South Carolina health officials have generally tested only fish for mercury contamination. Now they are planning to check people as well.
The Department of Health and Environmental Control is planning a study to see if there are clusters of people suffering mercury illnesses.
The Charleston Post and Courier reports that in some rivers in the state, people are warned not to eat certain fish species because the mercury levels are unsafe.
The department hopes to start studying humans later this year and is working out how many will be tested and other details.
An earlier study by the newspaper tested people who eat freshwater fish and found that, in some areas, they had high mercury levels.