Lead in drinking water in the Greater Bilbao Area (Basque Country, Spain).

The concentration of lead in drinking water prior to distribution in the Greater Bilbao Area (905,000 inhabitants) does not exceed 10 micrograms/l, however, the distribution network, service lines and domestic plumbing, can affect this concentration. This study determined what proportion of homes built in this Area before 1950 and between 1951 and 1975 exceeded specified lead levels in water and estimated the level of exposure to lead through drinking first draw water. A random stratified sampling was carried out based on the home's construction year. It was concluded that 84% (CI = 75.5-91.4) of the homes built before 1950 and 99% (CI = 93.3-100) of the homes built between 1951 and 1975 received first draw water containing lead levels below 10 micrograms/l, the geometric mean being 2.74 micrograms/l. Based on the geometric mean found in our study the calculated lead intake from drinking water of the infant population of 5 kg weight consuming 0.75 l/day, would be 2.9 micrograms/kg/week, i.e. 12% of the Provisional Tolerable Weekly Intake.