[en] Physiological studies of environmental pollutants are reported in which a major emphasis is on factors involved in the secretion of these materials into milk. Elements of concern relate to the energy production field, both nuclear and non-nuclear. The distribution of ²⁰⁷Bi, ²⁰³Pb, ²¹⁰Po, and ²⁰¹Tl between milk, urine, and feces of lactating goats was determined after oral and intravenous administration. Data is presented showing that these elements are poorly absorbed and in consequence appear in milk in only small amounts. However levels in goats appear to be greater than in cows. Experiments relating to mammary transfer of non-actinide series elements are summarized. Included are observations of significant temperature effects on radioiodine transfer, sites and rates of resorption of iodine, zinc, and calcium from the mammary gland, and the use of radio indicators in determining in vivo milk volume. Experiments with zinc have provided blood level, secretion, and balance data necessary for modeling zinc metabolism in lactating goats. A method is presented for compartmental analysis of models involving a pool of cycling volume such as the mammary gland