Across the country, special fares were on offer in operation on public transport, exhibitions will show the effect of pollution on people and buildings, and new non-polluting types of transport will be on display.

BBC: News | Europe | Off the roads

She outlined the reasons for a more cautious approach, which included the ban or moratorium placed on fracking in other countries, concerns cited by NI Water for the effect of pollution on water supply, and the dangers of well blowouts and earth tremors.

BBC: Hydraulic fracturing

Fossil fuel companies do not take into account the external effect of the cost of pollution or carbon emissions.

FORBES: The Case For A Green Bank

Although he cannot definitely rule out a direct effect by the pollution on the birds' metabolism of the yellow pigment, or its incorporation into their feathers, the correlation between a shortage of caterpillars and faded plumage is strong evidence of a link between pollution, diet and bird colour.

ECONOMIST: Great tits