Fri Mar 14 08:30:00 UTC 2025: ## California Cities Top List of Worst Air Pollution in North America
**Los Angeles, CA –** A new report from IQAir reveals that California cities dominated the list of North America’s most polluted areas in 2024. Ontario, California, took the unfortunate title of the most polluted city in the U.S., followed by Los Angeles as the most polluted major U.S. city. Bloomington and Huntington Park, California, also ranked among the worst in North America.
The findings, based on data from over 40,000 air quality monitoring stations globally, focused on PM2.5, a dangerous pollutant linked to fossil fuel combustion, dust storms, and wildfires. Conversely, Seattle emerged as the cleanest major U.S. city, while Mayaguez, Puerto Rico, held the global title for cleanest metropolitan area.
Despite the localized concerns, the report indicates a significant 22% decrease in average PM2.5 levels across the U.S. compared to 2023. Globally, however, only 17% of cities meet World Health Organization (WHO) air quality guidelines. The report highlights the stark contrast between clean air pockets and areas struggling with severe pollution, with Central and South Asia housing the top seven most polluted cities globally, including six in India.
IQAir CEO Frank Hammes emphasized the critical threat air pollution poses to human health and environmental stability, stressing the life-saving potential of readily available air quality data in informing policy and empowering communities to take action. The report also underscores the value of low-cost air quality monitors in filling data gaps in many parts of the world. The full 2024 World Air Quality Report is available for download [link removed].
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