(Portland, OR) -- An Air Quality Advisory is in effect from the Portland-Vancouver area to Medford. It's being caused by elevated levels of ozone pollution, or smog. The advisory is in effect through Wednesday night. Residents can help reduce the pollution by limiting driving, postpone yard work with gas powered equipment and delay painting and aerosol projects. Smog can irritate your eyes, nose and lungs. It can also contribute to breathing problems.