In the show (and the stereotype; I have no idea if it is true), "burning trash" refers to burning trash at home, not at a controlled municipal facility.
http://www.epa.gov/solidwaste/nonhaz/municipal/backyard/inde...
http://www.epa.gov/solidwaste/nonhaz/municipal/backyard/inde...
suprisingly, its not as terrible for the environment as it looks. but its not pleasant to see or be around regardless.
obviously, don't do this in CA b/c wildfires...etc.