Urinary concentrations of heavy metals in healthy Japanese under 20 years of age: a comparison between concentrations expressed in terms of creatinine and of selenium.

Voided urine samples from 575 young Japanese under 20 years of age (297 males and 278 females including infants) and from 380 subjects (20-29 years old, 193 males and 187 females) were analyzed for levels of creatinine, selenium, zinc, cadmium and mercury. This investigation presents data regarding the normal urinary levels of these substances in age groups of 0-4, 5-9, 10-14, 15-19, and 20-29 years. Urinary levels of creatinine and cadmium showed remarkable increases with the age of the subjects, whereas that of selenium was constant at all ages under 20. Urinary concentrations of heavy metals were represented by creatinine and selenium ratios. Comparisons between these ratios revealed that selenium is an excellent index for representing the levels of the substances contained in a voided urine sample. Creatinine was not useful as an index for younger subjects, because the urinary concentration of this compound increased almost threefold as the subjects became older, up to 15 years of age.