Concerns over the fungicides applied to non-organic citrus fruits have made headlines and sparked debate this month, after a social media post by nutritionist Eva Humphries went viral.
The post pictured the label on a pack of limes from Lidl, which carried the warning, ‘peel unfit for consumption, conserved with: Azoxystrobin, Fludioxonil and Wax: E903.’
The use of fungicides on citrus fruit is nothing new. They are routinely applied after harvest to extend shelf life and prevent mould growth during transport and storage, particularly blue mould, which can quickly spoil the fruit. Treatment can involve dipping harvested fruit in a fungicide solution, spraying it directly onto the skin or incorporating fungicides into the wax coatings often applied to citrus.
But explicit warnings advising consumers not to eat the peel have prompted fresh questions about what these treatments mean for our health and the environment.
If you’ve never thought to check the labels of fruit and veg for unexpected ‘ingredients’, you’re not alone. Yet take a closer look at a bag of lemons or easy peelers and you’re likely to find a list of chemicals applied directly to the fruit. Supermarkets are advised, although not legally obliged, to declare the chemicals used in the production and preservation of fruit and vegetables.
Lidl has since confirmed that the warning was an error, with the wording “peel unfit for consumption” mistakenly added to a small number of citrus fruits. The supermarket chain explained that post-harvest treatment disclosures will remain on the packaging, while the products themselves have not changed and continue to meet all UK safety standards.
But the incident has brought a relatively little-known aspect of conventional fruit production into the spotlight. What exactly are these chemicals, what risks might they pose, and are they really necessary to keep our lemons, limes and oranges fresh?
What chemicals are used on citrus fruit?
Several fungicides commonly used on citrus fruit have attracted attention because of their potential effects on human health and the environment.
Imazalil, frequently found on citrus labels, is a suspected carcinogen and has been associated with endocrine (hormone) disruption and reproductive toxicity. Fludioxonil has also come under scrutiny because of its persistence in the environment. Sometimes described as a ‘forever chemical’, it can remain in the environment for a long time and has been associated with endocrine disruption and oxidative stress.
Thiabendazole, also frequently listed on citrus labels, can interfere with thyroid function, with high-dose animal studies pointing to potential developmental and reproductive effects.
The concerns around post-harvest fungicides aren’t limited to human health. Their use can also have consequences for the wider environment, particularly aquatic ecosystems.
“One of the biggest concerns is around aquatic ecotoxicity – these fungicides are applied in various ways like showers, dips, waxes etc and any runoff from packing houses can end up in wastewaters,” Zac Goodall, Head of Sustainability at Riverford explains.
Fungicides are designed to act in various ways against fungal enzymes and growth mechanisms. Fish, crustaceans and other aquatic life rely on the same biochemical mechanisms that fungicides target, so they also suffer when fungicides are released into the environment.”
Does it get beyond the peel?
The most obvious concern is when citrus peel or zest is used in cooking. If you’re adding zest to food, making a lemon drizzle cake, marmalade, or popping a slice of lemon into your drinks, you’re directly consuming the peel.
And even if you’re not eating the peel directly, there may be reason to think about what’s transferring from it. One study found that adding lemon peel to drinks transfers measurable amounts of post-harvest fungicides into the liquid – a finding with particular relevance for those who start the day with hot water and lemon.
But what about the flesh itself? A recent study found that fungicide residues can migrate into the pith and, to a lesser extent, the flesh of the citrus fruit.
These treatments are also specifically designed to adhere to the fruit’s surface, which also means that simply washing the peel isn’t an effective way to remove them.
Are fungicide residues safe at the levels found on citrus?
Some commentators have pushed back against concerns over fungicide residues, arguing that the health effects associated with these chemicals are generally linked to exposures at much higher doses than those likely to be encountered through eating citrus peel.
The chemicals are approved for use within regulated limits, with maximum residue levels (MRLs) set to ensure that exposure through food remains within established safety thresholds. However, testing sometimes finds residues above these limits, and many consumers would prefer to avoid exposure altogether.
There’s also a question around what’s known as the ‘cocktail effect’. Regulatory bodies generally assess the safety of individual chemicals in isolation against their own exposure thresholds, but commercially grown citrus is often treated with combinations of three to five different active ingredients. In other words, consumers may be exposed to several fungicides at once, rather than just one.
“Citrus fruit regularly tops our ‘Dirty Dozen’ list of produce found to be high in multiple pesticide residues,” explains Sarah Compson, Head of Policy and Campaigns at the charity, Pesticide Action Network UK.
“Safety testing isn’t carried out on real-life dietary exposure. People are exposed to more than one pesticide at a time. The regulations don’t do enough to protect public health.”
Is there an alternative?
You might assume that buying unwaxed citrus is the answer, but unwaxed doesn’t necessarily mean untreated. Fruit without a wax coating can still have been treated with post-harvest fungicides; it simply hasn’t received the additional wax layer.
Organic citrus is a good choice for those who would like to avoid these fungicides, which are not permitted under organic standards. So how do organic growers and suppliers manage shelf life and prevent mould without them?
In organic supply chains, preventing damage to the fruit and keeping it cool are particularly important. Careful harvesting and handling help avoid breaks in the skin, which can provide entry points for mould, while rapid refrigeration is also key.
Dale Robinson, Head of Safety, Quality Systems and Assurance at Riverford, explains, “it’s all about good farming initially to ensure the crop is clean and healthy. Then it’s harvesting with care and at the right time – slightly underripe so it travels well, and within the correct weather window, so we avoid harvest immediately after rain, and getting the fruit chilled as soon as possible. Once it’s chilled and packed, it’s about maintaining that through the supply chain – ensuring temperatures are maintained and care is taken through storage and handling all the way to our customers doorstep.”
Robinson also acknowledges that Riverford benefits from a shorter supply chain than supermarkets, with fruit arriving directly from farms at the pack house. “Citrus fruits are kept chilled all the way to our delivery vans and don’t linger on supermarket shelves for days,” he explains.
Organic citrus fruit may not keep quite as long in the fruit bowl, although keeping them in the fridge can help with this, but the trade-off is avoiding these post-harvest fungicides altogether. Organic fruit can also be more expensive, but if budget is a consideration, prioritising it when you’re planning to use the peel or zest is a practical compromise.
Beyond organic, there is research underway to find safe, environmentally friendly alternatives to conventional synthetic fungicides. These studies are looking at microbial options, plant extracts, and physical interventions such as UV radiation. But it appears we are still quite some way from a solution that poses a viable alternative commercially.
Hannah Neville-Green is a nutritional therapist and part of the Food Team at Riverford.
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