Which of these lakes is considered the most toxic in the world?

Lake Karachay is a small lake in central Russia. It is often referred to as the most polluted site on earth. Containing just one square mile of water, the lake formed a dumping ground for nuclear waste by for around 12 years.High level radioactive waste makes up almost the entire lake-bed to a depth of around 3.4 meters. Some areas surrounding the lake have radiation measurements of around 6 Sv/hour, which is enough to give a lethal dose to a human in as little as 30 minutes¹.