[en] The unique isotopic composition of lead from uranium ores can be useful in studying the impact of ore processing effluents on the environment. Common lead on the earth's surface is composed of 1.4% ²⁰⁴Pb, 24.1% ²⁰⁶Pb, 22.1% ²⁰⁷Pb, and 52.4% ²⁰⁸Pb. In contrast, lead associated with young uranium ores may contain as much as 95% ²⁰⁶Pb. These extreme differences provide the means to quantitatively evaluate the amount of lead introduced into the environment from the mining and milling of uranium ores by measuring variations of the isotopic composition of lead in environmental samples. The use of Pb isotopes as diagnostic tools in studying the hydrologic transport of materials from U ore dressing plants in the Grants Mineral Belt, New Mexico, is discussed. Preliminary measurements on effluents intimately associated with processing wastes are consistent with a simple model in which radiogenic lead from the ores is mixed with common lead from the uncontaminated environments