Long-timeexposure（暴露）toairpollutioncanleadtophysicalchangesinthebrainandcausetroubleinlearningandmemory，andevenanxiety．Thisissuggestedbytheresultsofnewresearchonmice．Whileotherstudieshaveshownthehar
Long-time exposure （暴露） to air pollution can lead to physical changes in the brain and cause trouble in learning and memory，and even anxiety．This is suggested by the results of new research on mice．
While other studies have shown the harmful effects of polluted air in the lungs and heart，this is the first to show the negative effect on the brain．
The team of Laura Fonken，Randy Nelson，from the Ohio State University，the USA，has spread to the brain a previous line of research which found that fine particulate（微粒） matter floating in the air mainly because of air pollution caused by humans，causes swelling in much of the body，and may be related to high blood pressure problems，and some other diseases．
In the research Fonken and his colleagues exposed mice to polluted air for six hours each day，five days a week，over a period of 10months，almost half the average life length of mice．
Polluted air contains fine particles created by cars，factories and natural dust．Fine particles of this kind are tiny，about 2.5micrometers in diameter（直径），or about one-thirtieth the width of a human hair．These particles can go deep into lungs and other organs．
The concentration of this particulate material to which they exposed mice is equal to the concentration at which people can be exposed in some polluted urban areas．
After a period of 10months，the researchers got the animals to have a series of behavioral tests．Both the behavior of mice and the results of neurological （神经的） tests done to them show that those within the polluted air had more problems in learning and memory，and higher levels of anxiety．
The results suggest that long-time exposure to polluted air can have measurable negative effects on the human brain and can cause a variety of mental health problems．This could have important consequences for those living and working in polluted urban areas．
28．The results of new research on mice first suggest that pollu