According to new research, farmlands across Europe are potentially the largest worldwide reservoir of microplastics due to the high concentrations found in fertilisers obtained from sewage sludge.
Between 31,000 and 42,000 tonnes of microplastics (or 86 710 trillion microplastic particles) are applied to European soils every year, mirrored the concentration of microplastics found in ocean surface waters.
Microplastics extracted from raw sewage from wastewater treatment plants are estimated to be at around 1% of the weight of sewage sludge, which is commonly used as a fertiliser on farms across Europe.
The United Kingdom is reported to have the highest amount of microplastic contamination in its soils, followed by 500 1000 microplastic particles per square meter of agricultural land per year.
The use of wastewater sludge on agricultural land is a durable and renewable source of fertiliser across Europe, partly because of EU guidelines that promote the removal of sewage sludge from landfill and incineration, as well as energy production and agriculture.
Microplastics spread onto farmland will be refilled into the natural watercourse when subjected to surface water run-off or infiltration to groundwater.
Microplastics are less than 5mm in length, which pose a risk to wildlife as they are easily ingested and can carry contaminants, toxic chemicals, and hazardous pathogens, posing a threat to the entire food chain.
According to the lead author of the study, microplastics are in fact being removed at wastewater treatment plants at all times, or they are effectively being relocated around the environment.
Water companies need to establish an objective to manage microplastics in wastewater sludge, which means these contaminants are taken back into the soil and will eventually return to the aquatic environment.
The team used sample data from the Nash Wastewater Treatment Plant in Newport, South Wales, which treats combined sewage from a total of 300,000.
Their study revealed that the treatment facility was 100% effective in extracting large microplastic particles, which were 1 5mm in length, from incoming sewage that would otherwise be released into the aquatic environment.
Each gram of sewage sludge was tested to contain up to 24 microplastic particles, which was roughly 1% of its weight.
On the back of data from the European Commission and Eurostat, we calculated the effect of sewage sludge on the use and application of it as a fertilizer across the continent.
The overall concentrations, which were not less than 1mm in length, are likely to be substantially higher than their estimates.
Our findings highlight the root of the problem across European soils and suggest that the practice of spreading sludge on agricultural land might potentially make them one of the largest global reservoirs of microplastic pollution, according to James Lofty.
Under the present administration, there is currently no European legislation which limits or controls microplastic input into recycled sewage sludge based on the loads and effects of microplastic exposure.
A greater standardised monitoring of microplastic concentrations in wastewater sludge and agricultural soils should be undertaken, which would give a better visual of contamination levels in soils across Europe.