Fungicide Residues Found in Nearly All Saudi Grape Samples, But Health Risk Mostly Low

Grapes are one of the world’s most versatile food crops, arriving on dinner tables as fresh berries, sweet dried raisins, and tender vine leaves wrapped around rice and meat in traditional dishes across the Middle East and beyond. In Saudi Arabia, where grape production reached roughly 125.5 thousand tons in 2024 from about 7.3 million trees, these commodities are everyday foods, and their safety is a matter of public health. A new study from Najran University and collaborating institutions has now delivered one of the most detailed looks yet at strobilurin fungicide residues across all three grape-derived food forms, combining an adapted analytical workflow with regulatory compliance checks and a full dietary risk assessment for adults and children.

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