Problem $4\mathrm{.}16($modified$),$ Masters and Ela, Introduction to Environmental Engineering and Science, $3$rd Ed$.$:

A man works in an aluminum smelter for $8$ years. The drinking water in the smelter contains $0\mathrm{.}062m\frac{g}{L}$ arsenic and $0\mathrm{.}444m\frac{g}{L}$ methylene chloride. His only exposure to these chemicals in water is at work.

a$.$ What is the hazard index $($HI$)$ associated with this exposure?

b$.$ Does the $HI$ indicate this is a safe level of exposure?

c$.$ What is the incremental lifetime cancer risk for the man due solely to the water he drinks at work? Does it seem to be an acceptable risk according to EPA?