[TeMPOraL]

Wikipedia suggests he ingested ~10 micrograms of polonium. If somehow even most of it reached the sewage, we'll be talking homeopatic quantities at this point. It's very unlikely it would go through water treatment and end up in someone's food in enough quantity to cause harm.

https://en.wikipedia.org/wiki/Poisoning_of_Alexander_Litvine...

[kislotnik]

I agree with you, we can estimate the amount of polonium he ingested, but we surely cannot estimate the amount of polonium involved in that operation.