> If you own a house with a modest sized lawn, the top meter of soil probably contains several kilograms of uranium. At first I thought "surely that cannot be

> If you own a house with a modest sized lawn, the top meter of soil probably contains several kilograms of uranium. At first I thought "surely that cannot be right", then did some calculation and it seems you are right? This report[1] states that: "Uranium is a naturally occurring radioactive element that is present in nearly all rocks and soils; it has an average concentration in U.S. soils of about 2 pCi/g (3 ppm)." I took the 3ppm figure from this and assumed that means 3g per million gram of soil. (This assumption might be a mistake, but I don't know how better to interpret it.) Then I googled and found 1000 square meter to be a reasonable size of estimate for the lawn size and 1400 kg/cubic meter seems to be a reasonable soil density. Then just multiplied these together "1000 * 1 * 1400 * (3 / 10*6) = 4.2" and found that indeed. As a rough estimation your statement seems to be right! (I mean of course you did know this :D I just wanted to show how I checked in case others are as surprised by the statement as I was.) 1: https://www.atsdr.cdc.gov/ToxProfiles/tp150-c6.pdf https://www.atsdr.cdc.gov/ToxProfiles/tp150-c6.pdf