It is easy to assume that once pesticides are banned, withdrawn, or no longer applied, the problem goes away. Evidence shows the opposite. Some compounds persist for years or even decades, especially organochlorines and certain newer synthetic chemicals that resist degradation. This means that even after a pesticide is banned or withdrawn, there is still a need to consider how to address the effects it has already left behind in human bodies, animals, and ecosystems.
Pesticide residues in human and animal bodies
A recent media investigative documentary interviewed a pathologist whose work involved tracing the presence of pesticide residues, specifically paraquat, in human bodies. They reported that even among farmers who had not worked on their farms for three or four years, traces of pesticide residues were still detected in their bodies. This finding is not new. Studies have long reported the presence of pesticide residues in animals as well, pointing to long-term retention rather than short-term exposure.
While some pesticides break down relatively quickly, others are persistent, often referred to as Persistent Organic Pollutants (POPs), and can remain in the body or the environment for years or even decades. One of the key processes involved is bioaccumulation, where small, repeated exposures build up in body tissues over time. These residues can also move up the food chain. For example, when pesticide residues enter water systems, they may be taken up by fish and then passed on to higher predators, including humans. As residues move higher up the food chain, their concentrations can increase, a process known as biomagnification.
Biomagnification can also occur during breastfeeding, where a lactating mother may pass pesticide residues to her infant through breast milk. For breastfeeding children, their exposure comprises what the mother has already accumulated through her diet and environment. Young children are particularly vulnerable populations, because their body systems are still developing and their small body weight increases their exposure and effects. A systematic review of 49 studies focusing on Latin American women reported a 100 percent prevalence of pesticide contamination in breast milk, with DDT and its isomers being the most commonly detected compounds.
Pesticide residues in water, soils, and air
Pesticides persist extensively in soils. According to recent studies, approximately 80 to 90 percent of sprayed pesticides persist in soils for extended periods. Because of their ability to interfere with soil microbial populations and disrupt nutrient cycling, pesticide residues are a major contributor to soil deterioration and declining soil fertility.
Pesticides are also found in the air, in solid, liquid, or gaseous forms. The atmosphere plays a significant role in pesticide movement through processes such as aerial spraying, wind erosion, volatilization from soils and crops, and emissions during production. From the air, pesticides can enter the human body through inhalation or skin contact.
At the November 2025 Pesticides, Environment & Health Symposium in Kisumu, in which Route to Food participated, scientists reported persistent pesticide residues in water, soils, and animals such as snails commonly found in farming ecosystems. Studies presented at the symposium showed extensive pesticide contamination in African soils, particularly from insecticides, with many sites containing multiple compounds, including substances not approved for use in the European Union. This contamination poses high risks to soil organisms and ecosystem functions and indicates the transboundary nature of pesticide movement. The studies are highlighted below:
- Faith Kandie, a lecturer and water quality researcher at Moi University, in a case study on pesticide pollution in the Lake Victoria South Basin in Kenya, found that 26 parent compounds and five transformation products of pesticides and biocides were detected in water samples. In biota, 19 pesticides were detected in snails, with atrazine showing the highest concentration at 375 ng/g wet weight and a detection frequency of 95 percent, followed by DEET at 93 percent. Sediment analysis identified 55 pesticides, with concentrations reaching up to 110 ng/g organic carbon. Some compounds, such as thiacloprid, were not detected in water but were present in both biota and sediments. Contamination patterns varied by land use, with rice and sugarcane areas showing substantially higher pesticide burdens than maize and tea-growing regions.
- Bernard Bwambale, a Public Health Nutritionist at the Global Consumer Centre Uganda, reported a study that investigated pesticide residues in Uganda’s water resources across four regions involving a total of 86 community water sources, including boreholes, springs, wells, lakes, streams, and taps. Overall, 94.2 percent of sampled water sources contained at least one pesticide residue. Twelve pesticides were consistently detected across regions, with glyphosate, dichlorvos, and chlorpyrifos showing the highest average concentrations. Among the top five detected pesticides, three, aldicarb, dichlorvos, and chlorfenvinphos, are classified as highly hazardous. Profenofos was detected in the largest number of sites, followed by atrazine and chlorpyrifos.
- Vera Silva of Wageningen University, through the Soil4Africa project, reviewed existing literature on pesticide contamination in African soils, identifying 88 studies across 25 countries. Only 56 of the 272 soil samples reviewed, about 21 percent, were pesticide-free, indicating widespread contamination. While water studies were dominated by fungicides, soil samples were primarily contaminated with insecticides, reflecting their higher persistence in soils.
- Mary Gikungu, a Natural Scientist and the Director at the National Museums of Kenya, highlighted the impacts of synthetic pesticide use on natural heritage. In birds, organochlorines and organophosphates cause high toxicity, leading to mortality, reproductive failure, and behavioural disruptions. In mammals, exposure through contaminated vegetation, water, or prey results in poisoning, reduced fertility, and weakened immunity, with wildlife poisoning incidents increasingly reported near agricultural landscapes. Broad-spectrum insecticides also kill beneficial insects, particularly pollinators such as bees, undermining pollination services and destabilizing ecosystems. In aquatic systems, pesticide runoff into rivers and wetlands causes fish, amphibian, and invertebrate deaths, reproductive impairments, and disruptions of aquatic food webs.
Addressing persistent pesticides through policy and practice
Thus, there is need to address persistent residues that are already present in the environment and in living organisms. This includes active remediation of contaminated soils and water, long-term biomonitoring of residues in people and animals, and sustained surveillance of environmental impacts. According to the Food and Agriculture Organization, bioremediation is a cost-effective and promising approach to restoring contaminated soils. It involves the use of biological agents such as plants, bacteria, and fungi to naturally degrade pollutants by metabolizing contaminants in the environment.
Addressing pesticide persistence also requires supporting farmers to transition away from pesticide-dependent systems altogether. Cultural methods that reduce pest pressure can significantly lower pesticide use. Safer biocontrol options and biopesticides should be encouraged as the first line of external inputs for pest management. Where synthetic pesticides are still required, non-highly hazardous pesticides should be the norm and used only as a last resort.
Lastly, persistence should be a vital consideration during pesticide registration, assessment and withdrawing by national regulatory agencies. Pesticide residues outlive policy decisions.
