• Burning fossil fuels – coal, gas, and oil – to generate electricity
• Emissions from industry, particularly the manufacturing of products in large factories
• Extracting raw materials for goods
• Transportation, including exhaust from motor vehicles
• Bad agricultural practices, like factory farming of animals and the overuse of fertilizers

• The inherent harmful nature of the pollutant
• Its concentration in the air
• How it reacts with other chemicals or elements in the air
• The overall health and vulnerability of the humans and other living organisms who are exposed
• The duration of the exposure

Emissions from burning fossil fuels trigger additional reactions that form more and new combinations of pollutants.

Gases: Burning fossil fuels releases, among other gases: nitrogen dioxide, sulfur dioxide, carbon dioxide (CO2), and methane.

How it enters our bodies:

• Our lungs: The image below shows what happens when we breathe in particulate matter of different sizes. 
  • Large particles are trapped by the body’s natural defenses and are usually stopped in the upper respiratory tract.Fine particulate matter of less than 2.5 microns (µ), also known as PM2.5, reaches the lower respiratory tract.Inhalable particles (less than 1 µ) reach deep into the tissue of the lungs.
  • Ultrafine particulate matter (<0.1 µ) is drawn deep into the lungs, where it can travel across lung tissue and into the blood stream. It can then make its way throughout the entire body.

• The Nose: Ultrafine particulate matter can also travel through the nose and go directly into the brain.

• Particles can make their way to the brain and cause harm directly (from the lungs to the brain via the bloodstream, or from the nose to the brain)
• Or damage it indirectly through inflammation. Our body reacts to particulate matter as it would to any foreign invader: calling upon the immune system to attack it. This creates inflammation, which helps destroy or impede the invader, but has, itself, problematic health consequences, especially if it becomes chronic. Chronic inflammation in any part(s) of the body (such as the lungs, the brain, our respiratory or cardiovascular systems) makes us more vulnerable to many diseases and conditions, including cancers. Though physical harms always carry a secondary emotional toll, less well-known are the direct impacts to our mental health.

• Short-term increases in air pollution is linked to more diagnosed cases of depression and increases in daily hospital admissions for depression and anxiety.
• Same day increases in PM2.5 is linked to more emergency department visits related to mental health.
• On days with poorer air quality, the risk of suicide is higher over a three-day period. Death from suicide attempts is higher on days with worse air pollution.

• Long-term exposure to multiple air pollutants is linked to higher risk of depression and anxiety, bipolar disorder, schizophrenia, and attention deficit hyperactivity disorder (ADHD).
• Higher levels of air pollution (NO2, NOx, and PM2.5) is linked to increased odds of psychotic episodes during adolescence.

• Higher levels of PM2.5 pollution is linked to more cases of Alzheimer’s disease, vascular dementia, and Parkinson’s disease.

• Air pollution affects our ability to think, and is linked to worse performance in verbal and math tests and other measures of memory and cognition.

Duration of exposure:

• Acute: Short-term exposure most often occurs in association with traumatic events, such as wildfires or toxic emissions released in accidents like refinery failures, and lasts anywhere from hours to weeks. Acute exposures can be extremely damaging, even life-threatening. These events can have direct mental health impacts, as well as indirect impacts from the air pollution released.

• Chronic: Long-term exposure occurs in the face of chronic conditions, such as the persistently bad air quality associated with urban pollution from motor vehicles and emissions from fossil fuel infrastructure. Chronic exposure to bad air is a leading cause of illness and early death worldwide.

• Prenatal development: Exposure to air pollution during pregnancy disrupts fetal brain development, increases risk of preterm birth and low birthweight, increases risk of autism spectrum disorder in children, and impaired behavioural development in children.
• Children: Early life exposure to air pollution is linked to lower IQ scores and difficulties with attention and hyperactivity, which affect schoolwork and performance. These cognitive impacts can reverberate over their entire life – affecting social relationships, academic success, career possibilities, and economic status. Children are more vulnerable than adults due to their developing brains, respiratory, and immune systems, and due to the fact that they breathe in more air per kilogram of body weight. One example: Researchers have found markers of Alzheimer’s disease in the brains of children living in highly polluted areas of Mexico city.
• The elderly: are less resilient due to their age and associated medical conditions, and the cumulative toll of exposure to air pollution. Air pollution increases the risk of dementias and degenerative illnesses.
  

• Poor communities: People in these communities are more likely to live, play, and go to school near areas of high exposure to pollutants, like near freeways, industrial parks, or oil refineries. They also may not have had access to good health care and nutrition that sets them up for healthy bodies later in life. For its potential for lifelong consequences, exposure to air pollution can easily be considered a social injustice of the highest order.
• Racial and ethnic minorities: In the United States, communities of color, particularly Black and Hispanic people, breathe in disproportionately more particulate matter air pollution than non-Hispanic whites.
• Low- and middle-income countries: Some 80% of people breathing harmful air pollution live in low- and middle-income countries.

Ultra-fine particulate matter pollution: Ultrafine particles, measuring less than 0.1 µ, can be more damaging than PM2.5 because their smaller size allows them to penetrate tissues. By number, they are the most abundant of all the particulate matter pollutants. Yet we don’t know how much ultrafine particulate matter is in the air because it’s not measured and there are no regulations for safe exposure limits. Even PM2.5 is not widely measured: only one-third of all counties in the United States measure particulate pollution.

Training and education: We need training and education for mental health practitioners and allied professionals to be effective advocates for science-based legislation and regulations that protect the health of the public. 

• Ending the need for fossil fuels by transitioning to renewable energy at home and in the workplace.
• Applying pressure to block the permits that allow companies to drill, extract, transport and refine fossil fuels, and to prevent building the infrastructure that ensures their use for years to come.

• Measure and report air quality in all communities; not just in major metropolitan areas, which are currently covered, but in rural areas, too, and areas near sources of pollution.
• Expand public alerts to warn of dangerously poor air quality.
• Assess the health harms from exposure to multiple toxic substances at the same time. Air pollution limits are currently based on exposure to specific levels of a single substance, but we take in a many different substances in each breath.
• Measure very small particles (nano or ultrafine), which are not currently regulated, and only measured in experiments.

• One example: In the United States, the Environmental Protection (EPA) agency develops policies to protect public health by reducing air pollution. It is under the influence of the presidential administration. During 2016-2020, the federal government rolled back more than 100 rules and regulations and substantially cut EPA funding. Many experienced scientists left the EPA. Efforts to restore and improve the agency have since been underway.

• American Lung Association
• Clean Air Fund
• Clean Air in London
• Clean Air Partnership
• Clean Air Society of Australia and New Zealand
• Clean Air Task Force
• Coalition for Clean Air
• Moms Clean Air Force
• Mothers & Others for Clean Air
• Physicians for Social Responsibility
• The Medical Society Consortium on Climate and Health

December 19, 2023

Authors: Lise van Susteren, M.D., and Robin Cooper, M.D.

Editor: Colleen Rollins, Ph.D.