They clearly have access to some excellent data.
Low Emission Zone [Transport UK]
London Low Emission Zone [London]
The paper is called:
Are current levels of air pollution in England too high?
The impact of pollution on population mortality [PDF]
We examine the relationship between common sources of airborne pollution and population mortality in present day England. The current air quality limit values are low by both historical and international standards, and these are set at levels which are believed not to be harmful to health. We assess whether this view is correct. We use data at local authority level for the period 1998 to 2004 to examine whether current levels of airborne pollution, as measured by annual mean concentrations of carbon monoxide, nitrogen dioxide, particulate matter less than 10 μm in diameter (PM10) and ozone, are associated with excess deaths. We examine all cause mortality and deaths from specific cardiovascular and respiratory causes that are known to be exacerbated by air pollution. We exploit the panel nature of our data to control for any unobserved time-invariant associations at local authority level between high levels of pollution and poor population health and estimate multi-pollutant models to allow for the fact that three of the pollutants are closely correlated. We find higher levels of PM10 and ozone are associated with higher mortality rates. The size of the effects we find translates into around 4,500 deaths per annum.