Although air is invisible, it has a major impact on public health. Santa Clara County received a failing grade for air quality in the American Lung Association’s 2009 State of the Air Report and currently surpasses unhealthy short-term pollution particles a yearly average of 11 days, the 24th highest level in the US. The number of people that airborne particulate pollution kills each year has tripled in California. ;Despite the invisibility of air, modern sensors can detect tiny particulate pollution levels in real time.