You just bought a new home with a view of a lake. After you close the deal, you learn that the lake may have been contaminated by a nearby natural thorium-232 processing facility. You take a sample from the lake, which reads 10 picocuries of radium-228 per liter (radium-228 is a "daughter" of thorium-232, or a product of the decay of thorium-232). Is the lake water above or below current Maximum Contaminant Level (MCL) standards? Proposed MCL standards? If so, by how much in each case?

 

 

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a) lake water exceeds MCL by 5 picocuries per liter, and
b) lake water is less than the MCL by 10 picocuries per liter.

For a detailed explanation of the answers, please contact IEER.