Risks
I think Mr. Palmer appropriately lays out the risks...exposure to cosmic rays in space increases the rick of cancer and lowers life expectancy. He also appropriately notes that these risks are far less significant to all of the other risks of space travel. But, the longer you remain in space the more significant cosmic ray risks become. It just one of many intractable difficulties facins us on a two year venture to Mars and back.
By the way, I see you're from Seattle. Olympia, here.
Regards,
Don