A growing number of studies are associating poor air quality with mental health issues, notably anxiety. Studies link exposure to fine particulate matter (PM2.5) and nitrogen dioxide (NO2) to elevated anxiety levels, thereby posing significant public health implications.

The American Journal of Epidemiology published a 2022 study that found exposure to PM2.5 exacerbated anxiety symptoms in individuals with pre-existing anxiety disorders. This finding is consistent with a 2019 study conducted in London and published in Environmental Health Perspectives, which examined over 6,000 persons and discovered that exposure to NO2 and PM2.5 was associated with greater anxiety symptoms in the general population.

The processes behind these connections are complex. According to research, exposure to PM2.5 causes systemic inflammation, which affects neurotransmitter modulation and brain areas associated with anxiety. Another side effect of pollution exposure is oxidative stress, which can damage brain cells and increase the risk of anxiety. A 2018 study published in Psychological Medicine on over 1,000 American adults found that PM2.5 enhanced symptoms of anxiety and sadness, demonstrating how air pollution's neuroinflammatory effects contribute to mental health issues.

Adding to this issue, the World Health Organization reports that nine out of 10 people worldwide breathe dirty air, which contributes to 7 million early deaths each year and an estimated 120 million anxiety cases. Similarly, data from the United States Environmental Protection Agency show that places with poor air quality had higher rates of anxiety and depression, highlighting the widespread impact of pollution on mental health.

Anxiety disorders are 1.5 times more common in locations with PM2.5 levels above 20 μg/m2 compared to those with levels under 10 μg/m2, according to quantitative research. Anxiety symptoms increase by 1.2% for every 10 μg/m³ increase in PM2.5 levels. A 2024 study in Psychological Medicine focused on Ireland, where PM2.5 concentrations are relatively low, but nevertheless identified a significant link between PM2.5 exposure and anxiety, highlighting the potential influence of even lower pollution levels on mental health.

However, studies indicate that exposure to natural areas may attenuate these impacts. Nature published a study that looked at 409,556 participants from the UK Biobank over nearly 12 years and found that being near residential greenery was related to lower rates of anxiety and sadness. The study indicated that green spaces mitigate the effects of pollution, with decreases in PM2.5, NO2, and other pollutants contributing significantly to mental health benefits.

The researchers emphasised the importance of environmental elements in mental health interventions by highlighting the link between long-term exposure to residential greenness and a decreased risk of incident depression and anxiety.

As the worldwide disease burden from mental health issues increases, our findings highlight the importance of measures that reduce air pollution and promote urban greenery. Preventive actions and enhanced knowledge are required to address the mental health consequences of environmental exposures, particularly as urbanization and industrial activity continue to raise air pollution levels.