The study found people who are exposed to high levels of mercury are 65 percent more likely to develop diabetes.
The Duke Energy Wabash unit in Terre Haute might close because of failure to meet new EPA rules regulating mercury release.
If the heatwave continues through the weekend as forecasted, it would be the longest heatwave to hit Indiana in 40 years.
Indiana is in the top five among states for the highest levels of mercury pollution.