Cadmium: A Focus on the Brown Crab (Cancer pagurus) Industry and Potential Human Health Risks

Overview

Lordan and Zabetakis review cadmium accumulation in brown crab (Cancer pagurus), the divergent regulatory limits applied in the European Union versus the People’s Republic of China and Hong Kong, the dietary-intake context that determines whether crab consumption contributes meaningfully to total cadmium exposure, and the clinical effects of chronic cadmium exposure on humans. The review is most useful to the wiki as compiled occurrence evidence for cadmium in brown-crab white meat, brown meat, and hepatopancreas across European fisheries, and as a synthesis of the EU/PRC regulatory divergence that has shaped live-export trade.

Key numbers

All concentration values below are reported as the review’s Table 1 summary of cadmium in brown crab on a wet-weight basis. Values are reproduced as the review presents them, with the underlying primary-study reference number from the review preserved in the right-hand column; consult the primary studies before using any single value in a routed pool.

Cadmium in brown crab tissues (Table 1, mg/kg wet weight)

Crab meat type (state)	Location	Cadmium (mg/kg ww)	Detection method	Underlying ref. (review)
White meat (raw), spring/summer	Portugal	0.07 ± 0.06 / 0.01 ± 0.01 (mean ± SD)	FAAS	[14]
White meat (steamed), spring/summer	Portugal	0.24 ± 0.38 / 0.10 ± 0.14	FAAS	[14]
White meat (boiled), spring/summer	Portugal	0.05 ± 0.05 / 0.10 ± 0.16	FAAS	[14]
Brown meat (raw), spring/summer	Portugal	8.4 ± 8.3 / 8.1 ± 14.2	FAAS	[14]
Brown meat (steamed), spring/summer	Portugal	7.6 ± 5.2 / 11 ± 13	FAAS	[14]
Brown meat (boiled), spring/summer	Portugal	5.6 ± 5.6 / 5.0 ± 8.2	FAAS	[14]
White claw meat (raw)	Northern Norway	0.024 ± 0.012 (mean ± SD)	ICP-MS	[30]
White claw meat (raw)	Southern Norway	0.007 ± 0.005	ICP-MS	[30]
Brown meat (raw)	Northern Norway	1.15 ± 0.76	ICP-MS	[30]
Brown meat (raw)	Southern Norway	0.21 ± 0.14	ICP-MS	[30]
White claw meat (boiled)	Northern Norway	0.30 ± 0.29	ICP-MS	[30]
White claw meat (boiled)	Southern Norway	0.065 ± 0.075	ICP-MS	[30]
Brown meat (boiled)	Northern Norway	0.45 ± 0.26	ICP-MS	[30]
Brown meat (boiled)	Southern Norway	0.16 ± 0.12	ICP-MS	[30]
Brown meat (raw)	Mausund, Norway	2.11–4.37 (yearly median range, 2016–2017)	ICP-MS	[33]
White meat (raw)	English Channel	0.10 (estimated mean)	FAAS	[13]
Brown meat (raw)	English Channel	15–18 (estimated mean)	FAAS	[13]
White meat (raw)	Scottish coast	0.10	FAAS	[13]
Brown meat (raw)	Scottish coast	20–30	FAAS	[13]
White meat (raw)	Birsay, Scotland	mean not reported / range 0.08–0.27	FAAS	[64]
Brown meat (raw)	Birsay, Scotland	7.30 / 1.12–49.4 (mean / range)	FAAS	[64]
White meat (raw)	Norwegian coast	0.62 / 0.002–4.5	ICP-MS	[33,65]
Brown meat (raw)	Norwegian coast	8.7 / 0.24–43.0	ICP-MS	[33,65]
White meat (raw)	Senja, Norway	0.53 / 0.03–3.2	ICP-MS	[33,66]
Brown meat (raw)	Senja, Norway	9.3 / 1.6–29.0	ICP-MS	[33,66]
White meat (raw)	Kvaløya, Norway	0.25 / 0.06–0.74	ICP-MS	[33,66]
Brown meat (raw)	Kvaløya, Norway	30.0 / 7.3–58.0	ICP-MS	[33,66]

Regulatory limits and dietary reference values

EU Commission Regulation (EU) No 488/2014 amending (EC) No 1881/2006: cadmium maximum level of 0.5 mg/kg applies to white crab meat from appendages only [18–20].
People’s Republic of China and Hong Kong: cadmium maximum level of 0.5 mg/kg applies to the combined white and brown crab meat of all imported crabs [9,17,21]. PRC public consultation has been opened to raise the brown-crab cadmium limit from 0.5 mg/kg to 3.0 mg/kg; an update on the consultation had not been released at the time of review.
EFSA tolerable weekly intake (TWI) for cadmium: 2.5 µg/kg body weight per week.
JECFA provisional tolerable monthly intake (PTMI) for cadmium: 25 µg/kg body weight per month, derived from a urinary cadmium excretion rate of 5.24 µg/g creatinine or 0.8 µg/kg per day as a nephrotoxicity threshold [148–150]. (The review itself uses the unprovisional shorter form “tolerable monthly intake” without the “provisional” qualifier; the JECFA-canonical designation is PTMI and is used here to match the regulation slug.)
EFSA critical β2-microglobulin urinary endpoint: 300 µg/g creatinine; EFSA-adopted cadmium excretion rate as nephrotoxicity threshold: 1 µg/g creatinine; uncertainty factor 0.36 µg/kg body weight per day for 50 years as benchmark dose [151].

Dietary-intake context

Lifetime cadmium dietary exposure for the European population is estimated at approximately 2 µg/kg body weight per week (within EFSA’s TWI of 2.5 µg/kg body weight per week).
Ireland: estimated adult weekly cadmium intake of 1.1–2.5 µg/kg body weight per week (44–62% of the EFSA TWI); 95% of National Adult Nutrition Survey participants had urinary cadmium below the 1 µg cadmium/g creatinine value EFSA has deemed safe [101,102]. Cereals contributed 39%, vegetables 36%, dairy 12%, and fish and shellfish approximately 1% of dietary cadmium [101].
United States (NHANES 2007–2012, n=12,523): average dietary cadmium intake 4.6 µg/day, or 0.54 µg/kg body weight per week (≈22% of TWI); leading contributors were cereals and bread (34%), leafy vegetables (20%), potatoes (11%), legumes and nuts (7%), and root vegetables (6%); leading individual foods were lettuce (14%), spaghetti (8%), bread (7%), and potatoes (6%) [103]. Fish and shellfish contributed 1%.
South Korea (cohort n=1,245): estimated average cadmium intake 20.8 µg/day [26]. Leading contributors were rice (40%), squid (12%), eel (11%), crab (9%), shellfish (4%), seaweed (3%), and kimchi (3%); crab specifically contributed 8.6% of cumulative cadmium intake in this cohort.
People’s Republic of China general population: mean dietary cadmium exposure 15.3 µg/kg body weight per month (30.6 µg/day for a 60 kg adult). Table 2 contributor percentages for the general Chinese population: rice 55.8%, wheat flour 11.8%, leafy vegetables 10.5%, shellfish 4.8%, meat 2.6%, seaweed 2.4%, other vegetables 2.4%, other cereals 2.1%, root and stalk vegetables 2.0%, mushrooms 1.1%, fish 1.1%, legumes 0.9%, fruits 0.6%, eggs 0.6%, nuts 0.4%, offal 0.4%, other 0.5% [108].
People’s Republic of China high-exposure subpopulation (≥95th percentile of mean dietary cadmium exposure): rice 58.6%, shellfish 13.2%, leafy vegetables 9.2%, seaweed 6.4%, wheat flour 2.0%, meat 2.0%, root and stalk vegetables 1.7%, mushrooms 1.5%, other vegetables 1.4%, fish 1.0%, other cereals 0.9%, legumes 0.6%, fruits 0.4%, eggs 0.2%, nuts 0.4%, offal 0.2%, other 0.3% [108].

Human-health and biomarker numbers

Cadmium biological half-life in the kidney: 10–30 years [81,135].
Critical kidney cadmium cortex concentration: approximately 200 µg/g wet weight (200 ppm); the urinary cadmium value corresponding to this kidney concentration is estimated at 10 µg/g creatinine [138,140,141].
Cadmium gastrointestinal absorption: 3–5% of ingested cadmium [20,118].
Bioaccessibility comparison from one cited study: cadmium 84% from fish versus 73% from shellfish [147].
Long Island Study of Seafood Consumption (n=252 avid seafood consumers): salmon intake associated with log-transformed blood cadmium (β = 0.20; p = 0.001); regular seafood intake not associated (β = −0.01; p = 0.11) [182].
Norwegian Fish and Game study (n=179): median urinary cadmium 0.16 µg/L (creatinine-corrected); median blood cadmium 0.45 µg/L; 24% of designated high-cadmium consumers and 8% of low-cadmium controls had intakes above the EFSA TWI [183].
Crab-consumer cohort: regular consumers averaging 447 g brown crab meat per week over 16 years showed no elevation in long-term cadmium exposure markers or kidney-toxicity biomarkers relative to low-consumption controls [143].
French seafood-consumer cohort: the review prints the mean dietary cadmium ingestion verbatim as “2.4 ± 3.3 mg/kg bodyweight/week” and the mean urinary cadmium verbatim as “0.65 ± 0.45 mg/g creatinine” (PDF p.16); the printed mg units are approximately three orders of magnitude above the EFSA TWI and almost certainly a units typo for µg in the review itself. Values are preserved exactly as the review prints them; see Verification notes for the typo flag, and do not propagate either interpretation without consulting the underlying primary study. Urinary cadmium was significantly higher in women than men.
US national geometric mean blood cadmium for non-smoking adults: 0.47 µg/L; smoker mean approximately 1.58 µg/L [98].

Methods (brief)

This is a narrative review. It compiles cadmium concentration tables for brown crab tissues from prior primary studies (Table 1) and summarizes dietary-exposure surveys, regulatory limits, biomarker thresholds, and toxicological evidence from European, US, South Korean, and PRC literature. The review does not generate new analytical measurements; concentration values reported in Table 1 are attributed to underlying primary references [13,14,30,33,64,65,66] and used the detection methods (FAAS or ICP-MS) reported by those primary studies. Cooking states (raw, steamed, boiled) and tissue types (white claw meat, brown meat, hepatopancreas) follow the primary-study sampling; basis is wet weight as reported by the underlying studies. The review notes that cadmium detection in biological samples is most commonly performed today by ICP-MS (limit of detection as low as 0.003 µg/L); graphite furnace AAS has a sample detection limit of 0.4 µg/L [67,68,70]. The review reports no de novo speciation or analytical work of its own.

Implications

Certification: The review is a useful entry point for HMTc cadmium-in-crustacean threshold work because it (a) consolidates wet-weight brown-crab concentration evidence across multiple European fisheries with the cooking state and tissue type preserved, (b) documents the EU/PRC regulatory divergence on what tissue the 0.5 mg/kg limit applies to (white meat only in the EU; combined white and brown meat in the PRC and Hong Kong), and (c) clarifies that the brown meat and hepatopancreas tissue compartments carry cadmium concentrations approximately one to two orders of magnitude higher than the white claw meat from the same animal. Routed-pool decisions should consult the underlying primary studies (Wiech et al. 2017, Wiech et al. 2020, Ervik et al. 2020, Maulvault et al. 2012, Barrento et al. 2009, and the Birsay Scotland study) for the raw observation data; this review row should not be pooled as if it were a primary observation.

Courses: Useful teaching example for explaining why “the cadmium limit for crab” is not a single number — the EU limits white meat to 0.5 mg/kg while ignoring brown meat, the PRC and Hong Kong apply the same 0.5 mg/kg limit to combined white plus brown meat, and the brown meat itself can run 8–30+ mg/kg in European fisheries. The disconnect between the regulatory framing and the tissue distribution of cadmium is the heart of the live-export trade dispute documented in the review.

App: Route as broad shellfish and seafood occurrence evidence for cadmium with the crab-specific brown-meat-versus-white-meat distinction preserved. Do not use the review’s compiled Table 1 values as if they were primary measurements when computing ingredient contamination_profile blocks; defer the pooled occurrence values to the underlying primary studies once those are ingested. Crab is not a separate ingredient slug in the current taxonomy; this review is therefore best treated as shellfish/seafood context until a crab-specific routing question forces a taxonomy decision.

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