Hanoi ranks second only to Delhi as world’s most polluted city amid PM2.5 surge

Exam-focused facts from the 12 December 2025 current affairs briefing.

Key facts

Hanoi has been ranked second with India’s capital New Delhi still holding the first rank in terms of worst AQI index.
Levels of PM2.5 pollutants were vastly higher than the World Health Organization’s recommended daily exposure limit.
Experts suggest that the cause of pollution can be the emissions from construction sites and the huge number of motorbikes and cars.