Concentration of nitrates in drinking water and its relationship with bladder cancer.

Environmental contamination is a characteristic of industrialized nations. The quality of public drinking water, particularly from underground reserves, has increasingly deteriorated. The fundamental cause of the contamination of underground water layers has been the growing worldwide use of nitrogen fertilizers and pesticides since the 1960s. The Valencian Community comprises three provinces on the East Mediterranean coast of Spain. Public drinking water in this community is obtained chiefly from underground sources. As a result, this area suffers the highest nitrates contamination of public drinking water recorded not only in Spain but in all of Europe. The aim of the present study was to investigate the existence of differences in the occurrence of bladder cancer between the population of Valencia province and the rest of the country. We studied the differences in bladder cancer incidence among populations exposed to different levels of nitrates in drinking water in the province of Valencia, as expressed in terms of relative risk. We found a statistically significant difference (p < 0.0001) between the occurrence of bladder cancer in the Valencia province and the rest of Spain, as reflected by the analysis of the corresponding regression curve slopes. Our analytical study revealed relative risks of over 1 in Valencia province in men and women, associated with the consumption of water containing a mean concentration of > 50 mg/L.