FERA / FSA 2015 — UK Total Diet Study of metals and other elements in food
This government-commissioned total diet study (TDS) is the UK’s most comprehensive post-2010 baseline for heavy metals and trace elements in the British food supply as consumed. The Food and Environment Research Agency (FERA) purchased 3,312 individual retail food samples across 138 food categories from 24 UK locations, prepared them as for consumption following FSA protocols, and composited them into 138 food-category pools and 28 food-group pools before analysis by ICP-MS. The study updates the prior UK TDS on metals from 2006 and is notable for simultaneously reporting total arsenic (tAs) and inorganic arsenic (iAs) as separate measurements, using separate validated extraction methods — a critical design feature for arsenic speciation. All data are reported on an as-consumed (wet weight) basis in mg/kg. Results for elements above LOD but below LOQ are flagged as semi-quantitative with the prefix ”~“.
Key numbers
All concentrations in mg/kg as-consumed (wet weight) unless otherwise noted. LODs and LOQs vary by sample weight; see Table 3 of the report for element-specific values at each sample weight tier (0.25 g, 0.5 g, 1 g, 2.5 g). Values prefixed ”~” are semi-quantitative (above LOD, below LOQ).
Group-level summary (Table 5 — 28 food groups)
Selected groups of highest relevance to heavy-metal certification and exposure assessment:
| Group | Description | Pb (mg/kg) | Cd (mg/kg) | iAs (mg/kg) | tAs (mg/kg) | tHg (mg/kg) | Ni (mg/kg) | Al (mg/kg) | Sn (mg/kg) |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Bread | ~0.027 | 0.021 | <0.012 | <0.006 | <0.02 | ~0.07 | 4.01 | 0.016 |
| 2 | Misc. Cereals | 0.065 | 0.067 | ~0.013 | ~0.009 | <0.02 | 0.17 | 3.67 | — |
| 3 | Carcass Meat | <0.004 | <0.0012 | <0.012 | <0.006 | <0.02 | ~0.05 | 0.49 | <0.02 |
| 4 | Offal | ~0.004 | 0.23 | <0.012 | <0.006 | 0.018 (fish-adj.) | <0.04 | ~0.29 | <0.02 |
| 7 | Fish | 0.0497 | 0.014 | <0.012 | 2.0 | 0.811 | 0.10 | 1.43 | ~0.02 |
| 11 | Green Vegetables | 0.017 | ~0.006 | <0.012 | <0.003 | <0.005 | ~0.06 | 1.28 | <0.01 |
| 12 | Potatoes | ~0.006 | ~0.020 | ~0.015 | <0.006 | ~0.006 | ~0.10 | 0.99 | <0.02 |
| 20 | Nuts | <0.002 | 0.02 | <0.012 | ~0.005 | <0.01 | — | 2.31 | <0.01 |
| 22 | Meat Substitutes | ~0.005 | ~0.007 | <0.012 | ~0.004 | 0.052 | 0.14 | 2.7 | <0.01 |
| 23 | Snacks | ~0.003 | 0.059 | <0.012 | 0.011 | 0.063 | 0.13 | 3.97 | <0.01 |
Note: Cd for offal group is 0.23 mg/kg — the highest by a wide margin across groups, reflecting kidney and liver accumulation. Fish group total arsenic (2.0 mg/kg) is organic-arsenic dominated; iAs in fish is below LOQ (<0.012 mg/kg).
Cereal/grain category detail (Table 7 — Miscellaneous Cereals)
All values in mg/kg as-consumed. The ”~” prefix denotes semi-quantitative (above LOD, below LOQ).
| Category | Description | Pb | Cd | iAs | tAs | tHg | Al | Ni | Sn |
|---|---|---|---|---|---|---|---|---|---|
| 2_6 | Flour | 0.006 | 0.03 | <0.012 | 0.008 | <0.0005 | 5.19 | 0.04 | <0.004 |
| 2_7 | Buns, cakes and pastries | ~0.006 | 0.012 | <0.012 | ~0.005 | <0.0005 | 5.04 | 0.16 | ~0.02 |
| 2_8 | Savoury biscuits | ~0.005 | 0.024 | <0.012 | ~0.004 | <0.0005 | 3.02 | ~0.06 | <0.01 |
| 2_9 | Sweet biscuits | ~0.005 | 0.015 | <0.012 | ~0.003 | <0.0005 | 2.83 | 0.09 | <0.01 |
| 2_10 | Chocolate biscuits | ~0.010 | ~0.017 | <0.012 | <0.006 | <0.001 | 6.9 | 0.35 | <0.02 |
| 2_11 | Breakfast cereals | <0.004 | 0.026 | <0.012 | ~0.010 | <0.001 | 2.42 | 0.35 | <0.02 |
| 2_12 | Rice (as consumed) | <0.004 | ~0.006 | ~0.028 | 0.036 | ~0.0012 | 0.59 | ~0.11 | <0.02 |
| 2_13 | Other cereal products | ~0.005 | 0.014 | <0.012 | ~0.005 | <0.0005 | 2.32 | ~0.03 | <0.01 |
| 2_14 | Pasta | <0.002 | ~0.009 | <0.012 | <0.003 | <0.0005 | 1.04 | ~0.03 | 13.3 |
| 2_15 | Pizza | ~0.005 | 0.015 | <0.012 | ~0.005 | <0.0005 | 3.72 | ~0.06 | <0.01 |
Rice (category 2_12) shows iAs ~0.028 mg/kg (28 µg/kg, semi-quantitative) and tAs 0.036 mg/kg (36 µg/kg) as consumed — consistent with iAs forming the majority of tAs in rice, typical of the literature. tHg in rice is semi-quantitative at ~0.0012 mg/kg (1.2 µg/kg as consumed). The pasta category shows a marked Sn elevation (13.3 mg/kg), likely an artefact of canning or packaging contact during sample preparation; noted in source context.
Bread category detail (Table 6)
| Category | Description | Pb (mg/kg) | Cd (mg/kg) | iAs (mg/kg) | tAs (mg/kg) | tHg (mg/kg) | Al (mg/kg) |
|---|---|---|---|---|---|---|---|
| 1_1 | White sliced bread | 0.008 | 0.021 | <0.012 | ~0.003 | ~0.0003 | 5.12 |
| 1_2 | White unsliced bread | ~0.005 | 0.019 | <0.012 | ~0.004 | <0.0005 | 5.88 |
| 1_3 | Brown bread | ~0.006 | 0.026 | <0.012 | <0.006 | <0.001 | 4.27 |
| 1_4 | Wholemeal and granary bread | ~0.004 | 0.025 | <0.012 | <0.006 | <0.001 | 2.72 |
| 1_5 | Other bread | 0.005 | 0.016 | <0.012 | 0.007 | <0.0002 | 4.02 |
Methods (brief)
3,312 retail food samples were collected from 24 UK locations by HallMark Meat Hygiene Ltd. Foods were prepared as for consumption (cooking, discarding inedible portions, using tap water) following FSA-specified protocols designed to reflect consumer practices. Prepared samples were homogenized and composited into 138 food categories and 28 food groups by proportion matching UK household food purchase data from three prior years of the Family Food Survey.
Multi-element analysis: 0.5 g (or up to 3 g fresh material) aliquots were digested in concentrated nitric/hydrochloric acid (4:1 v/v) using a microwave single-reaction-chamber system (UltraWAVE, Milestone), then analyzed by Agilent 7700x ICP-MS with yttrium and holmium internal standards. All methods UKAS-accredited (ISO 17025).
Inorganic arsenic (iAs): Separate method based on Munoz et al. (1999); HCl/hydrobromic acid/hydrazinium sulfate extraction with chloroform back-extraction, measured by ICP-MS. This is a validated, published speciation method that distinguishes iAs from total arsenic. The separate measurement of iAs alongside tAs is a key strength of this study.
Mercury (tHg): Measured in the standard multi-element ICP-MS run as total mercury; no speciation of MeHg vs inorganic Hg. For fish group, tHg was 0.811 mg/kg reflecting mixed organic/inorganic mercury; MeHg fraction not reported.
LOD/LOQ: Vary by sample weight taken; see Table 3. For the 0.5 g sample weight typical of this study: Hg LOD = 0.006 µg/kg, LOQ = 0.020 µg/kg (converted per weight factor). Measurement uncertainty estimated at 21% for Hg, 11–18% for most elements of primary interest.
QA/QC: 10% audit in duplicate, procedural blanks, spiked samples, certified and in-house reference materials in each analytical batch. Z-scores from FAPAS proficiency testing all within satisfactory range (−2 to +2). Reference materials included DORM-4 fish protein, NIST 1548a total diet, NIST 1547 peach leaves, NIST 1549 non-fat milk powder, powdered rice (IMEP-107), and rice flour (NMIJ7503a).
Basis note: All data are reported on an as-received/as-prepared (as-consumed wet weight) basis. Converting to dry weight requires moisture content data not provided in this report. Direct comparison to standards expressed on a dry-weight or as-sold basis requires a documented conversion factor.
Implications
Certification: This is the most authoritative post-2010 whole-diet baseline for metals in UK food as consumed. For HMT&C products sold or sourced in the UK, the TDS group and category data provide context for expected metal levels in cereal products, bread, rice, nuts, meat, fish, dairy, and vegetables. The rice-specific iAs value of ~0.028 mg/kg (28 µg/kg, semi-quantitative) as consumed is consistent with the broader literature and with EU/FDA guidance levels for iAs in rice-based products. The study confirms that iAs in fish is below detection even as total arsenic (fish group tAs = 2.0 mg/kg) is elevated — demonstrating the critical importance of iAs/tAs distinction in seafood contexts.
Courses: Excellent teaching example for TDS methodology (as-consumed compositing, proportional dietary weighting), arsenic speciation design (separate iAs and tAs measurements), and the pattern that high tAs in fish is dominated by organic arsenicals (arsenobetaine) of low toxicological concern, not iAs.
App: Group-level and category-level concentrations as consumed can inform the UK-market baseline for the app’s contamination estimates, with the caveat that these are composite averages reflecting the whole dietary basket, not point estimates for individual products.
Microbiome: Not addressed in this study.