Swimming pools can trigger their own distinctive brand of paranoia. The list of microbes that can be transmitted in the course of what is supposed to be a healthy activity is long, including viruses such as hepatitis A, bacteria-like pseudomonas aeruginosa (produces severe earache) and the parasite giardia, which causes a nasty stomach upset. Effective chlorination, nonetheless, does fulfil a disinfectant role in most cases, and even allows for the toddler who cannot resist temptation to "pee in the pool". But new indications suggest the biggest threat is from cryptosporidium, a parasite that causes gastrointestinal illness, characterised by abdominal cramps and diarrhoea that can last for weeks. It coincides with increasing cases reported globally.
The eggs laid by the parasite - classified as a protozoan - get into the water if an infected person has what is politely called a "faecal accident" in the pool, which happens most commonly if a toddler's nappy leaks. Researchers at the Centres for Disease Control and Prevention in Atlanta have found that the standard chlorination and filtration process used in swimming pools is not sufficient to kill off cryptosporidium. Pools commonly contain urine, faeces, hair, sweat, skin cells and suntan lotion, which means the chlorination process is less effective. The parasite's cysts remained infectious even when exposed to high levels of chlorine for 48 hours. The researchers call for improved filtering systems and for water pumped into the pool to be "turned over" more frequently. They also say young children should wear leakproof rubber pants while swimming. Dr John Lee, head of the water and environmental microbiology research unit in Nottingham, agrees: "Most viruses and bacteria are sensitive to chlorine, so a pool's normal disinfection procedure should deal with them. However, cryptosporidium and, to a lesser extent, giardia, are resistant to chlorine."
Before 1976 it was wrongly thought cryptosporidium only affected animals. Since then, many human outbreaks have been reported. In one of the largest, in 1996, some 3,000 people were infected after swimming in a water park in California. In Britain outbreaks have been associated with public water supplies, which prompted stringent new regulations. Last year there were 3,745 confirmed reports of it in England and Wales, though many cases go unreported. Most were infected by contaminated drinking water or through contact with infected animals, but some outbreaks were traced to pools - in a very small number of cases it can be fatal for young children and people with deficient immune systems.
An Irish expert, Dr Miriam Byrne, based at UCD Biotechnology Centre, confirms there have been no documented cases of cryptosporidium in Ireland - but then it wasn't monitored for until recently. Limited monitoring was introduced just over two years ago, and none is being done on swimming pools. "The problem is we never looked for it," Dr Byrne says.
Awareness of cryptosporidium has increased, however, and GPs are more likely to submit stool samples for testing. A UCD-based company, City Analysts, checks samples for some local authorities, concentrating on public water supplies (individual farm-related cases have been confirmed through person-to-person contact). The risk from pools/water is rapid transmission.
Environmental health officers (EHOs) employed by local authorities around the Republic routinely check pools, including those in hotels and leisure centres. Inspections involve physical inspection, poolside water tests and interviews with staff (including looking at their own results), says Martin Fitzpatrick, principal EHO with Dublin Corporation.
There are no mandatory standards, but there are guidelines, which up to now have been pretty fluid. The professional body, the Environmental Health Officers' Association (EHOA), and the Institute of Leisure and Amenity Management (ILAM), representing pool interests, have been working together on tighter environmental health standards and management protocols, even if they will not be legally binding. Progress has been made, with ILAM publishing its proposals and the EHOA about to report on the issue. Proper management practices are critical, Fitzpatrick stresses. On cryptosporidium, he adds: "Research is indicating there is an issue that we need to look at." A combination of treatments will probably be needed to deal with this and other pathogens. such as people who have AIDS it can produce a very nasty pro-longed illness."
THE Pool Water Treatment Advisory Group in the UK (an independent body) has published tougher guidelines. Its spokesman, Brian Guthrie, says: "We know you can't kill off the cryptosporidium cysts eggs unless you use enormous amounts of chlorine, which would be dangerous. But we thought until recently that, as long as the pool was emptied of people and the water filtered a couple of times, that would be sufficient." If a diarrhoea incident is reported, the pool should be evacuated immediately and the water filtered six times, PWTAG now recommends. However, in Britain (as in Ireland) there is no legislation which forces a pool to follow such guidelines. All swimming pools are not kept to the same standard. Some may have poor filtration systems or be badly managed. Others may still add chlorine to the pool by hand rather than automatically.
Most prevention techniques are centring on the use of "microfilters" which have tiny pores capable of excluding the minute parasite. The difficulty is that, in a lot of cases, diarrhoea can get into a pool without being reported or noticed by pool staff. Guthrie believes more needs to be done on prevention: "There should be signs warning people not to swim if they have suffered from diarrhoea recently, and babies should have to wear swim nappies and be restricted to baby pools."
But Dr Lee feels the risks of catching a disease should be kept in perspective: "With most well-managed pools, you are more likely to catch something in the changing rooms."