No assessment has been made of the effectiveness or cost of using titanium dioxide to reduce pollution in cities. We are watching with interest the trials of the technology, such as that under way in the City of Westminster. Minimising the impact of transport on the environment is a priority, and we will consider in what ways it would be appropriate to encourage local authorities to take up this technology when the overall costs and benefits are clear. In particular, we will want to ensure that the environmental costs of concrete manufacture do not nullify any prospective gains.