Answer: These are the right answers:
1. julio
2. ocho (8)
3. encierros
4. corren
5. 875
6. blancos
7. escribió
8. población
Explanation: Just to elaborate a little on the answer, it can also be added that the actual length of the race—the so-called running with the bulls or "encierro"—is 875 meters. In addition, I would argue that during the festival it is not the city the one that becomes larger than usual, but its population, due to its popularity all over the world.