The risk was very much known, as all male miners died at about 45. It was called the miners disease. Eg the nazis promised the Jachimov miners to close it, so

The risk was very much known, as all male miners died at about 45. It was called the miners disease. Eg the nazis promised the Jachimov miners to close it, so they won their support. When the Russians kept it going and expanded it, the risk was still known, and simple measures could have saved thousands of lives, but they didn't care.