October 21, 2015

expert reaction to new paper examining airport proximity and respiratory and cardiac health

A study of the effects of air pollution on people living in the areas around the 12 largest airports in California has been published in The Review of Economic Studies journal, in which they estimate health and related financial costs. All our previous output on this subject can be seen at this weblink: http://www.sciencemediacentre.org/tag/air-pollution/

Prof. Brian Golding, Fellow in Weather Impacts, Met Office, said:

“The prevailing westerly winds in the UK dilute local pollution sources more often in the UK than in California, especially in winter. However, the UK, and especially southeast England, has a number of periods each year (the number varying significantly between years) when the westerly winds are interrupted and stagnant air is able to accumulate pollutants. This can happen in both winter and summer. During such periods all sources of pollution accumulate, including aircraft pollution.”

Prof. Kevin McConway, Professor of Applied Statistics, The Open University, said:

“This is a thorough investigation into something that’s difficult to study.

“On the face of it, it might sound simple to investigate whether patterns of traffic at airports cause air pollution, and whether that in turn causes health problems in people living around the airport. Surely you would just measure the traffic patterns, and the air pollution, and the health problems, and see how they match up? Well, no, because these measures may interact in a very complex way that also includes other things such as weather. Weather clearly affects air traffic and air pollution and some aspects of health. So it’s very difficult to sort out what causes what. If, say, hospitalisations from asthma go up when airport congestion goes up, that might be because the congestion causes pollution which causes asthma, but it could instead be because certain weather causes flight congestion and, quite independently, increases asthma risk.

“This study has several refinements intended to throw more light on what causes what. For example, although the study is primarily about airport congestion and health in California, the statistical analysis also includes data on airport congestion at airports thousands of miles away in the Eastern US. This sounds strange, but it makes good statistical sense. In looking at airport congestion, pollution and health in just California, weather might affect the relationships, and there are all kinds of other things, local to California, that might come into the picture too. But how could airport congestion in New York affect air pollution and health at the other side of the continent? The New York congestion couldn’t affect the weather or other local features in California, but it could directly affect airport congestion in California, when flights do not leave or arrive on schedule. Measurements that work in that way – so-called ‘instrumental variables’ – can be taken into account statistically in ways that make it somewhat easier to judge what causes what.

“So does that mean that this study proves for sure that there is an adverse effect on people’s health if planes spend longer than usual idling on the airport tarmac or taxiing on the ground? Well, there’s no such thing as proof for certain in this kind of study. Such studies inevitably depend on assumptions that can’t be tested directly, so there’s always some room for doubt. The research is pretty complicated and will need to be carefully examined over time, and tested against new data. But it has certainly convinced me that there’s something here that we need to take very seriously.”

Prof. Nick Hewitt, Professor of Atmospheric Chemistry, Lancaster University, said:

“In this paper Schlenker and Walker show that increased emissions of carbon monoxide from aircraft delayed on the ground by airport congestion lead to significant increases in adverse health-related effects in the surrounding population, even though the ambient concentrations of carbon monoxide are significantly below current US air quality limit values. This implies that the current US Clean Air Act standard for carbon monoxide does not fully protect human health.

“These findings have significant implications for airports such as Heathrow that are located in areas of relatively high population density and that are subject to congestion. In the case of Heathrow, building a new runway may temporarily ease congestion but will lead to an increase in aircraft traffic, which itself will lead to an increase in pollutant emissions.”

‘Airports, air pollution, and contemporaneous health’ by Wolfram Schlenker and W. Reed Walker published in The Review of Economic Studies on Wednesday 21 October 2015. 

All our previous output on this subject can be seen at this weblink:

http://www.sciencemediacentre.org/tag/air-pollution/

Declared interests

Prof. Kevin McConway: “I have no relevant interests to declare”.

Prof. Nick Hewitt:  “I have no conflicts of interests to declare.”

None others received.