Lahore ranks as world's 'most polluted city'

• New Delhi ranks second in most polluted cities' list with AQI of 285.
• Pollution spirals in Lahore when cooler temperatures take hold.
• Citizens advised to exercise caution  to stay safe from air pollution. 

Lahore, the capital of Punjab, has been ranked the world's most polluted city, according to IQAir data released on Tuesday, as provincial authorities rush to tackle the worsening smog crisis. 

The latest data showed that Lahore has crossed the 400 US AQI mark which means its air quality is hazardous, the worst possible.

Speaking to Geo.tv, environmentalist Yasir Husain said that healthy air is below 50 US AQI, which measures PM2.5 particles. This means Lahore's air is 80 times more polluted than a healthy level, he added.

"With the season direction of air flows have changed. In winter, wind flows from Pakistan to India. Agricultural waste burning, vehicle exhaust and power production cause the most air pollution. 

Due to a slower pace of wind in winter, the polluted air stays in the city, combining fog and pollutants from burning into deadly smog.

Here is the air quality classification according to IQAir:

An AQI of 0-5 is considered "good", 51-100 is considered "moderate", 101-150 is "unhealthy for sensitive groups", 151-200 is simply "unhealthy", 201 - 300 is "very unhealthy", while more than 301 degrees indicates "hazardous". 

The second most polluted city in the IQAir's list is New Delhi, with a very unhealthy air quality as the AQI level in the Indian capital is 285. 

After Delhi comes United Arab Emirates' Dubai, where the AQI level is 166. 

Meanwhile, Karachi ranks 13th in the list of most polluted cities. Here, those sensitive to dust and other toxins and people with allergies are at risk as the AQI in the metropolis is 107. 

IQAir has recommended the citizens of Lahore to exercise caution in order to stay safe from effects of air pollution. The citizens are advised to avoid outdoor exercise, keep their doors and windows closed to prevent dirty air, wear mask outdoors and run air purifiers around them. 

Despite provincial government's measures to fight off smog, this is the second time in a week Lahore has topped the list of most polluted cities worldwide. 

Senior Punjab Minister Marriyum Aurangzeb on Sunday said that all arrangements to tackle with smog had been made.

She said that the option of artificial rain will be implemented in the province in case of rise in smog levels, with a cost of Rs5 million to Rs7 million.

Moreover, the crackdown against factories and vehicles producing toxic smoke will continue.

"Artificial rain will not be needed if we improve the environment through measures against smoke," Aurangzeb said, urging the masses to report such vehicles, factories or instances of stubble burning on government helpline 1373. 

When cooler temperatures take hold, pollution spirals, with Lahore and Delhi among the most polluted cities. 

The AQI in Lahore crosses 1000 in December every year. 

As the air quality deteriorates in cooler months due to temperature inversion that traps pollution closer to the ground, hospital wards are packed with patients with respiratory problems.

Rising air pollution can cut life expectancy by more than five years per person in South Asia, one of the world's most polluted regions, according to a report published last year which flagged the growing burden of hazardous air on health.

Additional input from Reuters