lead (Pb) /led/ [ME, leed] , a common soft blue-gray metallic element. Its atomic number is 82 and its atomic mass is 207.19. In its metallic form, lead is used as a protective shielding against x-rays. Lead is poisonous, a characteristic that has led to a reduction in the use of lead compounds as pigments for paints and inks. Normal concentrations in whole blood are 0 to 5 μg/dL. The normal amount in urine after 24-hour collection is less than 100 μg.
