A thick blanket of smog enveloped Lahore on Wednesday, prompting officials to warn that tens of thousands of the city's residents risk respiratory disease and eye-related problems while doctors urged people to stay at home.

The air quality in Lahore deteriorated to hazardous levels, putting an additional burden on the fragile healthcare system amid a surge in coronavirus deaths and new infections. The Air Quality Index at one point rose to 750 in the city's poorer areas — about 12 times the recommended level.

Earlier in the day, Switzerland-based air quality information platform IQair declared Lahore the second most polluted city, after New Delhi, India's capital. It is currently ranked as the fourth most polluted city in the world, preceded by Beijing, Delhi and Mumbai.

Pollution indexes peak dramatically in Pakistan in winter, when farmers burn off stubble in the fields. Winds worsen the pollution by further spreading smog across the region.

"The air quality level was hazardous today,” said Sajid Bashir, a spokesman for Environmental Protection Department.

By mid-day the situation had improved, he said, as authorities took steps to keep smoke emitting vehicles off the roads and shut brick kilns across the province of Punjab, where Lahore is the provincial capital.

Lahore, once dubbed as the city of gardens, remained pollution-free for months after March, when the government imposed a lockdown to contain the spread of coronavirus. But the restriction was lifted in May, allowing a return to industrial activities and normal businesses. With cars back on the roads, the air quality gradually deteriorated, falling again to unhealthy levels.

Cars are the top pollutants in Lahore but the city also has other sources of pollution, including the stubble burning, steel manufacturing furnaces and the city's famous brick kilns.

"Coughing, throat infection and irritation in the eyes are common," said Anza Farid, an environmental expert, warning that the situation could worsen in the coming weeks as more people burn garbage in the cities and farmers burn off the stubble in their fields.

Pollution levels rise in Abbottabad

Pollution levels in Abbottabad city have also increased to "very unhealthy" grade, according to Dr Qaisar Mehmood, head of the Department of Environmental studies COMSATS Institute of Technology Abbottabad campus. The particulate matter in the city, known for its greenery, has increased to 3.4G per cubic metre.

The city is clouded with dust and smoke. One of the causes of the increased pollution is said to be construction of the main Karakoram Highway road which has been underway for the past few months.

According to Dr Mehmood, prolonged construction work has led to increased traffic jams, which inevitably cause smoke. He disclosed that the increased pollution has led to an increase in Covid-19 cases in the city as particulate matter was a carrier of the coronavirus disease.

Dr Talha Ayub urged people to wear face masks for protection, both from pollution and the coronavirus. "People should try to stay at home if they can,” he appealed.

Covid-19 cases and deaths are rising in Pakistan despite government-imposed partial lockdowns in 4,136 residential areas across the country. The government is turning to sealing off hotspots in a bid to contain rising fatalities and infections from coronavirus.

Authorities also banned large gatherings, shut shrines, cinemas and theatres to contain the spread of the virus.

PM Imran's warning

Last month, Prime Minister Imran Khan had cautioned that a second wave of the novel coronavirus may hit cities with a high level of pollution in the coming months as the winter season approaches.

The premier said that several cities, where pollution levels are high, experience smog during October and November, when temperatures start to drop.

"I fear that in these two months — October and November [...] cities like Faisalabad, Lahore, Karachi, Peshawar, Gujranwala, where there is more pollution [...] there might be a second spike in coronavirus cases. The cases are rising gradually and we hope that they don't increase quickly and we are monitoring it," he said.

He further said that during the winter, "pollution becomes stagnant in the atmosphere", leading to the spread of diseases.