this problem is somehow circumvented since most existing watersupply systems have difficulties in meeting these standards and the new ongoing constructions mentioned in previous sections are in line with currently less stringent international accepted standards eg who or eu it also identifies a list of chemical substances for which sanitary maximum allowable concentrations are established including ammonia fluorine sulphates heavy metals and organic micropollutants in accordance with the law on water supply and wastewater drinking water sources should be protected through pollution prevention measures in order to meet the requirements of sanitary and environmental legislation