In many parts of the world, the air has become 1. ________. This is bad for people’s 2. ________. According to a new study by WHO, if you breathe unhealthy air for 3. ________ periods of time, you can become sick. Air pollution can lead to many illnesses, such as heart disease and 4. ________. Each year, there are 5. ________ people who die from air pollution.