Where does it occur?

 
Arsenic concentrations in groundwater can be quite variable; even wells in the same neighborhood can produce water with very different concentrations of arsenic.

There is no single map that shows arsenic concentrations in every aquifer in the entire State. However, there are two sources of information that provide a partial understanding of arsenic occurrence in Ohio groundwater:

 
As more wells are tested for arsenic, it may be possible to determine which parts of the groundwater system are most likely to have elevated arsenic concentrations.