The Vietnamese capital Hanoi was blanketed by a thick fog of air pollution on Tuesday, obscuring buildings and forcing its roughly nine million residents to breathe toxic air.
By early afternoon, the city was at the top of the world's most polluted cities, according to air quality monitoring company IQAir.
Levels of PM2.5 – microparticles that enter the blood and can cause cancer – were described as “very unhealthy”, reaching more than 24 times the World Health Organization (WHO) recommended limit.
In recent years, Hanoi has often been ranked among the most polluted cities on the planet, partly due to massive urbanization and emissions caused by the large number of two- and four-wheeled vehicles on the roads.
Carbon emissions from coal-fired power plants north of Hanoi and from agriculture are making the problem worse.
“For the past few days, I had to wear a mask every time I went out because the air quality was so bad,” Nguyen Minh Huong, an office worker I met in a park, told AFP.
“It's hard to breathe. I sneeze all the time so I had to limit my outings,” she added.
Last month, dozens of flights were affected by dense fog due to high humidity in Hanoi, leading to a rise in air pollution and a significant reduction in visibility.
Meteorologists regularly warn of dense haze, especially in the mountainous regions of northeastern Vietnam.
The World Bank's latest report on air pollution shows that 40% of Hanoi residents are exposed to levels almost five times higher than WHO recommendations.
According to the WHO, many serious health problems are linked to exposure to air pollution, including stroke, heart disease and lung cancer.