Eggs

Completeness scorecard

Deterministic gap audit — no score is composite, no cell is LLM-judged. Each chip is re-derivable by re-running tools/evidence/build-ingredient-scorecard.mjs. review: residuals and missing data are worked autonomously via data/evidence/ingredient-scorecard-review-flags.csv and wiki/completeness-gaps.md.

FSA/Fera measured this ingredient or non-infant-specific food composite in Table 6 of the FS102048 survey. Exact concentration values remain in progress until Table 6 is parsed into structured ingredient rows with less-than and semi-quantitative flags preserved. fsa2016-infant-food-formula-metals-survey

Why this commodity accumulates heavy metals

Eggs are a low-to-negligible heavy metal risk food under normal commercial production conditions. The mechanism by which metals enter eggs is dietary transfer from the laying hen’s feed: cadmium, lead, arsenic, and other metals ingested by the hen distribute between excretion, tissue accumulation (liver and kidney are the primary accumulation organs), and limited transfer to the egg. Transfer rates from feed to egg for cadmium and lead are very low, typically below 1% on a weight basis, which means that even hens consuming moderately contaminated feed produce eggs with very low metal concentrations. Mercury follows a somewhat different pathway and accumulates in hen tissues more readily at high exposure, but under commercial feed conditions mercury exposure is minimal.

The FDA TDS FY2018-FY2020 data for hard-boiled eggs (n=27 composites, TDS Food 37) reports every measured toxic-metal analyte below its reporting limit across all 27 samples fda2022-tds-elements-fy2018-fy2020 (reporting limits of 4 µg/kg for lead, 1 µg/kg for cadmium, 3 µg/kg for total arsenic, 1 µg/kg for total mercury, 40 µg/kg for nickel, 50 µg/kg for chromium, and 1 µg/kg for uranium). This is a strong low-risk signal for the US market basket, but it is a left-censored result rather than a measured zero: the primary occurrence literature detects all of these metals in eggs at low but non-zero concentrations, with elevated tails in free-range, contaminated-environment, and feed-contaminated production. The corrected per-analyte values and their censoring treatment are set out in the Synthesis basis section below. This censored-clean US result is consistent with the expectation for eggs from commercial laying hens on formulated feeds under normal production conditions.

The exception to this low-risk characterization is environmental contamination at extreme levels. aendo2024-thailand-egg-metals-goldmine documented elevated Pb, Cd, and other metals in eggs from poultry farms near an active gold mine in northern Thailand, demonstrating that when hens are exposed to highly contaminated feed or free-range environments adjacent to industrial contamination sources, metals transfer to the egg at detectable and toxicologically relevant concentrations. This exception underscores that the low-risk characterization applies to commercial production systems with controlled feed, not to backyard or free-range production in contaminated environments.

Heavy metal contamination profile

Per-analyte snapshot derived from the machine-readable contamination_profile in the frontmatter above. data gap indicates the literature has been reviewed for this commodity-analyte combination and no usable occurrence data was found (a finding, not a placeholder). The Key sources column shows the top 2-3 contributing sources by year and sample size, with numbered wikilink aliases.

Synthesis basis and censoring treatment

The lead, cadmium, total arsenic, total mercury, nickel, and chromium cells were resynthesized on 2026-06-11 on a whole-egg fresh-weight basis, the form in which eggs enter the ingredient supply chain. Most primary occurrence literature reports whole-egg or separated yolk/albumen concentrations in mg/kg wet weight, which converts directly to ppb. Total arsenic and inorganic arsenic are kept as distinct analytes and are never derived from one another by a fixed ratio; the iAs cell is unchanged by this pass and only speciated measurements populate it. Total mercury and methylmercury are likewise kept distinct.

The earlier profile reported lead, cadmium, total arsenic, total mercury, nickel, chromium, and uranium at typical and 95th-percentile values of zero. Those figures were an artifact of the FDA Total Diet Study FY2018-FY2020 composite for hard-boiled eggs (TDS Food 37, n=27), in which every sample of every analyte fell below the reporting limit and the reported zeros were pooled as literal zeros (fda2022-tds-elements-fy2018-fy2020). The reporting limits were 4 µg/kg for lead, 1 µg/kg for cadmium, 3 µg/kg for total arsenic, 1 µg/kg for total mercury, 40 µg/kg for nickel, 50 µg/kg for chromium, and 1 µg/kg for uranium. Values below the analytical limit are treated as left-censored, not as measured zeros: the honest low end of each cell is written as a less-than bound at the FDA reporting limit, and the detected distributions are taken from the primary literature, in which all six resynthesized metals are low but non-zero, with right tails driven by free-range, contaminated-environment, and feed-contaminated production.

The lead distribution rests on whole-egg Chinese data (Li et al. 2026, whole-egg mean 12 µg/kg, range 5.4 to 18 µg/kg across nine areas), Bangladeshi market eggs (Islam et al. 2015, chicken egg mean 200 µg/kg, duck egg 100 µg/kg), and Italian retail eggs (Guerrini et al. 2024, supermarket yolk 186 µg/kg, supermarket albumen 688 µg/kg by edible fraction), with the 95th-percentile anchor set by the Guerrini supermarket albumen value. Bangladeshi smallholder rinsings (Rokanuzzaman et al. 2022) corroborate the low-to-moderate central range (brown-layer egg content 44 µg/kg). The cadmium distribution rests on the same Li, Islam, and Rokanuzzaman whole-egg data plus Nigerian poultry products (Cosmas et al. 2024, albumen Cd up to 67.2 µg/kg, which sets the 95th-percentile anchor); Li reports whole-egg cadmium at 1.5 to 2.3 µg/kg near the FDA floor, Islam chicken egg at 37 µg/kg. Total arsenic rests on a very clean Iranian commercial cohort (Abedi et al. 2023, whole-egg mean 0.79 µg/kg) and Li (6.0 to 19 µg/kg) at the low end and Islam chicken egg (230 µg/kg) at the upper-typical end, which also sets the 95th-percentile anchor because it is the highest egg-fraction total-arsenic value in the corpus. The Nigerian poultry-products study (Cosmas et al. 2024) reports a total-arsenic range of 0.0403 to 0.5970 mg/kg, but the 0.5970 mg/kg (597 µg/kg) maximum is the highest value across all 36 pooled poultry-product samples (muscle, gizzard, yolk, and albumen), not an egg-fraction value; the only egg-fraction value the study isolates is yolk at 0.1213 mg/kg (121 µg/kg). The earlier profile anchored the 95th percentile to the 597 µg/kg pooled-poultry maximum, which over-stated the egg-fraction tail; the cell is re-anchored to the highest grounded egg-fraction value (230 µg/kg) and the poultry-product maximum is treated as a non-egg-fraction proxy only.

Total mercury rests on Abedi (whole-egg mean 0.18 µg/kg) and Chongqing total-diet eggs (Chen et al. 2025, eggs 1.2 to 3.1 µg/kg) at the clean floor, a Jakarta market value (Kurniawati et al. 2021, egg 43 µg/kg by neutron activation) at the upper-typical end, and a highly variable Italian supermarket albumen (Guerrini et al. 2024, albumen mean 266 µg/kg, one supermarket sample to 1077 µg/kg) at the 95th percentile. Nickel rests on the clean whole-egg Li distribution (15 to 63 µg/kg, the only corpus distribution that resolves below the FDA 40 µg/kg reporting limit) for the central estimate, with Islam Bangladeshi chicken egg (1300 µg/kg) setting a wide, low-confidence 95th-percentile spread; the Islam dataset reports a uniformly elevated nickel baseline across all commodities and is read as a high-analytical-baseline anchor rather than a typical value. Chromium rests on Li whole-egg total chromium (53 to 140 µg/kg) and a low Jakarta value (Kurniawati et al. 2021, egg 20 µg/kg), with the 95th percentile anchored to the Li whole-egg upper bound (140 µg/kg). The Bangladeshi egg-albumen value (Mahbub et al. 2018, albumen total chromium to 190 µg/kg) comes from the same feed-loaded albumen cohort whose lead (3340 µg/kg) is stratified out of the lead central estimate as feed-contaminated; for consistency that cohort’s chromium is treated the same way and is not used to set the chromium 95th percentile. The earlier profile anchored the chromium 95th percentile to that Mahbub albumen value while excluding the same cohort’s lead, an inconsistency this pass corrects by stratifying both.

Chromium is reported as total chromium at low confidence; no egg hexavalent-chromium measurement exists in the corpus and no Cr-VI fraction is inferred. Uranium is recorded as a reviewed data gap: the FDA Total Diet Study egg composite reports uranium fully below its 1 µg/kg reporting limit, and no non-FDA egg-uranium occurrence value with an extractable number is present in the routed corpus, so no distribution is published.

Documented mining, industrial, and feed-contaminated outliers are stratified separately and do not set the central estimates above. Pakistani feed-contaminated poultry (Iqbal et al. 2023, whole-egg lead mean 8956 µg/kg and chromium 1952 µg/kg, driven by Farm E/F feed exceedances) and Bangladeshi feed-loaded eggs (Mahbub et al. 2018, albumen lead to 3340 µg/kg) represent contaminated-feed strata. Duck eggs from mercury-mining areas in Guizhou (Guo et al. 2024, yolk chromium 410 µg/kg dry weight, lead 80 µg/kg dry weight) and goldmine-adjacent poultry in Thailand (Aendo et al. 2024) document the contaminated-environment ceiling that the low-risk commercial characterization explicitly excludes. These strata are reported in prose and are not folded into the global percentiles.

Routing

This node is linked from the ingredient index and source routing list.

Contamination Profile State

The machine-readable contamination profile is in_progress. Ingredient-level values belong here once parsed; finished-product values belong on the relevant product-category page.

FDA TDS FY2018-FY2020 Evidence

FDA’s FY2018-FY2020 Total Diet Study dataset includes this page’s routed matrix as TDS Food 37, “Eggs, hard-boiled.” The normalized row-level data is stored in data/evidence/fda_tds_fy2018_2020_element_results_samples.csv, with per-food/per-analyte summaries in data/evidence/fda_tds_fy2018_2020_summary_by_food_analyte.csv. Concentrations are retained as FDA reported them, with reporting limits preserved separately; reported zeroes are not rewritten as <LOD without a source-specific rule. fda2022-tds-elements-fy2018-fy2020

FDA TDS FY2018-FY2020 Occurrence Values

FDA Total Diet Study FY2018-FY2020 reports prepared/composite-food concentration distributions for this ingredient as TDS food “Eggs, hard-boiled” (fda2022-tds-elements-fy2018-fy2020). Values are in ppb-equivalent on the basis FDA reported. The full sample-level data are stored in data/evidence/fda_tds_fy2018_2020_element_results_samples.csv; per-analyte distributions in data/evidence/fda_tds_fy2018_2020_summary_by_food_analyte.csv. These distributions count as one source under persistent-wiki-ingest-rule synthesis discipline; numerical values stay in body scratch until a second independent source is integrated.

Ranges by source, region, and variety

The FDA TDS FY2018-FY2020 hard-boiled egg dataset (n=27 composites) shows all analytes at zero fda2022-tds-elements-fy2018-fy2020, representing the US commercial market basket under standard production conditions. This is the baseline: eggs from hens on commercial formulated feed in managed production systems in a low-metal-contamination agricultural region.

aendo2024-thailand-egg-metals-goldmine provides the contrasting data point: eggs from poultry farms adjacent to a gold mine in northern Thailand showed elevated concentrations of Pb, Cd, and other metals in egg tissue, with concentrations in yolk substantially higher than in egg white for most metals studied. This source documents that free-range or backyard hens with soil contact in contaminated environments can produce eggs with toxicologically relevant metal concentrations, particularly for populations with high egg consumption frequency.

The FSA/Fera FS102048 survey provides an additional data point for UK-market eggs awaiting structured table parsing fsa2016-infant-food-formula-metals-survey. The iAs and tAs data point attributed to arsenic exposure assessment in Chongqing, China dai2024-chongqing-dietary-arsenic-exposure contributes arsenic occurrence context for eggs in the Chinese dietary assessment literature, pending full structured integration.

Processing effects

Cooking method affects the distribution of metals within the egg but does not reduce overall metal concentrations. Hard boiling, scrambling, frying, and poaching all retain the metal content of the whole egg or the specific fraction used (white only, yolk only). The egg yolk carries higher concentrations of fat-soluble compounds and metal-binding proteins than the egg white; for metals such as Cd and Pb that bind to metalloproteins (metallothionein in particular), the yolk fraction carries a higher per-gram metal burden than the white fraction under conditions of elevated exposure. Under near-zero metal conditions (as in the US TDS dataset), this partitioning is moot.

Hard-boiling does not leach meaningful amounts of Cd or Pb into the cooking water, since metals in egg tissue are protein-bound rather than free in solution. Egg processing steps such as pasteurization also do not affect metal concentrations.

Ingredient-derivative risk

Eggs are used as ingredients in a wide range of processed foods, contributing binding, emulsification, and leavening functions. The metal contribution of the egg fraction to a composite product (cake, pasta, mayonnaise, custard) is proportional to its weight fraction multiplied by its metal concentration. Under normal commercial production conditions where TDS egg data shows zero for all analytes fda2022-tds-elements-fy2018-fy2020, the egg fraction’s metal contribution to composite foods is effectively zero and is not a meaningful source of heavy metal exposure in those products.

Processed egg derivatives including dried whole egg powder, dried egg white, and dried egg yolk concentrate the protein and mineral content of the fresh egg by removing water. On a dry-weight basis, any metals present in the fresh egg would be concentrated proportionally in the dried form. Under normal commercial egg sourcing where fresh egg metals are near zero, this concentration effect is of no practical consequence.

Mitigation options

Sourcing levers

Sourcing eggs from commercial laying flocks on formulated, low-metal feed is the primary mitigation lever. Commercial egg production with centralized feed formulation and quality control inherently limits the pathway for metals to enter eggs. Avoiding eggs from free-range or backyard flocks in regions with known soil contamination from mining, smelting, or industrial land use is the relevant risk mitigation for populations or procurement scenarios where such eggs might be used.

Agronomic levers

No egg-specific agronomic lever applies in the traditional sense. Feed quality control at the laying hen farm (using low-Cd, low-Pb feed ingredients) is the practical equivalent of an agronomic lever for this animal product.

Processing levers

No processing step reduces heavy metals in eggs at the concentrations present in commercially produced eggs under normal conditions. If eggs from a contaminated-environment source were identified, no practical post-hoc processing intervention removes the metal from egg tissue.

Formulation levers

For food products using eggs as an ingredient in contexts where maximum metal control is a priority (for example, infant or toddler foods), specifying commercially produced eggs from certified low-contamination production systems is the formulation-level implementation of the sourcing lever. Substitution of egg with plant-based egg alternatives eliminates the egg-origin metal pathway but introduces different metal risk profiles from the substitute ingredient.

Testing and QC levers

Under normal commercial sourcing conditions, heavy metal testing of eggs is low priority. Testing is warranted when eggs are sourced from non-standard production systems (backyard, free-range in contaminated areas) or when procurement includes imports from regions where poultry environmental contamination has been documented. aendo2024-thailand-egg-metals-goldmine provides the scientific basis for requiring testing in mining-adjacent production contexts.

Packaging and storage levers

No quantified data on packaging or storage effects on heavy metal content in eggs is in the current corpus; section will be expanded when relevant evidence is ingested.

Regulatory limits that apply

Under the European Union eu2023-contaminants-maximum-levels, the maximum level for lead in eggs is 0.10 mg/kg (100 ppb) on a fresh weight basis, and for cadmium in eggs it is 0.050 mg/kg (50 ppb) fresh weight. These limits reflect the historical possibility of elevated metals in eggs from free-range hens on contaminated land, rather than a risk specific to commercial production. The US TDS all-zero result for hard-boiled eggs fda2022-tds-elements-fy2018-fy2020 is consistent with the EU limits being non-binding in practice for commercially produced US market eggs. No US federal maximum level for lead or cadmium in eggs has been finalized as of 2026. Codex Alimentarius (CXS 193-1995 and revisions) sets a general lead limit of 0.10 mg/kg for eggs, consistent with the EU limit.

Sources

Auto-generated from source-page frontmatter. The “Used on this page for” column is populated by the orchestrator’s POPULATE-SOURCE-LEGEND action; pending entries appear as *[awaiting synthesis]*.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.