Twenty five per cent of the population in the developing world have no access to drinking water. Infectious and parasitic diseases are still the principal cause of death and illness throughout the world, mostly because of the poor quality of water, and diarrhoea ranked globally in 1997 as the first cause of morbidity and the sixth cause of mortality.1 The actual burden of waterborne diseases is unknown because of underreporting in both developed and developing countries.2 A recently published work shows that infectious intestinal disease occurs in one in five people each year in England, but only a small proportion of cases are recorded by national laboratory surveillance system.3 In communities with a high economic and public health development access to abundant and good quality water is stated as a basic right, and consumption of tap water is not seen as an important risk. Otherwise, in recent years some concern has been raised about the safety of drinking water, both in Europe and North America. On one hand, in some regions of Europe, specially those in the former Soviet Union, there is evidence of increase in disease attributable to restricted water supply.4 Apart from that, the privatisation of water supplies in some countries (for example, UK), and its subsequent price increase, could lead to a reduction of its use for low income groups introducing potential detriment of their health.5 In addition, chemical products in drinking water have been associated with bladder and pancreatic cancer,6-8 and also with reproductive effects.9-11

In countries with good epidemiological surveillance systems, a series of waterborne outbreaks have been reported in communities with adequate established measures of water quality control. This represents a warning about the potential risks from drinking water despite the state of the art water treatment. …