Poor air quality is a widespread problem. Nine of out ten people worldwide breathe polluted air, according to the World Health Organization. One innovation aimed at battling the issue on a local level is Dutch artist and designer Daan Roosegaarde’s 7-metre-tall Smog Free Tower. The tower uses positive ionisation technology to clean the air surrounding it by removing particulate matter. Whether the tower’s tech can be truly effective and scalable remains to be seen. Roosegaarde is also working on a bicycle that cleans air as the cyclist pedals.