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Environmental Factors and Health

9 Swimming pools, spas and similar recreational water environments

All municipalities in Denmark have one or more swimming pools representing an important source of recreation as well as being used for training purposes, treatment for hospital patients and other uses.

In contrast to coastal and fresh waters, pool water is recirculated and disinfected. Disinfection is a process whereby pathogenic micro-organisms are removed or inactivated so that they represent no significant risks of infection. In Denmark, disinfection is performed with chlorine or hypochlorite, which are reactive chemicals. They react with organic and inorganic materials in the water and materials contributed by the swimmers, which include sweat, urine, soap residues, cosmetics etc. to form various disinfectant by-products (e.g.. trihalomethanes).

The large number of visitors to swimming pools and the resulting load on the water in a confined space makes them potential sources of substances and micro-organisms harmful to health. Regular monitoring of the water quality in the swimming pools is therefore essential.

9.1 Human exposure to environmental factors

9.1.1 Environmental factors

The primary environmental factors are summarised in table 9.1

Table 9.1
Summary of the origin, characteristics and health impacts of some critical pollutants.

9.1.2 Sources of pollutants

In swimming pools both the number of visitors and the way the pools and surroundings are constructed and managed can increase the potential for harmful effects.

Faecally and non-faecally derived micro-organisms, which may lead to adverse health effects include bacteria, viruses, protozoa and fungi. Faecal contamination may be due to faeces released by swimmers or contaminated source water. Many of the outbreaks of illness related to swimming pools have occurred because disinfection was poorly or not applied (WHO 2000a).

Non-faecal human shedding (e.g., from mucus, saliva, skin) in the swimming pool, spa or similar recreational-water environments is a source of potential non-enteric pathogenic organisms. Infected users can directly contaminate pool or spa waters and the surfaces of objects or materials at a facility with sufficient numbers of primary pathogens (notably viruses or fungi), which can consequently lead to skin infections in other patrons who come in contact with the contaminated water or surfaces (WHO 2000a).

Chemicals found in pool water include those that are related to water treatment — both the chemical additives themselves and the by-products that are produced from chemical reactions between the additives (particularly the reactive disinfectants) and organic and inorganic materials in the raw water — and those that are contributed by the swimmers, which include soap residues, cosmetics, suntan oil, sweat and urine (WHO 2000b).

Many chemical by-products associated with disinfection of pool waters are produced at levels that are at least comparable to those produced in drinking-water disinfection. In fact, as initial and make-up water entering the pool has in most cases already undergone drinking-water treatment and contains disinfectant and by-products, and as typical pool waters are recycled and additional precursors and disinfectant are added, the levels of disinfectant by-products found in disinfected pool water could easily exceed drinking-water levels. (WHO 2000b).

9.1.3 Human exposure

The ways of influence from micro-organisms and chemicals in bathing water in swimming pools are by direct exposure through ingestion of water or inhalation of aerosols and gases like chloroform during swimming and/or through breaks in the protective skin barrier. Some of the various sources are outlined above.

9.2 Level of Protection

The level of protection is based on cleaning and disinfection routines as well as monitoring of the water quality. The Danish level of protection is considered high, however, the present regulation is under revision to account for the newest knowledge and technical progress.

The new requirements for bound chlorine and trihalomethanes are issued based on both the technical possibilities, but also a consideration for sports people who spend a considerable amount time in the chlorinated water.

9.3 Regulation and strategy

The regulatory requirements for swimming pools are given in the Statutory Order no. 195 of 5 April 1988 issued by the Ministry of Environment and Energy. The new statutory order, already drafted, on swimming pools and their water quality is expected to come into force in 2001. This order will tighten the current requirements outlined in section 9.4.1. This includes a reduction in the maximum allowed levels of free chlorine, bound chlorine and trihalomethanes. The allowed amount of free chlorine is however maintained at a level, which is considered safe in relation to control of Legionella. The statutory order also includes a demand for automatic chlorine and pH-dosing, a facility which is already available in most public swimming pools today.

A new parameter, the bacteria Pseudomonas aeruginosa, has been introduced for hot-water systems, because the bacteria is resistant to disinfectants including chlorine.

DEPA has also investigated whether plasticisers migrating from surface dressings, e.g. PVC foil, or from toys, bathing suits or remains of cosmetics can be found in swimming pool water. Plasticisers are removed by activated charcoal filters, which are available in most indoor swimming pools (75%). DEPA has therefore concluded that there is no need to introduce a demand for regular analysis of plasticisers. For outdoor swimming pools and those indoor swimming pools without charcoal filter, the municipalities should make a concrete evaluation of the need for analyses.

The new statutory order stipulates that chemical substances, identified in spite of the regular monitoring and control and not assigned a quality criteria, e.g. plasticisers, must follow the quality criteria for drinking water. DEPA has also suggested that the Ministry of Building and Housing should establish an approval system for materials used for surface dressings in swimming pools following the same principles, which apply to materials for drinking water systems.

9.4 Instruments

9.4.1 Regulatory instruments

In order to reduce exposure and risk to an acceptable level, a combination of demands for cleaning of visitors, floors, walls, pools etc. and disinfection and other ways of treatment of pool water have been established. This means that the control of water quality comprises a combination of several indicators. Some of these concern micro-organisms, other chemical and physical factors.

The microbiological indicator used in Denmark is the germ count. When the germ count is higher than a certain limit value, counts of thermotolerant coliforms and pseudomonas are performed.

Daily monitoring of pool water based on chemical and physical measurements by the responsible for the daily operation and monthly measurements of germ count, plus chemical and physical factors by the official authorities (most often the municipality) are the key elements of Danish regulation on swimming pool bathing water quality in order to enable rapid response and protection of the population.

Daily monitoring of the physical and chemical parameters includes temperature (normally between 24 - 28^oC), pH-value (pH = 7 - 8, preferably between 7.2 - 7.6), free chlorine (0,5 - 3 mg per l) and chlorine in compounds (max. 1.0 mg/l, preferably as low as possible).

Monitoring by the official authorities includes:

	Monthly measurements of germ count, temperature, pH and chlorine.
	If the germ count is higher than limit value (500 per 100 ml), the water is analysed for coli and pseudomonas.
	Measurement of content of organic material four times a year.
	Measurement of disinfectant by-products two times a year.
	Inspection of the pool, the surroundings, and the daily written reports on operation and monitoring.

The requirements are given in the above-mentioned Statutory order no. 195 of 5 April 1988 issued by the Ministry of Environment and Energy.

Restrictions on bathing

Should the hygienic conditions and/or the quality of water in a swimming pool fail to meet the quality criteria, the municipal council shall order conditions improved or - in severe cases - close the pool.

9.5 Actors

The primary actors concerning regulation on swimming pools are listed in table 9.2.

Table 9.2
Actors, roles and responsibilities concerning swimming pools: 

9.6 Evaluation

The health objective of the regulation covering recreational waters is to ensure that swimming pools, spas and similar recreational water facilities are operated safely in order to avoid adverse health effects and illness in people using the facilities. Vulnerable groups, like children, asthmatics, and sports people who are more frequently exposed, are also considered. The goal is to ensure that the swimming pool water has a quality, which will not impair the health of the population and to keep a disinfection level, which prohibits the existence of pathogenic micro-organisms.

The measures to achieve this objective include cleaning of the body before entering the water, cleaning and disinfection of the pool and water, and regular monitoring and control of chemicals and micro-organisms.

A systematic registration of health related effects from exposure to swimming water and other recreational waters is not available. There are however, known incidents of e.g. legionellosis from inhalation of aerosols in private spas, and Legionella has been identified in public hot-water pools. Acute effects like skin and respiratory irritation resulting from exposure to disinfectants and by-products in the water and in the breathing zone have been described but the resulting impact on human health is not known as it is also the case in relation to possible long-term effects from exposure to these chemicals.

DEPA considers the existing level of protection sufficient to protect human health. However, as it is now technically possible, new and more stringent regulation will be introduced in the near future, which will tighten the requirements regarding water quality and monotoring.

In addition, DEPA is working to introduce an approval system for materials used for surface dressings in pools, following the same principles as for drinking water systems.

In order to further improve safety in relation to recreational waters and the regulatory measures, more knowledge is needed about the by-products from disinfectants used in the pool water and their toxicological properties.

Assessment of possible substitutes to chlorine gas and hypochlorite, which are allowed for disinfection today, is another area of interest. This assessment must also include determination of a monitoring programme and identification of relevant parameters to control as well as a toxicological evaluation of possible by-products.

Any use of alternative disinfectants will also require knowledge about their effect on the pathogenic micro-organisms, which may occur in the water.

9.7 References

WHO (2000a): "Guidelines for Safe Recreational-water Environments. Vol 2: Swimming Pools, Spas and Similar Recreational-water Environments. Chapter 3: Microbiological Hazards" (Final draft for consultation, August 2000).

WHO (2000b): "Guidelines for Safe Recreational-water Environments. Vol 2: Swimming Pools, Spas and Similar Recreational-water Environments. Chapter 4: Chemical Hazards. (Final draft for consultation, August 2000).

Statuary Order no. 195 of 5 April 1988 on Water Quality in Swimming Pools.

Draft statutory order on Water Quality in Swimming Pools. (December 2000).

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