Microplastics have infiltrated every part of the planet. They have been found buried in Antarctic sea ice, within the guts of marine animals inhabiting the deepest ocean trenches, and in drinking water around the world. Plastic pollution has been found on beaches of remote, uninhabited islands and it shows up in sea water samples across the planet. One study estimated that there are around 24.4 trillion fragments of microplastics in the upper regions of the world’s oceans.

But they aren’t just ubiquitous in water – they are spread widely in soils on land too and can even end up in the food we eat. Unwittingly, we may be consuming tiny fragments of plastic with almost every bite we take.

In 2022, analysis by the Environmental Working Group, an environmental non-profit, found that sewage sludge has contaminated almost 20 million acres (80,937sq km) of US cropland with per- and polyfluoroalkyl substances (PFAS), often called “forever chemicals”, which are commonly found in plastic products and do not break down under normal environmental conditions.

Sewage sludge is the byproduct left behind after municipal wastewater is cleaned. As it is expensive to dispose of and rich in nutrients, sludge is commonly used as organic fertiliser in the US and Europe. In the latter, this is in part due to EU directives promoting a circular waste economy. An estimated 8-10 million tonnes of sewage sludge is produced in Europe each year, and roughly 40% of this is spread on farmland.