Vacuum and temperature NASA can handle; spacesuits and habitats provide plenty of air and insulation. Radiation, though, is trickier.
The surface of the Moon is baldly exposed to cosmic rays and solar flares, and some of that radiation is very hard to stop with shielding. Furthermore, when cosmic rays hit the ground, they produce a dangerous spray of secondary particles right at your feet. All this radiation penetrating human flesh can damage DNA, boosting the risk of cancer and other maladies.Above: The surface of the Moon is exposed to space radiation.
According to the Vision for Space Exploration, NASA plans to send astronauts back to the Moon by 2020 and, eventually, to set up an outpost. For people to live and work on the Moon safely, the radiation problem must be solved.
"We really need to know more about the radiation environment on the Moon, especially if people will be staying there for more than just a few days," says Harlan Spence, a professor of astronomy at Boston University.
link:
http://science.nasa.gov/science-news/science-at-nasa/2005/08sep_radioactivemoon/