France, Dec. 18 -- Pollution in India's second city Mumbai was worse this week than even the notoriously smoggy capital, Delhi, as experts warned that hazardous air pollution was likely to affect more parts of the country in future.

Air quality in Mumbai was murky on Tuesday and fell to "poor" on a national weather meter. In comparison, the pollution charts moved Delhi'sindex to "moderate" the same day.

At the start of the week, the Air Quality Index or AQI stood at 321 in places in Mumbai, India's financial hub and one of the world's most congested cities.

Thenumbers were well over Delhi's air pollution levels- a shock, since coastal Mumbai typically has better air quality than the inland capital.

"It has become difficult for the res...