Within the UK, there are areas with a relatively high population density like south-east England, and areas of low population density, like north-east Scotland.

In 2020, the population of the UK rose to over 67 million people. The major cities of the UK can be seen on the map. London is the UK’s largest city and Birmingham is its second largest city.

This allowed researchers to observe trends in the litter's accumulation and abundance, while also enabling them to explore any connections between quantities of litter and population density.