Age dependence of metals in hair in a selected U.S. population.

Concentrations of 28 metals were determined in hair samples from 199 children (age less than or equal to 12 years) and 322 adults (age 13-73) years. Levels of calcium, barium, magnesium zinc, and strontium all show a similar age-dependent increase up to about 12-14 years; levels of aluminum show a decrease with age. Relationships of elemental concentrations with age were examined by using correlation, linear regression, t tests, and discriminant analysis. Statistically significant differences in mean concentration values between children and adults were shown for these metals. Discriminant analysis gave about 95% accuracy in classifying a test data set into the categories of children and adults. A hypothesis suggested by the data is that there is an age-dependent excretion in hair of alkali metals during skeletal growth and development. The observed decrease in aluminum is largely unexplained at this time.