A woman wears a protective mask to fight bad air pollution in Beijing on October 22 Image Credit: AFP

Exposure to air pollution could increase our risk of developing dementia, according to a British study. But dementia is not the only illness that has been revealed to be triggered or worsened by contaminants in the air we breathe. Many people die every year because of health problems caused by exposure to air pollution, according to a report by the Royal College of Physicians and the Royal College of Paediatrics and Child Health. And the problems are likely to worsen as increasing urbanisation, climate change and population growth mean air pollution is on the rise, with the average level of fine particles in the air increasing by 18 per cent worldwide between 2010 and 2016.

So how is our polluted air harming us — and is there anything we can do about it?

Dementia

This British study is the latest in a growing body of evidence that pollution increases the risk of developing dementia.

Scientists do not yet know why, but one theory is that tiny particles and chemicals in polluted air absorbed into the body through the lungs cause damage or inflammation in the brain. The King’s College London research found that Londoners who lived in the worst areas in the city for fine particles (known as PM2.5) were 20 per cent more likely to develop dementia within seven years, while those who lived in the worst areas for nitrogen dioxide (NO2) were 40 per cent more likely to develop it, even after accounting for age, class and other lifestyle factors.

It follows a Canadian study of 2.2 million people, which last year found those who lived next to a busy road were 12 per cent more likely to develop dementia.

And earlier this year, a Chinese study suggested that air pollution leads to a decline in brain power, or cognitive function. Researchers who tested people’s maths and verbal skills found their average scores decreased over three years of exposure to pollution.

Professor Martie Van Tongeren, of the University of Manchester, says: “As most people in the UK live in urban areas, exposure to traffic-related and other air pollutants is ubiquitous. Hence, even a relatively small increase in risk will result in a large public health impact.”

Asthma

Studies have suggested children who are exposed to air pollution at an early age are more likely to develop asthma and lung infections, which can be fatal. “Air pollution is detrimental to all health, but it can have major implications on the developing child,” says Professor Jonathan Grigg of the Royal College of Paediatrics and Child Health.

But pollution has not just been linked to causing asthma — it worsens the condition, too. At times of high pollution, such as the height of summer when the heat can exacerbate levels of chemicals in the air from traffic fumes, people are more likely to suffer asthma attacks.

Children are most at risk. A recent report by Global Action Plan on Clean Air Day found that primary and pre-school-age children were exposed to up to 30 per cent more pollution than adults simply because they were closer to the fumes from car exhausts.

With many schools built along busy roads, this is a serious problem. Charity Asthma UK advises affected children to avoid walking along congested roads and to carry their reliever inhaler with them at all times in case pollution triggers an attack.

Heart attacks and strokes

Breathing in polluted air over many years can cause arteries to become furred up or narrowed, a condition known as atherosclerosis, which can lead to heart attacks or strokes.

Spikes in pollution can also trigger heart problems in the short term. People are more likely to suffer heart attacks in the hours after having been exposed to a lot of traffic fumes, according to data from the Myocardial Ischaemia National Audit Project.

Pollution can start to take its toll on the heart and circulation system from an early age, with studies on children in Europe and Mexico finding those exposed to high levels of fine particles and NO2 have higher blood pressure by the age of 12.

Dr Gary Fuller, of King’s College London, whose book on pollution The Invisible Killer is published this month, says: “What you’re breathing in might not just affect you today or tomorrow or over the next year, it might actually cause some permanent, life-changing damage now which might only manifest itself in decades to come.

“It does seem incredible that a tiny amount of contaminants in our air can have such an effect but there is evidence from thousands of studies that the air pollution we breathe in every day is causing us harm.”

Children’s development

Children can be heavily affected by pollution and the problems it causes can begin in the womb, research increasingly suggests.

Soot particles were found inside the placentas of five women who gave birth to healthy babies at the Royal London Hospital, according to a study published this year. The tiny bits of carbon — typically created by burning fossil fuels — had been breathed in by the pregnant mothers and travelled through their bodies into their placentas.

Scientists don’t yet know if the particles can reach babies in the womb, but previous research has found links between pregnant women exposed to air pollution and problems such as premature births, low birth weights, unexpected deaths of their babies and lung problems in childhood.

In 2015, an American study found that children whose mothers had been exposed to polycyclic aromatic hydrocarbons (PAHs) — present in exhaust fumes and coal and cigarette smoke — were also more likely to have behavioural problems, including attention deficit hyperactivity disorder.

Fertility

Pollution can cause problems even before a child is conceived. Doctors suspect pollution is having an effect on sperm quality — the number of sperm cells that are the correct size and shape to fertilise an egg.

A recent study of 6,500 Taiwanese men showed exposure to fine particles was linked with a rise in sperm abnormalities. It found that for every increase in the level of pollution particles in the air of 5 micrograms per cubic metre, the number of normal sperm produced by the men dropped by 1.29 per cent.

An earlier Italian study found the quality of sperm of men who worked on motorway tolls — with a high amount of exposure to traffic fumes — was significantly lower than that of men who worked away from busy roads. It is not yet known exactly why pollution affects quality, but tests have shown that toxic elements in polluted air can damage sperm cells.

What can I do about it?

If you live in a busy city, avoiding air pollution can be tricky, but avoiding walking or exercising outside at peak traffic times like rush hour can help.

Londoners can use the online Clean Air Route Finder (breathelondon.org/plan-lower-pollution-travel-route), which maps out the cleanest routes between destinations using real-time air pollution measurements.

Dr Fuller recommends choosing routes through parks or wooded areas in cities where possible. But he warns even those living in the country are not safe as chemicals used in farming also contribute to air pollution.

Doing your bit to cut down on pollution will also help, such as taking low-emission buses or trains, or walking or cycling instead of driving.

“There should be a focus on cracking down on the polluters,” Dr Fuller adds. “If you are vulnerable or have a health condition it is not fair that you should have to change your lifestyle in order to avoid it.”

–The Telegraph Group Limited, London 2018