There’s no longer any doubt that cities aren’t healthy environments for people to live in. Besides the lack of green spaces and the increased ability of an epidemic to spread, there’s the matter of air pollution. In particular, I’m talking about particulates less than 2.5 micrometers across, which are typically spewed out by traffic and fossil fuel power plants.
This isn’t just a guess or me making what should be an obvious statement. Previous research has shown that living one’s life in an environment saturated with these tiny particles leads to an increase in heart problems like coronary heart disease and deaths related to other cardiac problems. The issues certainly don’t stop there. With the closely related ties between mind and body, surely there must be some psychological effects too?
This is the question that intrigued Laura Fonken, a doctoral student at the Ohio State University. The problem in answering the question, however, is that it is extremely difficult to differentiate mental health problems caused by separate sources. I mean, sure there might be more depressed, crazy people in the cities, but maybe it’s just from having to deal with taxi drivers all the time or GTL assholes.
To take a stab at narrowing down the potential causes, Fonken looked to mice. She took four-week-old mice and had them live in enclosed environments. One group got filtered, perfectly clean “country” air, while the other got to inhale concentrations of particulate air pollution consistent with today’s major cities. Five days per week for 10 months, the mice did nothing but inhale typical air pollution concentrations. After that time, they were put through a smattering of physical and mental tests.
The results? Both sets of mice looked exactly the same. They had all the same physical characteristics and seemed like equally health adult mice.
But appearances can be deceiving.
As they got further into more complex tests, differences began to emerge. Put into a maze with a cheesy reward waiting at the correct location several times in a row, the “city” mice had trouble remembering where the grub was located. It took them twice as long to find it on the second try as the “country” mice and 50 percent longer on tries number three and four. And when they took the prize away and let the mice explore on their own, the city mice returned to the cheese’s previous location less times than their counterparts.
In short, they seemed to have memory problems.
They also showed more signs of depressive behavior. In a classical test, the mice were thrown into a tub of water and forced to swim. The question is how long does it take before a mouse falls into despair and gives up, relegating themselves to simply floating and waiting for death’s cold grip. (Don’t worry, none were actually drowned.)
Again, there seemed to be something up with the city mice. They gave up and began floating almost twice as fast as the country mice, gave up about a third more often and stopped swimming for periods twice as long.
These were truly depressive mice.
Finally, the scientists froze their brains, sliced them up and looked for some actual physical differences. While an understated effect, the city mice’s brains seemed to be slightly swollen, which is a physical reaction consistent with this type of air pollution; it’s also what causes all of the cardiovascular problems. This inflammation and reaction to it seemed to be strongest in the hippocampus, a brain region disproportionately vulnerable to injury and inflammation. Throw in the fact that certain changes to the structure of a region of the hippocampus are associated with depression and learning and memory, and you’ve got yourself a smoking gun.
So when do we all get standard issue breathing filters?