Sir – Pollution in Oxford is falling, not rising, as suggested in your front page story last week (April 4). Overall levels of nitrogen dioxide should be at no more than 40 parts per million and levels have fallen significantly in the last 10 years.
The city council is working with the county council and the bus companies to steadily reduce pollution from buses. From  January 1, 2014, only clean Euro-5 standard buses will be able to operate through the centre of Oxford. This will not only cut pollution in the city centre but have a beneficial impact across the city and beyond.
The city council takes detailed daily measurements of pollution in the city centre. Since the bus stops were taken out of Queen Street pollution has fallen almost everywhere.
Worryingly pollution has gone up in St Aldates where the numbers of buses have increased. But overall the level is still down. 
Measuring pollution everywhere in Oxford would be very expensive. But we do take readings of nitrogen dioxide at traffic junction hot spots in the city from time to time. Pollution levels vary and are affected a lot by the weather. But we will always act  to protect the health of Oxford people by continuing to bring down pollution levels.
John Tanner, Board member for a Cleaner, Greener Oxford, City councillor for Littlemore & county councillor for Isis, Oxford