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Air Pollution Linked to Higher Suicide Risk: PM2.5, PM10 and Nitrogen Dioxide Show Strongest Associations, Study Finds

Exposure to certain air pollutants may be associated with a higher risk of suicidal thoughts, suicide attempts and death by suicide, according to a new systematic review and meta-analysis published in the Journal of Epidemiology and Community Health.

The review examined 45 studies investigating whether environmental exposures—including air, water, noise and light pollution—were associated with suicide-related outcomes. The clearest evidence involved fine particulate matter, particularly PM2.5 and PM10, as well as nitrogen dioxide (NO2).

The research, led by Sophie Marie Jones and colleagues, found statistically significant associations between short-term exposure to PM2.5 and PM10 and suicide-related outcomes. Long-term exposure to PM2.5 and NO2 was also significantly associated with these outcomes.

However, the researchers emphasised the complexity of suicide risk, and independent experts have cautioned that the findings do not establish that Air Pollution directly causes suicidal behaviour.

What Did The New Study Find?

The researchers searched databases for relevant studies published in English between January 2010 and April 2024. From an initial group of 287 studies assessed in full text, 45 studies met the eligibility criteria.

Of these:

• 33 studies examined deaths by suicide.
• 7 studies examined suicidal thoughts or ideation.
• 5 studies examined suicide attempts.

Air pollution dominated the available evidence. Thirty-eight of the 45 studies investigated air pollution, while three examined water pollution, three investigated noise pollution and one examined light pollution. Twenty-nine studies contributed to pooled quantitative analyses, while 16 were included in a narrative review. 1

PM2.5 And PM10 Were Among The Main Pollutants Linked To Risk

Fine particulate matter emerged as one of the most consistently studied environmental exposures.

PM2.5 refers to airborne particles with a diameter of 2.5 micrometres or smaller. Because these particles are extremely small, they can penetrate deep into the respiratory system and have been associated with a wide range of health effects.

PM10 refers to particulate matter measuring up to 10 micrometres in diameter. These particles can also enter the respiratory tract and are an important component of air pollution in many urban and industrial environments.

The pooled analysis found statistically significant associations between short-term exposure to PM2.5 and PM10 and suicide-related outcomes. Long-term exposure to PM2.5 was also significantly associated with these outcomes. 2

Long-Term Nitrogen Dioxide Exposure Was Also Associated With Risk

Nitrogen dioxide, or NO2, was another pollutant for which the review found a statistically significant association.

Long-term exposure to NO2 was associated with increased risk of death by suicide, suicide attempts and suicidal ideation in the pooled evidence.

NO2 is commonly produced through combustion processes, including emissions from road traffic and the burning of fossil fuels. Consequently, exposure can be higher in areas with substantial traffic or other combustion-related sources.

The researchers’ findings add suicide-related outcomes to the wider body of research investigating potential links between air pollution and neurological and mental health outcomes.

What About Ozone And Sulphur Dioxide?

The review also examined other air pollutants, including sulphur dioxide (SO2) and ozone (O3).

Positive associations with suicide-related outcomes were observed for these pollutants, but the evidence did not reach statistical significance in the available analyses.

This distinction is important. A positive association in the available studies does not necessarily mean that researchers have established a reliable relationship. Statistical significance and consistency across studies are important when evaluating the strength of evidence.

Noise And Light Pollution Need More Research

The researchers also considered environmental exposures beyond conventional air pollution.

Some evidence suggested possible associations between noise pollution and suicide-related outcomes, but the evidence was not statistically conclusive.

The evidence concerning water pollution and light pollution was even more limited. The number of available studies and differences in how outcomes and exposures were measured prevented meaningful pooled quantitative analysis.

As a result, the researchers described the evidence for these environmental exposures as inconclusive.

How Could Air Pollution Potentially Affect Mental Health?

The biological mechanisms linking pollution exposure with suicide-related outcomes remain uncertain. The researchers point to several possible pathways that warrant further investigation.

Air pollutants such as PM2.5, PM10 and NO2 have been associated in previous research with inflammation, oxidative stress and effects on the nervous system. These processes could potentially influence brain function, mood regulation and the body’s response to stress.

Pollution may also interact with other biological systems. For example, inflammation and changes in vascular or neurological function have been investigated as possible pathways connecting environmental exposures with mental health outcomes.

For noise and artificial light, researchers have proposed different mechanisms. Persistent noise and excessive nighttime light may interfere with sleep and circadian rhythms, which can affect stress and mental wellbeing.

These mechanisms remain hypotheses in the context of the current review and should not be interpreted as proof of a direct biological pathway from pollution exposure to suicide.

Pollution Is Only One Part Of A Complex Suicide Risk Profile

Suicide and suicidal behaviour are complex outcomes influenced by multiple interacting factors.

These can include mental health conditions, previous suicidal behaviour, substance use, chronic illness, trauma, social circumstances, financial stress, access to healthcare and many other individual and environmental factors.

This complexity makes it particularly important not to interpret the new findings as suggesting that exposure to polluted air independently determines an individual’s suicide risk.

One independent expert, Rosie Cornish of the University of Bristol, noted that factors associated with higher pollution exposure may also be associated with suicide risk. These include socioeconomic deprivation, availability of green space, housing quality and lifestyle differences between urban and rural populations. 3

Why The Study Cannot Prove That Pollution Causes Suicide

The distinction between association and causation is central to interpreting this research.

The review combined evidence from observational studies conducted in different populations and using different methodologies. Although statistical adjustments can account for some potential confounding factors, they cannot necessarily eliminate every source of bias.

For example, people living in areas with higher air pollution may differ from people living in cleaner environments in many other ways. Differences in income, housing, occupation, healthcare access, neighbourhood characteristics, urbanisation and social stress could potentially influence both pollution exposure and mental health.

The researchers themselves acknowledged limitations including the relatively small number of studies available for some exposures and considerable differences in study design and methodology. 4

Why This Research Still Matters

Despite these limitations, the findings are important because environmental exposures are potentially modifiable at a population level.

Unlike many individual risk factors for suicide, air pollution can be influenced by policies and infrastructure. Cleaner transportation, reduced industrial emissions, improved urban planning and stronger air-quality standards can reduce population exposure to harmful pollutants.

The authors therefore argue that environmental health should be considered alongside mental health in public-health planning.

Their conclusion is not that pollution reduction alone will prevent suicide. Rather, they suggest that reducing potentially harmful environmental exposures could become one component of broader suicide-prevention and population-health strategies. 5

What The Findings Mean For People Living In Polluted Areas

The study does not provide an individual risk calculator and cannot determine how much a particular person’s suicide risk changes when pollution levels rise.

For individuals, the findings should therefore be interpreted as part of the larger evidence on air pollution and health rather than as a reason to assume that pollution exposure is responsible for changes in mood or suicidal thoughts.

People experiencing suicidal thoughts or feeling at immediate risk should seek urgent support from a mental-health professional, emergency medical service or trusted person rather than attempting to manage the situation by focusing on environmental exposure alone.

What Researchers Want To Investigate Next

More research is needed to determine whether the observed relationships are causal and to understand how different pollutants may affect different suicide-related outcomes.

Future studies could benefit from more consistent exposure measurements, better adjustment for socioeconomic and psychological factors, longer follow-up periods and research across different geographic populations.

Researchers also need to determine whether interventions that reduce pollution exposure actually lead to measurable reductions in suicidal behaviour. That would provide stronger evidence for a causal relationship than observational associations alone.

Key Takeaways

• A systematic review and meta-analysis examined 45 studies on environmental pollution and suicide-related outcomes.
• Thirty-eight studies investigated air pollution, making it the most extensively studied environmental exposure.
• Short-term exposure to PM2.5 and PM10 was significantly associated with suicide-related outcomes.
• Long-term exposure to PM2.5 and NO2 was also significantly associated with suicide-related outcomes.
• Positive associations were observed for SO2, ozone and noise pollution, but these findings were not statistically conclusive.
• Evidence concerning water and light pollution was insufficient or inconsistent.
• The study shows associations rather than proof of causation.
• Socioeconomic conditions, housing, green space, lifestyle and other factors may influence both pollution exposure and suicide risk.

Bottom Line

A new systematic review suggests that exposure to certain air pollutants, particularly PM2.5, PM10 and nitrogen dioxide, is associated with higher rates of suicide-related outcomes. The findings are significant because they suggest that environmental conditions may be one of several modifiable factors relevant to population mental health.

However, the research does not establish that air pollution directly causes suicidal thoughts, suicide attempts or suicide deaths. Suicide risk is shaped by a complex combination of biological, psychological and social factors, and researchers say more rigorous studies are needed to determine whether reducing pollution exposure can directly reduce suicide risk.

The study was published in the Journal of Epidemiology and Community Health with the DOI 10.1136/jech-2025-225491. 6