Post-harvest chemical use in agriculture receives far less attention than pesticide application in the field, although food may continue to be treated during storage, transport, ripening, packing and preparation for sale. Fumigants protect grain from insects, fungicides limit decay, sprout suppressants extend storage life, sanitising agents control microbes, and ripening treatments or surface coatings influence marketability.
These interventions are not automatically unsafe. Properly authorised and correctly applied treatments can reduce pest damage, prevent avoidable food loss and protect export consignments. Concern arises when substances are unapproved, doses are incorrect, treatments are poorly recorded, workers are inadequately protected or residues are not systematically monitored.
The policy objective should therefore not be an overnight chemical-free post-harvest economy. It should be an accountable system that progressively replaces hazardous or unnecessary treatments while preserving food safety and supply.
Post-Harvest Chemical Use in Agriculture Is Poorly Measured
There is no reliable global figure for how much chemical is used specifically after harvest. National datasets usually report pesticide sales by broad class or record applications at farm level. They rarely separate treatments made in silos, warehouses, packhouses, ripening chambers, shipping containers and wholesale markets. International guidance also recognises that pesticide statistics can be difficult to compare because definitions, reporting practices and the distinction between sales and actual use vary between countries.
The European Union reported approximately 316,000 tonnes of pesticide sales in 2024. That figure covers the wider market for plant-protection products and cannot be treated as a post-harvest estimate. Sales data also reveal little about whether a product was applied correctly, left a residue or could have been replaced by better storage technology.
This measurement gap matters. Governments may know which products are registered and laboratories may test selected commodities, yet still lack a complete picture of where, why and how frequently post-harvest treatments occur. For Sri Lanka and similar economies, better data should precede sweeping restrictions.
What Happens After Crops Leave the Field?
Post-harvest use varies by commodity. Rice, maize, wheat, pulses and spices may be fumigated against storage insects. Fresh fruit can receive fungicidal treatment or approved coatings to reduce decay and moisture loss. Potatoes may be treated to suppress sprouting. Bananas and mangoes may be exposed to ethylene under controlled conditions for uniform ripening.
The risks also differ. Some treatments can leave residues that must comply with maximum residue limits. Fumigants may create their greatest danger during application and ventilation, exposing operators, warehouse staff or nearby communities. Certain substances can also remain in buildings, equipment or dust and contaminate later consignments.
A credible framework must therefore address dietary exposure, occupational safety, environmental release, illegal substances, resistance among storage pests and cross-contamination.
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Health Risk Depends on the Substance and Exposure
Public debate sometimes treats any chemical residue as proof that food is unsafe. That is not scientifically accurate. The World Health Organization explains that pesticides can cause acute or chronic effects depending on the substance, dose and route of exposure. International assessments establish acceptable daily intakes, acute reference doses and residue recommendations to support national food-safety standards.
A residue detected below an authorised limit does not mean that the food contains no chemical. An exceedance is a compliance failure requiring investigation, but it does not automatically prove that a consumer will become ill. The higher-risk governance failures are unapproved use, repeated exposure not captured by limited sampling, weak enforcement and the absence of records between harvest and retail.
This distinction is important for public policy. Regulators should neither minimise legitimate concerns nor create unnecessary alarm by presenting every detectable residue as evidence of poisoning.
What Developed Markets Have Achieved
The strongest global lesson is that confidence comes from routine surveillance and public reporting rather than broad assurances.
European authorities analysed 132,793 food samples for pesticide residues in 2023. Ninety-eight per cent complied with European Union legislation, while 58 per cent contained no quantifiable residues.
In the United States, more than 99 per cent of samples tested through the 2024 Pesticide Data Program were below Environmental Protection Agency tolerances, and 42.3 per cent had no detectable residues. The programme places particular emphasis on foods consumed by infants and children.
These results do not prove that every food item is risk-free. They show the value of large, continuing programmes that expose non-compliance, guide regulatory review and give the public measurable evidence.
Europe’s experience with chlorpropham provides a specifically post-harvest lesson. The chemical was widely used to suppress sprouting in stored potatoes. The European Commission did not renew its approval in 2019 and required member states to withdraw authorisations by January 2020.
The European Food Safety Authority later found that chlorpropham could migrate to potatoes placed in storage facilities where it had previously been used. Regulation therefore had to consider contaminated buildings, crates, dust and equipment, not only current applications.
Australia offers another lesson through its management of phosphine, a major stored-grain fumigant. Long dependence on the treatment has contributed to resistance among storage pests, prompting national resistance monitoring and detailed best-practice programmes. Incorrect or sublethal fumigation can make future control more difficult and increase operational risk.
The policy lesson is clear: replacing a chemical is only one part of regulation. Authorities must also monitor historical contamination, treatment quality and whether pests are becoming resistant.
Safe Ripening Requires Precision, Not Generalisation
Artificial ripening demonstrates why regulators must distinguish an approved process from a dangerous shortcut. Ethylene is a naturally occurring plant hormone and is used internationally in controlled chambers. The problem is not controlled ethylene itself, but direct chemical contact, excessive application, unsafe facilities or prohibited substances.
India’s food regulator prohibits calcium carbide for fruit ripening while permitting ethylene under specified conditions. Its guidance addresses chamber design, ventilation, temperature, humidity, exposure time and operating procedures. Industrial-grade calcium carbide can contain arsenic and phosphorus impurities, making its uncontrolled use particularly concerning.
This regional model is relevant to Sri Lanka. Enforcement should remove illegal practices while providing traders with an affordable lawful alternative.
A prohibition without infrastructure can drive activity underground. Regulation works better when certified ripening facilities, training and access to approved technology are available to wholesalers and producer organisations.
Sri Lanka Needs a Clearer Post-Harvest Framework
Sri Lanka regulates pesticides through the Office of the Registrar of Pesticides, whose mandate includes minimising associated health and environmental risks while ensuring that necessary products are managed effectively.
National food standards also refer to SLS 910 for maximum pesticide residue limits. Sri Lanka therefore possesses important elements of a regulatory framework, including product registration, standards and laboratory testing capacity.
The Department of Agriculture promotes alternatives in particular crops. Its mango guidance, for example, identifies hot-water treatment as an effective post-harvest intervention against major mango diseases.
The problem is not necessarily the absence of institutions. It is the limited public visibility of post-harvest-specific information across the domestic chain.
Registration, laboratory testing, standards, occupational safety, market inspection and export controls can operate in separate administrative channels. Regulators may identify individual failures without seeing recurring patterns by commodity, warehouse, treatment or operator.
Post-harvest chemical governance should therefore be treated as a food-system issue, not only a pesticide-registration function.
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A Reform Agenda for Sri Lanka and Other Countries
First, authorities should publish a national inventory of approved post-harvest treatments. It should specify the commodity, purpose, dose, application method, ventilation or withholding requirement, operator qualification and applicable residue limit.
Second, licensed warehouses, fumigators, packhouses and ripening facilities should keep digital treatment records linked to batch or lot numbers. A standard mobile reporting system could establish traceability without requiring an expensive national platform.
Third, residue surveillance should be risk-based. Testing can prioritise:
- Commodities stored for extended periods.
- Fruits commonly subjected to artificial ripening.
- Foods associated with previous domestic or export violations.
- Products consumed heavily by children.
- Warehouses and operators with recurring compliance problems.
Annual publication should show compliance rates, substances detected, affected commodities and enforcement action. The experience of the European Union and United States demonstrates how consistent public reporting can strengthen consumer confidence without suggesting that the food system is entirely free from risk.
Fourth, investment must support alternatives. Reliable drying, hermetic storage, temperature and humidity management, cold chains, improved sanitation, hot-water treatment, controlled atmospheres and biological controls can reduce repeated chemical intervention.
FAO assessments show that dependable refrigeration can slow spoilage, preserve food safety and extend shelf life. Developed countries generally experience lower losses in the middle stages of food supply chains partly because of stronger storage, transport and cold-chain systems.
Fifth, hazardous fumigants should be restricted to trained and certified applicators. United States pesticide labels for phosphine products require certified application or direct supervision, reflecting the occupational danger involved. Comparable safeguards should include gas monitoring, protective equipment, exclusion zones, ventilation requirements and emergency procedures.
Finally, public communication must avoid two extremes: dismissing all concern or describing every detectable residue as poisoning. Consumers need explanations of approved treatments, illegal practices, residue standards and the limits of household washing.
The United States Environmental Protection Agency advises washing fresh produce thoroughly under running water, but also notes that washing cannot remove every pesticide residue.
Reducing Chemical Dependence Without Increasing Food Loss
Post-harvest chemicals are often compensating for weak storage and logistics. Removing them without improving drying, refrigeration, packaging, transport and market coordination could increase spoilage, insect damage and food prices. Poor storage can itself allow losses caused by insects, moulds, rodents and other pests.
The realistic objective is progressive substitution:
- Eliminate prohibited and high-risk practices first.
- Reduce routine treatments through better infrastructure.
- Retain necessary treatments under strict controls.
- Review approvals as new scientific evidence emerges.
- Help smaller operators adopt affordable non-chemical technologies.
- Measure both residue outcomes and actual post-harvest application.
Developed markets show that stronger outcomes come from residue surveillance, transparent reporting, product review, operator controls and investment in alternatives. Sri Lanka and other emerging economies need not copy every mechanism.
They can adopt the central principle that every post-harvest treatment should be authorised, recorded, justifiable and verifiable.
Post-harvest chemical use is not merely a technical issue hidden inside warehouses. It tests whether food-safety policy can follow a product from the field to the consumer.
Closing that gap would protect health, preserve market access and create a more efficient agricultural system without ignoring the practical need to prevent food loss.
This analysis is for educational and public-affairs purposes only. It does not constitute medical, agricultural, regulatory or legal advice.
