Long term exposure to air pollution could damage the brain and lead to learning and memory problems and even depression, new research has revealed.
The tests on mice showed that in the long term dirty air could cause actual physical changes to the brain which in turn had negative effects.
While other studies have looked at the impact polluted air has on the heart and lungs this is one of the first to look at the effect on the brain, lead author Laura Fonken noted.
She said: “The results suggest prolonged exposure to polluted air can have visible, negative effects on the brain, which can lead to a variety of health problems.
“This could have important and troubling implications for people who live and work in polluted urban areas around the world.”
Ms Fonken, a doctoral student, and her colleagues at Ohio State University exposed mice to either filtered air of polluted air six hours a day, five days a week for almost half their lifespan which was 10 months.
The polluted air was the same as that created by cars, factories and natural dust and contained fine particulates about a thirtieth the size of a human hair, 2.5 micrometers, which can reach deep areas of the body’s organs.
The concentration of particulates mimicked what humans are exposed to in some polluted urban areas, researchers claimed.
Pollution
In previous studies in mice it was found that fine air particulate matter caused widespread inflammation in the body and that it could be linked to high blood pressure, diabetes and obesity, and the researchers wished to expand on these findings by looking at the brain.
Professor Randy Nelson, a co-author, said: “The more we learn about the health effects of prolonged exposure to air pollution, the more reasons there are to be concerned.
“This study adds more evidence of pollution’s negative effects on health.”
After 10 months of exposure behavioural tests were carried out on the rodents including a learning and memory test where after five days of training they were placed on a brightly lit area and given two minutes to find the dark escape hole where they would be more comfortable.
The mice who breathed the polluted air took longer to learn where the escape hole was and at later tests they were more likely to forget where it was.
In another experiment, mice exposed to the polluted air showed more depressive-like and higher levels of anxiety-like behaviours in one test, but not in another.
To find out how the pollution led to changes in learning, memory and mood the researchers tested the hippocampal area of the mice brains and found clear physical differences.
Ms Fonken said: “We wanted to look carefully at the hippocampus because it is associated with learning, memory and depression.”
They looked at the dendrites, which are the branches that grow off of nerve cells or neurons, which have small projections growing off them called spines, which transmit signals from one neuron to another.
Mice exposed to polluted air had fewer spines in parts of the hippocampus, shorter dendrites and overall reduced cell complexity.
They also discovered some inflammation in the hippocampus and more active chemical messengers that cause inflammation in the mice who breathed the polluted air.
Professor Nelson said: “Previous research has shown that these types of changes are linked to decreased learning and memory abilities.”
Ms Fonken added: “The hippocampus is particularly sensitive to damage caused by inflammation.
“We suspect that the systemic inflammation caused by breathing polluted air is being communicated to the central nervous system.”
The study appears online this week in the journal Molecular Psychiatry.
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TINY particles emitted by diesel exhaust fumes can raise the risk of heart attacks, according to new research.
Scientists from Edinburgh University discovered ultra-fine particles produced when diesel burns are harmful to blood vessels and can increase the chances of blood clots forming in arteries, leading to a heart attack or stroke.
The research sheds further light on the risks of traffic fumes after another study from Italy warned high levels of exposure to tiny particles in emissions can dramatically raise the risk of deep-vein thrombosis.
Glasgow has a long-standing problem with air pollution and was recently named as one of three areas in the UK – alongside Greater London and north-east Scotland – which were expected to fail European limits for nitrogen dioxide emissions.
The British Heart Foundation said the research confirmed people with heart disease should not spend long periods of time outdoors in areas where there are high levels of traffic pollution.
The researchers compared the carbon monoxide and nitrogen dioxide found in diesel fumes to the ultra-fine particles from exhausts and found it was the chemicals – which are less than one-millionth of a metre wide – that interfered with the way the blood vessels control blood-flow.
Dr Mark Miller, of Edinburgh University’s Centre for Cardiovascular Science, said: “While many people tend to think of the effects of air pollution in terms of damage to the lungs, there is strong evidence it has an impact on the heart and blood vessels as well.
“Our research shows that while both gases and particles can affect our blood pressure, it is actually the miniscule chemical particles emitted by car exhausts that are really harmful. These particles produce highly reactive molecules called free radicals that can injure our blood vessels and lead to vascular disease. We are now investigating which of the chemicals carried by these particles cause these harmful actions, so we can try and remove these chemicals, and prevent the health effects of vehicle emissions.”
A report last month by the Department for the Environment, Food and Rural Affairs showed Glasgow and north-east Scotland were breaching European Union safe levels for nitrogen dioxide air pollution.
The EU annual average target for nitrogen dioxide levels is 40 micrograms per cubic metre but two years ago Glasgow’s Hope Street, a main bus corridor, recorded an annual average of 82 micrograms, while St John’s Road in Edinburgh averaged 75 micrograms a year.
The study, which is published in the European Heart Journal, was funded by the British Heart Foundation, which said there may be an argument for taking chemicals out of fuel to reduce the initial risk.
Its associate medical director, Professor Jeremy Pearson, said: “We’ve known for a long time air pollution is a major heart health issue and that’s why we’re funding this team in Edinburgh to continue their vital research.
“Their findings suggest lives could be saved by cutting these harmful nanoparticles out of exhausts – perhaps by taking them out of the fuel, or making manufacturers add gadgets to their vehicles that can trap particles before they escape. The best approach isn’t clear yet.
“For now our advice remains the same – people with heart disease should avoid spending long periods outside in areas where traffic pollution is likely to be high, such as on or near busy roads.”