Which US cities are the most polluted? While Ontario, California was the most polluted city in the U.S. in 2024, the most polluted major U.S. city was Los Angeles, according to the report.

PHNOM PENH (Khmer Times): Cambodian capital Phnom Penh now ranks as second most polluted city in the world on Friday morning, according to live IQAir results. According to the ‘Live most ...