Hammer, D. I. (Ecological Research Branch, DHER, BCS, NAPCA, 411 West Chapel Hill St., Durham, N.C. 27701), J. F. Finklea, R. H. Hendricks, C. M. Shy and R. J. M. Horton. Hair trace metal levels and environmental exposure. Amer J Epidem 93: 84–92, 1971.—Hair trace metal levels were related to environmental exposure in a study of fourth-grade boys in cities representing exposure dose gradients for arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn). Hair samples were carefully and stringently washed before analysis for As by spectrophotometry and for Cd, Cu, Pb, and Zn by atomic absorption spectroscopy. Hair trace metal distributions for As, Cd, Cu, and Pb were positively skewed while those for Zn were symmetrical. Means were in accord with exposure rankings for As, Cd, and Pb but not for Cu and Zn. When grouped across a ranking gradient, differences among the means for As, Cd, and Pb were statistically significant while those of Cu and Zn were not. The present study minimized possible effects of age, sex, hair color, varying hair length, and chemical treatments. Despite the problems of exogenous deposition, endogenous absorption routes, and relationships of hair metal to body burden, mean hair metals levels for As, Cd, and Pb accurately reflected community exposures.