Focus on the impacts of microplastics has almost entirely been on the world’s oceans, but researchers say an even bigger problem could be hiding under our feet.

Microplastics are particles smaller than five millimetres. About 800,000 to 2.5 million tonnes of these tiny pieces of plastic are estimated to end up in oceans each year, according to the International Union for Conservation of Nature and Natural Resources.

However, not much is known about the damage these particles cause to landscapes as they make their way to the sea.

Agricultural lands are likely to be the most plastic-contaminated places outside of landfill and urban spaces, according to research published in the Environmental Science and Technology journal.

The plastics find their way into agricultural soils through recycled wastewater and rubbish.

Between 107,000-730,000 tonnes of microplastic are added to European and North American farmlands each year, according to researchers at the Norwegian Institute of Water Research.