According to a new report released by AirVisual, Hanoi ranked seventh on a list of the world’s most polluted capital cities in 2019.

Last year, air pollution levels in the Vietnamese capital rose from an average PM2.5 level of 40.8 in 2018 to 46.9 in 2019, meaning Hanoi has overtaken Beijing on the company’s rankings.

AirVisual acquires data from a mix of sources including government data, monitoring stations and local organizations to keep track of air quality, particularly PM2.5 levels, in approximately 3,000 cities across the globe, VnExpress reports.

The company’s 2019 World Air Quality Report measures air pollution in 85 of the world’s major capital cities that regularly suffer from poor air quality.

All of the world’s top 10 polluted capital cities on the list are located in Asia. New Delhi easily topped the list, with Dhaka and Ulaanbaatar ranking second and third. Beijing ranked ninth.

The app itself has come under scrutiny in Vietnam. In October last year, AirVisual faced a sustained online attack after Vu Khac Ngoc, a Hanoi-based chemistry teacher with nearly 350,000 Facebook followers, claimed in an online post that the app was deliberately manipulating pollution levels in order to sell air purifiers made by its parent company, IQAir.

In response, the Vietnamese government announced plans to create its own air pollution tracking app.

Worsening air quality, often exacerbated by farmers burning their fields, led to a thick, gloomy smog descending over Hanoi for weeks at a time late last year. The city’s air pollution reached its worst level in five years last autumn, according to a government report released on October 2.