The Scottish Longitudinal Study has recently been expanded to include an extensive set of environmental data. Using data which is freely available from the Met Office and DEFRA. SLS researchers can now investigate environmental effects by socioeconomic characteristics in a way not previously possible.

The linkage was originally created as part of a joint project of the SLS and the Scottish Health Informatics Programme – see the SHIP website for more background information.

Weather data is currently available as monthly averages from January 1981, though it is possible to explore some variables from much earlier if needed. Rather than being based on weather station data, the variables report on 5x5km grids covering the whole of Scotland. Measurements include:

• Temperature
• Frost
• Sunshine
• Precipitation
• Cloud cover

Pollution measurements are based on 1x1km grids, again covering the whole of Scotland. Annual averages are currently available for:

• Carbon monoxide (2001-2008)
• Nitrogen oxide (1994-2008)
• Ozone (1994-2005)
• Particulate matter < 10 microns (1994-2008)
• Particulate matter < 2.5 microns (2002-2008)
• Sulphur dioxide (1994-2008)

These weather and pollution data open up several new fields of SLS-based research – including environmental health and environmental justice – as well as extending the Study’s potential for public health research. And for environmental researchers, the linkage to the SLS allows them to control for known confounding factors such as socioeconomic status. The SLS can also offer the large sample sizes required in order to detect what are often relatively small effects.

The use of grid-based rather than station-based data is particularly useful for Scotland, which contains many sparsely populated areas that would not otherwise be covered. The increase in spatial coverage afforded by the grid-based approach also provides increased spatial variability. This means researchers can look at annual average exposures in a large number of small areas rather than focusing on the accumulated exposure of people living in a more concentrated area.

Data from the Scottish Air Quality Monitoring Network SAQMN can also be added in to the SLS. This provides hourly time series data from air pollution monitoring stations across Scotland. These data can be used on their own, or together with the grid-based data to improve exposure estimation. More information about SAQMN can be found on their website.

For an example of how the data have been used, see SLS Project 2007_011: “Time-space geographies and exposure to air pollution: examining the impact of varying exposure to air pollution on the health of adults and birth outcomes”.

The SLS team is also exploring other environmental data linkages, most notably to Road Network Data. This dataset can be examined by vehicle type, and would, for example, allow analysis of the effects that living close to busy roads can have on health. Other potential linkages are with levels of radioactive pollution (e.g., radon) and proximity to landfill sites.

For more detailed technical information about the weather and pollution data available, please explore the Met Office, DEFRA and SAQMN links below:

• Met Office: www.metoffice.gov.uk/climatechange/science/monitoring/ukcp09/available/monthly.html
• DEFRA: www.uk-air.defra.gov.uk/data/pcm-data
• SAQMN: www.scottishairquality.co.uk/

If you are interested in using these or any other environmental dataset in combination with the Scottish Longitudinal Study, please contact us to discuss your ideas.