i mean, REALLY? Have you even tried talking to them? its a free country, people can burn candles and omg incense if they want.
good luck!

they shouldn't be allowed to burn anything in public space where it affects air quality and people walking by

How is this effecting the daily flow of traffic that comes through the neighborhood?

I completely understand how you feel but if people can smoke cigarettes outside so that the smoke comes into one's house then they can burn incense. Believe me I wish people were forbidden from smoking anywhere someone else can breathe it in but unfortunately they arent.