Scottish House Condition Survey (SHCS) and lead plumbing: EIR release

Information requested

Any current, historical (within 20 years) or recent assessments, reports, or studies on lead exposure in the Scottish population, particularly in Edinburgh and other areas with older housing stock (e.g., tenements with lead plumbing or historic use of lead-based paints and pipes).

Response

As the information you have requested is ‘environmental information’ for the purposes of the Environmental Information (Scotland) Regulations 2004 (EIRs), we are required to deal with your request under those Regulations. We are applying the exemption at section 39(2) of the Freedom of Information (Scotland) Act 2002 (FOISA), so that we do not also have to deal with your request under FOISA.

This exemption is subject to the ‘public interest test’. Therefore, taking account of all the circumstances of this case, we have considered if the public interest in disclosing the information outweighs the public interest in applying the exemption. We have found that, on balance, the public interest lies in favour of upholding the exemption, because there is no public interest in dealing with the same request under two different regimes. This is essentially a technical point and has no material effect on the outcome of your request.

I enclose a copy of the information you requested.

The Scottish House Condition Survey (SHCS) records the presence of lead plumbing in dwellings in the achieved sample through two questions L9 and L10.

However, it should be noted that the SHCS is a non-invasive survey and does not for example involve searches within walls or underneath floorboards.

Therefore the presence of lead in question L9 “Is the underground water main (or communal rising main to the flat) lead free?” and question L10 “Is the entire water distribution and storage system within the dwelling lead free?” is generally recorded through observing the rising main, typically located under the kitchen sink, as well as pipes observable in the bathroom or attic.

As such while there are very few properties that have lead piping it is possible that some could be hidden beneath floors or in walls that the surveyor was unable to find which will not be reflected in the attached figures or in our data when shared with researchers.

The SHCS team previously provided data from questions L9 and L10 to a University of Edinburgh Study entitled “Estimating the number of homes in Scotland with internal lead piping” which is available here.

We have also included in our response the data for questions L9 and L10 broken down by year, and by local authority, in the attached annex.

The SHCS is a sample survey which has a sample size of about 3,000 dwellings per survey year. Like all sample surveys the results of the SHCS are estimates of the corresponding figures for the whole population and these results might vary from the true values in the population.

This variability becomes much more important when small sub-samples of the population or small estimates are examined, and there is therefore greater uncertainty around figures. For example, a subsample with only 100 households might have had very different results if the sampling had been run on 1,000,000 households.

Therefore it should be stressed that all figures provided are estimates which lie at the midpoint of a confidence interval which depends primarily on sample size. Due to the small sample sizes and estimates in the attached data it should be noted that there is greater uncertainty around these estimates than typical estimates from SHCS data.

In order to produce local authority level estimates, three years of survey data is combined to mitigate the smaller sample sizes involved when analysing sub-national geographies. The most recent local authority data is therefore an average for the period 2017-2019.

The LA analysis is designed to provide a snapshot of Local Authority average results for a range of house condition descriptors, not to measure year-on-year change or to make direct comparisons between consecutive groups. This is because the three-year averages are updated on a rolling basis, so each edition of the tables has two overlapping years of data with the previous edition. Therefore, when analysing Local Authorities over time, these estimates should only be used to get an indication of long-run trends and a sense of direction in the series of interest.

To help prevent the spread of COVID-19, all Scottish Government face-to-face interviewing, including the Scottish Household Survey (SHS) was suspended in March 2020. As a result, there was no further physical survey (Scottish House Condition Survey) data collection in 2020, and the 2021 SHCS was undertaken using an External + approach. Due to these enforced changes the results of the 2021 survey were published as Experimental Statistics and are not comparable to other waves of the survey.

The lack of SHCS data for 2020 and the enforced changes for 2021 cause issues for the production of  local authority estimates from the SHCS for two reasons. Firstly, there is no SHCS data for 2020 so we cannot produce a three-year average for 2019 to 2021. Secondly, the data from the 2021 external+SHCS is not directly comparable with that for earlier years due to the methodological differences and it would not be appropriate to combine it with the data for 2019 (or earlier) to produce a multi-year average. Therefore we won’t be able to return to the usual approach for producing local authority estimates from the SHCS until the 2024 wave of the SHCS has completed and published in early 2026.

It should also be noted that the tables included provide an estimate of the total population living in dwellings which have lead water mains or in the dwellings water system. However, the SHCS is weighted to the occupied dwelling stock within the survey year, calibrated by dwelling age and type. It is not weighted to the overall population and therefore population estimates from the SHCS may not reflect population counts from official sources such as the census. Due to this the percentage of the population figures provided as part of this request should be taken as approximate figures.

Additionally, the scope of this EIR is limited to information held by Scottish Government. You may wish to contact the Drinking Water Quality Regulator, who could have information on lead plumbing which is not contained in this response.

You can submit an information request to them at DWQR@gov.scot.

About FOI

The Scottish Government is committed to publishing all information released in response to Freedom of Information requests. View all FOI responses at https://www.gov.scot/foi-responses.

EIR 202500467147 - Information Released - Annex

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Excel document

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