Unseasonably wet and windy weather led to low air pollution during June. Short periods of moderate air pollution were measured in London and Sheffield, and both Port Talbot and Grangemouth experienced pollution from industry. Fine weather from the 19th to 22nd caused a brief return to more typical June pollution when summer-time smog formed over the Midlands, East Anglia and southern England as far west as Bournemouth.

via Pollutionwatch: Diesel cars emit more nitrogen oxides than petrol cars | Environment | The Guardian.