ATLANTA, July 4 — At 6 a.m. his time, as the sun spread over the pancake-flat desert around him, William G. Halicks, a Navy captain stationed in Hillah, Iraq, measured the temperature at 95 degrees. It was hot, certainly, but with only a light breeze, the chances of having a throat-choking dust storm seemed low. For Captain Halicks, that meant it was a fine day for a foot race. He was runner No. 1 in the 2007 Peachtree Road Race, which organizers call the largest 10K run in the world, and which for most runners takes place in Atlanta. Participants...