Potentially toxic sewage being spread across UK farms must be subject to stricter checks, as evidence grows of its potentially harmful effects to food and water supplies, experts have warned.
Around 170,000 truckloads of sludge, a byproduct of the sewage treatment process, are spread on farmlands as fertiliser across the country each year.
Last year The i Paper reported scientists were becoming increasingly concerned that the sludge is full of dangerous contaminants, such as “forever chemicals” that are polluting crops which are then consumed by humans.
Sludge spread can also harm biodiversity and lead to water pollution when the material washes off into rivers. In the US some farmers have been forced to abandon land due to contamination from sludge.
Now the UK Government is being urged to toughen the regulation of sludge and test it routinely before it is spread onto farmland.
A new study by the Scotland-based James Hutton Institute, which researches sustainable approaches to agriculture, found that the use of sludge in the UK could be destroying soil health and the wider environment.
It calculated sewage sludge contains a number of contaminants, such as microplastics, pharmaceuticals and PFAS “forever chemicals”, at levels that are likely to exceed the safe limit for organisms living in soil.
Microplastics presented a risk after as few as two applications of sludge to land, while some pharmaceuticals posed a notable risk after just one application, the study found.
“It’s going to impact on soil health, that is for certain,” the report’s author Rupert Hough, told The i Paper.
“And there’s knock-on effects on the water system, because many of these chemicals and microplastics end up in the water as well. So there’s impact on the environment and biodiversity from the practice.”
When the waste from our homes and businesses arrives at sewage treatment plants, the wastewater is processed before being released back into our waterways.
The leftover solid product is known as “sludge”. Water companies produce millions of tonnes of it each year and must find a way to get rid of it.
For years it has been used in agriculture as a fertiliser.
This is “a win-win deal” for water companies, explained Dr Antonis Myridakis, environmental scientist at Brunel University. “Instead of producing waste, producing something you can sell.”
However, sludge contains a variety of harmful substances that are not removed as part of the sewage treatment process.
These are all things that are present in our urine or in products we throw down the drain, including microplastics, forever chemicals, pharmaceuticals, antibiotics, heavy metals and illicit drugs.
These contaminants can damage the soil and the surrounding environment. They can also be absorbed by the plants they are spread on, ultimately being consumed by humans and making their way into our bloodstreams.
Natasha Kitching from the environmental charity Fidra, which commissioned the research, said the results should be of particular concern for farmers.
She said: “If you’re looking at it as a farmer, it really does impact the sort of health and productivity of your soil…you don’t want to be putting these contaminants onto your land, and then in a few years, you’ve got contaminated land.”
In the US state of Maine, some farmers have been forced to stop producing food on areas of land after discovering it had become dangerously contaminated by sludge.
The state has banned the use of sludge on farmland entirely. The practice is also not permitted in countries including the Netherlands and Switzerland.
Alongside the environmental impacts, scientists are concerned about the human health risk. This is because the contaminants that make their way into soil can be absorbed by the food products that humans go on to consume.
“When we are feeding plants with this, we fortify them with these chemicals, essentially. This is a good reason to strictly regulate what is there and what we are putting as fertiliser into agricultural production,” Dr Myridakis said.
A growing body of scientific evidence has shown that many humans have some level of PFAS in their bloodstream, which can make their way into our systems through the food we eat, the water we drink or the products we use.
PFAS – perfluoroalkyl and polyfluoroalkyl substances – are known as “forever chemicals” due to the fact that some can take more than 1,000 years to degrade. While the full effect of these substances on humans is still little understood, studies have linked them to a wide range of health problems, including increased cancer risk, reduced fertility and developmental issues.
In January, the US Environmental Protection Agency issued a warning that PFAS present in sludge can increase the cancer risk of those who regularly consume milk or beef from farms where it is spread.
It followed a risk assessment looking at farmers and people who lived nearby sites where sludge was used.
While such a study has not been carried out in Britain, samples of UK-produced sludge obtained recently by Watershed Investigations found PFAS at levels that would not be considered safe on allotments.
Hough said the threat to human health is not as likely to be as acute as the threat to soil and the environment, as the chemicals pass through a number of processes before the point at which they reach human bodies.
However, he said the growing evidence demonstrates why sludge must be regulated in the same way as composts and digestates, which are tested before being applied to soil.
“There’s no real controls on what you and I put down the drain or flush down the toilet. It’s all sorts of things that end up in it, but there’s currently no standard,” he said.
“No one has really pushed forward developing a standard and saying, ‘If the sewage meets this standard then we use it for this application, if it doesn’t then we do something different with it.’ That’s quite important, because it is the food chain after all.”
Kitching called on the Scottish and UK Governmenst to “further regulatory efforts to mitigate harmful contamination of our soils from contaminated sewage sludge”.
She said this should include “upstream solutions” that limit the use of toxic chemicals and therefore prevent them entering the sewerage system in the first place, as well as “future proofing our sewage management systems”.
Water UK, which represents water companies in England and Wales, has previously called on PFAS to be banned entirely.
A spokesperson for the Department for Environment, Food and Rural Affairs said it was “working closely with the Environment Agency to assess the current legal framework in this area”.
A Scottish Government spokesperson said it was “working with Scottish Water and SEPA to further our understanding of emerging contaminants”.
“In the meantime, ministers will also shortly lay regulations that seek to enhance environmental and human health protection by reducing the limits of some contaminants and introducing treatment standards for sewage sludge.”
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