Definitely due to cutting down of trees in the name of urbanization. Also, hot climate could be the reason but lack of trees being no.1.
In US dust is reduced in houses because the doors always remain closed. There are air tight glass windows to save energy during extreme cold season and so that also reduces dust in the house. When I keep my windows open during spring and summer I have observed how dust collects so quickly on TV,tables etc just like in India though not that much because my house here is surrounded by trees.
Also, pollution from cars, buses using low quality gasoline is another reason.
Go Green
Adara