Determination of total mercury in Spanish samples of baby food, fast food, and daily meal

Summary

Spanish preprint study determining total mercury (THg) by direct mercury analyser (DMA-80) in twenty-eight composite meal samples representing three intake categories consumed in Valencia, Spain: thirteen commercial jarred baby foods for infants 6–12 months old, six children’s fast food menus, and nine adult canteen menus. Concentrations are reported per kilogram of dry weight and converted to daily intake per person using the measured moisture content (57–87 % w/w) and the fresh mass of each menu. The paper compares the resulting daily intakes to the Joint FAO/WHO Expert Committee on Food Additives (JECFA) Provisional Tolerable Weekly Intake (PTWI) for total mercury of 4 µg kg⁻¹ body weight (Tolerable Daily Intake of 0.57 µg kg⁻¹ bw day⁻¹). The dataset’s dominant signal is that mercury content tracks fish content of the meal: the highest THg concentrations are in fish-containing baby foods (39.8–41.9 µg kg⁻¹ d.w.), the highest fast-food value is in a single menu (67.7 µg kg⁻¹ d.w., the carrier of which the authors cannot attribute to any one component), and the single canteen menu containing grilled tuna reaches 638 µg kg⁻¹ d.w. — equal to 395.7 % of the adult TDI in a single meal. The paper concludes that baby food and most canteen menus pose low total-mercury risk, that children’s fast food can exceed 50 % of the TDI in a single meal at the lower body-weight assumption, and that the tuna meal alone contains half of the PTWI for adults.

Key numbers

Analytical performance (Results §3.2; Table 2):

• LOD 0.1 µg kg⁻¹; LOQ 0.3 µg kg⁻¹ (both derived from ten independent blanks using a 50 mg sample mass of Hg-free wheat flour).
• Relative standard deviation across triplicates spanning 0.43–638 µg kg⁻¹: 0.8–11 % (generally < 5 %).
• Recovery of spikes at 2.5 / 10 / 25 / 500 µg kg⁻¹: 98.6 ± 0.9 % / 99.2 ± 2.0 % / 102 ± 3 % / 104.9 ± 1.9 %.
• Certified reference material agreement (found vs certified, µg kg⁻¹): Chicken NCSZC73016 2.94 ± 0.18 vs 3.6 ± 1.5 (UΔ 1.5); Fish Protein NRC DORM-3 331 ± 6 vs 382 ± 60 (UΔ 60); Lobster Hepatopancreas NRC TORT-2 280 ± 58 vs 270 ± 60 (UΔ 90). All within combined uncertainty.

Total mercury by sample, dry-weight basis (Table 4; mean ± SD, n = 3 per sample):

Baby foods (range 0.57–41.9 µg kg⁻¹ d.w.; mean 15.5):

Children’s fast food menus (range 0.54–67.7 µg kg⁻¹ d.w.; mean 15.6):

Adult canteen daily menus (range 0.43–19.4 µg kg⁻¹ d.w., except DM8 at 638; mean 76.9 with DM8, 6.65 without DM8):

Effect of sample mass on direct mercury (Hg) determination (Table 3; one trio per intake category):

• Baby Food 1 (Hg ≈ 21 µg kg⁻¹ d.w.): 20.98 ± 0.19 (50 mg single) → 19.76 ± 0.16 (50 + 50) → 19.5 ± 0.4 (100) → 19.86 ± 0.05 (50 + 50 + 50) → 19.45 ± 0.17 (150 mg). Differences ≤ 5 %; sample mass selected at 50 mg for the rest of the study.
• Fast Food 2 (Hg ≈ 0.5 µg kg⁻¹ d.w.): values drift from 0.56 ± 0.01 (50 mg) down to 0.40 ± 0.07 (150 mg) as the sample mass increases; the paper notes that masses ≥ 100 mg give worse results when sample THg is near the LOQ.
• Daily Meal 1 (Hg ≈ 14 µg kg⁻¹ d.w.): 14.7 ± 0.4 (50 mg) → 13.77 ± 0.14 (150 mg); ≤ 7 % drift across the mass range.

Reference intake parameters (Methods §2.5; WHO 2011):

• JECFA PTWI for total Hg: 4 µg kg⁻¹ body weight per week, equivalent to a TDI of 0.57 µg kg⁻¹ bw day⁻¹.
• Age-group TDIs in µg day⁻¹ used by the paper: infants 7–12 months 5; toddlers 13–24 months 7.4; children 3–7 years 11; children 7–12 years 20; adults 34.
• Body weights: 9 kg (7–12 mo), 13 kg (13–24 mo), 19 kg (3–7 yr), 35 kg (7–12 yr), 60 kg (adults).
• Daily Meal 8 contributes 134 µg Hg in a single meal versus the PTWI of 240 µg per 60-kg adult per week — i.e., a single tuna-containing meal carries 56 % of an adult’s weekly tolerable intake.

Cross-country baby food comparison (Table 5; literature pull):

• Spain (this work, n = 13): 0.57–41.9 µg kg⁻¹; mean 15.5.
• China, Spain, UK, USA (Carbonell-Barrachina et al. 2012): China < 4–15 (mean < 4), Spain < 4–21 (mean 5), UK < 4–10 (mean 5), USA < 4–6 (mean < 4).
• Italy / Slovakia / Spain / Sweden (Pandelova et al. 2012): 2.7–29.9 µg kg⁻¹; mean 9.2.
• Portugal (Martins et al. 2013): < 0.10–19.6 µg kg⁻¹; mean 0.40.
• Czech Republic / Hungary / Slovakia (Tóth et al. 2014): 0.3–10.2 µg kg⁻¹; mean 1.82.
• Italy (de Roma et al. 2017): mean 1.69 µg kg⁻¹ (range not given).

Evidence Fitness

This source supports occurrence evidence for total mercury in Spanish jarred baby foods (n = 13, sampled from local markets in Valencia), and exposure context for children’s fast food menus and adult canteen menus (smaller n, single-city draw). The dataset is reconstructable down to the individual sample because Table 4 reports each composite meal’s concentration, daily intake per person, and % TDI separately rather than only the group mean.

Limitations the source itself acknowledges:

• Total mercury only; no methylmercury speciation, so the high tuna value in Daily Meal 8 cannot be partitioned into the methylmercury (MeHg) fraction directly responsible for the EFSA developmental TWI.
• Each “menu” is a single composite sample (one purchase × three analytical replicates), not a triplicate sampling of independent purchases of the same menu type. Sample-to-sample variability of the same menu type cannot be estimated from this dataset.
• TDI percentages are computed against the single meal in question, not the rest of the day’s diet; the paper explicitly states “the studied menus did not represent the food intake for a whole day.”
• Fast-food samples (n = 6) share an almost identical composition (burger + chips + ketchup + yogurt or milkshake + drink), and the paper notes that variation in THg “could not be assigned to any of the components, and no relation with the brand was found” — i.e., the source itself flags an unexplained 100-fold spread (0.54–67.7 µg kg⁻¹ d.w.) within a nominally homogeneous menu.
• Status as a preprint: posted on Research Square 2022-05-05, DOI 10.21203/rs.3.rs-1614710/v1; the Research Square header explicitly states “Preprints are preliminary reports that have not undergone peer review.” No subsequent peer-reviewed version has been located by the wiki ingest at the access date below.

Methods

Sampling. Twenty-eight composite meal samples purchased in Valencia, Spain. Thirteen jarred baby food samples from different brands available in Spain were obtained at local markets and classified by meat / fish / vegetable content. Six children’s fast food menus were purchased from different commercial brands in Valencia town and shopping centres; each menu was composed of a hamburger bun, beef hamburger, cheddar cheese, gherkin, ketchup, mustard, a regular portion of French fries, yogurt or milkshake, and a soft drink. Nine adult daily canteen menus were purchased at the University of Valencia canteens; each menu was composed of a starter, main dish, dessert, and 50–70 g bread. Twenty-eight samples total; Table 1 lists each menu’s composition and fresh mass. Moisture ranged from 57 to 87 % w/w.

Sample preparation. Samples were crushed, homogenised, frozen at −20 °C and freeze-dried for ≥ 48 h at 0.05 mBar to remove water and pre-concentrate Hg, then homogenised again in a domestic mixer (Braun, Kronberg, Germany) and stored in polyethylene tubes. No acid digestion was performed (the DMA-80 accepts solid samples directly).

Instrumentation. Direct Mercury Analyzer DMA-80 (Milestone, Sorisole, Italy). Solid sample (50 mg, weighed into a nickel crucible) was dried and thermally decomposed in the instrument; the decomposition products were carried by an oxygen flow over a catalyst that completed sample oxidation and trapped halogens and N/S oxides; the remaining gas passed through a gold amalgamator that collected Hg⁰. The amalgamator was heated to 850 °C, the released Hg⁰ was transported into the absorption cell, and total mercury was quantified by atomic absorption at 253.7 nm. Two analytical curves were used to span low (0–20 ng) and high (20–1000 ng) Hg masses (different optical path lengths; r² > 0.99 in both ranges). Oxygen was used as the carrier gas. Operating conditions are listed in supplementary Table S1.

Calibration. Aqueous standards prepared from Hg(II) 1000 µg mL⁻¹ Merck standard solution and ultrapure water (Milli-Q, 18.2 MΩ cm). Calibration verified each session with certified reference material.

Sample-mass study (Table 3, Results §3.3). Three representative samples (Baby Food 1, Fast Food 2, Daily Meal 1) were analysed at 50, 100, and 150 mg, and also as 2 × 50 mg and 3 × 50 mg amalgamator stacks, to evaluate matrix loading effects on accuracy. A 50 mg single load was selected for the full set; the authors note that masses ≥ 100 mg degrade accuracy at near-LOQ concentrations.

Reference materials used for QC. Chicken NCSZC73016 (China National Analysis Center for Iron and Steel, Beijing); Fish Protein NRC DORM-3 and Lobster Hepatopancreas NRC TORT-2 (National Research Council of Canada, Ottawa). Prior validation by the same research group also covered Fucus IAEA 140-TM, Coal Fly Ash NIST 1633b, and NIES Rice 10-a/b/c (cited as da Silva et al. 2014).

Risk-assessment calculation. Daily intake (DI, µg day⁻¹) = DCM × MMC × 1000, where DCM is daily consumption of the menu (g day⁻¹) and MMC is the mean Hg concentration (µg kg⁻¹). %TDI = DI / (4 µg kg⁻¹ × body weight ÷ 7 days) × 100 with body weights from de Lara et al. 2010 and Hernández-Martínez et al. 2013. Both DI and %TDI are reported per-single-meal, not per-day.

Speciation. Total mercury only. No MeHg / iHg / Hg⁰ separation. The paper explicitly notes that “mercury dietary intake mainly comes from fish and shellfish consumption” and treats fish-containing menus as expected high-THg contributors, but does not measure the methylated fraction.

Implications

• Occurrence — Spanish jarred baby foods. Contributes 13 sample-level THg values on a d.w. basis spanning 0.57–41.9 µg kg⁻¹, with explicit composition descriptors (fish / meat / vegetable) that allow downstream routing to fish-containing-baby-food vs vegetable-only baby food sub-rows. Mean 15.5 µg kg⁻¹ d.w. sits at the upper end of the European range reported in Table 5 (Portugal 0.40; Czech / Hungary / Slovakia 1.82; Italy 1.69; pooled European range across Pandelova 2012 et al. 2.7–29.9, mean 9.2). Seven of the thirteen baby food jars contain a fish component (BF1, BF3, BF5, BF6, BF11, BF12, BF13; THg 11.5–41.9 µg kg⁻¹ d.w., mean 23.93) and sit well above the two pure-vegetable jars (BF7, BF8; 0.57 and 0.63 µg kg⁻¹ d.w., mean 0.60). The remaining four jars are meat-or-poultry-bearing without fish (BF2 lamb 21.8; BF4 beef 2.51; BF9 chicken 2.85; BF10 chicken-broth 7.38; range 2.51–21.8, mean 8.64) and sit between the two extremes.
• Occurrence — children’s fast food menus, Valencia. Six near-identical composite menus span a 100-fold range (0.54–67.7 µg kg⁻¹ d.w.) with no source attribution the authors could resolve. This is a small but relevant occurrence input for the broader “prepared meal / fast food” category, with the caveat that all six samples were drawn from a single city and a near-uniform menu composition.
• Occurrence — adult canteen menus, single canteen system. Nine composite menus span 0.43–19.4 µg kg⁻¹ d.w. plus one outlier at 638 µg kg⁻¹ d.w. carrying grilled tuna; the outlier is a single dish-level value rather than a population estimate. Useful as illustrative high-Hg event evidence; not adequate for percentile-setting on its own.
• Tuna-containing dish as PTWI-fraction signal. Daily Meal 8 contributes 134 µg Hg in one meal — i.e., 56 % of the JECFA PTWI for a 60-kg adult (240 µg/week). This is consistent with the broader literature pull the paper cites (tuna 222–776 µg kg⁻¹ in Martorell et al. 2011; swordfish 856 µg kg⁻¹ in González et al. 2019) and is illustrative of the dominant role predatory marine fish play in adult Hg exposure.
• Method. The DMA-80 direct mercury analyser is reproducible and accurate against three independent certified reference materials at this lab’s concentration range; LOD 0.1 µg kg⁻¹ and LOQ 0.3 µg kg⁻¹ on 50 mg dry mass loads are usable for category-level occurrence work on foods at the µg kg⁻¹ d.w. scale.

Provenance notes

• Source is a Research Square preprint, DOI 10.21203/rs.3.rs-1614710/v1, posted 2022-05-05 under CC BY 4.0. Preprint status is explicit on the manuscript header; no subsequent peer-reviewed version located at ingest date. Evidence tier B reflects preprint status; should an indexed peer-reviewed version appear, this page should be superseded.
• PDF retrieved via the discover skill into the archived source file. SHA-256 8fb127b5a0871d10a7f53f1d17dce4fc3b1f2e75b86a204ee3adab0338d4a49c. Twenty-two pages including five tables and a reference list. Tables 1 and 4 are rendered as proper tabular elements in the PDF; values were read directly from the rendered cells.
• No supplementary files were retrieved; the manuscript references SupplementaryMaterial.docx (DMA-80 operating conditions, Table S1) and GraphicalAbstract.docx as available downloads on the Research Square landing page, neither pulled into this ingest.

Related evidence

• Mercury, Total
• Baby Food
• Fish
• Baby Food
• Fish-Containing Baby Foods
• EFSA — Inorganic Mercury Tolerable Weekly Intake (4 µg/kg b.w./week)

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git.