I went looking for such a better list. One thing I found is this, for drinking water contaminants:

https://www.sciencedirect.com/science/article/pii/S240584401...

It would be nice to have a list like this for the Group 1 substances, I mean something that shows the amount vs. the risk and the number of cases caused by the substance.

For benzene in drinking water it has 0.15 μg/L corresponding to 10e−6 lifetime cancer risk. Estimated number of cancer cases from benzene in drinking water in the USA is 1 vs. 43500 from arsenic.