The study, published in Environmental Monitoring and Assessment, arrives at a moment when the legacy of the 2019 spill remains uncertain. Tar balls chemically linked to that disaster continued to reach Brazilian beaches years afterward, echoing the pattern seen after the Prestige spill off Spain, where polycyclic aromatic hydrocarbons persisted in coastal ecosystems long after the acute emergency ended. PAHs are among the most worrying compounds released in oil spills because they are persistent, they bioaccumulate in fatty tissues, and several members of the family carry mutagenic and carcinogenic potential. Humans encounter them continuously through airborne particles, polluted water, and contaminated food, which makes reliable monitoring of seafood a genuine public health concern rather than an abstract environmental exercise.

Guanabara Bay is arguably the most challenging possible proving ground for such a method. The estuary, the second-largest bay on the Brazilian coast at roughly 384 square kilometers, is ringed by a metropolitan region of more than 16 million people and hosts a dense concentration of petrochemical infrastructure, including refineries and oil-storage terminals in its northwestern sector. Its sediments carry PAH burdens reflecting both chronic petrogenic inputs from oil handling and pyrogenic inputs from urban and vehicular combustion. Yet the bay also sustains artisanal mussel fisheries that provide an important protein source for local communities, creating an urgent need for affordable, routine contamination surveillance in exactly the kind of resource-limited setting where sophisticated analytical infrastructure is often unavailable.

Mussels are ideal sentinels for this task. As filter feeders, they ingest contaminants suspended in the water column and accumulate lipophilic pollutants in their tissues, and they tolerate a broad range of environmental conditions. Their track record in Guanabara Bay is well documented: after a fuel oil spill in 2000, PAH burdens in mussels collected from the pillars of the Rio-Niterói Bridge rose two to fivefold, tracking changes in the surrounding water closely. But extracting PAHs from lipid- and protein-rich mussel tissue has always been analytically awkward. Conventional approaches such as matrix solid-phase dispersion, accelerated solvent extraction with gel-permeation clean-up, or supercritical fluid extraction work, but they demand expensive equipment, large volumes of hazardous solvent, and considerable time per sample.

The new method borrows a trick from food safety chemistry. The QuEChERS approach, whose name stands for Quick, Easy, Cheap, Effective, Rugged and Safe, was originally devised in 2003 for extracting pesticide residues from produce. It relies on simple salting-out chemistry: homogenized tissue is vortexed with a mixture of acetonitrile and dichloromethane, then magnesium sulfate and sodium chloride are added to drive analytes into the organic layer. The researchers adapted this for mussel tissue and added a solid-phase extraction clean-up step using Florisil, silica gel, and alumina columns to strip out co-extracted lipids before instrumental analysis. The combination proved remarkably effective at minimizing the matrix interference that normally plagues PAH analysis in fatty biological samples.

The analytical team collected 210 mussels from four artisanal fishing communities around the bay, including Itaipu, Copacabana, Barra da Tijuca, and Recreio dos Bandeirantes, across four seasonal campaigns between September 2021 and June 2022, roughly two to three years after the spill. Each pooled sample of about twenty individuals was homogenized and analyzed in triplicate. The validated method achieved strong linearity, with coefficients of determination exceeding 0.995 for most compounds, and acceptable recoveries between 51.1 and 109.0 percent for 15 of the 18 target PAHs. Detection limits ranged from 0.009 nanograms per gram for naphthalene to just over one nanogram per gram for the most problematic analytes, figures comparable to those reported for far more expensive tandem mass spectrometry setups.

Not every target compound cooperated. Benzo(j)fluoranthene and benzo(k)fluoranthene share an identical retention time of 40.944 minutes on the DB-5MS capillary column used, a documented limitation of five-percent phenyl methylpolysiloxane phases that even laboratories running triple quadrupole instruments encounter. Both isomers were excluded from quantitative interpretation, a decision the authors note does not disadvantage the dataset because regulatory indices such as the EFSA-endorsed PAH4 already omit benzo(j)fluoranthene. Indeno(1,2,3-cd)pyrene yielded no quantifiable signal at any fortification level and was likewise excluded. Benzo(a)pyrene, the single most notorious carcinogenic PAH, showed precision marginally above the 20 percent threshold but was retained for reporting given its environmental significance. This transparent accounting of limitations, the researchers argue, is what makes the method genuinely useful for future monitoring programs.

The environmental findings were as instructive as the analytical ones. Only five PAHs were quantified above the limit of quantification across all 210 samples: naphthalene, phenanthrene, 5-methylchrysene, benzo(a)anthracene, and benzo(a)pyrene. Concentrations were low and statistically homogeneous across sites and seasons, with benzo(a)pyrene reaching the highest mean at just 0.308 nanograms per gram, far below the European Union maximum of 5 nanograms per gram for bivalve molluscs. Crucially, the compositional pattern told a story: the total PAH burden of 4.27 nanograms per gram was dominated almost entirely by high-molecular-weight, combustion-derived compounds rather than the light petrogenic compounds, such as naphthalene and phenanthrene, that would signal lingering petroleum from the spill. The contamination signature points instead to diffuse, continuous pyrogenic inputs from vehicle emissions, industrial combustion, and atmospheric deposition.

That counterintuitive result carries a sobering implication. Benzo(a)pyrene is classified by the International Agency for Research on Cancer as a Group 1 confirmed human carcinogen, acting through reactive diol-epoxide metabolites that form covalent DNA adducts, while benzo(a)anthracene and 5-methylchrysene are Group 2B possible carcinogens. None of these genotoxic compounds has a recognized safe exposure threshold, and mussels remain a staple protein for the fishing communities surrounding the bay. The authors caution that without pre-spill baseline data or an uncontaminated reference site, low burdens cannot be read as recovery from the 2019 disaster, nor can the spill be disentangled from chronic urban-industrial pollution. What the study does establish is that the threat to these communities comes less from dramatic spill events than from the quiet, ceaseless combustion chemistry of a megacity.

The broader significance of the work lies in accessibility. Compared with pressurized solvent extraction, QuEChERS-based workflows have been shown to cut per-sample costs roughly fivefold while increasing throughput tenfold, and other studies report cost reductions approaching 97 percent relative to Soxhlet extraction. Because the new method uses matrix-matched calibration rather than costly isotope-dilution standards and relies on a single quadrupole mass spectrometer, it can be adopted by laboratories that could never afford tandem instrumentation. For oil-impacted tropical estuaries worldwide, from Jakarta Bay to the Gulf of Guinea, the message is that meaningful PAH biomonitoring no longer requires a flagship budget, only mussels, modest solvents, and a well-validated protocol.

Subject of Research: Development and validation of a QuEChERS-SPE-GC-MS method for PAH biomonitoring in Perna perna mussels from an oil-impacted tropical estuary

Article Title: Development of a short and sensitive QuEChERS-SPE-GC-MS method for polycyclic aromatic hydrocarbon (PAH) biomonitoring in Perna perna (Linnaeus, 1758) mussels from an oil-impacted tropical estuary

Article References: de Pinho, J. V., Tessaro, L., Silva Melo, P. T., de Andrade, J. C., Celano, M. R., de Almeida Rodrigues, P., Castro Cardoso de Almeida, A. E., Hauser-Davis, R. A., & Conte-Junior, C. A. (2026). Development of a short and sensitive QuEChERS-SPE-GC-MS method for polycyclic aromatic hydrocarbon (PAH) biomonitoring in Perna perna (Linnaeus, 1758) mussels from an oil-impacted tropical estuary. Environmental Monitoring and Assessment, 198(11), Article 1184. https://doi.org/10.1007/s10661-026-15980-0

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15980-0

Keywords: polycyclic aromatic hydrocarbons, QuEChERS, GC-MS, Perna perna, Guanabara Bay, biomonitoring, oil spill, mussels, benzo(a)pyrene, pyrogenic contamination, solid-phase extraction, environmental monitoring

The findings, published in Discover Chemistry, challenge a widespread household assumption in resource-constrained settings: that washing grains in hot water before cooking reduces contaminant levels. In southeastern Nigeria, where access to clean water and reliable energy can be limited, many families routinely rinse staples with warm or hot water to shorten cooking times and save fuel. The practice is often believed to strip away impurities, including pesticide residues. But dieldrin, formed in the environment through the epoxidation of the related pesticide aldrin, is a notoriously stubborn molecule. Its high chemical stability, low volatility, and strong lipophilicity allow it to bind tightly to soil organic matter, persist in sediments for decades, and accumulate in the fatty tissues of living organisms, climbing the food chain through biomagnification.

To test whether domestic processing could dislodge the compound, the research team, led by Ogechi Irene Eboh-Ajoku of Nnamdi Azikiwe University, collected composite samples of local and imported rice, yellow and white corn, red and white guinea corn, pearl and finger millet, three wheat varieties, and several bean types from five Awka markets between May and August 2024, the peak rainy season when pesticide application is at its highest. The 162 samples were divided into three treatment groups: washing with tap water at ambient temperature around 25 degrees Celsius, mild heating at 50 degrees Celsius for fifteen minutes, and boiling at 100 degrees Celsius for ten minutes. These conditions were chosen to mirror real household practices, from warm-water pre-washing to standard cooking durations.

Residues were extracted using a modified QuEChERS method, a technique prized for being quick, easy, cheap, effective, rugged, and safe, and then quantified with gas chromatography coupled to mass spectrometry. The analytical method showed strong performance: calibration curves spanning 0.005 to 1.000 milligrams per kilogram displayed correlation coefficients between 0.992 and 0.999, detection limits ranged from 0.001 to 0.005 milligrams per kilogram, and mean recovery of spiked samples reached 95 percent. Procedural blanks and calibration verification standards were run throughout to guard against background contamination. Dieldrin was identified by matching retention times and mass spectra against certified reference standards and the National Institute of Standards and Technology spectral library.

The results were sobering. Concentrations ranged from undetectable to 0.376 milligrams per kilogram, with white soft wheat showing the highest contamination, followed by iron white beans at 0.258 milligrams per kilogram and brown beans at 0.244. Local Anam rice carried 0.030 milligrams per kilogram, more than double the 0.013 found in imported foreign rice, a disparity the authors attribute to differences in agricultural practices, pesticide application intensity, storage conditions, and the stricter adherence to international residue standards that imported rice may enjoy. Yellow corn registered 0.071 milligrams per kilogram. Across all treatment conditions, approximately 66.6 percent of food crop samples met or exceeded the FAO/WHO maximum residue limit of 0.01 milligrams per kilogram.

Thermal processing barely moved the needle. Local rice held steady at 0.030 milligrams per kilogram through ambient washing and 50-degree heating, dipping only slightly to 0.027 after boiling. Iron white beans fell from 0.258 to 0.213 milligrams per kilogram at 100 degrees, a marginal reduction that leaves the residue far above the safety threshold. An independent samples t-test comparing concentrations at 50 and 100 degrees found no statistically significant difference, with p-values of 0.128 to 0.135 across standard, unequal-variance, Monte Carlo permutation, and exact permutation tests. The explanation lies in dieldrin’s molecular architecture: as a highly chlorinated cyclodiene compound with a rigid structure and strong carbon-chlorine bonds, it resists breakdown at kitchen-scale temperatures. Meaningful degradation of such compounds typically requires advanced oxidation conditions far beyond any cooking process.

Perhaps the most intriguing finding concerns the cooking wastewater itself. Dieldrin is poorly soluble in water, yet the researchers detected it in the liquid left behind after washing, at concentrations ranging from 0.001 to 0.017 milligrams per liter depending on the crop and temperature. In some samples, such as white hard wheat, wastewater concentrations rose from 0.004 to 0.015 milligrams per liter as heating progressed. The authors caution that these variations were not statistically significant and likely represent minor numerical fluctuations rather than thermally enhanced desorption. Still, the detection of dieldrin in wastewater suggests that thermal washing primarily induces partitioning, redistributing a fraction of the compound from the food matrix into the aqueous phase, rather than eliminating it. That raises the possibility of secondary exposure pathways, since contaminated cooking water is often discarded into household surroundings or reused.

The health risk calculations are where the study becomes genuinely alarming. Using United States Environmental Protection Agency guidelines, the team estimated daily intakes based on a consumption rate of 0.33 kilograms per person per day and a standard adult body weight of 65 kilograms, then divided by the World Health Organization’s acceptable daily intake of 0.0001 milligrams per kilogram of body weight to yield a hazard index. Any value above unity signals potential non-carcinogenic risk. At ambient temperature, white soft wheat scored a hazard index of 19.09 and white hard wheat 10.92, while iron white beans reached 13.10 and brown beans 12.39. Local rice and yellow corn also exceeded the threshold, at 1.52 and 3.60 respectively. Even after boiling, local rice (1.37), yellow corn (3.35), white soft wheat (18.02), white hard wheat (10.71), iron white beans (10.81), and brown beans (10.71) remained above the risk line. The authors acknowledge that their uniform consumption and body weight assumptions are conservative and do not capture variability among sensitive populations such as children, meaning actual risks for some groups could differ.

The toxicological stakes are considerable. Dieldrin is associated with carcinogenic, teratogenic, endocrine-disrupting, and reproductive effects. Experimental studies cited in the paper show it interferes with steroidogenesis, estrogen signaling pathways, and thyroid hormone homeostasis, contributing to reduced fertility, altered fetal development, spontaneous abortion, and gestational abnormalities. Its teratogenic effects include skeletal malformations, cleft palate, and increased fetal resorption. Acute neurotoxicity arises from the compound’s ability to interfere with neuronal action potentials, producing symptoms ranging from headache, dizziness, and nausea to muscle twitching, tremors, convulsions, and, in extreme cases, death. Because dieldrin resists both abiotic and microbial degradation, it poses long-term ecological hazards to fish, birds, mammals, and humans alike.

A multivariate layer of the analysis added further texture. Bray-Curtis hierarchical clustering grouped the food crops into four clusters with remarkably high similarity coefficients of 98 to 99 percent, pairing local rice with iron white beans and white soft wheat with yellow corn, among others. The wastewater samples formed three distinct clusters. The authors interpret these groupings as reflecting similar contamination levels rather than confirmed shared sources, noting that dieldrin’s hydrophobicity and persistence promote consistent adsorption across different crop matrices, and that shared post-harvest handling and market aggregation may contribute. The study’s limitations are acknowledged: sampling was confined to Awka markets during a single four-month window, so regional and seasonal variation remains unexplored. Even so, the baseline it establishes is unsettling. If routine cooking cannot mitigate exposure to a pesticide banned across much of the world, the burden of protection falls squarely on monitoring, agricultural reform, and regulatory enforcement, and the researchers argue that without targeted interventions, chronic dietary exposure will continue to accumulate among populations who depend on these staples most.

Subject of Research: Dieldrin pesticide residues and dietary health risks in Nigerian staple crops and cooking wastewater

Article Title: Multivariate analysis and dietary risk assessment of dieldrin in Nigerian staple crops and cooking wastewater

Article References: Eboh-Ajoku, O. I., Nduka, J. K., Anagboso, M. O., & Offor, C. C. (2026). Multivariate analysis and dietary risk assessment of dieldrin in Nigerian staple crops and cooking wastewater. Discover Chemistry, 3(1), Article 556. https://doi.org/10.1007/s44371-026-01012-w

Image Credits: AI Generated

DOI: 10.1007/s44371-026-01012-w

Keywords: dieldrin, organochlorine pesticides, food safety, Nigeria, staple crops, thermal processing, GC-MS, QuEChERS, hazard index, dietary exposure, bioaccumulation, maximum residue limits

A team at Korea’s National Institute of Food and Drug Safety Evaluation, led by Ye-Bin Jang and corresponding author Mi-Ok Kim, has now closed that gap. Writing in Food Science of Animal Resources, the researchers describe an optimized liquid chromatography–tandem mass spectrometry (LC–MS/MS) method that simultaneously quantifies 18 structurally diverse anthelmintic and antiparasitic compounds across nine animal-derived food matrices: beef, pork, chicken, eggs, milk, porcine fat, flatfish, eel, and shrimp. Beyond niclosamide, the method brings rarely monitored compounds such as derquantel, bithionol, and nitroxinil into quantitative reach, expanding both the chemical and the biological scope of routine residue surveillance.

The analytical challenge is formidable because the target compounds span six major chemical classes with very different physicochemical personalities. Benzimidazoles such as triclabendazole attack larval and adult parasites alike; salicylanilides including closantel, rafoxanide, and niclosamide also knock down ectoparasites like ticks; tetrahydropyrimidines such as morantel and pyrantel act as nicotinic receptor agonists; imidazothiazoles like levamisole target roundworms; and the macrocyclic lactones—abamectin, ivermectin, doramectin, eprinomectin, and moxidectin—are large, extremely lipophilic molecules that cling stubbornly to fatty tissue. Add praziquantel and nitroxinil to the list, and a single run must coax compounds ranging from small polar bases to sprawling lipid-like structures through the same column and ion source.

Sample preparation began with the QuEChERS approach—Quick, Easy, Cheap, Effective, Rugged, and Safe—which uses salt-induced phase separation to pull analytes from homogenized tissue into acetonitrile. The team compared three salt formulations: the unbuffered Original method with magnesium sulfate and sodium chloride, the citrate-buffered EN 15662 version, and the acetate-buffered AOAC variant. The verdict was decisive. In flatfish, the buffered methods produced calibration curves for abamectin with coefficients of determination of just 0.2304 and 0.0385—essentially useless—while the Original salts delivered R² values above 0.99 for all 18 compounds. The researchers attribute the failure of buffered systems to citrate and acetate ions altering salting-out efficiency and promoting co-extraction of lipids, proteins, and phospholipids, which then suppress ionization of the lipophilic macrocyclic lactones during electrospray.

Extraction used acetonitrile acidified with 0.1% formic acid, a combination known to improve recovery and precision for veterinary drugs in animal tissue. Clean-up followed with dispersive solid-phase extraction, and here the sorbent recipe mattered enormously. C18 alone left chlorfluazuron, levamisole, triclabendazole, and keto-triclabendazole with substandard linearity; PSA alone failed for chlorfluazuron and triclabendazole. Only the pairing of 400 milligrams of PSA with 400 milligrams of C18, plus 1,200 milligrams of magnesium sulfate, achieved R² values of at least 0.99 across the entire panel. PSA’s amino groups mop up organic acids and sugars, while C18 adsorbs nonpolar fats and fat-soluble interferences—a synergy the team standardized by purifying a fixed 8-milliliter extract volume for every matrix.

On the instrument side, chromatographic separation ran on a Waters Xbridge C18 column with a gradient of water containing 5 millimolar ammonium formate and 0.1% formic acid against acetonitrile with 0.1% formic acid. Retention times spanned from 1.9 minutes for morantel to 6.4 minutes for ivermectin. Detection used a Shimadzu LCMS-8060 triple quadrupole in multiple reaction monitoring mode, switching between positive and negative electrospray ionization, with precursor ions, product ions, and collision energies optimized by direct infusion of standards. The most intense transition served for quantification while secondary transitions confirmed identity.

Matrix effects proved to be the method’s central analytical adversary. Co-extracted lipids and proteins distort electrospray ionization, and the team measured signal changes of at least 20% for most analytes. Ion suppression dominated, ranging down to −96.08%, with abamectin, levamisole, pyrantel, and triclabendazole suppressed in every single matrix. Moxidectin, by contrast, showed ion enhancement in several foods, including chicken, milk, and all three fishery products. Rather than turning to isotope-labeled internal standards—impractical and costly for an 18-compound panel—the researchers built matrix-matched calibration curves in blank extracts of each food, so standards and samples ionize under identical chemical conditions and systematic signal bias cancels out at the quantification stage.

Validated under CODEX guideline CAC/GL-71, the method met every performance criterion. Matrix-matched calibration curves exceeded R² of 0.99 for all compounds in all nine matrices. Limits of quantification ranged from 0.0033 to 0.0054 milligrams per kilogram, all below half of the established MRLs. Intraday recovery and precision across the matrices fell between 72.0 and 119.1% with coefficients of variation no higher than 18.2%, comfortably inside CODEX windows, and interday testing on three consecutive days with two analysts held recoveries between 72.0 and 118.7% with CVs at or below 19.0%.

To test real-world utility, the team analyzed 60 market samples—30 livestock and 30 fishery products chosen for high Korean consumption. None of the 18 target analytes was detected, a reassuring snapshot of the domestic supply, though the authors stress that continued surveillance remains essential. The method’s true significance lies in what it enables going forward: quantitative enforcement for drugs like niclosamide that previously escaped numeric scrutiny, a single validated workflow spanning meat, dairy, eggs, and seafood, and a technical foundation for setting and revising safety standards. As veterinary drug use intensifies globally and resistant parasites push dosing upward, tools like this one turn regulatory limits from paper promises into measurable, enforceable protections for the food supply.

Subject of Research: Development and validation of a QuEChERS-based LC–MS/MS method for quantifying multiclass veterinary anthelmintic residues in animal-derived foods

Article Title: Optimized LC–MS/MS method for simultaneous determination of multiclass veterinary anthelmintic residues in animal-derived matrices

Article References: Optimized LC–MS/MS method for simultaneous determination of multiclass veterinary anthelmintic residues in animal-derived matrices. (n.d.). https://doi.org/10.1007/s44463-026-00098-1

Image Credits: AI Generated

DOI: 10.1007/s44463-026-00098-1

Keywords: anthelmintics, LC-MS/MS, veterinary drug residues, QuEChERS, food safety, maximum residue limits, matrix-matched calibration, livestock products, fishery products, niclosamide, mass spectrometry, residue monitoring

The research, published in the Journal of Saudi Chemical Society, focused on seven strobilurin fungicides: azoxystrobin, dimoxystrobin, fluoxastrobin, kresoxim-methyl, picoxystrobin, pyraclostrobin, and trifloxystrobin. These compounds belong to the quinone outside inhibitor group, designated FRAC Code 11, and they work by blocking mitochondrial respiration in fungi at the cytochrome bc1 complex. That single-site mode of action makes them highly effective against downy mildew, powdery mildew, and Botrytis bunch rot, but it also carries a well-documented risk of fungal resistance, which is why vineyards often alternate active ingredients. Crucially for food safety monitoring, the same potency means residues can persist into harvested fruit, leaves, and dried products.

The team analyzed 200 retail samples purchased in Najran during 2025: 100 fresh grape berry samples, 50 grape leaf samples, and 50 raisin samples, all marketed as domestically produced. Berry and leaf samples were identified as Vitis vinifera L., cv. Thompson Seedless. Using a QuEChERS extraction coupled to liquid chromatography with tandem mass spectrometry, the researchers validated the method separately for each commodity, reflecting the very different chemistry of high-moisture berries, sugary dried raisins, and structurally complex leaves. Matrix-matched calibration achieved correlation coefficients between 0.9948 and 0.9995, recoveries ranged from 80.6 to 102.1 percent with relative standard deviations of 4.0 to 13.8 percent, and verified limits of quantification reached as low as 1 microgram per kilogram in berries and raisins.

Getting reliable numbers from each matrix required tailored preparation. For raisins, the team tested three rehydration volumes and settled on 5 milliliters of water per 5 grams of sample, which delivered recoveries between 90.87 and 96.19 percent with minimal matrix effects. Grape leaves proved the toughest challenge of all: co-extracted leaf compounds suppressed the mass spectrometric signal by as much as 33 percent for kresoxim-methyl. The solution combined dispersive solid-phase extraction cleanup with a tenfold dilution of the final extract, cutting mean suppression to 14.06 percent and yielding excellent precision, at the cost of higher detection limits in that matrix.

The occurrence findings are striking. At least one target strobilurin was detected in 88.0 percent of grape berry samples, 100 percent of grape leaf samples, and 82.0 percent of raisin samples. Multiple residues appeared together in 36.0 percent of berry samples and 26.0 percent of leaf samples, though raisins showed no co-occurrence. Azoxystrobin was the most frequently detected compound in berries at 40.0 percent, while in leaves azoxystrobin and pyraclostrobin led at 44.0 and 42.0 percent, respectively. Kresoxim-methyl produced the highest individual leaf residue at 1.338 milligrams per kilogram, and trifloxystrobin peaked at 1.141 milligrams per kilogram in berries. Fluoxastrobin, dimoxystrobin, and picoxystrobin were never detected in any market sample.

Compliance results tell a more reassuring story than the raw detection rates might suggest. In grape berries, only one kresoxim-methyl result, at 1.114 milligrams per kilogram, directly exceeded the Saudi Food and Drug Authority limit of 1.0 milligram per kilogram. But applying the SANTE decision rule, which subtracts an expanded measurement uncertainty of 50 percent from the measured value, the lower decision value fell to 0.557 milligrams per kilogram, comfortably below the limit. Not a single grape berry sample was therefore classified as non-compliant. In raisins, all measurable trifloxystrobin, pyraclostrobin, and kresoxim-methyl residues sat below their applicable SFDA maximum residue limits, while azoxystrobin in raisins was reported descriptively because no applicable Saudi or Codex limit exists for that combination.

Grape leaves were the exception that reveals a regulatory gap. Because neither the SFDA nor Codex has established maximum residue limits for grape leaves, the researchers used European Union limits for grape leaves and similar species purely as external comparative references, explicitly not as formal Saudi non-compliance findings. Against those EU values, the picture was sobering: all 22 azoxystrobin-positive and all 13 trifloxystrobin-positive samples exceeded reference limits of 0.01 milligrams per kilogram, with 90.9 percent and 92.3 percent of positive samples respectively remaining above the limits even after uncertainty adjustment. Nineteen of 21 pyraclostrobin-positive samples also exceeded the 0.02 milligram per kilogram reference. The authors argue these findings support clearer regulatory guidance for grape leaves, a commodity consumed in substantial quantities yet essentially invisible in national residue standards.

Dietary risk assessment used the EFSA PRIMo revision 3.1 consumption model, with conservative surrogate scenarios for grape leaves and raisins where direct consumption data were lacking. Chronic exposure results were uniformly reassuring: every estimate for the four detected fungicides stayed below 0.35 percent of the acceptable daily intake, with pyraclostrobin producing the highest chronic estimates across all three commodities. Acute exposure was assessed only for trifloxystrobin and pyraclostrobin, the two compounds with established acute reference doses. Here one result stands out: pyraclostrobin in grape berries reached 179.1 percent of the acute reference dose for children under the direct PRIMo scenario, while adult exposure remained at 83.3 percent. Notably, all pyraclostrobin residues in berries were below the Saudi maximum residue limit, demonstrating that regulatory compliance and acute dietary risk are genuinely separate endpoints. All grape leaf and raisin acute estimates remained well below 100 percent under the stated assumptions.

The authors are careful about the limits of their conclusions. Because the samples were collected from Najran outlets without farm-level traceability or nationally stratified design, the findings describe that specific retail market in 2025 and should not be read as national prevalence estimates. Farm-level spray records were unavailable, so explanations for the commodity-specific patterns, such as canopy interception driving higher leaf residues or dissipation during drying lowering raisin residues, remain plausible interpretations rather than proven mechanisms. Still, the study’s core contribution is clear: by integrating a validated matrix-adapted analytical method, rigorous uncertainty-adjusted compliance evaluation, and tiered dietary exposure modeling, it shows that widespread residue detection does not automatically mean widespread risk, while simultaneously flagging pyraclostrobin in fresh grapes for children as a genuine acute-exposure signal and grape leaves as a standards vacuum that regulators would be wise to fill.

Beyond the headline findings, the study illustrates why commodity-specific validation matters so much in residue chemistry. The three matrices differ not only in water content but in sugar concentration, pigment load, and structural complexity, all of which alter how efficiently analytes are extracted and how strongly co-extracted compounds interfere with ionization in the mass spectrometer. The authors deliberately avoided internal standards, relying instead on separate matrix-matched calibration for each commodity, a choice that compensates for matrix-induced signal changes but demands careful validation for every new food type. Their use of multi-walled carbon nanotubes alongside conventional PSA and C18 sorbents during dispersive solid-phase extraction reflects a broader trend toward carbon-based cleanup materials that strip pigments and waxes from dark, leafy matrices without excessive analyte loss.

The analytical framework also highlights the distinction between three outcomes that are often conflated in public discussion: detection, non-compliance, and health risk. A residue can be present at measurable levels yet remain far below any regulatory threshold, and a sample can technically exceed a limit while still passing a compliance decision once measurement uncertainty is applied, as happened with the single kresoxim-methyl finding in berries. Conversely, the pyraclostrobin acute estimate for children exceeded 100 percent of the acute reference dose even though every berry sample met the Saudi maximum residue limit, underscoring that limits are not designed to guarantee zero acute risk under all consumption scenarios. The acute reference dose represents a single-day exposure threshold, and the 179.1 percent figure derives from conservative model assumptions rather than observed illness.

Methodologically, the work aligns with the European Commission SANTE guidance, the de facto international benchmark for pesticide residue method validation, covering linearity, recovery, precision, matrix effects, and expanded uncertainty. The verified limits of quantification, ranging from 1 to 50 micrograms per kilogram depending on the matrix, sit comfortably within the sensitivity typically required for enforcement monitoring at low regulatory limits. The finding that drying can either diminish or concentrate residues, depending on the compound and process, echoes earlier processing studies on azoxystrobin and kresoxim-methyl in raisins and reinforces the case for analyzing foods as actually consumed rather than extrapolating from raw commodity data.

Finally, the grape leaf results carry implications beyond Saudi Arabia. Grape leaves are widely eaten across the Mediterranean, Middle East, and Caucasus regions, yet they remain absent from most national residue registries, which typically focus on the fruit. Without commodity-specific limits, regulators cannot formally classify violations, consumers receive no tailored protection, and exporters face ambiguous standards. The authors’ call for dedicated maximum residue limits for this traditional food commodity is a concrete, actionable outcome of an otherwise routine monitoring exercise.

Subject of Research: Strobilurin fungicide residues in grape berries, raisins, and grape leaves from the Saudi retail market, with dietary risk assessment

Article Title: LC–MS/MS analysis of seven strobilurin fungicides in grape berries, raisins, and grape leaves: occurrence, compliance, and dietary risk assessment

Article References: Alhamami, M. A. M., Algethami, J. S., Alqahtany, F. Z., Al-Marri, A. H., Alzahrani, A. Y., Ramadan, M. F., & Abdallah, O. I. (2026). LC–MS/MS analysis of seven strobilurin fungicides in grape berries, raisins, and grape leaves: occurrence, compliance, and dietary risk assessment. Journal of Saudi Chemical Society, 30(5), Article 67. https://doi.org/10.1007/s44442-026-00122-5

Image Credits: AI Generated

DOI: 10.1007/s44442-026-00122-5

Keywords: strobilurin fungicides, LC-MS/MS, QuEChERS, grape berries, raisins, grape leaves, pesticide residues, maximum residue limits, dietary risk assessment, food safety, Saudi Arabia, pyraclostrobin