US President Donald Trump referred to what he called the "filthy air" in India, China and Russia as he defended his decision to pull out of the Paris accord and denounced Democrat rival Joe Biden's plans to tackle climate change in a presidential debate today. "Look at China, how filthy it is. Look at Russia. Look at India. The air is filthy. I walked out of the Paris Accord as we had to take out trillions of dollars and we were treated very unfairly," he said during the second and final debate ahead of the November 3 US polls.