Los Angeles, California experienced very poor air quality over several days in October and November, 2021. Residents take it for granted that Los Angeles and its suburbs are normally exposed to worse air quality than much of the country. However, air quality monitoring stations across the Los Angeles Basin measured more widespread and worsened air quality than usual on the morning of November 10.

Air quality in the region is often rated “Good” to “Moderate” according to the U.S. AQI (air quality index). Since October 29, Los Angeles has recorded air quality rated “Moderate” to “Unhealthy for Sensitive Groups” – far worse than the norm.

The interactive IQAir air quality map visually represents air pollutant concentrations by a number and color code corresponding to a range of air quality categories. Yellow corresponds to “Moderate,” while orange shows “Unhealthy for Sensitive Groups,” an air quality ranging from 101 to 150. That range of air quality also corresponds with PM_2.5 concentrations of 35.5 to 55.4 micrograms of PM_2.5 per cubic meter, or µg/m3.

It should be noted that all concentrations of airborne pollutants – even in the “Good” range – are dangerous to human health.

Pictured: Air quality image of greater Los Angeles, California. Source: IQAir

Pictured: A closer look at mostly “Unhealthy for Sensitive Groups” air quality (shown in orange) recorded by air quality monitoring stations from Santa Monica to the eastern Los Angeles suburbs. Source: IQAir

Poor air quality affects millions

With an estimated 18.7 million people in metropolitan Los Angeles in 2019, poor air quality poses a significant threat to a population larger than the total estimated population of the country of Zambia.^1,2

Concentrations of PM_2.5, particulate matter measuring smaller than 2.5 microns in diameter, were measured at 36.8 µg/m3 in the city of Los Angeles on November 10. That measurement is 3.7 times above the World Health Organization’s (WHO) annual air quality guideline value for 2005. And according to the recently updated WHO air quality guidelines released in 2021, Los Angeles’ air quality is 7.4 times worse than the standard.

PM_2.5 and even smaller, more insidious ultrafine particles, are connected to a wide range of health concerns. When inhaled, PM_2.5 and ultrafine particles can enter the bloodstream and reach all organs in the body. Heart and lung illnesses are common for people affected by airborne particle pollution.³

Pictured: Top ten California cities experiencing poor air quality on November 10, 2021. Source: IQAir

Most of the cities with the worst air quality in California on November 10 were located in Southern California. Cities impacted included:

• Claremont
• Colton
• Cypress
• Fontana
• La Habra Heights
• Loma Linda
• Rialto

Cypress and La Habra Heights are southeast of Los Angeles, within or bordering Orange County. Claremont, Colton, Fontana, Loma Linda, and Rialto are further east of Los Angeles, either in or bordering San Bernardino County.

Pictured: Historical graph of daily average air quality in Los Angeles from October 11 through November 9. Air quality began to degrade on October 29. Source: IQAir

Why is air quality bad in Los Angeles

Los Angeles is no stranger to poor air quality.

As with any major metropolitan urban population, vehicle emissions and emissions from manufacturing contribute to poor air quality. Aside from particle pollution, vehicles also emit nitrogen oxides and volatile organic compounds (VOCs) – by themselves potent airborne pollutants. When sunlight reacts with those pollutants, ground-level ozone is created. And ozone is the primary component of smog.

Due to the warm climate, many sunny days, heavy traffic and industrialization, ozone and smog are ever-present regional health concerns.

The area’s geography plays a role in airborne pollution as well. Los Angeles, along with Salt Lake City, Denver, and Mexico City, are all known for experiencing temperature inversions. While temperature inversions are usually associated with winter weather, Los Angeles can suffer inversions during warm weather. The area’s valleys, basins, and surrounding mountains encourage ocean air – and the pollutants within them – to remain trapped at ground-level without an easy exit from the region by wind dispersal.

As pollution mixes with cool, trapped air, poor air quality can build up at the base of mountains. This is especially true in communities like Claremont and Fontana founded adjacent to the ranges.

Poor air quality in Eastern U.S.

Los Angeles wasn’t alone in experiencing poor air quality on November 10. Several cities in the eastern United States woke to air quality that also fell in the range of “Unhealthy for Sensitive Groups.” Poor air quality was particularly notable across Georgia, Illinois, Indiana, Iowa, and Ohio.

However, by 1:30 PM EST, much of the air quality in that part of the U.S. had returned to the “Good” or “Moderate” ranges.

Those cities included:

• Atlanta, Georgia
• Cincinnati, Ohio
• Columbus, Ohio
• Dayton, Ohio
• Des Moines, Iowa
• Indianapolis, Indiana
• Little Rock, Arkansas
• St. Louis, Missouri
• Wichita, Kansas

Pictured: Most cities in the Eastern U.S. experienced poor air quality falling within the ranges of “Moderate” to “Unhealthy for Sensitive Groups” on November 10. Source: IQAir

The takeaway

Poor air quality can affect anyone, no matter where they live. But there are air quality technology solutions available to make you aware of when air quality is poor and how to respond.

• Install indoor and outdoor air quality monitors so that you have total air awareness wherever you live.
• If you need to go outdoors, help keep your breathing space safe with an air pollution mask.
• Run an air purifier to help keep your indoor air clean.

• Download an air quality app for your smart phone to receive real-time information and have access to seven-day air quality air quality forecasting.