I can not breathe

This year is the 13th year since I have lived in Beijing,
I feel that the air is getting worse year by year.
The first four years I lived in a dorm in college, that is located in the center of the city.
I frequently rode (if you are talking about riding in the past tense) bicycle to go somewhere, at that time, I did not feel so much difference with my hometown which is a rural area,
After I graduated (Past tense of graduate), I got a job working as an auditor, I got lot of chances to go on business trips, when I return to Beijing, at the moment of getting off the plan in airport, I can feel the scent of the air is a little pungent>
Until last winter, the atmosphere pollution in here can not (Do you men went from bad to worse?) be bad to worse, people can't go out without masks, all the city is surrounded with dirty fog, even the vision is so limited,
now summer is soon, but the clear, blue sky is seldom, still most of day is grey and the fresh air is hardly can be breathed.
Yesterday. one of my friend is back from Japan in few many years, he says he can't stay here for long because of the air, he want to go back to the Japan.

Your English level is higher than my Chinese! I just made some corrections to help you. Good luck!