Mind Cleaner Air on the day of ULEZ Expansion in London
I live in Camberwell, in Southeast London, just a few minutes away from the Institute of Psychiatry, Psychology and Neuroscience where I currently work as a senior lecturer. Camberwell, as an area, has been historically impacted by poor air quality and high prevalence of mental disorders, compared to the rest of the UK.
Thus, I was very pleased to be invited again to write a blog for the online magazine, InSPIre the Mind. I previously wrote on the topic of air pollution and mental health on 4th March 2020 to highlight an emerging field of research that I am passionate about.
My first blog on 4th March 2020 was part of a series of articles around climate change and mental health to celebrate the first-year anniversary of InSPIre the Mind. Little did we know back then about what would follow and how the COVID-19 pandemic would completely alter our lives, our physical and mental health, the environment and become the prevailing topic of discourse in our lives.
Unfortunately, my second blog does not come at a time when there is a better hope for our global future. In August 2021, the Intergovernmental Panel on Climate Change (IPCC) issued their starkest warning yet about the climate disaster that is now upon us ahead of the COP26 UN climate change conference.
Ambient air pollution (air pollution in outdoor environments) is not only harmful for the planet’s climate but is also the leading environmental cause of deaths globally.
Cities like London have historically been impacted by air pollution. The Great Smog of London in 1952, one of the most significant air pollution events of the 20st century, resulted into 12,000 deaths and had significant effects on environmental research, government regulation, and public awareness of the relationship between air quality and health.
However, even after sixty years, we are still experiencing a “slow pandemic in motion” not only in London but globally, despite considerable efforts to improve air quality in cities.
In 2019, 119,000 people in London lived with illegal levels of polluted air, with 98 per cent of schools being in areas exceeding World Health Organization pollution limits in London alone.
Several London-based studies have shown associations between city-wide air pollution with adverse effects on the heart and lungs, but there is now an increasing body of evidence suggesting that air pollution isn’t great for our brain either.
Recent research from our team has found that adults exposed to high levels of traffic-related air pollution are more likely to experience common mental disorders, such as anxiety and mild depression. In this study, we analysed data from over 1,600 participants from the South East London Community Health (SELCoH) study, a survey of Southwark and Lambeth adults. Participants were assessed for common mental disorders, psychotic experiences and physical symptoms indicative of mental distress based on clinical interviews and validated questionnaires over a five-year period. Mental and physical health data from the survey were linked with the concentration of air pollution at the residential address of the participants.
Particulate matter, otherwise known as particle pollution, refers to the microscopic particles of solid and liquid matter found in the air as a result of pollution. Two main types of particle pollution include:
o PM2.5: very small inhalable particles that are around 2.5 micrometres
o PM10: small inhalable particles that are around 10 micrometres
We found that as levels of pollution increased, the odds of common mental health disorders also increased. Specifically, for each 5 microgram per cubic meter increase in very small particulate matter (PM2.5), and 3 microgram per cubic meter increase in nitrogen dioxide (NO2), odds of common mental disorders were increased by 18% to 39%.
We also assessed the relationship between exposure to air pollution, PM10, and psychotic experiences and found an associated 33% increased chance of psychotic experiences per 3 microgram per cubic meter increase in small particulate matter (PM10).
Until now, little was known about whether air pollution exposure contributes to the course and severity after the onset of more serious mental illness. To answer this question, we recently conducted a second study, which is one of the first of its kind, to examine whether air pollution exposure leads to a more severe course of illness in people experiencing first episodes of psychotic disorders (e.g., schizophrenia) and mood disorders (e.g., depression) which affect, respectively, ~3% and ~17% of people over their lifetime.
We analysed data from over 13,000 people aged 15 years and over who had face-to-face contact with South London and Maudsley NHS Foundation Trust (SLaM: an NHS foundation trust specialising in mental health) services between 2008 and 2012. Individuals were followed from the date of their first face-to-face contact for up to seven years.
South London and Maudsley NHS Foundation Trust provides comprehensive secondary mental healthcare to approximately 1.36 million people within the London boroughs of Croydon, Lambeth, Lewisham and Southwark. These inner-city areas have high traffic flows and high average air pollution concentrations compared to other urban UK areas. In addition, they are areas that reflect London’s high level of diversity both in terms of ethnicity and wealth.
We linked anonymised electronic mental health records with modelled concentrations of air pollutants (20x20 metre grid points) at the residential addresses of the participants.
Our second study found that people exposed to higher residential levels of air pollutants used mental healthcare services more frequently in the months and years following their initial presentation to mental healthcare services compared to those exposed to lower air pollution.
We found that for every 3 micrograms per cubic meter increase in very small particulate matter (PM2.5) and 15 micrograms per cubic meter increase in nitrogen dioxide (NO2), over a one-year period there was an increased risk of being admitted to hospital for a mental health illness as an inpatient (residential stay) of 11 per cent and 18 per cent respectively.
Results also showed increases in particulate matter and nitrogen dioxide (NO2) were associated with a 7 per cent and 32 per cent increased risk of requiring community-based mental healthcare for the same period. These findings were also replicated over a seven-year period.
We observed findings for both mood disorders and psychotic disorders, as well as for both inpatient and community-based mental healthcare. This suggests that air pollution may contribute towards a broad range of mental health problems, affecting a wide spectrum of clinical services, over long periods of time.
We also found that, if the UK urban population’s exposure to very small particle matter was reduced by just a few units closer towards the World Health Organisation’s recommended annual limit (10 micrograms per cubic metre), this would reduce usage of mental health services by around 2% thereby saving tens of millions of pounds each year in associated healthcare costs.
If the associations reported above are causal, reducing air pollution exposure could significantly improve mental health prognosis and reduce healthcare costs even further than our original estimates.
The two above-mentioned studies indicate that air pollution is a major environmental risk factor, not only for the incidence of mental health disorders, but also for the severity of mental disorders.
It is also a risk factor that is easily modifiable which suggests more public health initiatives to reduce exposure could improve mental health outcomes as well as reduce the high healthcare costs caused by long-term chronic mental illness.
Typically, low emission zones (LEZs) are one type of city-wide intervention to improve air quality in cities and subsequently, physical and mental health. LEZs require vehicles to meet exhaust emission standards to enter the area, with non-compliant vehicles either banned or charged to enter. There are now more than 260 LEZs across Europe, since its first introduction of the LEZ in 1996.
Within this context, London is taking an important step today to further clean its air for 3.8 million more people with the expansion of the ultra-low emission zone (ULEZ), which only permits vehicles which emit very low emissions.
Originally introduced in 2019, ULEZ have shown to have remarkable results in reducing air pollution in London for example, in relation to traffic related nitrogen dioxide (NO2) was reduced by 44% within the first ten months.
The majority of areas in Southwark, Lambeth, and Croydon where the two studies took place will now be included in the ULEZ-expansion. Thus, it would be important to explore on how ULEZ-expansion could potentially improve not only physical but mental health trajectories.
I would like to conclude with a quote from Dr Adrian James, President of the Royal College of Psychiatrists on our recent study on air pollution and severity of mental illness:
“Our health is fundamentally linked to the quality of our environment, whether that’s about cleaner air, access to green spaces or protection from extreme weather. As we look ahead to our post-pandemic future, it is vital that we find ways to build back greener and prevent poor health”.
The ULEZ-expansion is one of the ways towards the right direction in order to protect our mental health and the future quality of our neighbourhoods.
