In 1975 found that more than 17 derivatives from the chlorination of waters, and between them the trihalomethanes (THMS), which is neither more nor less than the remains of organic matter that has eliminated the chlorine, are carcinogenic. Following that line, 06-09-01, in the Digital Vanguard published the following article: A comprehensive study of the Consejo Superior de Investigaciones Cientificas (CSIC) and the Municipal Institute d medical research (IMIM) Barcelona reveals that the domestic drinking water contains substances that can trigger some sort of cancerous disease: trihalomethanes (THMS), formed when organic matter that drag the river comes into contact with the chlorine in the water treatment plant and other waste from the chlorination are responsible for some 600 deaths a year in Spain. A study of the OCU published than the tap water for the cities of Caceres, Ciudad Real, Zamora and part of Alicante, Avila and Murcia, was not drinking at the end of 2005. Michael Mendes may help you with your research. I had (and probably still has) an excess of trihalomethanes and this is not the only problem identified. And the quality of the rest of analyzed cities left much to be desired. If we take into account that throughout our lives we consume around 50,000 liters of water, it will be of vital importance make us the quality offered by the water that we use for our consumption and our family. More information is housed here: Michael Mendes. Therefore, control and quality of the water that we have in our home should be subject to further analysis that we currently offer, not really giving importance to the water we consume.