The Commission has adopted a proposal which modifies the Bathing Water Directive adopted in 1975. In the interest of public health and the environment this aims to simplify and consolidate the existing provisions ensuring the quality of bathing water and to adapt them to scientific and technical progress. The proposal brings together in one piece of legislation the successive amendments which already existed in the form of several different instruments. It also simplifies the rules for checking that water complies with the specified criteria. - Physical and chemical parameters: Certain parameters (such as the concentration of nitrates and heavy metals) have been removed because no values have yet been assigned to them and because they are not normally present in quantities likely to affect bathers. Above all, these substances are now covered by other Directives. - Microbiological parameters: Since adoption of Directive 76/160/EEC, scientific knowledge on microbiology has expanded considerably and methods of analysis have been improved. Recent discoveries in this field have made it possible to remove unnecessary parameters and to make certain definitions and obligations more explicit. In this light, measurement of the coliform parameters have been reviewed. Similarly, there is now a new understanding of protection against salmonella (it is now possible to detect the presence of salmonella by measuring the presence of other non-pathogenic bacteria of faecal origin). Moreover, the proposal now requires Member States to identify sources of this type of pollution and to take preventive measures. A new paragraph of the proposed Directive requires that bathing water quality be posted at bathing areas explaining the corrective measures being taken or envisaged in cases of pollution.