselves, and other substances in the air, do not cause asthma, but may provoke an attack.
The bather load generally introduces pollution to a pool. If this is controlled to avoid overcrowding, at the same time as maintaining standard hygiene procedures and normal pool disinfectant levels, then cross-contamination of pool users is minimised. When appropriate, emergency procedures are established and used in conjunction with regular maintenance, cross-contamination is unlikely to then occur.
People suffering from diarrhoea or gastroenteritis should not use a pool until at least one week after the symptoms have cleared. Faecally incontinent people should not use a pool or spa unless their condition is managed by a health professional. Signage to this effect should be displayed.