Increase in pollution, wrong eating habits, and ever increasing stress levels, our skin suffers the most. This leads to Acne.

Lots of liquid and less oil and sugar in your diet definitely helps. My sister had terrible problem with acne but with some corrective measures , mainly right diet, exercise and lots of liquid and last but not least personal hygiene she has been able to overcome and even get rid of acne marks and now has clear complexion without any marks or blemish..

A good and healthy lifestyle which includes nutritious food like veggies and fruits will take care if any ailment including acne.

Hereditary, age, medicines, work pressures, cosmetics can cause acne or pimple. 

Yes. The reasons you mentioned also contribute to Acne in a big way.

Dust is one the main reason of acne. One should wash face after coming back home from outside. Also I was told by a doctor dandruff is also the reason of acne as dandruff when sticks to face blocks skin pores of face causing a pimple there.

Unknowingly some employ wrong ways like popping out pimples, using makeup Brushes on which dirt is accumulated, wrong way of scrubbing to name a few contribute to Acne in a big way.

Lifestyle and food habits coupled with polluted environments could cause acne. 

Though there are many causes behind Acne, life style changes along with physical exercise will prevent acne.

some time hormonal imbalance to reason behind acne.