Toxic particulate matter from cars and fossil fuels has long been linked to rapidly increasing rates of disease in the UK and the developed world. Now, a major review on behalf of the UK’s Health Safety Agency has confirmed the link after analyzing dozens of human studies. The researchers concluded that “air pollution is likely to contribute to cognitive decline and dementia in the elderly.” They believe the primary way this happens is with tiny toxic particles that enter the bloodstream after being inhaled into the lungs. The pollutants then irritate blood vessels and disrupt circulation to the brain. Over time, this can lead to vascular dementia. It is also possible that in rare cases very small air pollution particles can cross the blood-brain barrier and directly damage neurons. However, this does not appear to be an important mechanism in the level of air pollution currently in the UK, according to the report. Air pollution is fueling rise in dementia, UK government admits for 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 by 2040 (left) to 10mcg/m3. But this is still above the World Health Organization (WHO) recommended level of 5 mcg/m3 Although a link has been made, there is not yet enough evidence to say how many cases of dementia are a result of air pollution. Some studies have shown that up to one-fifth of patients with the disease are linked to exposure to toxic pollutants. The 290-page report was carried out by the Committee on the Medical Effects of Air Pollutants (COMEAP), led by Imperial College London Professor Frank Kelly. The researchers reviewed 70 human studies, which included population-based research taken from 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 consists of a huge variety of 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 carried throughout the body, taking up residence in the heart, brain and other organs. Therefore, exposure to PM can have serious health effects, especially in vulnerable groups of people such as the young, the elderly and those with respiratory problems. Meanwhile, nitrogen dioxide (NO2) is a gas produced mainly by burning fossil fuels. Short-term exposure to high concentrations of NO2 can cause airway inflammation and increase susceptibility to respiratory infections and allergens. NO2 can worsen the symptoms of those who already have lung or heart disease.
Source: Department of Environment Food & Agricultural Affairs It has been known for decades that air pollutants can contribute to heart disease, stroke and other circulatory problems by making blood vessels narrower and harder. Scientists had theorized that this process could also lead to vascular dementia, which is caused by damage to the brain’s blood vessels and is the second most common form of the disease after Alzheimer’s. Writing in the report, the researchers said the evidence for this had grown stronger over the past 15 to 20 years. They concluded: “We believe there is a strong case for effects of air pollutants on the cardiovascular system having a secondary effect on the brain. “…we consider it possible that such effects have an effect on the blood supply to the brain. That such an effect may well lead to brain damage seems likely. “Therefore, we consider the association between exposure to air pollutants and effects on cognitive decline and dementia to be likely causal in relation to this mechanism.” The most dangerous type of air pollution is known as PM2.5, which is less than 2.5 micrometers in diameter. That’s one fortieth of a millimeter, or about 3 percent of the width of a human hair. Some scientists believe that PM2.5 can also have a direct effect on the brain, traveling directly from the lungs to the brain via the bloodstream. Current evidence suggests that only a small percentage of the tiny particles can cross the blood-brain barrier, the report found. And it’s not clear whether enough of them can enter the brain and cause enough damage to lead to dementia. The researchers found, however, that once they enter the brain, the particles are cleared slowly, if at all. “This is clearly a point in favor of the proposition that particulate matter entering the brain can have deleterious effects,” they wrote. In animal studies, diesel engine exhaust has been shown to create an inflammatory response in the brain and damage cells. But it’s unclear how this translates to humans. “We consider the current evidence base insufficient to directly quantify the effects of air pollutants on cognitive decline or dementia,” the researchers said. It comes as the Government today called on councils across England to bid for funding from a £7 million pot to find innovative ways to improve air quality in their areas. The air quality grant will be used to implement measures that benefit schools, businesses and communities affected by high levels of pollution. Areas can only qualify if air pollution levels exceed UK targets. Earlier this year, the government revealed that the legal limit on PM2.5 would be halved by 2040 as part of Prime Minister Boris Johnson’s upcoming “green industrial revolution”. Currently, England’s maximum allowable PM2.5 level is set at an annual average of 20 micrograms per cubic meter of air (mcg/m3). But this will drop to 10mcg/m3 over the next two decades. A 2020 report by the British Heart Foundation estimated that 15 million people – a quarter of the UK population – live in areas where average levels of toxic particles in the air exceed 10 mcg/m3. In London, PM2.5 concentrations are in the region of 13mcg/m3 on average, while in Birmingham it is around 14mcg/m3 and in Bristol it rises above 20mcg/m3. Pollution rates fluctuate daily, however, with research suggesting that tens of thousands of air pollution deaths were avoided worldwide during the pandemic as people used their cars less during the lockdown. Only rural areas, mainly in the north and south-west of England, meet the WHO recommendation of 5 mcg/3. Ministers have repeatedly claimed that leaving the EU has enabled them to boost targets for reducing air pollution. The bloc has revealed it will stick to the 20mcg/m3 target.