hick smog covers Long Biên Bridge in Hà Nội on November 17, 2021. — Photo VNA/VNS Thành Đạt

HÀ NỘI — Many northern localities registered bad Air Quality Index (AQI) scores on Wednesday, according to data from various air monitoring systems.

Air quality in the north is in the most polluted time of the year, said experts. This is due to the dry weather and the inversion phenomena, which causes pollutants to increase. PM 2.5 numbers are usually higher around midnight and early morning.

Hà Nội and nearby areas were covered in thick smog Wednesday morning. As the wind was weak, the pollutants can linger and spread further.

In the north, there are currently seven red alert areas in 37 monitoring stations, according to the Directorate for Environment’s VN Air app.

In these areas, normal people’s health will be affected, while sensitive groups might have more serious complications. These areas are mostly in Bắc Ninh, Hà Nội, Thái Nguyên, Cao Bằng and Lạng Sơn.

The AirVisual monitoring app registered 60 red alert areas in Hà Nội, Hưng Yên, Hải Dương, Nam Định, Bắc Ninh, Vĩnh Phúc, Thái Nguyên, Ninh Bình and Thanh Hóa.

Five purple alert areas – “all people affected” - were located in Hà Nội. The capital was the fourth most polluted globally today of all 95 cities monitored by AirVisual.

Việt Nam’s independent monitoring app, PAM Air, registered 18 purple alert areas, mostly located in Hà Nội. — VNS