Summary: Yes, new research indicates exposure to elevated levels of air pollution is associated with increased risk factors for various types of mental illness, with different risk profiles for different demographic groups.
Key Points:
- Previous research establishes clear causal relationships between exposure to air pollution and various serious chronic conditions, including lung cancer
- Evidence suggests connections between exposure to air pollution and neurological and cognitive deficits
- New findings show structural and functional changes in brain areas associated with emotion regulation associated with exposure to air pollution
The Environment and Mental Health
Discussions about environmental influences one mental health typically focus on things like growing up in a dysfunctional family, experiencing trauma, or exposure to overwhelming, toxic stress.
Over the past few years, several studies have identified another environmental factor that may have a powerful impact: the environment itself. To be more specific, studies link poor air quality with higher rates of anxiety, depression, and several other mental health disorders.
Defining Air Pollution
To establish a connection between air pollution and health problems, researchers first define what qualifies as polluted air. According to the World Health Organization (WHO), the airborne toxins with the greatest impact on public health include:
- Particulate matter (PM)
- Carbon monoxide (CO)
- Ozone (O3)
- Nitrogen dioxide (NO2)
- Sulphur dioxide (SO2)
Fine particulate matter (PM2.5), which experts define as aerosol particles with a maximum diameter of 2.5 microns, appear to pose the largest risk.
The WHO reported that the strongest evidence about the health effects of air pollution currently involves:
- Ischemic heart disease
- Chronic obstructive pulmonary disease
- Lung cancer
- Pneumonia
- Stroke
The WHO also noted that suggestive evidence links polluted air with:
- Adverse pregnancy outcomes
- Diabetes
- Other types of cancer
- Neurological diseases
- Cognitive impairments
To monitor air quality, the U.S. employs both ground-based instruments and satellites. The Environmental Protection Agency (EPA) assigns a numerical value to the amount of each pollutant type in the air, then adds those values to determine the Air Quality Index (AQI):
- Good (0-50)
- Moderate (51-100)
- Unhealthy for Sensitive Groups (101-150)
- Unhealthy (151-200)
- Very Unhealthy (201-300)
- Hazardous (301 and above)
The AQI guidance focuses on potential physical effects, primarily heart and lung damage. If future research confirms recently revealed information about air pollution and mental health, EPA leadership can revise the guidance accordingly.
Linking Air Pollution With Mental Illness
In July 2023, the open access, peer-reviewed journal BJPsych Open published a narrative review of several prior studies on air quality and mental health. Evidence suggests that exposure to outdoor air pollutants may be risk factors for:
- Anxiety disorders
- Bipolar disorder
- Depressive disorders
- Personality disorders
- Schizophrenia
Additional findings, specific to children and adolescents, included:
- Exposure to air pollution linked with cognitive impairments at age 5.
- Prenatal exposure to nitrogen dioxide and nitrogen oxides may increase risk of mental illness by 29%-74%.
- Psychotic episodes were “significantly more common” among participants with the greatest annual exposure to nitrogen dioxide and PM2.5.
- Adolescents in the top quartile of PM2.5 exposure scored higher than all other participants on general psychopathology tests.
For adults, the review team reported:
- Pollution exposure associated with elevated rates of bipolar disorder
- 27% increase in bipolar disorder cases in the parts of the U.S. with the worst air quality.
- Greater prevalence of depression, schizophrenia, and personality disorders among participants with the highest level of pollution exposure (Demark).
- Exposure to PM2.5 and PM10 (slightly larger particulate matter) associated with anxiety, bipolar disorder, depression, psychosis, and suicidality.
- Exposure to PM2.5 for six months or longer strongly associated with increased depression risk.
How Does Air Pollution Affect Mental Health?
When someone breathes contaminated air, particulate matter and other pollutants enter their lungs. Especially small contaminants, such as PM2.5 and ultrafine particulate matter, or PM0.1, can easily pass from the lungs to the bloodstream and organs, tissues, and cells throughout the body.
Fine and ultrafine particulate matter may also cross the blood-brain barrier, which directly impacts cognition and mental health.
Clara G. Zundel, the lead author of a study on air pollution, anxiety, and depression, reported that 95 percent of studies identify “significant physical and functional changes within the emotion-regulation brain regions” in people exposed to elevated levels of air pollution.
Most studies, Zundel wrote, link air pollution with brain inflammations and impaired neurotransmitter regulation.
Air Pollution, Mental Illness, and the Human Brain: Areas Impacted
- Amygdala: A small area in the midbrain involved with learning, memory, emotions, and communication
- Hippocampus: A region just below the amygdala that plays a significant role in memory, learning, and spatial cognition
- Prefrontal cortex: A large region near the front of the brain that regulates executive functions, attention, memory, and language processing
Zundel’s findings align with a June 2023 study from China, which determined that air pollution may be a source of both neuroinflammation and oxidative stress throughout the central nervous system.
These effects, the Chinese researchers reported, can cause both structural and functional brain abnormalities, such as:
- Decreased gray-matter volume in the Cortico-Striato-Thalamo-Cortical neurocircuitry, a structure that controls reward and habit formation.
- White matter hyperintensities (brain lesions) in the prefrontal lobe.
Zundel’s study indicates relatively few studies have investigated the mechanisms by which air pollutants impair brain functioning in humans. Most research in this area has been conducted in the past 10 years, primarily on animals.
The relative dearth of research on the mental and cognitive effects of air pollution on toddlers, children, and adolescents is a primary concern, according to Zundel. Brains in the process of developing may be at elevated risk of pollution-related damage.
The Chinese researchers expressed a similar concern. Though their study focused on the link between air pollution and elevated levels of depression and suicidality among adolescents, they highlight a need for additional research in this area:
“There is concern that children and adolescents are especially vulnerable in view of their ongoing brain development. … Because young people not only spend more time on outdoor activities but also breathe faster and live closer to the ground, they are more likely to experience greater impacts of exposure to air pollution than adults.”
How Can People Protect Themselves?
From a public health standpoint, understanding that air pollution is a risk factor for mental illnesses is valuable. Experts can identify communities at elevated risk and healthcare providers can allocate resources to places in greatest need.
These steps can mitigate the long-term damage of pollution-related mental health challenges. But they don’t address the root cause: the pollution itself.
The WHO, which describes air pollution as “the biggest global health threat in the current century,” identifies a range of potential solutions.
How We Can Improve Air Quality Worldwide
- More efficient technologies to reduce smokestack emissions
- Improvements in the management of urban and agricultural waste
- Prioritizing rapid urban transport, walking, and bike riding in cities
- Shifting to low-emission vehicles and fuel sources
- Increased use of solar, wind, and other renewable, combustion-free power sources
The good news is that solutions exist. The not-so-good news is that national and local leaders have been slow to mandate these solutions. As a result, an estimated 99 percent of the global population lives in areas that fail to meet WHO air quality standards.
Individuals and families cannot implement widespread changes to improve air quality, but everyone can take steps to protect themselves and their loved ones.
Here’s what the American Lung Association (ALA) advises.
10 Tips to Improve Air Quality: Individuals and Families
- Monitor the AQI in your area and adjust your plans as needed.
- Don’t exercise outside when the AQI is at an unhealthy level.
- Minimize your energy use at home.
- Pay attention to the air quality within your home.
- Encourage your local schools to limit student exposure to bus emissions.
- When possible, walk, bike, or carpool.
- Never burn wood, paper, or other trash.
- Prepare for natural events or disasters that cam reduce air quality, such as wildfires, extreme heat, or extreme cold.
- Replace gas-powered lawn care equipment with hand-powered or electric devices.
- Encourage elected leaders to take a stronger stand against pollution-generating policies and practices.
Also, if you or someone that you care about develops a mental illness, don’t ignore the warning signs or delay getting help. With proper care, most people can learn to manage their symptoms and improve their quality of life.
To learn more about treatment options for complex mental illnesses in southern California, visit our Contact page or call Crownview Psychiatric Institute today. A member of our team will be happy to answer your questions and help you determine if our center is the ideal place for yourself or your loved one.
Gianna Melendez
Jodie Dahl, CpHT