The puzzling link between air pollution and suicide

The puzzling link between air pollution and suicide  BBC

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Sep 10, 2023 - 17:00
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The puzzling link between air pollution and suicide

Could cleaner air reduce the risk of suicide?

BBC Future looks at the evidence.

Introduction

How do you prevent people from taking their own lives? There are no easy answers, but one thing is clear: suicide is a major public health problem. More than 700,000 people kill themselves worldwide every year, according to the World Health Organization (WHO).

Every year, on 10 September 2023, the WHO marks World Suicide Prevention Day, aiming to focus attention on the scale of the death toll and its causes.

People in the US might be particularly troubled to learn that the suicides there have increased by around 40% over the past two decades. Last year, almost 50,000 people in the US took their own life – one death every 11 minutes – and the nation now has one of the highest rates of wealthy, developed countries. (For comparison, the UK suicide rate is around 25% lower than that of the US).

Preventing these deaths is a complex problem, and there are no silver bullets. However, research in recent years has suggested that there are interventions that politicians and public health officials can make – and they extend beyond established responses like investing in mental healthcare provision, or reducing loneliness.

The Link Between Air Pollution and Suicide

Now a new frontier of potentially preventative research is emerging that might, at first, seem unrelated: improving air quality. Over the past few years, various studies have identified associations between raised levels of air pollution and suicide risk. What should we make of this evidence?

Research Findings

In 2021, Seulkee Heo and colleagues at Yale University reviewed 18 studies that explored the association between air pollution and suicide. They found significant associations with increased suicide risk for particulate matter – the stuff emitted by wood burners, wildfires or construction dust – as well as the gases sulphur dioxide and nitrogen dioxide emitted by industrial facilities, fossil-fuel burning and some vehicles.

Possible Biological Mechanism

It’s not known for certain, but researchers have their suspicions. Air pollution entering the lungs can inhibit the flow of oxygen into the bloodstream, and then the brain. Other studies unrelated to suicide have shown that this can lead to cognitive impairments, among other effects.

In the case of suicide risk, researchers suspect that pollution can lead to inflammation in the brain, deficits in serotonin, and disrupt stress response pathways, which can in turn make depressive behaviors and impulsivity more likely. It’s possible, then, that bad air can affect how people think: leading to a brain fog that could encourage suicidal ideation without them realizing.

Caveats and Uncertainties

The studies reviewed by the teams at Yale and UCL looked at associations – comparing statistics – rather than fully unpicking into the mechanisms and factors that could cause pollution to affect the brain.

As with any research that examines correlations, there could well be other environmental influences at play. For example, in their analysis Heo and colleagues also reviewed studies that found a correlation between suicide and high temperature, finding there is also a significant association between hot days and increased suicide rates. All else being equal, a 7C increase in temperature leads to a 9% higher suicide rate, explains co-author Michelle Bell of Yale. “A larger increase in heat would have a larger risk,” she says.

Implications for Suicide Prevention

Past experience, from the likes of Denmark and elsewhere, shows that successfully reducing suicide rates requires multiple interventions, at a local and national scale. Air pollution increases the likelihood of suicide by a few percentage points, but eliminating it won’t solve the problem.

However, if the link with suicide is confirmed and elaborated by more research, it would provide all the more reason for public warnings and awareness campaigns when bad air is elevated. With climate change, desertification, droughts, and wildfires become more likely, all of which are known to increase air pollution. These problems will be bad enough, and if we factor in the additional risk of people killing themselves too, then tackling them will require extra urgency.

Conclusion

Breathing air pollution is bad for us in many other ways – that science is well-established. The potential link between air pollution and suicide risk adds another dimension to the public health implications of poor air quality. While more research is needed to fully understand the mechanisms and factors involved, it is clear that addressing air pollution should be a priority in the pursuit of achieving the Sustainable Development Goals (SDGs), particularly SDG 3: Good Health and Well-being.

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