Tanzania’s Rising Pesticide Use Poses Growing Health and Environmental Risks

A sweeping synthesis of 25 years of research has concluded that pesticide use in Tanzania has escalated dramatically since 2000, fueling widespread contamination of food, water, and soil while inflicting a substantial and largely hidden burden of poisoning on the country’s farmers. The systematic review, published in the journal Environmental Challenges, pulled together 78 studies conducted between January 2000 and April 2026 to construct the most complete picture yet of how synthetic agrochemicals have transformed agriculture in the East African nation, and at what cost.

Tanzania’s economy is deeply rooted in agriculture, which contributes roughly a quarter of gross domestic product and employs about two-thirds of the national workforce. Smallholder farmers tilling plots of 0.5 to 3 hectares make up more than 90 percent of the agricultural labor force. Over the review period, several structural forces converged to drive pesticide demand upward: the liberalization of pesticide trade policies, which produced an approximately 80-fold increase in private retailer involvement from the late 1980s onward; the rapid commercialization of horticulture, the fastest-growing agricultural subsector with annual growth rates of 6 to 10 percent; expansion of irrigated farming that allows up to six cropping cycles per year and sustains continuous pest pressure; and the Southern Agricultural Growth Corridor of Tanzania initiative, an ambitious intensification program in the country’s south. FAO statistics corroborate the trend, documenting steadily rising imports of insecticides, fungicides, and other hazardous pesticide classes from the mid-1990s through the 2010s, while surveys of farmers across Iringa, Arusha, Manyara, and Kilimanjaro found that 58.4 percent reported increasing use on their own farms.

The chemistry of this expansion has shifted over time. Organophosphates such as profenofos, chlorpyrifos, and dimethoate now dominate, appearing in 96.6 percent of pesticide classes used in smallholder vegetable production, followed by carbamates and pyrethroids, with neonicotinoids such as imidacloprid rising steadily since 2015. More troubling is what persists beneath this modern portfolio. Organochlorine compounds, including DDT, endosulfan, aldrin, dieldrin, and lindane, remain officially banned yet continue to be detected in soils, water, fish, vegetables, and even chicken eggs, signaling either ongoing illegal use or stubborn environmental persistence. A national soil survey found hexachlorocyclohexane in 88 percent of agricultural samples, with DDT most abundant in the productive Southern Highlands. Sugarcane plantation soils in Kilimanjaro still contained DDT and metabolites more than two decades after their official use ceased.

The quantities being applied frequently exceed international norms by wide margins. One assessment reported fungicide application rates of 17.18 kilograms of active ingredient per hectare in tomato and 13.05 in onion cultivation, alongside insecticide rates of nearly 6 kilograms per hectare, all far above world averages. More than half of vegetable farmers in northern Tanzania spray five or more times per cropping season, and mixing pesticides is the norm rather than the exception: 93.7 percent of surveyed farmers in the Ulanga and Kilombero districts combined products, often near water sources and without label guidance. WHO Class II moderately hazardous compounds account for 68.9 percent of what smallholders use, but extremely and highly hazardous Class Ia and Ib products remain in circulation, reflecting weak enforcement and the influence of unscrupulous agro-dealers.

The review found that unsafe handling is a structural, sector-wide problem rather than a localized one. More than 90 percent of farm workers use no personal protective equipment, farmers in one Arusha study ate, drank, and smoked while spraying, and repacked agrochemicals sold in unlabeled containers are common, with some containers later reused domestically. Fewer than half of farmers have received any formal safety training, most rely on pesticide dealers for instructions, and over half discard empty containers into rivers or bushes. Knowledge gaps extend into the clinic: a survey of 104 physicians, clinical officers, and nurses in agricultural areas found that only 1 percent could identify the pesticide groups predominantly used in their communities, compounding chronic underdiagnosis and underreporting of poisoning cases.

The human toll is substantial. In cotton-growing communities, 48 percent of 1,074 surveyed farmers experienced symptoms of unintentional acute pesticide poisoning within a year, yet only 6 percent sought formal medical care. Hospital surveillance documented 108 poisoning cases among women in a single year, with suicide the leading circumstance and organophosphates, zinc phosphide, paraquat, and endosulfan the principal agents. Biomonitoring tells a parallel story: exposed horticultural farmers showed significantly depressed acetylcholinesterase levels, a marker of organophosphate neurological impact, and long-term professional sprayers faced a 7.7-fold higher risk of peripheral neuropathy. A case-control study at Tanzania’s Ocean Road Cancer Institute found that agricultural workers had 2.6 times the odds of head and neck cancers, rising to 5.1-fold among those with more than a decade of farm work. Women, who make up 65 to 70 percent of the horticultural labor force and increasingly handle spraying and contaminated laundry, face added risks of endocrine disruption and reproductive harm.

Food safety surveillance reveals contamination reaching consumers directly. In the largest multi-regional study, 613 vegetable samples were tested and 74.2 percent of those with detectable residues exceeded Codex maximum residue limits, with organophosphorus compounds dominating. Tomatoes from Dar es Salaam markets carried chlorpyrifos at concentrations up to 3,810 nanograms per gram, while Makambako tomatoes showed residues in 78.5 percent of samples. Recent testing of Dar es Salaam cucumbers and watermelons found imidacloprid at 15.71 milligrams per kilogram, far above the 1.0 milligram per kilogram limit. Nile perch and tilapia from Lake Victoria carried DDT and endosulfan at levels indicating recent exposure, and poultry eggs from Ilala and Kibaha contained DDT at 8.14 milligrams per kilogram, multiples of international standards. Irrigation water in Arusha contained lindane and endosulfan sulphate at concentrations that violated WHO drinking water guidelines.

The review also documents a striking cross-sector consequence: agricultural pesticide use is undermining malaria control. Mosquitoes from villages with heavy agrochemical use showed resistance to pyrethroids and other public health insecticides, while those from low-use villages remained susceptible. National monitoring data show pyrethroid resistance in Anopheles mosquitoes rising from zero percent of sentinel sites in 2004 to more than 80 percent by 2020. Because lambda-cyhalothrin and cypermethrin are both top agricultural insecticides and mainstays of insecticide-treated nets and indoor spraying, farming practices now threaten to erode decades of progress against one of the country’s deadliest diseases.

Regulatory capacity has not kept pace with the market. Tanzania has 1,182 registered pesticide products, yet unregistered and counterfeit formulations abound, inspections are inconsistent, and porous borders allow banned products to enter. The Tanzania Plant Health and Pesticides Authority, successor to the Tropical Pesticides Research Institute, faces chronic staffing and laboratory constraints, and the Vikuge obsolete pesticide stockpile site remains a cautionary tale of incomplete remediation decades later. Meanwhile, proven alternatives struggle for traction: farmer field schools trained in integrated pest management cut use of the most hazardous pesticide classes by 85 percent, and a best-practice training program reduced synthetic pesticide spending by 51 percent while boosting vegetable profits by 72 percent, yet most farmers surveyed in Morogoro and Iringa had never heard of integrated pest management at all.

The authors of the review frame their conclusions with appropriate caution, noting that the evidence base skews toward the better-studied northern horticultural zones and relies heavily on cross-sectional, convenience-sampled studies. Even so, they argue the convergent findings demand urgent action: expanded inspector capacity and market surveillance, a national acute poisoning surveillance system, mandatory point-of-sale training for pesticide vendors, accelerated phase-out of WHO Class Ia and Ib compounds, mainstreaming of integrated pest management into national policy, gender-responsive interventions, and routine residue monitoring linked to enforcement. As Tanzania pursues agricultural intensification under SAGCOT and expands irrigation nationwide, the review warns that without such reforms the pesticide burden on public health, food safety, and the environment, already severe, is likely to worsen before it improves.

Subject of Research: A systematic review of pesticide use trends, exposure pathways, health risks, environmental contamination, and policy challenges in Tanzanian agriculture from 2000 to 2026.

Article Title: Pesticide use trends (2000–2026), exposure pathways, human health risks, environmental contamination, and policy challenges in Tanzania

Article References: Pesticide use trends (2000–2026), exposure pathways, human health risks, environmental contamination, and policy challenges in Tanzania. (n.d.). https://doi.org/10.1016/j.envc.2026.101666

Image Credits: AI Generated

DOI: 10.1016/j.envc.2026.101666

Keywords: Tanzania, pesticides, organophosphates, DDT, acute pesticide poisoning, pesticide residues, food safety, integrated pest management, malaria vector resistance, environmental contamination, smallholder farmers, pesticide regulation