An environmental group says levels of mercury in Columbus rainfall are more than five times the government's safety standard.
Touching or drinking water with such levels of mercury is safe, but the National Wildlife Federation says eating fish where mercury can become concentrated can be unhealthy.
The federation released a report today from a study conducted on the city's rain in May. A similar study found mercury levels more than eight times the federal safety standard in Cleveland rainfall earlier this year.
A spokeswoman says the federation is calling for the Environmental Protection Agency to strengthen a proposal to reduce mercury emissions.
The group says the emissions are primarily produced by coal-burning power plants.