Long-time exposure to pollution can lead to changes at the level of the brain that can cause multiple problems of memory and learning. Studies made on lab rats demonstrated the direct negative effects that pollution has on the brain;they also identified the fact that thereís a close connection between air pollution and a high level of depression and anxiety,and scientists think this aspect doesnít apply only to rats,but also to humans. During these experiments some lab rats were exposed to filtered air,while others were exposed topolluted air,for about 6 hours a day and 5 times a week.The first part of the experiment lasted for 10 months,which is about half the life of a rat.The polluted air contained fine particles,almost similar to those inhaled by people because of cars and factories.The concentration of particles inhaled by rats was the equivalent of the one to which people who live from polluted urban areas are exposed. The second phase of the experiment took part at the end of the 10 months,when lab rats were subjected to a series of behavior tests.In one of those tests rats were placed in an extremely bright area,from which they were supposed to get out quick by finding the evacuation zone.The mice had already been trained in that sense for five days.The conclusion was that rodents who breathed the polluted were disoriented and confused and needed much more time than the others to leave the area with the disturbing light.Another experiment showed that those who had been exposed to polluted air were also much more depressed than the rest. The conclusion of the experiments was that prolonged exposure to polluted air can have visible negative effects on the brain,and therefore trigger a variety of health problems,affecting people not only physically,but also mentally.Pollution is definitely a serious threat to our health from all points of view and itís obvious that we have to do more efforts to reduce its disastrous consequences.