Marshalls are working with Mitsubishi Materials Corporation to introduce a paving to the UK that is claimed to neutralise nitrous oxide from car exhaust fumes and convert them into nitrates, which are then washed down the drain.
Called Noxer, the paving works by setting up a photocatalytic reaction between titanium dioxide contained in the top 15 mm of the block and ultraviolet radiation from the sun. The result is a layer of oxygen molecules on the block's surface, which combines with the nitrous oxides in the air to form a surface coating of nitrates.

When it rains, these nitrates are turned into a dilute nitric acid, which is then washed away to allow further reactions to take place. The paving is claimed to have the same strength and slip resistance as standard interlocking blocks and is available in a wide range of colours. It has already been used in Japan for several years and is now being trialled in Westminster before being launched on the UK market in the spring.