As someone who grew up in New Delhi, I think the government has taken quite a few steps like passing laws that require all public transport to run only on CNG, mandating industries to be positioned outside the city and more recently having policies to curb number of cars on the road. But the problem of pollution never seemed to improve. Optimistically I've told myself that if those measures weren't taken we would have been in a worse position much earlier. Though that does little good in the long run. Unless action is taken to effect negative growth to pollution I think anything you do won't quite cut it.

To be fair though, like in any Indian metropolitan, there is immense pressure on the infrastructure that takes solving such problems to the next level. The sheer growth in population(primarily due to immigrants from other parts of India) on a daily basis would put any government in a quandary.