Pesticides and Their Impact: Crop Protection, Exposure and Environmental Risk
A pesticide can save a crop and still create a pollution problem.
That tension explains why the pesticide debate is so difficult.
Farmers use herbicides, insecticides, fungicides and other pesticides because weeds, insects, pathogens and rodents can destroy food before or after harvest. Crop protection can reduce losses, stabilise yields and protect stored products. But a substance designed to disrupt a living organism can also affect non-target organisms if exposure is high enough.
The important scientific question is therefore not whether pesticides are simply good or bad. It is which pesticide, used for what purpose, at what dose, with what exposure, under what controls and with what alternatives.
Pesticide is a broad category
The word pesticide includes many different substances and biological agents.
Herbicides control unwanted plants. Insecticides target insects. Fungicides suppress fungal diseases. Rodenticides control rodents. Other products regulate plant growth or target specific pests in stored food and forestry.
These chemicals differ enormously in mode of action, toxicity, persistence and environmental fate. Some break down relatively quickly. Others persist. Some are highly toxic to particular insects but less toxic to mammals. Others create serious occupational or ecological hazards.
Treating them as one chemical family hides those differences.
Regulators therefore evaluate active ingredients and products individually, considering both hazard - the capacity to cause harm - and exposure - how much reaches a person or organism.
Risk emerges from the combination.
Global pesticide use remains large
FAOSTAT's 2025 update estimated that agriculture used about 3.73 million tonnes of pesticide active ingredients in 2023.
That was slightly lower than in 2022, but still about 14 percent higher than a decade earlier and roughly double the quantity reported in 1990.
These numbers do not measure risk by themselves. One kilogram of one active ingredient is not environmentally equivalent to one kilogram of another. Application rates, toxicity and exposure pathways differ.
But the scale of use matters because pesticides move through millions of farms, supply chains and ecosystems. Even low-probability failures become important when products are used widely.
Why farmers rely on pesticides
Agriculture creates concentrated food resources for organisms other than humans.
A large field of one crop can provide an abundant host for insects or pathogens adapted to that plant. Weeds compete for light, water and nutrients. Fungal diseases can spread rapidly in favourable weather. Stored grain can be damaged after harvest.
Pesticides can act quickly and predictably compared with some alternatives. That matters when a farmer has only days to prevent a major loss.
This is why pesticide reduction cannot be designed as if pest pressure were imaginary. If alternatives are expensive, slow or unreliable, growers may return to the chemical option that protects their livelihood.
Effective risk reduction has to solve the farm problem as well as the environmental one.
Exposure determines where harm can occur
A pesticide applied to a field can travel through several pathways.
Spray droplets can drift beyond the target area. Rain can move residues into ditches, streams or ponds. Soluble compounds can leach toward groundwater. Soil particles carrying residues can erode. Treated seeds can expose birds or other animals. Workers can be exposed while mixing, loading or spraying products.
Food residues are another pathway, although regulated food systems use maximum residue limits and monitoring to keep consumer exposure within established safety frameworks.
The size of each pathway depends on chemistry, soil, weather, application method and behaviour.
A product that binds strongly to soil behaves differently from one that is highly soluble. Windy application conditions create different drift risks from still conditions. A persistent chemical raises different long-term concerns from one that degrades rapidly.
Non-target organisms can be affected directly or indirectly
Pesticides are intended to control pests, but ecosystems do not contain clean boundaries between target and non-target species.
An insecticide can affect beneficial insects if they are exposed. Herbicide use can alter the abundance of flowering plants that provide food for insects and birds. Aquatic organisms can be exposed when residues enter surface water. Soil organisms can encounter products applied to land or residues returning in plant material.
Indirect effects can be as important as direct toxicity.
If a pesticide reduces an insect population, predators that depend on those insects may lose food. If weed control removes non-crop plants, habitat and food resources can change even when wildlife is not poisoned directly.
FAO's pesticide-risk framework therefore includes measures to limit exposure of bees, non-target arthropods, birds, mammals, aquatic organisms and soil organisms.
Highly hazardous pesticides deserve special attention
WHO and FAO use the concept of highly hazardous pesticides for products that present particularly serious acute or chronic hazards under recognised classification systems and use conditions.
These products are a major concern where farmers have limited access to protective equipment, training, medical care or safe storage.
Acute pesticide poisoning can occur after substantial short-term exposure. Chronic risk is more complex because different active ingredients have different toxicological profiles and long-term evidence.
It is misleading to attribute every reported health problem to pesticides as one group. It is equally misleading to ignore occupational exposure because products are registered.
Registration, labelling and protective rules reduce risk only when the system works in practice.
Resistance turns repeated success into a future problem
Pesticides create evolutionary pressure.
Within a pest population, some individuals may carry traits that allow them to survive a treatment. If the same mode of action is used repeatedly, survivors reproduce and the resistant trait becomes more common.
The product then loses effectiveness.
Farmers may respond by increasing application frequency, changing products or mixing modes of action. If resistance management is poor, a highly useful pesticide can become ineffective.
Resistance is therefore both an agronomic and environmental problem. It can increase costs and encourage heavier chemical use.
Rotating modes of action, using non-chemical controls and applying pesticides only when justified can slow this process.
Integrated pest management changes the order of decisions
FAO describes integrated pest management, or IPM, as an ecosystem-based approach that promotes healthy crops with the least possible disruption to agro-ecosystems while encouraging natural pest-control mechanisms.
The basic idea is not 'never spray'.
It is to avoid making pesticides the automatic first response.
A farmer may use resistant crop varieties, sanitation, crop rotation, planting dates, habitat for natural enemies, traps, monitoring and biological controls. Pest populations can be observed against thresholds so that treatment occurs when likely damage justifies it.
When a pesticide is needed, the farmer can choose a lower-risk product, target the application more precisely and protect non-target areas.
This sequence can reduce pesticide use while preserving the ability to intervene when crop loss becomes serious.
Regulation is a lifecycle problem
Safe pesticide management begins before a product reaches a farm.
Governments need registration systems that evaluate efficacy and risk. Labels must communicate approved uses and protective measures. Dealers need to sell legitimate products. Farmers need training, protective equipment and calibrated application tools. Empty containers and obsolete stocks need safe disposal.
Illegal or counterfeit pesticides bypass much of this system.
So do products that remain stored for years after cancellation or expiry.
FAO's lifecycle approach is important because a pesticide can create risk during manufacturing, transport, storage, application and waste disposal. Focusing only on residues on food misses much of the problem.
'Natural' pesticides still require risk assessment
Organic and biological farming systems often use substances derived from plants, minerals or microorganisms.
These can be useful alternatives, but natural origin does not guarantee harmlessness. A substance can be natural and toxic. What matters is its biological activity, persistence, dose and exposure.
The same standard should apply in the other direction. Synthetic origin does not tell us the full risk profile either.
Sound pesticide policy should compare real alternatives rather than labels.
The objective is lower risk, not merely fewer kilograms
A country can reduce the mass of pesticide applied while shifting toward a more hazardous product. Another can use a larger mass of a low-risk biological agent and reduce overall danger.
That is why simple tonnage targets are incomplete.
Useful indicators include toxicity, exposure, persistence, application frequency, area treated, resistance, poisoning incidents, residues and impacts on non-target organisms.
The strongest strategy combines prevention, monitoring, safer substitution, precise application and removal of highly hazardous products where risks cannot be controlled.
Pesticides will remain part of many agricultural systems because crop pests are real and food losses matter.
Better information can also reduce unnecessary treatment. Weather-based disease forecasting, field scouting, pest traps, remote sensing and local warning systems can help growers identify when intervention is actually needed. These tools do not eliminate uncertainty, but they can replace routine calendar spraying with decisions linked more closely to pest pressure and crop risk.
But dependence is not inevitable.
The long-term goal is a crop-protection system in which ecology, agronomy and monitoring do as much work as possible before a chemical intervention is considered - and in which any pesticide that is used is chosen and applied with a clear understanding of who or what else might be exposed.
Sources / Further Reading
FAO Statistics - Pesticides use and trade, 1990-2023
WHO - Chemical Safety and Health: Pesticides
FAO - Integrated Pest Management
FAO - Pesticide Management and Risk Reduction
FAO - Inventory of Pesticide Risk-Mitigation Measures
Suggested Internal Links
Understanding Organic Farming - Article 91
What Are the Effects of Chemical Fertilisers - Article 94
Why Pollinators Matter - Article 14
Understanding Soil Degradation - Article 95
What Is Water Pollution - Article 45
Approx. article body word count: 1421 words.
