The photographs of Yosuke Yamahata are a true testament of someone's passion to show the truth over the well-being of his own life. In essence, the radiation and complications causes from the bomb that was dropped on Nagasaki eventually cost him his life. To quote him:

"Human memory has a tendency to slip, and critical judgement to fade, with the years and with changes in life-style and circumstance. But the Camera, just as it seized the grim realities of time, brings the stark facts... before our eyes without the need for the slightest embellishment"

Please check out this link for more.
http://www.exploratorium.edu/nagasaki/mainn.html