The best (industry-offered) explanation of how this process works can be found here; the gist is that titanium dioxide (a common white pigment, used in everything from cream cheese to paint) embedded in the concrete acts as a catalyst for the polluting chemicals, breaking them down faster than ultraviolet light alone. Nowhere is the anti-pollution benefit of the sculptures quantified, however: But even if a couple of giant Ionic Breeze machines would work better, the sculptures are an important investment in a passive technology that until now has been used mainly in (gasp) France.
Dave has contributed to Dwell since its inception. He's a CalArts dropout, a former art critic for The New Yorker, and a producer of comedies on TV. He lives in, and writes from, Los Angeles.