You asked

1. Can you please provide a full explanation (to include how you are able to provide a custom output response on deaths involving air pollution from 2014 -2019 for Plymouth based on mortality data)

2. Please list the methodology used and the origins of the source data.

3. Can you please confirm what Public authorities would supply you with air pollution mortality data. I believe that the ONS do hold linked air pollution mortality data information for Plymouth, can you please supply what information is held.

We said

Thank you for your request.

In response to your original FOI request, we advised you to contact to enquire about a custom output. We have said that we might be able to produce, but this would need to be investigated to see what is feasible with the data we hold. There might be a charge for a custom output which would be subject to our charging policy. Although this falls outside of the Freedom of Information regime, we have looked into your enquiry further to check the feasibility of creating a bespoke analysis, and we do not hold the data necessary to fulfil your request.

The General Register Office (GRO) holds and supplies records of deaths in England and Wales.

ONS mortality data comes from the information collected at death registration. All of the conditions mentioned on the death certificate are coded using the International Classification of Diseases, Tenth Revision (ICD-10). From all of these causes an underlying cause of death is selected using ICD-10 coding rules. The underlying cause of death is defined by the World Health Organization (WHO) as:

a) the disease or injury that initiated the train of events directly leading to death, or

b) the circumstances of the accident or violence that produced the fatal injury

If air pollution is mentioned on a death certificate, it would be assigned the ICD-10 code Z58.1 'Exposure to air pollution'. Unfortunately, we do not have any records where air pollution (Z58.1) has been assigned as a cause of death or contributing factor by the doctor or the coroner. If ONS are not provided with the "defined" information we cannot code it as a cause of death.

Deaths from respiratory disease are usually certified by a doctor, without the need for referral to a coroner, so in many cases the underlying respiratory disease could be recorded without any mention of air pollution, especially if there was no definite evidence of a link.

The article published by ONS on 13th August 2020 called Does exposure to air pollution increase the risk of dying from the coronavirus (COVID-19)? was produced using different methodology. This report was created as a one off by analysing mortality records for the most polluted areas. This provides more accurate results because researchers were able to look for correlation between rates of respiratory disease and air pollution, however this article is not showing a count of deaths where air pollution was recorded as a contributing factor on the death certificate.

The areas with high air pollution are not defined by ONS and to carry out the analysis, our researchers developed a statistical model controlling for factors such as levels of deprivation, population density, public health (such as smoking rates) and pre-existing health conditions. This enabled us to compare deaths among populations of similar health from the same sort of area, with the main difference being long-term exposure to air pollution.

Detailed analysis is available here: Coronavirus (COVID-19) related mortality rates and the effects of air pollution in England. This analysis was carried out by specialist research officers and is not possible for us to re-produce this modelling for bespoke tabulations.

If you require further assistance, please contact