These are screening calculations, not evidence that consumption causes illness, and they depend on treating total mercury as a methylmercury surrogate and assuming that inorganic arsenic accounts for 10% of total arsenic. The researchers sampled muscle and liver from 86 dolphinfish, Coryphaena hippurus, and 65 striped marlin, Kajikia audax, collected during sport-fishing trips off Cabo San Lucas, Mexico, in 2018 and 2019. The sample comprised 40 male and 46 female dolphinfish, with a mean fork length of 81.2 ± 14.7 centimeters and mean weight of 4.7 ± 2.8 kilograms.

It included 32 male and 33 female striped marlin, whose mean lower-jaw fork length was 183.4 ± 19.4 centimeters and mean weight 31.9 ± 10.7 kilograms. Fish were selected because striped marlin commonly occur in the area and the Gulf of California receives contaminants from mining, intensive agriculture, shrimp aquaculture, fisheries and urban activity, according to the study. Tissue preparation and elemental analysis were designed to measure mercury, arsenic and selenium in both species and both tissues.

Muscle and liver samples were frozen at −19°C, freeze-dried at −48°C and 133 × 10−3 mbar for 48 hours, and ground with an agate mortar. Portions weighing 0.25 grams underwent overnight acid addition and three-hour digestion in capped vessels at 120°C. Total mercury was measured by cold-vapor atomic absorption spectrophotometry, total arsenic by hydride-generation atomic absorption spectrophotometry and selenium by graphite-furnace atomic absorption spectrophotometry. Duplicate samples, high-purity reagents, ultrapure water and certified reference materials were used for quality control, with reference-material recoveries of 94–96% for mercury, 92–95% for selenium and 98–102% for arsenic.

All reported concentrations were converted from dry weight to micrograms per gram of wet weight. Median concentrations in dolphinfish muscle were 0.08 micrograms per gram wet weight for mercury, 0.81 for arsenic and 0.20 for selenium. Its liver medians were 0.09 micrograms per gram for mercury, 2.40 for arsenic and 0.27 for selenium.

In striped marlin muscle, the corresponding medians were 0.29 micrograms per gram for mercury, 0.591 for arsenic and 0.27 for selenium; liver medians were 0.12 for mercury, 1.50 for arsenic and 0.23 micrograms per gram for selenium. Arsenic had the highest median concentration in every species-and-tissue combination, but the modeled risk rankings differed because the assessment incorporated element-specific oral reference doses and the assumed inorganic fraction of total arsenic. Element concentrations generally increased with fish size in significant associations identified by Spearman rank correlation and Bonferroni correction.

Mercury in both muscle and liver was positively associated with length and weight in both species, with correlation coefficients of 0.408–0.461 in dolphinfish and 0.463–0.551 in striped marlin. Dolphinfish length and weight were also positively associated with arsenic in muscle and liver, with coefficients of 0.429–0.461. In striped marlin, weight was positively associated with arsenic and selenium in muscle, at 0.497 and 0.435, respectively, but no significant relationships linked those elements to body size in liver.

Selenium in dolphinfish muscle was not significantly associated with size. The researchers did not directly measure fish age, so the observed size relationships do not by themselves establish that larger fish had experienced longer exposure. Comparisons between the 2018 and 2019 sampling periods found no statistically significant differences in elemental concentrations within the compared tissues of either species.

The researchers therefore pooled the two years for the dietary assessment. That finding covers only the sampled years and does not establish that contaminant levels remained stable over longer periods. The catch also had a size profile that may limit generalization: sampled dolphinfish were adults, apparently reflecting the tendency of sport-fishing tournaments to target larger fish, whereas most sampled striped marlin were below reported lower-jaw fork lengths at first maturity.

For the dietary calculations, researchers used estimated per-capita consumption rates in northwestern Mexico of 4.1 grams per day for dolphinfish and 21.9 grams per day for striped marlin. Exposure was estimated for three consumer groups: children weighing 30 kilograms, women of childbearing age weighing 65 kilograms and men weighing 75 kilograms. The assessment used oral reference doses of 0.0003 milligrams per kilogram of body weight per day for arsenic, 0.0001 for mercury expressed as methylmercury and 0.0005 for selenium.

For every species and consumer group, the hazard quotient for mercury was greater than that for selenium, which in turn was greater than the arsenic hazard quotient. Mercury accounted for more than 93% of the combined hazard index for dolphinfish: 93.2% for children, 93.26% for women of childbearing age and 93.43% for men. In striped marlin, its contribution was approximately 97.6% in each group, reaching 97.57% for children and women of childbearing age and 97.56% for men.

The different hazard-index results for the two species therefore emerged from the combined influence of measured concentrations, species-specific consumption rates and consumer body weights, rather than from a simple comparison of total mercury concentrations. All hazard-index values associated with dolphinfish were below 1. For striped marlin, 53 of 64 samples exceeded 1 in the children’s scenario, 29 of 64 did so for women of childbearing age and 21 of 64 for men.

The study describes these proportions as estimates for the specified groups and consumption assumptions, not observed clinical outcomes. The hazard index is a screening approach and does not establish that harm will occur. The analysis also did not characterize exposure from every fish species in a consumer’s diet, and its population-wide consumption rates may not capture differences associated with socioeconomic status.

Although fishing-dependent households may consume fish at higher rates, the study did not directly quantify those variations. The absence of direct chemical speciation also limited the assessment: methylmercury was not measured separately, and inorganic arsenic was represented by an assumed share of total arsenic rather than direct measurement. The researchers also calculated a selenium health-benefit value, or HBVSe, using the molar concentrations of selenium and mercury.

All values were positive in muscle and liver from both species, indicating a molar excess of selenium over mercury. Mean HBVSe values were 2.51 in dolphinfish muscle and 2.99 in striped marlin muscle; values were higher in liver. The authors interpreted the pattern as indicating potential selenium–mercury antagonism, in which selenium may mitigate effects associated with mercury.

This toxicological model does not directly show that selenium cancels dietary mercury risk in people, and the positive values coexist with the screening estimates in which mercury remains the principal source of potential risk. By measuring mercury, arsenic and selenium simultaneously in the muscle and liver of both species, the study expands a regional evidence base in which monitoring has been uneven and arsenic data are particularly limited. The results show that the highest measured median concentrations were for arsenic, while the modeled risk estimates were driven chiefly by mercury.

For people who consume fish frequently, the study supports continued monitoring and dietary risk assessment, particularly for children and women of childbearing age, as well as broader consideration of consumers with elevated fish-consumption rates. It does not establish that the sampled fish are broadly unsafe to eat, identify an actual clinical effect or resolve the uncertainties created by assumed chemical speciation, limited dietary data and a sport-fishing sample. Direct measurement of mercury and arsenic species, more representative sampling and more detailed information about individual consumption would be needed for a more precise assessment of exposure.

Subject of Research: Dietary mercury, arsenic and selenium risk assessment in Gulf of California dolphinfish and striped marlin

Article Title: Health risk assessment associated with Hg, As, and Se in the dolphinfish Coryphaena hippurus and the striped marlin Kajikia audax from the southern Gulf of California

Article References: Ruelas-Inzunza, J., Arriaga-Flores, Y. K., Sánchez-Osuna, K. G., Gil-Manrique, B., Escobar-Sánchez, O., Spanopoulos-Zarco, P., & Vega-Sánchez, B. (2026). Health risk assessment associated with Hg, As, and Se in the dolphinfish Coryphaena hippurus and the striped marlin Kajikia audax from the southern Gulf of California. Frontiers in Marine Science, 13, Article 1950335. https://doi.org/10.3389/fmars.2026.1950335

Image Credits: AI Generated

DOI: 10.3389/fmars.2026.1950335

Keywords: dolphinfish, striped marlin, mercury, arsenic, selenium, dietary risk assessment, hazard index, Gulf of California, marine fish, food contaminants, Health, risk

The research team, led by Omolara Jemimah Ojezele of the Federal College of Animal Health and Production Technology in Ibadan and Matthew Obaineh Ojezele of Delta State University, focused on Amaranthus cruentus, a leafy green vegetable that is a dietary staple across Nigeria and much of sub-Saharan Africa. Sampling was carried out at 30 sites spread across three major vegetable-producing settlements in Oyo State, yielding 240 matrix-season samples of water, sediment, soil, and vegetable tissue. After analytical duplicates were averaged, the dataset comprised 480 independent pesticide-specific sample-level observations. All samples were analysed using validated chromatographic methods, providing the analytical foundation for the layered statistical and risk assessments that followed.

The study’s first major finding concerns environmental partitioning, the tendency of a chemical to accumulate in particular compartments of an ecosystem. Glyphosate, a systemic herbicide that binds strongly to soil particles, predominated in soil and sediment samples, consistent with its known physicochemical behaviour. Cypermethrin, a synthetic pyrethroid insecticide, showed a different pattern, occurring at comparatively higher concentrations in the edible Amaranthus cruentus tissue itself. This divergence matters because it shapes the primary route of human exposure: while glyphosate residues largely remain locked in the ground, cypermethrin residues travel directly onto the plates of consumers through the vegetable crop, bypassing many of the natural attenuation processes that limit exposure to soil-bound chemicals.

To understand whether contamination was random or clustered, the researchers applied Moran’s I spatial autocorrelation analysis, a statistical technique that tests whether values measured at nearby locations are more similar than expected by chance. The results were striking for one compound: glyphosate in sediment displayed significant spatial autocorrelation, with a Moran’s I statistic of 0.783 and a p-value of 0.0003. In practical terms, this means that sites with high glyphosate contamination in sediment tended to sit near other highly contaminated sites, forming identifiable hotspots rather than a scattered pattern. Such clustering suggests that localised factors, such as application intensity, topography, and runoff pathways, drive glyphosate accumulation in sediments, information that could help regulators target interventions at specific zones rather than imposing blanket restrictions.

The team complemented the spatial analysis with hierarchical mixed-effects modelling and principal component analysis, statistical tools that allowed them to separate the influence of different environmental and seasonal variables on residue concentrations while accounting for the nested structure of the sampling design. Together with a structured survey of vegetable farmers, these methods revealed a troubling gap between residue levels in crops and the practices that produced them. The survey documented limited pesticide stewardship among growers, including short pre-harvest intervals, meaning farmers were applying pesticides and harvesting their crops with little time for residues to degrade. Substantial exceedances of selected European Union maximum residue limit benchmarks for spinach were recorded in the vegetable samples, underscoring the consequences of these practices.

The heart of the study lies in its dietary risk assessment, which the researchers conducted in two complementary ways. The first was a deterministic approach, which uses single point estimates of residue concentration and consumption to calculate a hazard quotient, the ratio of estimated exposure to a reference dose below which no adverse effects are expected. A hazard quotient above one signals a potential health concern. The deterministic results indicated acceptable dietary risk for adults for both pesticides, and acceptable risk for children for glyphosate. However, cypermethrin exceeded the hazard threshold in children, with a hazard quotient of 1.818, nearly double the level of concern for the youngest and most vulnerable consumers.

Because deterministic assessments rely on single values, they can obscure the true range of possible exposures. To address this, the researchers turned to Monte Carlo simulation, a probabilistic technique that runs thousands of virtual exposure scenarios by randomly drawing residue concentrations and consumption rates from their measured distributions. Each of the 10,000 iterations represents one plausible combination of real-world conditions, and the resulting spread of hazard quotients reveals how often risky exposures might actually occur. The simulation results sharpened the study’s central warning: hazard quotients above one appeared in 15.09 percent of adult cypermethrin exposure scenarios and a remarkable 70.47 percent of child exposure scenarios. For glyphosate, by contrast, no simulated exposure scenario for either group exceeded the threshold, suggesting the herbicide poses comparatively limited dietary risk under the conditions measured.

The contrast between the two pesticides carries important implications. Cypermethrin is prized by farmers for its effectiveness against the insect pests that devastate vegetable crops, but its persistence on leafy surfaces means that harvest timing is critical to food safety. The finding that roughly seven in ten simulated child exposure scenarios exceeded the hazard threshold points to a systemic problem rather than isolated lapses, one rooted in the short intervals between spraying and harvest documented in the farmer survey. Children are particularly sensitive in such assessments because their lower body weight means the same residue concentration in food delivers a higher dose per kilogram of body mass, and because developing systems may be more vulnerable to neurotoxic compounds such as pyrethroids.

The study’s authors argue that their findings support a coordinated response spanning pesticide stewardship, residue surveillance, farmer education, and regulatory oversight. In many smallholder farming systems across sub-Saharan Africa, extension services that once trained farmers in safe application practices have contracted, leaving growers to rely on agrochemical vendors and informal knowledge networks. The short pre-harvest intervals recorded in this study are a classic symptom of that gap, reflecting neither malice nor ignorance of risk so much as the absence of accessible, practical guidance. Simple interventions, such as clear labelling in local languages, community-level training on waiting periods, and routine market testing of leafy vegetables, could substantially reduce exposure without requiring farmers to abandon chemical pest control altogether.

The research also demonstrates the value of methodological rigour in regions where pesticide monitoring data have historically been sparse. By pairing validated chromatographic analysis with spatial statistics, mixed-effects modelling, and Monte Carlo simulation, the study transforms a set of field measurements into a nuanced risk picture that distinguishes between compounds, environmental compartments, and consumer groups. The strong spatial clustering of glyphosate in sediment, for instance, would have been invisible to a conventional point-sampling survey, and the probabilistic approach revealed a child-specific risk that a deterministic calculation alone might have understated or overstated. As pesticide use intensifies across African agricultural landscapes to meet growing food demand, studies of this kind provide the evidence base that national regulators and international bodies such as the Joint FAO/WHO Meeting on Pesticide Residues need to set meaningful, locally calibrated safety standards. For now, the message from Oyo State is clear: the greens on the market stall are nutritious and affordable, but for the children eating them, the invisible residues of an everyday insecticide may be crossing a line that better farming practice could hold firmly in place.

Subject of Research: Pesticide residue occurrence and dietary health risk assessment in agricultural ecosystems of southwestern Nigeria

Article Title: Environmental occurrence, spatial distribution, and probabilistic dietary risk assessment of cypermethrin and glyphosate residues in agricultural ecosystems of southwestern Nigeria

Article References: Ojezele, O. J., & Ojezele, M. O. (2026). Environmental occurrence, spatial distribution, and probabilistic dietary risk assessment of cypermethrin and glyphosate residues in agricultural ecosystems of southwestern Nigeria. Environmental Monitoring and Assessment, 198(11), Article 1171. https://doi.org/10.1007/s10661-026-15973-z

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15973-z

Keywords: cypermethrin, glyphosate, pesticide residues, Amaranthus cruentus, food safety, dietary risk assessment, Monte Carlo simulation, spatial autocorrelation, Nigeria, vegetable farming, pesticide stewardship, environmental 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