How many deaths from air pollution in London each year? You might think that is a simple question to answer because you have seen the headlines in the media – it’s 9,416 according to a report published by Kings College which is of course a nice exact figure. The press have abbreviated it to “nearly 9,500”.

The first problem though is that 9,416 is “premature deaths”, i.e. their lives were shortened to a greater or lesser extent. There were no actual deaths directly attributed to air pollution, i.e. present on the death certificate. Even the 9,416 is not a correct figure because there are a range of “shortenings”, which may stretch from hours to years. The estimated distribution of shortenings has been converted to a single figure of deaths so that the ignorant readers of the popular press, or those reading internet blogs, might understand it.

Yes this is an exceedingly complex topic which I won’t even attempt to explain in full in this brief article. But the latest news is that even the estimates used to calculate this number are dubious to say the least. New advice from the “Committee on the Medical Effects of Air Pollution” (COMEAP) set up by DEFRA is that the uncertainty about the evidence is growing. Although there appears to be a statistical association between air pollution factors and mortality, in the case of NO2 COMEAP have now said: “The Committee has not been able to come to a consensus view on how the epidemiological associations between NO2 and mortality can be used to either predict the benefits of interventions to improve air quality or to estimate the current mortality burden imposed on the UK population by air pollution. Some members are doubtful that the evidence is sufficient to allow a robust recommendation for quantification to be made. This is particularly the case for effects likely to be caused by NO2 itself.”

Regardless of that opinion, they still came down in support of giving specific recommendations on the likely impact of air pollutants on mortality.

Now this writer is not going to argue that cleaning up London’s air is not necessary, and it’s already happening of course. The key question, is by how much and what should be spent on doing it. What is the cost/benefit ratio of extending the ULEZ is one key point that needs to be answered.

If nobody has an accurate figure of the current disbenefits, how can we know what the benefits of cutting pollution are likely to be? Also TfL have been remarkably evasive in answering some simple questions about the costs of implementation of their proposals. They have refused to provide the data in response to an FOI request. Why are there no budgets that they are willing to disclose so we can attempt to work out the answers for ourselves.

One has to suspect that the case for really tough measures, such as effectively removing all diesel cars from London’s streets, is not as strong as it should be. When the costs imposed on car users can run into very substantial figures, we should be told the truth.

Making up policy based on guesstimates is not good enough.

Roger Lawson