Chinese Spitting Habit: Not a Culture

Walking on the street in any place in China, small town, big cities, I can always hear "hoerrrgghhh piuhhh...^%^#^$##" almost anytime. Mostly done by elderly, but sometimes also by young people, even students, the educated community. Is it kind of a culture in China (mainland)?

I know someone who does this habit. But, when he was in Hongkong for a short stay, he has never ever done spitting. At least that's what he said to me, as he was cautiously preventing to get a $HK 1500 penalty for spitting. He himself was the one who reminded me not to do spitting in Hongkong. He also told me that HK is a very very clean place, despite huge crowd of people. Spitting might be easily noticed in HK. Hmmm....

Anyway, when he returned back to China mainland... here we go again that disgusting sound&^%*&$#%$

I have tried to change his habit, but my effort seems to be nil... Environment plays an important role here. Yes, the environment! Where his environment here in China mainland, almost any time any place you can see or hear people spitting.

So, I'm just wondering whether this spitting habit can be eliminated? How to make them aware about the disease-induced effect of spitting. How to open their mind to change this habit? Should they, in order to change their habit, be brought to a place like Hongkong, Singapore where spitting is legally banned? Can this habit be changed?

So far, my starting point is just to keep telling someone I know, particularly when he wants to spit, then I should start delivering him some lecture against spitting, again and again. Well well...
>>>Bad habit, easy to learn, difficult to change<<<