Dick Powell started in show business as a singer, which led him into acting. After many years as a star, Powell directed his first film. Split Second (1953) was a thriller about escaped convicts and their hostages holed up in a desert ghost town, unaware that the government is going to conduct an atomic bomb test nearby the next morning.
Powell's next film as director was the costume epic The Conqueror (1956), starring John Wayne as Genghis Khan. Ironically, the exterior scenes were filmed in St. George, Utah, downwind of U.S. above-ground atomic tests. Many of the cast and crew later developed some form of cancer, with some dying of the disease, including Powell and Wayne.
From Wikipedia: Although the number of cancer cases among the cast and crew is in line with the average for adults in the US at the time, the perception of a link between the film's location and subsequent illness remains, not least because many of those involved in the film developed cancer at a younger age than average.
Powell directs Wayne on the set of The Conqueror.