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Environmental Factors and Health

8 Bathing Water – Coastal and Fresh-waters

Denmark has approximately 7,000 km of coastline and good beaches are common in all parts of the country. A large number of the population can reach the coast within 30 minutes and going to the beach, bathing or just enjoying the sea is an intricate part of life especially during the summer period. Lakes of a sufficiently good quality may also serve as bathing water during the summer. Good bathing water quality is therefore an important issue for a great deal of the population and the publications in local media by authorities on bathing water quality are followed with interest. Monitoring of bathing water quality along our coasts is essential as a number of sources e.g. sewage effluents, may threaten the water quality. The quality of bathing water has generally improved in Denmark, but nevertheless restrictions on bathing still have to be enforced due to local conditions, e.g. effluent from contaminated watercourses (overflow of untreated wastewater during heavy rain), discharges from scattered settlements in the countryside etc.

Both coastal and fresh waters may contain mixtures of pathogenic and non-pathogenic microbes derived from sewage effluents, from the population using the water, from farming activities, industrial activities (e.g. slaughter-houses) and wild-life (birds) in addition to indigenous micro-organisms. Furthermore, the water quality may also be influenced by effluents of chemical substances from industrial and farming activities as well as deposition from airborne pollution and contaminants in rain.

Human exposure to the constituents of the bathing water media thus covers both pathogenic agents and man-made substances comprising the environ-mental factors for this media.

8.1 Human exposure to environmental factors

8.1.1 Environmental factors

The primary factors of concern are summarised in table 8.1.

Table 8.1
Summary of the origin, characteristics and health impacts of some critical pollutants.

Abbreviations:

8.1.2 Sources of pollutants

Environmental factors in bathing water in Denmark primarily originate from wastewater. The primary impact is by overflow of untreated wastewater during heavy rain, but also by run-off from rural areas and from scattered housing in the countryside not being connected to a wastewater treatment plant. Also incompletely treated wastewater or breakdowns at treatment plants may be sources of environmental factors.

Today approximately 130.000 private residences and 13.000 summerhouses discharge wastewater directly from a settling tank, which is virtually untreated with respect to micro-organisms. The wastewater is discharged to drains, ditches, watercourses, lakes and to the sea resulting in unhygienic conditions, especially in recipients with low water exchange.

In May 1997, the Danish Parliament agreed upon an action plan for improved wastewater treatment involving approximately 64.000 scattered settlements in the countryside. The actions will include connection to public wastewater treatment, local sand infiltration plants or small wastewater treatment plants. This action plan will contribute to improvement of the general water quality in rivers, lakes and coastal waters and thereby also contribute to improvements of the bathing water quality (please refer to chapter 12 for further details on wastewater).

Other sources may be the population using the bathing water, birds and other animals, truly indigenous micro-organisms and to a lesser degree also industrial processes and farming activities. The bathing water quality around outlets of water courses may be reduced because of impact from grassing animals. The indigenous micro-organisms of concern are blue-green algae that often bloom during summer when temperature is highest. The algae secrete toxins, but only in rare cases are the concentrations high enough to affect humans. In Denmark, there are no fatal cases of human intoxication by algae and no reported epidemics.

Figure 8.1
Ways of human exposure to environmental factors in bathing water.

8.1.3 Human exposure

The ways of influence from micro-organisms in bathing water are by direct exposure through ingestion of water during bathing and/or through breaks in the protective skin barrier from bathing water contaminated with micro-organisms present in concentrations and amounts that pose a health risk. Some of the various sources are outlined above.

Similarly, chemical substances in water (including toxins produced by bacteria or algae) may be ingested or taken up through the skin as well as directly affect the skin and mucous membranes in e.g. the eyes. In studies of the relationship between health impairment and micro-organisms in bathing water in the sea or lakes, it has been found that the rate of most symptoms is significantly related to the count of enterococci (faecal indicator bacteria). However, it is generally difficult to relate impacts on public health to exposures in bathing water, because there is no systematic registration hereof.

8.2 Level of Protection

Regular monitoring of bathing water based on faecal indicators is the key element of Danish regulation on bathing water quality to enable rapid response by authorities and protection of the population.

The indicator organisms considered (WHO 1998) to correlate best with health outcome are generally enterococci/faecal streptococci for both marine and freshwater and E.coli for freshwater. In Denmark thermotolerant coliform bacteria have been chosen as indicators for E.coli.

It should be noted however, that an evaluation prepared by the Danish Water Quality Institute and the Institute of Medical Microbiology, University of Aarhus for DEPA in 1995 suggests that there is a risk that the traditional indicators (faecal coliforms) may not accurately reflect the quality of water. Many viruses, bacteria, worms and worm eggs appear to be far more resistant than faecal coliforms. The absence of faecal coliforms does therefore not necessarily prove that pathogens are not present in the recipient. For these reasons the Danish monitoring programme, including the choice of indicator parameters (bacteria, viruses and/or protozoans), is presently under revision.

The EU-directive on the quality of bathing water (76/160/EU) is presently also under revision. The review of the directive is required as it is outdated and the new directive shall make reference to the water framework directive currently under preparation.

Also the blooming of blue-green algae are monitored, especially during summer where the water temperature is at its highest.

8.3 Regulation and strategy

The regulatory basis for monitoring bathing water quality in seawater and lakes is given by Statutory order no. 292 of 23 June 1983 on bathing water and beaches from the Ministry of Environment and Energy. The order is in accordance with the EU directive from 1976 on quality of bathing water (76/160/EU). The directive is a minimum requirement directive enabling national legislation to set more stringent requirements.

The order covers:

	Freshwater and seawater designated as bathing water in the county regional planning (each of the 14 counties shall in accordance with the Planning Act prepare a regional plan for the county every 4 years covering all aspects of county jurisdiction including bathing water and beaches)
	Freshwater and seawater where bathing is not prohibited.

The objective of the order is in compliance with the EU directive to ensure and maintain good water quality in areas of freshwater and seawater used for bathing.

Today the evaluation of the bathing water quality is based on the monitoring results from the previous year. Therefore, there is an obvious need for a revised system with possibilities for early warning of bathing guests based on continuous monitoring, characterisation of the bathing water site including identification of potential contamination sources, prediction of rain events that may lead to overflow of untreated wastewater etc.

8.4 Instruments

8.4.1 Regulatory instruments

Limit values

According to the present regulation (Statutory order no. 292 of 23 June 1983) bathing water in sea or lakes during the bathing season (1 June - 1 October) shall not contain more than 10,000 coliform bacteria pr. 100 ml, and not more than 1,000 thermotolerant coliform bacteria (feacal coli / E.coli) pr. 100 ml. A statistical methodology developed by the DEPA is applied to assess analytical results.

In addition, bathing water shall have no sensory impairments, e.g. discoloration, smell and poor visibility. It is a requirement that the acidity/ alkalinity of the bathing water (pH-value) lies within the interval of pH=6 - pH=9.

A minimum of 10 samples shall be taken for water quality analysis during the season, starting one month before the bathing season (1 June - 1 October). Samples shall be taken in areas normally used for bathing. The municipal and county authorities in conjunction decide precisely where and when the samples shall be taken.

The number of samples for analysis may be reduced from 10 to 5 if bathing water at a specific locality over 2 consecutive years has a composition and quality in accordance with quality criteria given above. If bathing water statistically has a significantly poorer quality than the above given criteria, the number of samples shall be increased to 20 per year.

Restrictions on bathing

Should the quality of bathing water in seawater and lakes fail to meet the quality criteria and show significant indications of deterioration, the municipal council shall in collaboration with the regional authorities and the medical health officer instigate further microbiological analysis of the bathing water.

If the water quality cannot immediately be improved it is the responsibility of the municipal authorities to forbid bathing. In such cases, the same authorities shall inform the public of restrictions concerning bathing in appropriate local media (e.g. newspapers) and also ensure that signs are placed up at the relevant bathing localities.

8.5 Actors

Monitoring and supervision of beaches and bathing water quality is the responsibility of the local and regional authorities.

The primary actors concerning regulation of the bathing water media are listed in table 8.2. For general descriptions of the mentioned actors please refer to chapter 3.

Table 8.2
Actors, roles and responsibilities concerning bathing water in sea and lakes:

8.6 Evaluation

The health objective of the bathing water regulation is to prevent bathing guests from getting ill when bathing in waters appointed as bathing waters – e.g. zero effect level. Instruments for obtaining the objective are the counties and municipalities planning activities, design of wastewater systems (location of outlets, dimensioning of retention basins etc.), discharge requirements (wastewater treatment plants, industries etc.), monitoring of bathing water quality and occasionally bathing restrictions if the water quality is insufficient, until improvements have been obtained.

There have been no recognised cases of negative health impacts from contaminated bathing waters in many years, and during the last ten years there has been a further reduction in wastewater impact on the water environment (improved wastewater cleaning technology, sharpened discharge requirements, dimensioning of retention basins to minimise overflow etc.). However, some bathing waters are still influenced by wastewater. The primary impact is by overflow of untreated wastewater during heavy rain, but also by run-off from rural areas and from scattered housing in the countryside not being connected to a wastewater treatment plant.

Systematic registration of water carried disease caused by bathing is not performed, and there is therefore no exact knowledge of the impact on bathing guests. Furthermore, man-made chemical substances are not included in the monitoring programmes and long-term health effects of chemical substances in bathing waters are not known. The microbial quality of bathing waters are monitored, but it is questionable whether the traditional bacterial indicators (faecal coliforms) accurately reflect the quality of the water e.g. the occurrence of more resistant micro-organisms such as viruses and protozoa. Therefore, the Danish monitoring programme is presently under revision also with respect to indicator parameters, monitoring frequency and the reaction time between monitoring result and regulatory action when needed.

Hence, among the challenges are improved monitoring with suitable indicators and limit values, but also continued decrease of outlet of untreated wastewater even though it is already very low compared on an international scale.

New knowledge is needed in many fields: Suitable indicators are needed for monitoring the microbial quality of bathing waters. More knowledge is needed about human exposure to and effects of microbiological and chemical environmental factors in bathing waters originating from untreated as well as from treated wastewater. Also more knowledge is required to assess the impact from run-off from pastures with grazing livestock. Furthermore there is a need for more knowledge about viruses and protozoan in recreational waters. Such knowledge is necessary for the design of the regulation of tomorrow.

8.7 References

DEPA (1995): "Bathing Water - Microbiological Control. Report no. 314".

DEPA (1985): "Bathing Water Control, Guideline no. 2"

WHO’s Draft Guidelines for Safe Recreational Water Environments: Coastal and freshwaters.

Statuary Order no. 292 of 23 June 1983 on Bathing Water and Beaches.

Directive 76/160/EEC (1976): "Setting of quality standards for bathing water in the member states".

Directive 85/337/EEC (1985): "Effects of certain public and private projects on the environment - EIA".

Directive 91/676/EEC (1991): "Concerning the protection of waters against pollution caused by nitrates from agricultural sources".

Directive 97/11/EEC (1997): "Effects of certain public and private projects on environment (revision of Council Directive 85/337/EEC)"

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