method of age determination that makes use of the ratio of the radioactive lead isotope lead-210 to the stable isotope lead-206. The method has been applied to the ores of uranium. In the series of unstable products from the radioactive decay of uranium-238, lead-210 results from the decay of radon-222 and is a precursor of the stable isotope lead-206. Lead-210 dating is particularly useful for determining the ages of relatively recent lacustrine and coastal marine sediments and so has been applied increasingly to studies concerned with the impact of human activity on the aquatic environment (e.g., measuring the accumulation rates of pollutants in sediments).