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Accurate testing of bathing water

   
 
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The Sea Water Microbiology project was a large-scale collaborative effort involving 34 laboratories from 12 Member States. Their goal was to evaluate the wide variety of techniques currently used to test the quality of bathing water and improve the accuracy, reliability and comparability of the data available to regulatory authorities and to the public.
The project's conclusions, unanimously supported by all its participants, provide a rigorous scientific basis for the standardisation of testing methods. Its recommendations are likely to be adopted in full in the next European Directive on water quality, and will provide the framework for the progressive improvement of bathing water throughout the Union.

Every summer, millions of Europeans and large numbers of visitors from overseas swim in coastal waters off the beaches of the Aegean, the Adriatic, the Mediterranean, the Baltic and North Seas, and the Atlantic Ocean.
It has long been accepted that the pollution of sea water by human and animal sewage effluents constitutes a serious threat to human health, both directly to swimmers and indirectly to those eating contaminated shellfish. As long ago as 1976, the European Community issued a Directive which requires all Member States to carry out regular monitoring of bathing water quality, and sets out both desirable and minimum standards. Since 1991, the Commission has published an annual report which brings this data together and maps the quality of water at beaches across Europe.
The map receives widespread publicity, and is known to be a key factor in many holiday-makers' choice of destination. A poor showing on the water quality map guarantees that an area will suffer a significant loss of tourist income.
Unfortunately, the 1976 Directive is flawed. It permits, and even encourages, the use of difficult testing methods, and it does nothing to ensure the comparability of the analytical results submitted by different countries or regions. In fact, according to senior staff at the Institut Pasteur de Lille, which coordinated the Sea Water Microbiology project, until very recently the published maps were scientifically worthless.
The project itself, which involved 34 laboratories from 12 EU Member States, was financed by the EC's Standards, Measurements and Testing Programme, and represents an important first step towards improving the accuracy, reliability and comparability of the data available both to regulatory authorities and to members of the public.

Clouding the waters

The shortcomings of the Directive on the testing of bathing water have long been recognised by the scientific community. Test results from a single stretch of beach spanning the French-Belgian border, for example, had consistently shown water quality on one side to be better than that on the other. It was clear to both sides that the discrepancy arose solely from differences in the measuring techniques used.
Results from different Member States, regions or localities were simply not comparable, because they had been produced using different methods. It was perfectly possible for water which failed to meet European standards when measured by one widely used method to achieve compliance when measured by another.
Universal demand for a standard measurement technique is not readily translated into universal enthusiasm for any particular method, however. Predictably, each laboratory involved in the routine monitoring of sea water wanted its own technique to be adopted by all the others.

Testing test methods

A collaborative, pan-European study was therefore needed to evaluate the range of current testing methods. Each participating laboratory would test the same samples, using both its own techniques and common methods agreed with other participants.
Sea water, unfortunately, is highly unstable, so distributing centrally prepared samples to the participating laboratories would have made it impossible to guarantee uniform microbiological composition. It was therefore agreed to bring all 34 participants to work together in the same laboratory, testing the various techniques on the same samples on a single bench. Two groups of participants travelled to Lille for a series of week-long trials, where the Institut Pasteur was able to provide appropriate materials and apparatus, as well as transport and accommodation for the visiting technicians.
Despite initial language difficulties, both test groups rapidly gelled into friendly and constructive teams. Expertise was freely and enthusiastically shared, and clear results were produced, supported by all participants.

Conclusions

The study generated three main sets of conclusions. First, it found that experienced microbiologists obtain equivalent results when using a common test method, and significantly different results when using their own methods.
Some test methods in regular use - the three and five-tube Most Probable Number (MPN) tests - were imprecise and unreliable and should be abandoned altogether. They should be replaced by more recently developed Membrane Filtration (MF) or MPN 96-well techniques, which were found to give much better performance.
There were a number of conclusions regarding which measurement parameters to use. E. coli, for example - a dangerous faecal bacterium found in sewage and other wastes - was confirmed to be the only well-defined and easily measurable component of its group (the faecal coliform). Measurement of the larger but poorly defined faecal coliform and thermo-resistant coliform groups, therefore, should be discontinued.
Third, a reference method should be developed to serve as a benchmark for the evaluation of existing and newly developed test methods. For use in the routine monitoring of sea water quality, test methods must be relatively quick and easy, as well as accurate and reliable. A reference method, which need be neither quick nor easy, but whose accuracy is known, is essential if the equivalence of different routine methods is to be determined.
Development of this reference method fell outside the scope of the project itself, but the report indicates the participants' firm conviction that it should consist of two complementary techniques applied in parallel, in order to ensure complete accuracy.

A framework for improved performance

Some of these conclusions were published as early as 1992, following the project's first trial. Since then, very largely as a result of these results, there has been a steady improvement in the homogeneity of testing techniques, and therefore in the reliability of the published water quality maps.
Different techniques are still in use, but the project has at least provided a basis for assessing the comparability of results produced by different methods, and its recommendations have been progressively adopted by individual laboratories or countries. France, for example, has now specified a single measurement technique for all its bathing water monitoring.
The full set of recommendations, which are supported by all the participating laboratories, are not national but European. Indeed, they accord closely with the latest thinking of the International Standards Organisation (ISO), which has made extensive use of the project's findings, and has already adopted E. coli as the target measurement paramater for coliforms.
The Institut Pasteur is confident that the next European Directive on bathing water quality will also adopt the recommendations. When this will happen is, however, less certain. Individual Member States are, naturally, as protective of their own testing methods as individual laboratories.
The actual quality of the European bathing water depends not on the methods used to test it, but on the discharge of sewage and an effective, comprehensive management policy which includes a waste water collection network, storm run-off management, regulations not to build too close to the coastline and avoiding waterproofing nearby surfaces with concrete and tarmac. The project's achievement has been to provide a framework for the accurate, reliable and comparable measurement which is the prerequisite for effective regulation of these discharges.

 

Project Title:  
Sea water micro- biology.

Programmes:
Industrial and Materials Technologies (BRITE-EURAM/CRAFT/SMT)

Contract Reference: MAT1-CT92-0025

Cordis DatabaseFor more information on this project,
go to the CORDIS Database Record

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