Why we’re calling for stricter air pollution targets to tackle dementia risk

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By Michael Jones | Wednesday 17 May 2023

In recent months, you may have seen a growing number of news headlines linking levels of air pollution with risk of developing dementia.

That’s because more evidence is emerging around the harmful effects that air pollution has on our brain health and cognitive abilities.

As part of our Think Brain Health campaign, you’ll often hear us talk about the steps everyone can take to keep our brains healthy and reduce our risk of developing dementia later in life. This includes keeping active, eating a balanced diet and staying socially connected to friends and family. But at Alzheimer’s Research UK we’re particularly concerned about the impact of air pollution because it requires Government action to tackle it – as individuals, there is little we can do about the air we breathe.

With dementia now recognised as the leading cause of death in the UK, we urgently need tighter measures on air pollution to help reduce the number of people living with dementia in the future.

That’s why Alzheimer’s Research UK is calling on the UK government to lead from the front in reducing air pollution on a national level.

 

 

Air pollution and dementia risk – what do we know so far?

Air pollutants are tiny particles and gases in the air that come from various sources, including vehicle exhausts and tyres, and burning wood and fossil fuels. It’s well known that high levels of air pollution pose a danger to our health, leading to serious lung conditions, heart disease and cancer. But now there is a growing body of evidence that suggests air pollution could also be putting us at a greater risk of developing dementia.

Last year, the UK Committee on the Medical Effects of Air Pollutants (COMEAP) – a group of scientists convened by the UK’s Health Security Agency – reviewed nearly 70 high-quality research studies that looked at the impact of air pollution on humans. They concluded that it is “likely” that exposure to air pollution leads to cognitive decline and increased risk of dementia. Although outdoor air quality in the UK has improved significantly since the 1980s – when some of these studies were carried out – it’s far from perfect, with 97% of UK addresses estimated to be surrounded by unsafe levels of air pollution. It’s thought that this is driven by increasing levels of private car ownership.

As England’s Chief Medical Officer, Sir Chris Whitty, highlighted in his annual report last year, “The path to better outdoor air quality is clear, and we now need to go down it.”

Fast forward to April 2023, and US scientists reported in the British Medical Journal that a particular type of air pollution known as PM2.5 fine particulate matter “might be a risk factor for dementia, as well as nitrogen dioxide and nitrogen oxide”. The analysis suggested that for every two micrograms per cubic metre increase in average annual PM2.5 concentration, the overall risk of dementia increases by 4%.

And at our Research Conference this year (read the highlights here), we heard from Dr Louise Kelly, a Postdoctoral Researcher at Southampton University who is working in this area. She is trying to address one of the big unknowns:

What is the mechanism behind the link between air pollution and dementia?

Dr Kelly’s research investigates how exposure to diesel fumes changes the brain’s ability to remove amyloid, the hallmark protein of Alzheimer’s disease. The results – which Dr Kelly hopes to publish later this year – will give us a better understanding on the underlying biology behind dementia and exposure to air pollution.

Other ideas to what this link might be have been outlined by authors of the COMEAP report who “think it’s likely that air pollution contributes to mental decline and dementia caused by effects on the blood vessels.” In other words, since air pollution damages the heart and circulatory system, it’s plausible that damage to the blood vessels in the brain is a key factor leading to cognitive decline and dementia.

But this isn’t the only unanswered question. The report’s authors listed others: How do pollutants enter our brains? Can our brain remove these pollutants once they have entered? What is a safe level of pollution to which we can be exposed?

 

We want to see more ambition from government

Reflecting on current air quality guidelines, Dr Kelly commented: “Based on available data, the World Health Organization recently revised and reduced their recommended pollution exposure limits, yet most of the world’s population live in areas which breach these recommendations. It is likely that the risk of dementia in the modern world is increased due to exposure to air pollution.”

Despite this, action to-date from the UK government to reduce air pollution has fallen disappointingly short. In December, the government missed a clear opportunity for decisive action on air pollution. It set an unambitious and inadequate target for maximum PM2.5 levels of 10 micrograms per cubic metre by 2040 – far less stringent than what we and the World Health Organization recommended.

The government’s target places the UK significantly behind our global counterparts, who are waking up to the harms of air pollution based on the growing body of evidence.

Since 2012, the USA has had a stronger legal target for PM2.5 than the UK, and the USA’s Environmental Protection Agency is proposing to lower this further, to between 9 and 10 micrograms per cubic metre, based on the latest evidence and independent scientific advice.

The EU Commission has also shown a higher level of ambition than the UK by proposing to reduce PM2.5 levels to 10 micrograms per cubic metre by 2030.

 

Are the UK government’s air pollution targets sufficient?

Just last week, the Environmental Audit Committee (EAC) launched a new inquiry considering outdoor and indoor air quality targets. The focus of this will be to examine whether government targets are sufficient.

Along with our fellow members of the Healthy Air Coalition, we’ll be contributing evidence to the inquiry and will continue to call on the government to tackle air pollution with the urgency it needs.

Keeping your brain healthy through following our Think Brain Health guidelines in still important – but as individuals, we need the Government to help out as well.  Watch this space for more news coming on Clean Air Day on June 15th, and, if you’d like to get involved in our parliamentary activity, and help us campaign for change, then sign up to be a campaigner here: https://www.alzheimersresearchuk.org/campaigns/sign-up-to-our-newsletters/?newsletters=Campaigner.

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About the author

Michael Jones

Policy Advisor