The research team, led by Magdalena Wlodarz and Angela Schmitz Ornés of the University of Greifswald together with Friederike Habedank of the State Office for Agriculture, Food Safety and Fisheries in Rostock, focused on the two largest Black-headed Gull breeding colonies in the southern Baltic region. One colony sits on the island of Boehmke in the Achterwasser Lagoon, a sheltered body of water near the island of Usedom. The other occupies Riether Werder in the Szczecin Lagoon at the German-Polish border, a system heavily influenced by the Oder River, which drains a large mixed agricultural and industrial watershed. These two lagoons differ in hydrology, water exchange, and pollution sources, making them an ideal natural experiment for comparing how legacy contaminants reach coastal birds.

Over two consecutive breeding seasons, 2023 and 2024, the researchers collected fifteen eggs per colony per year, one random egg per nest, for a total of sixty eggs. Sampling took place early in the laying period before incubation began, and the removal of early-season eggs allowed the gulls to initiate replacement clutches, minimizing the impact on colony productivity. At each nest, both attending adults were captured and measured, with skull length used to distinguish females from males, yielding forty-seven identified females for the analysis of body condition. The design allowed the team to test whether contaminant burdens were linked to the physical state of the egg-laying mothers or to characteristics of the eggs themselves.

The analytical work was carried out at an accredited official food surveillance laboratory in Rostock, using a validated gas chromatography-tandem mass spectrometry method. Half a gram of homogenized egg, a one-to-one mix of yolk and white, was extracted with hexane and acetone, cleaned up through automated gel permeation chromatography, and then quantified against matrix-matched calibration curves with linearity coefficients exceeding 0.99. The researchers targeted six indicator PCB congeners, the non-dioxin-like compounds PCB 28, 52, 101, 138, 153, and 180, as well as DDT and its metabolites DDE and DDD, the fungicide hexachlorobenzene, and several isomers of hexachlorocyclohexane. A conservative reporting level of 0.01 milligrams per kilogram was applied, meaning that anything below that threshold was treated as zero in the statistics, an approach the authors acknowledge may underestimate true contaminant levels.

The results were unambiguous. All sixty eggs contained both DDT residues and PCB congeners above the reporting level. Mean total DDT concentrations ranged from 0.42 to 0.63 milligrams per kilogram across the four island-year combinations, while mean total PCB concentrations ranged from 0.135 to 0.268 milligrams per kilogram. The PCB profile was dominated by the heavier, more persistent congeners PCB 138, PCB 153, and PCB 180, each detected in one hundred percent of samples at median concentrations above 0.04 milligrams per kilogram. The lighter congeners appeared less consistently and at lower levels, a classic signature of aged industrial contamination, because heavier PCBs bind to organic particles and sediments while lighter ones remain more dissolved and degrade or disperse more readily.

Within the DDT family, the story was one of old, weathered residues rather than fresh applications. The metabolite DDE, the primary aerobic breakdown product of DDT, was quantified in every egg, with p,p’-DDE alone accounting for a mean of 0.57 milligrams per kilogram. Parent p,p’-DDT itself was present in 55 percent of eggs at concentrations up to 0.13 milligrams per kilogram, but DDD was found in only a single sample. Diagnostic ratios, which chemists use to date contamination, showed a median metabolic ratio of about 24, indicating overwhelmingly aged residues. The authors note that the presence of parent DDT does not by itself prove recent input, since residual DDT can persist in environmental reservoirs such as sediments and be remobilized into aquatic food webs, but the near-exclusive dominance of DDE points firmly to legacy sources from the historical use of technical DDT.

Two other pesticides told a story of relative success. Hexachlorobenzene was quantified in only five eggs, all at low levels of 0.01 to 0.02 milligrams per kilogram, and all from the Riether Werder colony near the Polish border, though the authors caution that such sparse detections do not allow conclusions about site-specific sources. Hexachlorocyclohexane, including the insecticide lindane, was not quantified in any sample at all, consistent with its rapid biotic degradation and the absence of substantial recent inputs. This contrasts sharply with historical data from the Elbe estuary, where Black-headed Gull eggs once showed high lindane concentrations, and suggests that the ban on these compounds in the 1980s has genuinely reduced their presence in the Baltic environment.

The comparison with history is where the study becomes most striking. In 1986, researchers Holz and Starke sampled gull eggs from the same Boehmke island and reported total PCB concentrations exceeding 2 milligrams per kilogram, roughly ten times the current mean of 0.18. That decline represents real progress attributable to the bans of the 1970s and 1980s. Yet DDE tells a different story: the historical mean of 0.59 milligrams per kilogram reported for the region is almost identical to the 0.57 milligrams per kilogram measured today. DDT metabolites, in other words, have barely budged in nearly forty years, a persistence explained by their environmental half-lives, which range from two to fifteen years for DDT and a decade or more for DDE, combined with continuous slow release from contaminated sediments.

Crucially, the researchers found no evidence that these contaminant burdens are harming the gulls today. Eggshell thickness, measured at three positions on each shell with a precision gauge, showed no significant correlations with DDT or PCB concentrations, apart from a single weak negative association at the blunt pole that the authors interpret as providing no evidence of an effect. Egg volume and female body condition, calculated from body mass and skull length, were likewise unrelated to contaminant levels. The measured DDE concentrations remain far below the thresholds above which eggshell thinning has been documented in Herring Gulls, and the colonies themselves have shown stable growth over the past decade. Still, the authors emphasize that acute toxicity was not directly assessed, that sublethal effects cannot be ruled out, and that the two-year window and modest sample size limit the power to detect subtle trends.

The study’s limitations are candidly acknowledged. Eggs were collected at random without recording laying order, even though the first-laid egg in a clutch often carries the highest pollutant load, introducing potential variance. Historical comparisons are complicated by differences in analytical methods and sample composition. Yet the broader message stands: legacy persistent organic pollutants remain an active presence in the Baltic Sea food web, transferred from mother to egg and passed through fish, insects, and molluscs to opportunistic gulls. By establishing a modern baseline for a previously understudied sentinel species, the researchers have given Baltic monitoring programmes a critical reference point, and a reminder that even well-regulated chemicals demand continued surveillance long after their use has ended.

Subject of Research: Legacy persistent organic pollutant contamination in Black-headed Gull eggs from the southern Baltic Sea

Article Title: Still exposed? DDT and PCB levels in Black-headed Gull eggs collected from the Baltic Sea

Article References: Wlodarz, M., Habedank, F., & Ornés, A. S. (2026). Still exposed? DDT and PCB levels in Black-headed Gull eggs collected from the Baltic Sea. Environmental Monitoring and Assessment, 198(11), Article 1156. https://doi.org/10.1007/s10661-026-15987-7

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15987-7

Keywords: DDT, PCBs, Black-headed Gull, Baltic Sea, persistent organic pollutants, DDE, eggshell thickness, bioaccumulation, biomonitoring, organochlorine pesticides, hexachlorobenzene, seabirds

The research team, funded by the International Science Programme at Uppsala University, Sweden, purchased 96 dried fish samples from 44 stations across 32 districts, spanning all eight administrative divisions of the country. Half the samples were Bombay duck, Harpadon nehereus, and half were ribbon fish, Trichiurus lepturus, the two most widely marketed dried marine species in Bangladesh. Sampling took place during the monsoon seasons of 2022 and 2023, a deliberate choice: consumer demand for dried fish peaks when fresh fish becomes scarce, and the season’s humidity and rainfall raise the risk of insect infestation, creating conditions in which illegal pesticide use would be most likely. Dhaka, the largest consumer market, contributed the most samples, followed by Chattogram, a hub of dried fish production and trade.

Chemically, the analysis targeted not just the parent pesticide but its two principal breakdown products, 4,4′-DDE and 4,4′-DDD, which had been largely overlooked in earlier Bangladeshi surveys. The researchers ground each fish sample into powder, extracted the lipophilic contaminants with ethyl acetate using a solid-phase dispersion technique, and cleaned up the extracts through acid sulfonation, which destroys fats and lipids while leaving chlorinated pesticides intact. Quantification was performed by gas chromatography with an electron capture detector, a pairing prized for its sensitivity to halogenated compounds because chlorine atoms have a strong affinity for electrons. The method showed excellent linearity, detection limits below 0.4 micrograms per kilogram, and recoveries between roughly 82 and 97 percent, comfortably within international acceptance criteria.

The headline result is striking: the parent compound 4,4′-DDT was detected in only 10 of the 96 samples, meaning nearly 90 percent were free of the banned insecticide. Where it did appear, concentrations ranged from 1.41 to 11.02 micrograms per kilogram, with the highest level found in a Bombay duck sample from Thatari Bazar in Dhaka. These figures represent a dramatic decline from earlier studies. Work published in 2010 reported total DDT levels in Dhaka market dried fish reaching nearly 11,881 micrograms per kilogram, and other surveys from the 2000s and early 2010s documented residues in the hundreds. The authors attribute the improvement to stricter regulatory control, growing public awareness, and the natural degradation of legacy residues.

The metabolites told a subtler story. 4,4′-DDE ranged from 0.95 to 16.63 micrograms per kilogram, peaking in a sample from Kuakata Shutki Polli in Patuakhali, while 4,4′-DDD reached 17.62 micrograms per kilogram in a sample from Bhola. Total DDTs climbed as high as 29.40 micrograms per kilogram in a Bombay duck sample from Port Road Bazar in Barishal. Statistical analysis revealed significant regional variation, driven almost entirely by a difference between the Barishal and Chattogram divisions, with Barishal, in the lower Ganges-Brahmaputra-Meghna delta, bearing the heaviest burden. The researchers suggest that historical agricultural applications across inland floodplains continue to leach into the delta’s dense network of rivers, which flush legacy residues downstream into estuarine sediments where fish absorb them, a process amplified by monsoonal flooding and runoff.

The relative abundance of the metabolites offers a chemical fingerprint of contamination’s age. DDE forms under aerobic conditions through dehydrochlorination, while DDD arises from anaerobic reductive dechlorination in oxygen-poor sediments. In this study, DDE exceeded DDD in 42 samples, DDD exceeded DDE in only 13, and the two were equal in 41, a pattern indicating that aerobic degradation dominates in the regions investigated. Moreover, the ratio of parent DDT to total DDTs fell below 0.5 in seven of the ten DDT-positive samples, a threshold commonly used to distinguish aged, historical residues from recent inputs. Collectively, these signatures point to legacy contamination cycling through aquatic food webs rather than widespread ongoing application of the pesticide.

There were exceptions, however. Three samples showed parent DDT either alone or with ratios approaching unity, hinting at limited degradation and therefore possible recent introduction. Given that this pattern appeared in only about 3 percent of samples, the authors conclude it reflects sporadic illicit use rather than a systematic practice, echoing findings from coastal China where a small minority of bivalves similarly indicated localized recent inputs. The study’s authors caution that without confirmatory mass spectrometry, which was unavailable to them, the GC-ECD results rest on retention-time matching and validated quantification alone, though the method’s performance parameters support the reliability of the measurements.

On the question consumers care most about, the health risk assessment delivered good news. Using U.S. Environmental Protection Agency models, the team calculated estimated daily intakes based on an average Bangladeshi adult consumption rate of 15 grams of dried fish per day and a body weight of 60 kilograms. Hazard quotients for all three compounds remained far below the safety threshold of 1, with the highest cumulative value, 0.1497, recorded for the Bhola sample, indicating no meaningful non-carcinogenic risk. Incremental lifetime cancer risks were predominantly in the negligible range below one in a million; seven samples exceeded that threshold, all still well within the acceptable band of one in a million to one in ten thousand defined by the EPA. Notably, three of the highest-risk samples all originated from Barishal Division, mirroring the contamination hotspot identified in the residue data. No sample came close to the U.S. Food and Drug Administration action level of 5,000 micrograms per kilogram for fishery products.

The findings place Bangladesh in a favorable position internationally. Comparable low levels have been reported in South Korean seafood, and long-term monitoring in Zhejiang, China, shows declining DDT in coastal bivalves. By contrast, smoke-dried fish in Nigeria has shown concentrations above 700 micrograms per kilogram, and Canadian brook trout still carry legacy residues from aerial spraying in the 1950s and 1960s, a reminder that DDT’s environmental half-life of 4 to 30 years, and far longer in aquatic sediments, means historical contamination can persist for generations.

The authors emphasize that the acceptable risk profile at current consumption rates does not eliminate the need for vigilance. DDT is lipophilic and bioaccumulative, and heavier consumers of dried fish could face greater exposure, while the pesticide’s links to cancer, endocrine disruption, reduced fertility, and developmental disorders justify continued scrutiny. The team recommends intensified monitoring of fish-drying practices, strict enforcement of the pesticide ban, training for processors and retailers in safe preservation methods, and public awareness campaigns. They also call for routine surveillance of other food-chain items, including poultry and dairy, to build a national residue database capable of tracking contamination trends over time. For now, the millions of Bangladeshis who rely on Shutki can take measured comfort in the science: the ghost of DDT still haunts the delta’s waterways, but it is fading from the dinner plate.

Subject of Research: DDT and metabolite residues in dried marine fish from Bangladesh and associated consumer health risks

Article Title: DDT and Its Metabolites in Two Marine Dried Fish Species From Bangladesh: Residue Levels, Distribution Patterns, and Health Risk Assessment

Article References: Ghosh, O. K., Islam, M. M., Nesa, F., Hasan, M. S., Abid, A. A., Arham, S. A. A., Shoeb, M., & Mamun, M. I. R. (2026). DDT and Its Metabolites in Two Marine Dried Fish Species From Bangladesh: Residue Levels, Distribution Patterns, and Health Risk Assessment. Food Science & Nutrition, 14(9), Article e72286. https://doi.org/10.1002/fsn3.72286

Image Credits: AI Generated

DOI: 10.1002/fsn3.72286

Keywords: DDT, dried fish, Bangladesh, pesticide residues, food safety, organochlorine pesticides, DDE, DDD, health risk assessment, Bay of Bengal, GC-ECD, bioaccumulation

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