Air pollution has been linked to poor brain development, as well as a higher risk of dementia and stroke. A link has also been established between exposure to air pollution and depression as well as higher suicide rates.

The subject received attention at the second WHO’s global conference on air pollution and health in Cartagena, Colombia this week.

“Air pollution is increasing the risk of new mental health problems and worsening mental health in people with pre-existing mental health problems,” Alessandro Massazza, policy and advocacy advisor at United for Global Mental Health, a global non-profit that focuses on mental health advocacy, told Health Policy Watch.

The societal costs of mental disorders due to air pollution, climate-related hazards, and inadequate access to green space are estimated to reach around $47 billion annually by 2030 — a significant portion of the massive $8.1 trillion annual price tag for the overall health impacts of air pollution.

Around 99% of the world’s population breathes air that does not meet the air quality standard set by the World Health Organization (WHO). Exposure to high levels of air pollution claim over eight million lives worldwide every year.

“It’s not just that we’re all exposed to air pollution, not just that it affects everybody, but it affects non-communicable diseases (NCDs),” said Mark Miller of the World Heart Federation. He pointed out that NCDs are already the world’s biggest killer, responsible for 74% of all deaths annually.

“Tackling NCDs has to be one of the greater priorities for the world, no matter what sector of life that you’re in,” Miller said.

 How air pollutants reach the brain 

The exact pathway through which air pollutants reach the brain is now becoming clearer.

“The pollutants from the air enter our brains through two mechanisms. One is directly from our nasal cavities up to our olfactory bulb, but also from systemic inflammation,” Burcin Ikiz, neuroscientist and director at EcoNeuro, a research and consulting company working in global health, told Health Policy Watch.

“When the lungs get inflamed due to the pollutants in the air, those send inflammatory responses into the bloodstream, and through the bloodstream reaches the blood-brain barrier,” Ikiz explained. “Normally, our blood-brain barrier should be our protective layer that protects the brain from any outside pollutants or harmful substances. But it’s not perfect. It’s a leaky system.”

Children, the elderly population, and those living with other neurological conditions such as multiple sclerosis and Alzheimer’s are especially vulnerable, she added.

“We know less about what may be driving this association between air pollution but it’s likely to be the result of a mixture of biological (e.g., inflammation), social (e.g., not being able to go outside or socialize outdoors), and psychological (e.g., impact on mood, cognition, or sleep) mechanisms,” Massazza said.

Air pollution is also linked to poor brain development in children, starting in utero.

“Looking at pregnant women and their babies that are still in the womb being exposed to abortion, we see their brain structures changing. We see them having…after they were born, having their developmental delays and lower IQs and so on,” Ikiz said.

Adolescence has been identified as another crucial period during which many mental health disorders first develop.

The risk of strokes in which the blood flow to the brain is reduced, also increases due to air pollution, studies have found. Air pollution is also among the 14 modifiable risk factors for dementia.

Air pollution has also been found in several studies to be associated with depression on both short and long-term time scales, drawing attention to its impact on poor mental health outcomes.

Need for evidence-based interventions

The additional societal costs of these mental health disorders influenced by environmental factors are expected to rise further, according to an estimate that pegs it at US $537 billion by 2050, relative to the baseline scenario in which the environmental factors remain at 2020 levels.

“People with chronic and severe mental health problems often live with co-morbid non-communicable diseases such as respiratory or cardiovascular conditions, which can further increase their vulnerability to the physical health impacts of air pollution,” Massazza.

Limited research on interventions shows that significant mental health gains are seen when air pollution is reduced. One study from China demonstrates how the country’s clean air policies are not only contributing to large reductions in air pollution but have also been deemed responsible for preventing 46,000 suicides over just five years.

Significant data gaps remain, with only a handful of studies on air pollution’s impact on mental health coming from low- and middle-income countries. Experts say efforts are needed to improve research in understanding the pathways between environmental stressors and mental illness.

In September, the UN headquarters in New York will host a high-level meeting on NCDs and mental health, where the impact of climate change on NCDs and mental health is likely to be discussed.

“Clean air policies are mental health policies. From reduced energy poverty and more access to green spaces to increased physical activity resulting from active modes of transport, actions aimed at reducing air pollution have considerable potential co-benefits for mental health,” Massazza said.

Sophia Samantaroy contributed reporting. 

Image Credits: Unsplash, By arrangement, Elaine Fletcher, Air quality and mental health: evidence, challenges and future directions.