Complex sentence: Concerned over the adverse health consequences Europeans experienced from uranium mines, an independent study headed by William Bale and John Harley led the government to start the United States Public Health Study (USPHS) on Uranium mine workers.
Split into simpler sentences: Concerned over the adverse health consequences which Europeans experienced from uranium mines, William Bale and John Harley conducted an independent study. Their work led the US government to start the United States Public Health Study (USPHS) on uranium mine workers.