Hundreds of millions of Indians breathe some of the world’s most toxic air all year round. Air pollution in the capital area that’s home to about 30 million people is especially stubborn. In winter, the cold weather actually makes the smog even worse — and potent.

India's capital city of Delhi has virtually shut down as air pollution hit "severe plus" levels, according to Indian government officials in its pollution control authority.

Unhealthy

India's capital was left gasping this week as air pollution smog reduced visibility to near zero and raised air quality levels more than 130 times safe limits.

A thick, toxic smog has enveloped India's capital, home to more than 33 million people. One technology firm which monitors air pollution ranked New Delhi as the most polluted city in the world.

The AQI in Delhi remained in the severe category from Monday to Wednesday last week and thereafter witnessed slight improvement on Thursday and Friday. However, it deteriorated to the severe category on Saturday.

The Supreme Court is set to review on Monday whether to continue emergency measures under Stage 4 of the Graded Response Action Plan (GRAP) to address Delhi's air pollution crisis.