On April 26, 1986, operators at the Chernobyl Nuclear Power Plant triggered the worst nuclear accident in human history by running a test to see what would happen to its nuclear reactors in a power outage, resulting in a partial meltdown of Reactor 4. The Chernobyl disaster led to the evacuation of hundreds of thousands of people, immediate deaths of two workers, and long-term health effects on emergency responders and nearby residents due to exposure to radioactive iodine, strontium, and cesium.