Long-term breathing of polluted air increases the risk of depression, according to two recent studies, adding to growing evidence of the impact of harmful pollution on mental health.   The first study, published last week in the journal Gamma Psychology, included a group of about 390 people in the UK who were followed for about 11 years, and the levels of pollution they were exposed to were studied based on their home addresses.   The researchers studied the levels of particulate matter (PM2.5 and PM10), nitrogen dioxide (NO2) and nitric oxide (NO), which are polluting gases from fossil fuel power…