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Air pollution levels in your neighborhood can vary several times in a day. What’s safe to do in the morning might not be safe in the afternoon, due to changes of weather and emission sources.

You can check hourly air quality estimates in your neighborhood, from Stockton to Bakersfield, and read clear directions on what activity is safe right now using the Real-time Air Advisory Network and Real-time Outdoor Activity Risk.

The tool is available at the San Joaquin Valley Air Pollution Control District’s website at, or through the ValleyAir app available for iPhone or Android.

You can also sign up to receive notifications of poor air quality via email, text or app.

As wildfire smoke blankets the San Joaquin Valley this fall, air quality can shift from good to very unhealthy within hours, depending on your location. Valley-wide air quality forecasts simply might not be accurate for your neighborhood.

The district’s Real-time Air Advisory Network updates hourly.

Air quality monitors aren’t located in every community and the closest monitor may be dozens of miles away. The localized real-time information is developed using GIS and common weather patterns, according to Valley Air. It’s meant to guide your decision about whether it is safe to go on a jog or let your kids play outside.

You can also look at for more neighborhood-level information from additional air quality monitors. That map pulls data from the official air quality monitors, as well as a network of low-cost air quality monitors placed in disadvantaged communities.

Sometimes, particles from wildfire smoke or ash are too large to be measured by monitors, which is why Valley Air staff say if you can see or smell smoke, you should remain indoors.

Exercising outdoors in poor air quality increases your risk

Valley Air developed the Real-time Outdoor Activity Risk Guidelines 10 years ago, in part, in response to scientific findings that exercise magnifies exposure to ozone and PM 2.5.

That’s because the amount of air you inhale increases when exercising, as you breathe faster and more deeply, and pollution with fine particulate matter is more likely to enter deep tissue in the lungs and bloodstream, according to Valley Air.

“A 2003 study found that during moderate exercise, 80% of inhaled ultrafine particles were deposited in the lungs, compared with 60% lung retention while at rest,” according to Real-time Outdoor Activity Risk. “However, as shown below in Figure 1, because the volume of air exchanged per minute increases substantially during exercise, overall UFP deposition increased by 450%.”

Heart and lung disease can be worsened by exposure to fine particulate matter like PM 2.5, which has been documented by increased emergency room visits during bad air events.

How to use the air quality activity risk chart

The Real-time Outdoor Activity Risk site shows charts of ozone and PM 2.5 levels in your area, along with a guideline for health-protective activities. New data points are updated about 18 minutes after each hour, according to a guide to the system.

If you sign up to receive air quality alerts, you will be notified of the estimated air quality level in your location, whenever the air quality reaches unsafe levels or improves.

Here is what the levels mean:

Level 1: Outdoor activity OK for all

Level 2: Sensitive individuals should consider reducing prolonged and/or vigorous outdoor activities.

Level 3: Sensitive individuals should exercise indoors or avoid vigorous activities.

Level 4: Sensitive individuals should exercise indoors. Everyone should avoid prolonged or vigorous outdoor activities.

Level 5: Everyone should avoid outdoor activity.

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