A banana with a bright yellow peel or a mango that looks perfectly ripe may appear ready to eat. But can consumers tell whether fruit has been exposed to potentially harmful ripening chemicals simply by looking at it?
A study by researchers from Kenya Methodist University raises concerns about fruit safety in Kenyan markets, particularly the use of calcium carbide and other chemicals to control ripening.
Published in the International Journal of Professional Practice, the study analysed 392 fruit samples and surveyed 180 farmers and traders in Nairobi, Meru, Murang’a and Kirinyaga counties between September 2024 and April 2025.
Its findings raise an important question for consumers: Can you identify chemically treated fruit before buying it?
The short answer is that appearance alone cannot reliably establish whether fruit has been treated with potentially harmful chemicals.
The study did not develop or validate a visual test that consumers can use to distinguish chemically treated fruit from naturally ripened produce. Its assessment relied on laboratory analysis and statistical modelling.
The researchers explain that artificial ripening and delaying agents are used to “synchronise ripening, extend shelf life, and preserve the visual appeal of produce during storage and transport”.
However, they warn that “improper usage, inadequate dosage control, and reliance on industrial-grade chemicals can compromise fruit quality”.
This means shoppers should be cautious about social media claims that colour, smell, texture or simple home experiments can conclusively reveal chemical treatment.
The research found that 63 per cent of surveyed farmers and traders used chemical agents to speed up ripening or delay maturity.
Calcium carbide was the most commonly reported agent, at 42 per cent, followed by ethephon at 27 per cent.
Laboratory analysis detected contaminants in 26 per cent of the 392 fruit samples. The researchers also reported that modelled acetylene concentrations in carbide-treated fruits exceeded the study’s stated reference threshold of 0.7 milligrams per kilogramme.
Bananas recorded the highest proportion of samples above relevant limits, at approximately 40 per cent. Mangoes followed at 20 per cent, while tomatoes recorded 17 per cent. Arsenic was detected in eight per cent of mango samples.
These findings apply to the fruits sampled in the four counties, not all fruit sold across Kenya.
The researchers identify calcium carbide as a particular concern because it releases acetylene gas to accelerate ripening. They state that it “poses recognized risks to human health”.
The report identifies potential health concerns associated with exposure to contaminants from inappropriate chemical use.
It describes possible effects from prolonged exposure, including “gastrointestinal disorders, neurological impairment, and possible long-term carcinogenic outcomes”.
The researchers also note that calcium carbide may contain toxic impurities, including arsenic and phosphine, which are associated with carcinogenic, neurological and respiratory health risks.
However, the study did not track consumers to establish whether eating the tested fruits caused illness. Its findings identify potential exposure risks, not confirmed cases of disease among consumers.
Washing fruit under clean running water remains a good food hygiene practice. However, it should not be treated as a guarantee that chemical residues or contaminants have been eliminated.
The study did not test household washing methods or establish that washing makes chemically contaminated fruit safe.
Consumers should also avoid relying on colour, smell, peeling or online home tests as proof that fruit is safe. The research provides no validated visual method for detecting harmful residues.
The researchers link chemical use to climate variability, market pressure and inadequate postharvest infrastructure.
They write that “climate variability and market pressure jointly drive chemical use in postharvest systems”.
Their analysis found rainfall variability was a significant predictor of chemical use, with a coefficient of 0.41, while market pressure recorded 0.36.
Changing weather can accelerate fruit maturation, shorten shelf life and increase postharvest losses. Traders may consequently turn to chemicals to preserve produce and maintain market value.
Limited access to safer alternatives, including controlled ethylene systems and cold storage, also contributes to the problem.
The researchers call for stronger coordination among the Kenya Bureau of Standards (KEBS), the Pest Control Products Board, the National Environment Management Authority, county governments and public health departments.
They recommend mobile residue-testing laboratories to enable “real-time screening of fruits and vegetables in high-risk markets”.
They also advocate stronger market inspections, farmer and trader training, improved traceability and investment in cold storage and solar-powered refrigeration.
For Kenyan consumers, the message is clear: a fruit’s attractive appearance cannot guarantee that it is free from harmful chemical residues. There is no reliable visual shortcut established by this study.
Protecting consumers will require better laboratory testing, safer fruit-handling practices and stronger enforcement across Kenya’s fruit supply chain—not leaving shoppers to guess whether the bananas and mangoes they buy are safe.
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