Over half a million people across the United States have been urged to stay indoors and seal their windows as toxic substances, harmful to human health, pervade the atmosphere. This warning comes from the US Environmental Protection Agency (EPA), which has identified significant areas of severely polluted air in Arizona, California, and Oregon. Particularly concerning are the high concentrations of dangerous toxins known as fine particulate matter, or PM2.5.

PM2.5 refers to microscopic particles composed of toxic compounds or heavy metals. These fine particulates, often generated by industrial activities and vehicle emissions, are small enough to penetrate deep into the lungs, potentially causing inflammation, respiratory difficulties, and other health problems upon inhalation.

Arizona, especially, is experiencing the worst levels, with major urban areas such as Gilbert and Chandler being heavily affected. Together, these cities house more than 580,000 residents and have registered air quality levels deemed ‘hazardous’ by the EPA as of Monday morning. These cities lie less than 20 miles east of Phoenix, a city with a population exceeding 1.6 million people.

The air quality monitoring platform IQAir has reported that PM2.5 concentrations in areas just east of Gilbert and Chandler are alarmingly over 15 times higher than what the World Health Organization considers safe. This situation underscores the urgent need for residents in these areas to heed warnings and take precautionary measures to protect their health.

The EPA has warned that air quality levels in both cities registered as ‘hazardous’ Monday morning – their worst rating for air quality measurements. Both are less than 20 miles east of Phoenix, which has a population of more than 1.6million people.

Air quality-tracking website IQAir noted that PM2.5 levels just east of Gilbert and Chandler were more than 15 times higher than the World Health Organization’s recommended safe limits.

IQAir has also reported that wind patterns are moving this air pollution north, resulting in dust and sand blowing through nearby Scottsdale, home to a quarter-million Americans.

When air gets this bad, health officials urge anyone in the affected areas to close their windows to avoid dirty outdoor air, avoid outdoor exercise, wear a face mask when leaving the house and run an air purifier if they own one.

This is a breaking story. More details to follow.

A dust storm seen in Arizona in 2025 (Stock Image)

The EPA’s live air quality tracking data has warned of hazardous air over Arizona (Pictured), California and Oregon on Monday, March 30

Another major plume of hazardous toxins was detected over Oregon’s major city of Eugene, home to more than 170,000 people.

The EPA’s live tracking data warned that highly polluted air was centered over the heart of the city and was spreading west towards the Pacific Ocean, reaching communities over 40 miles away.

In California, a potentially dangerous dust storm pouring over the US-Mexico boarder has created ‘very unhealthy’ conditions in the Southern California city of El Centro, home to more than 40,000 people.

IQAir registered an air quality index of 204, which was worse than any major city being monitoring worldwide on March 30.

Air quality levels are measured on a scale from 0 to 500: good (0–50) carries little risk, moderate (51–100) may affect sensitive individuals, unhealthy for sensitive groups (101–150) poses increased risk and unhealthy (151–200) impacts everyone, limiting outdoor activity.

The air pollution along the US southern boarder was also filled with PM10, a type of particulate matter made up of tiny solid particles or liquid droplets floating in the air that are less than 10 micrometers in diameter, thinner than a human hair.

These inhalable particles can get deep into your lungs when you breathe them in and are typically created by dust from construction, pollen, mold, smoke, soot, industrial emissions, and wind-blown dirt – like the dust and sand sweeping into the US.

PM10 is noticeably larger than PM2.5, the microscopic particles from cars and factory emissions. However, both can damage the lungs, worsen respiratory issues such as asthma and contribute to heart attacks and strokes that cause premature death.

The city of Eugene, Oregon saw local air quality reach ‘hazardous’ levels, with a zone of unhealth air (Seen in Red) spreading out roughly 40 miles west

Air quality readings in the southeastern California city of El Centro reached dangerous levels on March 30, fueled by dust and sand blown north from Mexico

As of 10am ET, the EPA revealed that the plume of air deemed ‘unhealthy’ near El Centro had spread over 150 miles, from Boulder Park, California to Tyson, Arizona.