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It’s well-known that smoke and car emissions can be dangerous for our lungs, but emerging research shows that pollution can also be dangerous for our brains.

The ways in which environmental factors like air pollution contribute to dementia risk isn’t fully understood. However, researchers are continuing to make strides in learning about this complex issue.

Air Pollution and the Brain


Studies have found associations between exposure to air pollution and increased brain inflammation. While inflammation is normally a protective process against foreign materials that enter the body, too much inflammation can damage cells in the brain. Increased inflammation may also worsen the hallmark plaques and tangles in the brain associated with Alzheimer’s disease.

Brain Health Registry Newsletter – March 2022, UCSF Brain Health RegistryAir pollutant particles fewer than 2.5 micrometers in diameter, known as PM2.5, are particularly dangerous. Their miniscule size (they are about 30 times smaller than the width of the average human hair), allows them to slip past the body’s natural defenses, and infiltrate the lungs and blood.

PM2.5 can cause difficulty breathing and worsening heart health. And now, researchers are examining how these pollutants sabotage the brain. Exposure to air pollution, even at low levels, is linked with worse performance on brain tests and smaller brain volume.

The impact of cigarette smoke on brain health is another area of concern, and there is evidence that smoking can heighten a person’s risk of developing dementia.

Brain Health Registry Newsletter – March 2022, UCSF Brain Health RegistryInhaling tobacco smoke has been linked to oxidative stress. Oxidative stress happens when unstable molecules in your body overwhelm protective substances called antioxidants, causing damage to your cells. Oxidative stress itself has been tied to the development and progression of dementia.

Even exposure to secondhand smoke can have negative consequences. A study tracking hundreds of participants over decades found that ongoing childhood exposure to secondhand cigarette smoke is associated with increased risk for dementia and Alzheimer’s disease.

What can you do to protect yourself and stay healthy?


  1. Pay attention to the Air Quality Index (AQI), a measure of air pollution that you can access here: or on many weather apps. If air quality is unhealthy, consider reducing the amount of time you spend outside.
  2. Try an alternative to driving, when it’s possible! Walking or biking (when air quality is good), and public transportation are great options. If you do need to drive and air quality is poor, avoiding peak commute hours can help reduce exposure to smog.
  3. If you’re planning to exercise and the air quality is poor, staying active indoors, or choosing a less intense activity (walking, rather than jogging) can be helpful.

Brain Health Registry Newsletter – March 2022, UCSF Brain Health Registry

Thank you to our participants for all the work you do to help us understand more about the complex issues that impact brain health!