As schools in Lahore remained closed on Thursday for the first time due to the prevalence of "smog" in the city, Punjab Chief Meteorologist Mahr Sahibzad Khan said that the current smoke levels should not be confused with "smog".

"Smog components become visible after smoke and fog combine. Until now, the fog has not developed," he said while talking to DawnNewsTV.

"Fog has its own criteria under which it develops: the visibility must reduce to less than 1 kilometre, the humidity levels must be more than 90 per cent, the air must be still and the sky clear. Only then are there chances for fog," Khan explained.

"These phenomena (required for fog) are not currently present. There is smoke, because of car and factory emissions, as well as transboundary smoke coming in from India due to crop burning. So the smoke levels have risen significantly owing to these factors. And there are components in the smoke that raise the air quality index. People start calling it smog, but it isn't. There are alarmingly high levels of smoke, however."

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Khan said that it had rained yesterday and there are chances of rain today as well. "The weather is pleasant and it seems it will be tomorrow as well," he added.

Lahore’s Air Quality Index (AQI) appeared to have improved on Thursday from a day earlier, falling to 106 in the late afternoon which is within the 'Unhealthy for Sensitive Groups' category.

On Wednesday, Punjab Chief Minister Usman Buzdar had announced the closure of public and private schools in Lahore today after the sudden spike in smog levels from less than 200 to over 500.

From November 9-12 the city's AQI will be in the 'Unhealthy' category, the daily index shows.

'Terrifying'

Following the unprecedented measure of schools closure yesterday, journalists took to Twitter to express alarm at the constantly rising levels of air pollution.

The head of communications for Amnesty International, Rimmel Mohydin, criticised the government for continuously monitoring pollution levels and "never actually doing anything".

Iman Zia also shared her "smog" experience, saying it had entered her house.

"Barely slept last night from the pounding heaviness from the smog drooping in the bedroom. Also honestly terrifying walking out into the corridor and noticing smoke INSIDE THE HOUSE." she wrote.

Omar Waraich, in response to Chief Minister Buzdar's notification for schools closure due to a "sudden increase in smog" said that the government had had plenty of time to deal with rising pollution levels.

"You had 15 months to deal with this. There’s nothing ‘sudden’ about this environmental crisis that is violating people’s human rights to education, health and even life," he said.

Meanwhile, the Punjab Health Department issued an advisory for citizens instructing them to take certain measures to guard against the effects of pollution.

Punjab Environmental Protection Department Director Misbah-ul-Haq Khan Lodhi said that the Punjab government, ahead of November, had decided to close conventional kilns in consultation with the Smog Commission, which had been tasked with identifying the root causes of fog generation and to formulate a policy by prescribing a plan to protect the people's health.

Punjab Minister for Environment Protection Bao Muhammad Rizwan said that the Punjab government has taken several emergency measures to counter smog, including a strict ban on burning crops and solid waste.

He said that last year more than 100 people were arrested for crop burning and this year hundreds of factories have been shut down for not having proper emission-control equipment.