In April 1986, the most catastrophic nuclear accident the world has ever seen happened in the former USSR, near the city of Chernobyl. A nuclear reactor exploded and burned, spreading radiation as far away as Sweden. More than 300,000 people were eventually evacuated, and an exclusion zone was established around the site. The long-term effects of the disaster are still being seen and studied today. Thousands of people have developed cancer, and albinism and cataracts are more common among animals living in the zone. Experts estimate that the area may not be safe for human habitation for up to 20,000 years.