Bay Area faces harmful air quality due to Northern California, Oregon wildfires

Anthony Robledo, USA TODAY
Updated ·2 min read
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California's Bay Area is grappling with poor air quality caused by northern smoke coming into the region from wildfires in California and Oregon.

The Bay Area Air Quality Management District issued an air quality advisory for Tuesday and Wednesday as smoky and hazy skies are scattered in parts of the region.

Health officials advise anyone who smells smoke to stay indoors, make sure windows and doors are closed and use air conditioning units and car vent systems to prevent outside air from intruding.

The National Weather Service placed a fire-weather watch for parts of the interior North Bay effective Wednesday night through Thursday morning.

San Francisco was ranked as the most polluted major city in the world Tuesday evening by IQAir with no other U.S. locations on the top 30.

The Department of Emergency Management said San Francisco is in the red category for unhealthy air quality status, urging people, especially children and adults with respiratory issues, to limit outdoor activity.

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Air quality map for San Francisco, California

Oregon wildfire tracker

Northern California wildfire tracker

How does AQI work?

The AQI is measured on a scale of 0 to 500. The higher the AQI values, the greater the level of air pollution and health concern there is, according AirNow.gov. Conversely, the lower the AQI values, the air quality is more satisfactory and the health risks are lower.

The EPA determines the AQI values based on five major air pollutants which are regulated by the Clean Air Act:

  • Ground-level ozone

  • Particle pollution (also known as particulate matter)

  • Carbon monoxide

  • Sulfur dioxide

  • Nitrogen dioxide

According to the National Weather Service, ground-level ozone and airborne particles present the greatest health threat to humans.

The AQI is measured in six levels:

  • 0 to 50

  • 51 to 100

  • 101 to 150

  • 151 to 200

  • 201 to 300

  • 301 and higher

Each has a different "level of concern" in relation to the air pollutants. It ranges from "good" to "hazardous." This is based on how someone would be affected after breathing in polluted air for a few hours or days.

Each level is also assigned a corresponding color, with green representing "good" ranging to maroon representing "hazardous."

If the AQI values are at or are below 100, air quality is generally deemed as satisfactory. However, once the AQI goes above that value, it is unhealthy. This impacts certain sensitive groups of people first, but will affect everyone as the AQI values increase.

Contributing: Olivia Munson

This article originally appeared on USA TODAY: Dangerous air quality in Bay Area due to California, Oregon wildfires