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A paving slab that removes nitrogen oxides from the air has been developed by
Mitsubishi Materials in Japan. The slabs are impregnated with a catalyst,
titanium dioxide, which in sunlight helps convert the oxides into nitric acid.
The acid doesn’t hang around to rot your shoes: it’s simply washed away by rain
or neutralised by the alkalinity of the concrete. Mitsubishi estimates that 80
per cent of the NOx gases that come into contact with the “Noxer” slab can be
removed from the air. Yoshihikoi Murata of Mitsubishi told a London meeting of
the Society of Chemical Industry last week that trials have begun in Chiba, near
Tokyo, and Osaka.