In order to evaluate possible innate toxic effe'cts of small doses of scandium, hexavalent chromium, gallium, yttrium, indium, rhodium and palladium in terms of growth and survival, 958 mice divided as to sex were raised in an environment limited in metallic contamination and given 5 ppm metal in drinking water from weaning until natural death. Body weight was measured at monthly intervals up to 6 months, at 1 year and at 18 months of age. The feeding of gallium was accompanied by significant but not marked sup pression of weight at 14 of 16 intervals in both sexes; the feeding of scandium was associated with growth suppression at 10, of indium at 8, of palladium at 7 and of rhodium at 6 of 16 intervals compared to mean weights of controls. The feeding of yttrium and hexavalent chromium were associated with significant lessening of growth at 12 and 8 of 16 intervals, respectively. Survival of gallium- fed females at older ages was less than that of controls, whereas survival of pal ladium-fed males and yttrium-fed mice of both sexes were greater. Tumors were found at necropsy in 16.3% of one group of controls, 27.4% of the scandium, 26.0% of the gallium, 13.0% of the indium, 28.8% of the rhodium and 29.2% of the palladium groups. Malignant tumors were increased in rhodium and pal ladium groups, at a minimally significant level of confidence (P < 0.05), all but one tumor being malignant. In a second series, tumors were present in 26.8% of controls, 27.6% of the mice fed chromium (VI) and 33% of the mice fed yttrium. All rumors in these latter two groups were malignant. Rhodium and palladium appear to exhibit slight carcinogenic activity in mice. J. Nutr. 101: 1431-1438, 1971. Continuing studies of the innate effects reported. We have also reported effects of of low doses of various abnormal trace elements in the second transitional series elements in drinking water on mice and and related groups: zirconium, niobium, rats exposed for life are being conducted cadmium, tin, antimony (1-3); molyb- in an environment built so as to exclude denum and tellurium (IV and VI) are corn- metallic contaminants. We have reported pleted. To complete the second series, ex- alterations in growth, survival and life eluding technetium, ruthenium and silver, span, or lack of them, associated with the we hereby report on yttrium, rhodium, feeding of titanium, vanadium, chro- palladium and indium. Innate long term mium(in), nickel, germanium and arsenic effects of fluorine and lead have also been to mice ( 1, 2 ), and the study of the effects studied ( 1, 3 ). In this way the subtoxic of selenium(IV and VI) is completed, effects of elements with atomic numbers Other trace elements of the first transi- 21 to 34, and 39 to 52 with three excep tional series of the Periodic Table, man- Received for publication june 8, 1971. gaA±ese, iron, Cobalt, Copper, Zinc are es- i Supported by the Public Health Service Research sential for mammals. In order to complete £rant,HE,,05376 Aromth? Nati^S^ S?art Institute,-