Tag Archives: polluted air

Pollution link to mental health

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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

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.

Pollution and heart health

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A study by scientists, has suggested that chronic inhalation of polluted air triggers the release of white blood cells that leads to inflammation and risk of heart disease.

Ohio State University scientists have described studies in mice suggesting that chronic exposure to very fine particulate matter triggers events that allow white blood cells to escape from bone marrow and work their way into the bloodstream.

Their presence in and around blood vessels alters the integrity of vessel walls and they also collect in fat tissue, where they release chemicals that cause inflammation.

“Our main hypothesis is that particulate matter stimulates inflammation in the lung, and products of that inflammation spill over into the body’s circulation, traveling to fat tissue to promote inflammation and causing vascular dysfunction,” said Sanjay Rajagopalan, professor of cardiovascular medicine at Ohio State and senior author of the study.

“We haven’t identified the entire mechanism, but we have evidence now that activation of toll-like receptor 4, or TLR4, influences this response.”

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Heart health

For this study, the scientists exposed different groups of mice to either filtered air or air containing between eight and 10 times more fine particulates than the ambient air in an urban environment – an average of approximately 111 micrograms per cubic meter. The mice were exposed for six hours per day for five days per week for at least 20 weeks.

The polluted air contained fine particulates that are so tiny – 2.5 micrometers or smaller in diameter, or about 1/30th of the average width of a human hair – that they can reach deep areas of the lungs and other organs in the body.

For most of the experiments, the effects of exposure to pollution were compared in normal mice and mice deficient in TLR4.

After exposure to polluted air, the normal mice showed higher levels of white blood cells known as inflammatory monocytes in their spleens and circulating in their bloodstream than did mice breathing filtered air.

Deficiency of TLR4 diminished this effect in mice breathing dirty air. That suggested that if the receptor is not active, the monocytes would not be released.

Other findings implicated yet another potential compound involved in the damage. The increase in monocytes was accompanied by an increase in superoxides in the blood vessels. These compounds are designed to kill pathogens, but they are toxic if they have no bug to fight. They are produced by an enzyme called NADPH oxidase – and NADPH oxidase is found inside monocytes.


In an experiment comparing normal mice and mice lacking a component of the NADPH oxidase enzyme, the mice without the enzyme produced fewer oxygen free radicals in response to polluted air than did normal mice.

Yet another model of mice genetically altered so their monocytes express yellow fluorescent protein allowed the researchers to observe exactly where the monocytes traveled in segments of mouse muscles and fat tissue. In mice breathing polluted air, the monocytes began to stick to blood vessel walls and fat cells.

“This is a sign that the monocytes are responding to inflammatory stimuli – which in our case is particulate matter – and then in turn they can cause more inflammation because they release inflammatory factors,” said Rajagopalan.

Those factors include what are called proinflammatory cytokines, including TNFa (tumor necrosis factor alpha), MCP-1 (monocyte chemoattractant protein) and IL-12 (interleukin-12). These are chemical messengers that cause inflammation, most often to fight infection or repair injury. When they circulate without an infection to fight, the body experiences excess inflammation.

Mice breathing polluted air showed higher levels of these cytokines in their blood than did mice breathing filtered air. And the mice deficient in the TLR4 receptor showed dramatically lower levels of the cytokines.

The research is published in a recent issue of the journal Circulation Research.