The East Sides of cities such as London, Vancouver, New York and Paris have historically been the poorest. Some, but not all, have gentrified more recently, and this gentrification has been at the centre of media attention. These observations uncover two questions. Why were these neighbourhoods poor to begin with, and why did some gentrify while others did not? Research conducted by Stephan Heblich (University of Bristol), Alex Trew of the School of Economics & Finance (University of St Andrews) and Yanos Zylberberg (University of Bristol) (http://www.spatialeconomics.ac.uk/textonly/SERC/publications/download/sercdp0208.pdf) suggests that this observation is the most visible consequence of the historically unequal distribution of air pollutants across neighborhoods. During the Industrial Revolution, many areas of Manchester, for example, were covered with layers of soot. Black stains on the pavements and buildings of areas such as Victoria Station or Ancoats in North-East Manchester remained until very recently. With the wrong weather, some areas could be submerged under dark, thick smog. This environmental disamenity made them unpleasant places to live and, in response, those who could afford moved to the neighbourhoods spared by the pollution. This sorting resulted in an unequal distribution of social classes across the city. Since the prevailing winds (The Westerlies) in London, Vancouver, New York, Paris or Manchester blow from the West to the East, the most visible component of such process ended up being the observed West-East differential in neighbourhood composition.
The authors examined nearly 5,000 industrial chimneys in 70 English cities in 1880 and use an atmospheric dispersion model to recreate the spatial distribution of pollution. The exercise was possible because of the fastidiousness of Victorian cartographers. These pioneering map-makers marked each building with landmarks such as factory chimneys. In addition, Victorian census-takers conducted detailed population studies over the nineteenth century.