Photocatalytic tiles

In April 2015, the Supreme Court instructed the UK government to establish a plan by the end of 2015 to tackle air pollution. The ruling was made following a five year legal battle fought by environmental lawyers ClientEarth after it was revealed that 16 UK cities had been breaching EU limits for nitrogen dioxide (NO2) since 2010. Nitrogen dioxide is emitted by diesel-fuelled vehicles and can exacerbate health problems such as asthma.

Lawyer Alan Andrews said, “Air pollution kills tens of thousands of people in this country every year. We brought our case because we have a right to breathe clean air and today the Supreme Court has upheld that right.”

The Court’s president, Lord Neuberger, demanded immediate action saying, "the Government must prepare and consult on new air quality plans for submission to the European Commission... no later than December 31 2015".

Marley Eternit, supplier of roofing and cladding products, have suggested that the problem might be tackled by the use of photocatalytic technology, which can be applied to roads and buildings, to remove nitrogen dioxide and nitric oxide (NOx) from the air.

Their ‘Ecologic’ range of tiles include a titanium dioxide coating, a granular layer embedded in a slurry fused to the surface of the tiles. In the presence of ultraviolet rays from the sun, this coating acts as a catalyst, accelerating the natural degradation of nitrogen, converting it to nitric acid, which then reacts with excess calcium carbonate in the tiles to form calcium nitrate, which is soluble and harmless and is washed away by rainwater.

Marley Eternit suggest that during the life of an average-sized roof, the tiles will remove NOx from the atmosphere equivalent to that emitted by a modern car covering over 100,000 miles.

Gavin White, product manager at Marley Eternit, said, “If (the government) only addresses the polluter, rather than the pollution itself, then the UK is missing a trick … A better option is to take a two pronged approach and also look to reduce the amount of pollution that is still being produced with the use of photocatalytic technology on our buildings and roads to absorb the toxic mix of NOx generated by road traffic exhaust fumes.”

“Using photocatalytic technology on just one roof has an impact on surrounding air pollution levels, but imagine the impact that thousands or millions of roofs could have.”

Photocatalytic technology is already used in cement on pavements in Japan, America and in the Netherlands.

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