ECJ EUROPEAN Cleaning Journal

Research in the US has shown that air-pollution removal technology used in 'self-cleaning' paints may cause more problems than they solve.

The study by environmental scientists at Indiana University has revealed that titanium dioxide coatings, said to break down airborne pollutants on contact, are likely to convert ammonia to nitrogen oxide which is linked to harmful ozone pollution.

Ozone is produced by reactions involving nitrogen oxides - which come primarily from motor vehicle emissions - and volatile organic compounds resulting from industrial processes. Equipping cars with catalytic converters has been effective at reducing ozone in urban areas but other technologies are being sought to meet increasingly stringent air-quality standards.

'Self-cleaning' surfaces coated with titanium dioxide are claimed to be capable of breaking down the chemical grime that would otherwise adhere to urban buildings.

"As air quality standards become more stringent, people will be thinking of other technologies that can reduce pollution," said Jonathan D Raff, an author of the study. "Our research suggests that this may not be one of them."

The researchers calculate that in areas where titanium dioxide technology is used, ammonia degradation could account for up to 13 per cent of the nitrogen oxides in the immediate vicinity. This suggests that widespread use of the technology could contribute significantly to ozone formation.

The findings come as the US Environmental Protection Agency develops stricter regulations for ground-level ozone, a primary component in photochemical smog. The pollution is linked to serious health problems including breathing difficulties and heart and lung disease.