The streets are black with soot because it is a coal mining community.
Katniss lives in District 12, which is the poorest of the remaining districts in Panem. The industry for District 12 is coal mining, a dangerous and dirty job.
Our part of District 12, nicknamed the Seam, is usually crawling with coal miners… Men and women with hunched shoulders, swollen knuckles, many who have long since stopped trying to scrub the coal dust out of their broken nails, the line of their sunken faces. (Ch 1, p. 4)
There is an electrical fence surrounding the village, and people are not allowed to go into the woods. The fence is supposed to protect them from animals, but it also prevents them from hunting. Weapons are not allowed. Katniss has a bow and arrow from her father, and is an excellent hunter.
The danger and dirt of District 12 demonstrate how little the Capital cares about or respects it. The fence and banning of weapons shows that they are also a little afraid of it. When we first meet Katniss, she demonstrates that she is very aware of the virtual enslavement of her people, and she is already showing talent and industrious independence as a hunter.