Air pollution causes dementia: UK government advisers admit link for first time

Air pollution is contributing to the rise in dementia for the first time, the UK government has said.

Airborne toxic particles from cars and fuels have long been linked to a rapid rise in disease in the UK and the developed world.

Now, a major independent review on behalf of the UK’s Healthcare Safety Agency has confirmed the link after analyzing dozens of human studies.

The researchers concluded that “air pollution contributes to cognitive decline and dementia in the elderly.”

They believe that the main reason for this is that small toxic particles enter the bloodstream after inhalation into the lungs.

The pollutants then irritate blood vessels and impair circulation in the brain. Over time, this can lead to vascular malformations.

Also, in rare cases, very small air pollution particles can cross the blood-brain barrier and directly damage neurons.

But this does not appear to be an important mechanism for air pollution levels in the UK at the moment, the report said.

UK government says air pollution is driving rise in dementia for the first time (file)

The graph above shows the current legal limit for air pollution in the UK (left) and plans to halve it in England to 10mcg/m3 by 2040 (left).  However, this is still higher than the World Health Organization (WHO) recommended level of 5 µg/m3.

The graph above shows the current legal limit for air pollution in the UK (left) and plans to halve it in England to 10mcg/m3 by 2040 (left). However, this is still higher than the World Health Organization (WHO) recommended level of 5 µg/m3.

Although a link has been established, there is not yet enough evidence to say how many cases of dementia are the result of air pollution.

Some studies suggest that up to one-fifth of patients with this disease are linked to exposure to toxic pollutants.

The 290-page report was produced by the Committee on the Medical Effects of Air Pollutants (COMEAP), chaired by Professor Frank Kelly of Imperial College London.

The researchers reviewed 70 human studies, including population-based studies, the general public, and laboratory experiments.

What are particulate matter and nitrogen dioxide?

Particulate matter (PM) is anything in the air that is not a gas.

It contains many chemicals and materials, some of which can be toxic.

Because of the small size of many of the particles that make up PM, some of these toxins can enter the bloodstream and be transported around the body, where they can be deposited in the heart, brain, and other organs.

Therefore, exposure to PM can have serious health effects, especially in vulnerable groups of the young, the elderly, and people with respiratory problems.

Meanwhile, nitrogen dioxide (NO2) is a gas produced mainly during the burning of fossil fuels.

Short-term exposure to high concentrations of NO2 can cause airway inflammation and increase susceptibility to respiratory infections and allergens.

NO2 may worsen symptoms in patients with lung or heart disease.

Source: Department of Environment, Food and Rural Affairs

For decades, air pollutants have been known to contribute to heart disease, strokes, and other circulatory problems by narrowing and hardening blood vessels.

The researchers theorize that this process is caused by damage to the blood vessels in the brain and may also lead to vascular dementia, the second most common form of the disease after Alzheimer’s.

The researchers writing in the report said that evidence for this has grown over the past 15 to 20 years.

They concluded: “We hypothesize that the effects of air pollutants on the cardiovascular system have secondary effects on the brain.

“…We think that these effects affect the blood supply to the brain. Such an effect can lead to brain damage, for us, probably.

“Therefore, we believe that the association between exposure to air pollutants and effects on cognitive decline and dementia may be due to this mechanism.”

The most dangerous type of air pollution is called PM2.5, which has a diameter of at least 2.5 micrometers.

That’s four hundredths of a millimeter, or about 3 percent of the width of a human hair.

Some scientists believe that PM2.5 can directly affect the brain by passing directly from the lungs to the brain through the bloodstream.

Current evidence suggests that only a fraction of small particles can cross the blood-brain barrier, the report said.

And it’s unclear whether enough of them can enter the brain and damage it enough to cause dementia.

The researchers found that after entering the brain, the particles are gradually cleared.

“This is a clear finding in favor of the proposition that particles entering the brain can cause harmful effects,” they wrote.

Animal studies have shown that diesel exhaust causes an inflammatory response in the brain and damages cells. However, it is unclear how this translates to humans.

“We believe that the current evidence base is insufficient to directly determine the effect of air pollutants on cognitive decline or dementia,” the researchers said.

It comes as the government today invited councils across England to bid for £7m of funding to find innovative ways to improve air quality in their areas.

The Air Quality Grant will focus on implementing measures that benefit schools, businesses and communities affected by high levels of air pollution.

Regions can only meet the requirements if their air pollution levels exceed UK targets.

Earlier this year, the Government revealed that the legal limit for PM2.5 would be halved by 2040 as part of outgoing Prime Minister Boris Johnson’s “green industrial revolution”.

Currently, the maximum allowable level for PM2.5 in England is set at an annual average of 20 micrograms per cubic meter of air (µg/m3).

However, this will decrease to 10mcg/m3 in the next two decades.

According to a 2020 report by the British Heart Foundation, 15 million people – a quarter of the UK population – live in areas where the average level of toxic particles in the air exceeds 10 µg/m3.

In London, PM2.5 concentrations sit on average in the region of 13 µg/m3, around 14 µg/m3 in Birmingham and above 20 µg/m3 in Bristol.

Pollution levels vary from day to day, but studies have shown that thousands of deaths from air pollution around the world were prevented during the pandemic because people used their cars less during the lockdown.

Only rural areas, mostly in the north and south-west of England, meet the WHO recommendation of 5mcg/3.

Ministers have repeatedly claimed that leaving the EU has allowed them to increase their targets for reducing air pollution.

Block has declared that it will stick to the target of 20mcg/m3.


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