Twenty-five years ago Tuesday, a catastrophic explosion at the Chernobyl power plant in Ukraine spewed nuclear fuel into the air. Over 20 days, radioactive smoke and other products emanated from the plant, spreading out over parts of Russia, Ukraine and Belarus and extending, in lower concentrations, around the world.
In the immediate aftermath of the disaster, about 30 people -- mostly firefighters -- died from acute radiation poisoning. A few more died of radiation poisoning over the next decade, and in 2008, a United Nations report concluded that 6,000 thyroid cancers in young people were linked to the accident, too. (Exposure to iodine-131, which was released into the atmosphere during the accident, is known to cause thyroid cancer.)
But even after decades of study, experts are still debating the long-term health effects of the disaster. While the U.N. and other investigators have determined that there is no evidence of excess cancers resulting from the accident, others -- for instance, this blogpost from the Union of Concerned Scientists -- suggest that excess cancers and cancer deaths worldwide will number in the tens of thousands, or even higher.