​India's toxic smog hides Taj Mahal, delays flights

Toxic smog obscured India's famed monument to love, the Taj Mahal, as well as Sikhism's holiest shrine, the Golden Temple in Amritsar, and delayed flights on Thursday, becoming too thick to see through in several places.

The city of Lahore in neighbouring Pakistan ranked as the world's most polluted in winter's annual scourge across the region, worsened by dust, emissions, and smoke from fires burnt illegally in India's farming states of Punjab and Haryana.

In the city of Agra, the Taj Mahal was barely visible from the gardens in front of the 17th-century monument, while dense fog wreathed worshippers at the Golden Temple in Punjab, television images showed.

Delhi flights faced delays, with tracking website Flightradar24 showing 88% of departures and 54% of arrivals were delayed.

Officials blamed high pollution, combined with humidity, becalmed winds and a drop in temperature for the smog, which cut visibility to 300 m (980 ft) at the city's international airport, which diverted flights in zero visibility on Wednesday.

More patients flocked to hospitals, particularly children.

"There has been a sudden increase in children with allergies, cough and cold ... and a rise in acute asthma attacks," Sahab Ram, a paediatrician in Punjab's Fazilka region, told news agency ANI.

Delhi's minimum temperature fell to 16.1 degrees Celsius (61°F) on Thursday from 17 degrees C (63 degrees F) the previous day, weather officials said.

Its pollution ranked in the 'severe' category for the second consecutive day, with a score of 430 on an index of air quality maintained by the top pollution panel that rates a score of zero to 50 as 'good'.

Pollution in New Delhi is likely to stay in the 'severe' category on Friday, the earth sciences ministry said, before improving to 'very poor', or an index score of 300 to 400.

The number of farm fires to clear fields in northern India has risen steadily this week to almost 2,300 on Wednesday from 1,200 on Monday, the ministry's website showed.

Why has smog hit visibility in New Delhi?

Visibility fell sharply in Delhi this week as a toxic mixture of smoke and fog shrouded the Indian capital even before winter sets in.

Here is a look at the problem, and what triggered it.

How bad was the smog?

Delhi was swathed in 'dense' to 'very dense' smog early on Wednesday and Thursday. Visibility in the 'very dense' category falls into a range of zero to 50 m (164 ft), while 'dense' refers to visibility over 50 m to 200 m (164 ft to 656 ft).

The smog dispersed slightly on Thursday, when visibility stayed above 300 m (984 ft), after being too thick to see through in some areas the previous day, such as around the city's international airport.

What caused the smog?

Officials blamed weather conditions such as high humidity that allows the formation of fog droplets, low wind speed, and a slight drop in minimum temperature, to 16.1 degrees Celsius (61 degrees F) on Thursday from 17.9 C (64 F) on Tuesday.

Was pollution also a factor?

Authorities said pollution also contributed, pushing New Delhi to pole position as the world's most polluted capital in Wednesday's live rankings by Swiss group IQAir.

Daily air quality in the region crossed into the 'severe' category for the first time this season, or an index score higher than 400, which persisted on Thursday morning, with a reading of 430.

Did smog afflict Delhi alone?

Dense smog has engulfed other parts of northern India, such as the states of Punjab and Uttar Pradesh, where visibility fell to zero in some areas on Thursday.

Neighbouring Pakistan's Punjab province, which shares a border with India, also faces similar conditions.

Will Delhi's situation improve soon?

Delhi's pollution is likely to remain 'severe' on Friday, but is expected to improve to the 'very poor' category afterwards, falling in an index range of 300 to 400.

Wind speed is also expected to increase from Friday.

Authorities expect both factors to disperse the smog in the city and improve visibility.