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City-dwellers prone to depression, memory problems, from pollution

By Martin Leggett - 05 Jul 2011 9:0:0 GMT
City-dwellers prone to depression, memory problems, from pollution

It seems that the air breathed in by many city-dwellers could be responsible for those 'concrete-canyon blues' - with particulate-laden air being blamed for memory difficulties, slowness in learning and even a greater risk of depression. That's according to a new study in today's issue of the journal Molecular Psychiatry.

Previous research has pinned down ill-health in the lungs, and heart, to exposure to fine particulates from pollution. These are spewed out from a host of vehicle tailpipes and industrial processes, and are particularly prone to high concentration in densely-packed cities.

The particles produced are so fine, at 2.5 micrometers, that they are easily absorbed through the lung's surface, entering into the rest of the body. That can then lead to a low-level inflammation of the body's tissues, and onto the previously reported health problems - such as asthma, lung cancer and heart attacks.

This study, however, is the first long-term research into the effects of prolonged exposure to particulate matter (PM) on the brain. The work involved a collaboration between neuroscientists from Ohio State University (OSU) and a team from the university's Davis Heart and Lung Research Institute, who had previously demonstrated the ill effects of PM on mice.

In this case, the researchers raised two batches of mice - one-half exposed to filtered air, the other unfortunate half to PM-polluted air, over the course of ten months. They reckoned this was equivalent to the levels of PM breathed in by some people living in polluted cities.

On testing the mice, they found that not only did the PM-exposed individuals have problems learning a route to a hidden, darkened snug - they often forgot where the bolt-hole was, a short-time after becoming familiar with it. The team also went a step further, running tests that stretched the mental health of the mice. Again, those who had breathed the polluted air showed more signs of anxiety and depression than the clean-breathing mice.

It turned out that the reason for this discrepancy lay deep in the brain - in the hippo-campus This seahorse-shaped part of the brain has an important role to play, in memory and behavior. Laura Fonken, lead author of the study, said ''We wanted to look carefully at the hippo-campus because it is associated with learning, memory and depression.''

What they found was that the hippo-campus in the two sets of mice had developed quite differently. The dendrites of the PM-exposed mice were shorter, had fewer spines for communicating between neurons, and showed higher levels of inflammatory-producing cytokines.

The discovery of inflammation in the hippo-campus strongly suggests that it is the particulate matter that is causing the observed mental health problems. ''The hippo-campus 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,'' Fonken said.  ''This could have important and troubling implications for people who live and work in polluted urban areas around the world.''

Top Image Credit: © Kadmy