Researchers have found convincing evidence that exposure to particulate matter increases the risk of dementia, even when annual exposure is below the ‘safe’ standard used by the European Union.
More than 57 million people worldwide are currently living with dementia. And the numbers are only expected to increase. Estimates suggest that this debilitating condition will affect as many as 153 million people by 2050. A pressing question is why dementia is becoming more common. And a new study provides additional and compelling evidence that air pollution is a major culprit.
Air pollution
We have known for some time that particulate matter is bad for your health. In particular, very small particles with a diameter of 2.5 micrometres or smaller (PM2.5) are associated with numerous disorders. For example, these are linked to several serious health problems, such as heart and lung disease, cancer and respiratory problems. Meanwhile, several studies have also found evidence that air pollutants may increase the risk of dementia. However, this has not yet led to a definitive conclusion. And so in a new study, researchers decided to take a closer look at the topic, taking into account study differences that could influence the findings.
More about particulate matter
Particulate matter (PM) is a term used to describe a mixture of solid particles and droplets in the air. It consists of particles of different size, origin and chemical composition and is divided into two categories. The first category consists of PM10; particles with a diameter of 10 micrometres or smaller. The second category is PM2.5; particles that have a diameter of 2.5 microns or less. Both PM10 and PM2.5 are considered major pollutants released by the combustion of fossil fuels including gasoline, diesel and other fuels such as coal, oil and biomass. Other industrial activities – such as construction, mining and the production of materials such as cement, ceramics and bricks – can also cause an increase in particulate matter. It means that good air quality is certainly not self-evident. It is estimated that as many as nine out of ten people worldwide breathe polluted air. Air pollution is therefore a major cause of premature death and disease and represents the greatest environmental risk in Europe. This is because dirty, polluting particles penetrate deep into the lungs and the cardiovascular system. And that can lead to heart disease, stroke, lung disease and lung cancer.
In the study, scientists examined the role of air pollutants in the risk of dementia. The researchers reviewed more than 2,000 studies and identified 51 studies that found a link between air pollutants and dementia. Surprisingly, these were all published within the last ten years. The lion’s share of the studies dealt with PM2.5.
Mortgage
After the researchers had thoroughly studied the studies, they came to an unequivocal conclusion. And it says that exposure to air pollution can indeed be associated with an increased risk of dementia. The team found that the risk of dementia increased by 17 percent when average annual exposure to particulate matter increased by 2 micrograms per cubic meter (2µg/m3). The results also suggest an increased but small increase in the risk of dementia with exposure to nitrogen dioxide (2 percent for every 10 μg/m3 increase) and nitric oxide (5 percent for every 10 μg/m3 increase), but this was based on more limited data . The study found no link between ozone and dementia.
Norm
While the researchers say the uncertainties are still not resolved, the findings add to the growing evidence that air pollutants are risk factors for dementia. In fact, the team even found a link between PM2.5 and dementia when annual exposures were below current standards. This is how the Amerikaanse Environmental Pollution Agency (EPA) exposure to 12 µg/m3 per year as safe. The European Union even uses a limit value of 25 μg/m3. But even when the annual exposure is lower than these standards that are considered safe, the researchers believe that there is an increase in the risk of dementia.
PM2.5 concentrations in major cities
Particulate matter is a major problem all over the world. Because many cities are densely populated and there is a lot of industry, there is often air pollution. Some cities have relatively few particulate matter floating around, such as the Canadian city of Toronto, where residents are exposed to less than 10 micrograms of PM2.5 particulate matter per cubic metre. In contrast, air pollution is excessively high in some other cities in the world. The Indian city of Delhi in particular scores high, with no less than 100 micrograms of PM2.5 particulate matter per cubic meter.
Although the researchers note that smoking and education are still greater risk factors, the likely link between air pollution and dementia is worrisome. “Because of the number of people exposed to air pollution, the health impacts for the whole population could be really significant,” the researchers write.
The team therefore advocates effective measures to reduce air pollution. For example, they believe that global legislation and policy programs are needed, aimed, among other things, at a rapid transition to a sustainable energy supply. “In addition, the results can be used by organizations such as the Environmental Protection Agency, who are currently considering tightening limits on PM2.5 exposure,” says study leader Marc Weisskopf. “People have some influence over their exposure to PM2.5 and other air pollutants. But even more important is better regulation and legislation.”