I thought the numbers from wikipedia looked a little shaky, maybe. I couldn't find those specific numbers in the reference UN PDF.

Google says soil concentration of Uranium is like 3ppm. But, if you do the math, 668 x 1200 x 1000 x (1/1000000) = 802g for every ppm. 3ppm Uranium would be 2.4kg by this number.

Lead is at like 15-40ppm (https://ag.umass.edu/soil-plant-nutrient-testing-laboratory/... ), so between 12 and 32 kg of lead in everyone's back yard?