Rodriguez-Mendivil et al. 2019 — Heavy metals in canned tuna and fresh fish, Tijuana, Mexico

This 2019 peer-reviewed study measured total Hg (tHg), Pb, Cd, and Cr in 48 canned tuna samples from 8 brands and 20 fresh fish samples from 4 species sold in Tijuana, Mexico, then calculated hazard quotients (HQs) and total hazard quotients (THQs) using the USEPA region III risk-based concentration table. Note that mercury was measured as total Hg by cold vapor atomic absorption spectrometry (CVAAS) — the paper does not speciate MeHg from inorganic Hg. The authors concluded that all HQ and THQ values fell below 1.0 under their Mexican general-population consumption scenario; however, two canned tuna samples (4.16%) exceeded the author-cited Mexican 1.0 mg/kg maximum permissible limit for Hg, and two samples exceeded the EU Pb limit of 0.20 mg/kg.

Key numbers

Canned tuna (n=48, wet weight, mg/kg)

• Overall canned tuna (n=48, combined): Hg 0.005–1.170, mean 0.278; Pb 0.07–0.32, mean 0.113; Cd 0.000–0.007, mean 0.0029; Cr 0.02–0.65, mean 0.167 mg/kg ww.
• The highest anonymized canned-tuna group mean was 0.560 ± 0.450 mg/kg for Hg and 0.270 ± 0.199 mg/kg for Cr; the lowest group mean was 0.115 ± 0.070 mg/kg for Hg and 0.113 ± 0.032 mg/kg for Cr.
• Two of 48 canned-tuna samples exceeded the Mexican Hg MPL of 1.0 mg/kg (1.170 and 1.040 mg/kg), and two exceeded the EU Pb limit of 0.20 mg/kg (0.322 and 0.289 mg/kg).

Fresh fish (n=20, wet weight, mg/kg)

60% of fresh fish samples had Hg concentrations above the Mexican MPL of 1.0 mg/kg. Both shark species (mako mean 1.286 mg/kg, soupfin mean 1.128 mg/kg) exceeded the MPL on average.

Detection limits (mg/kg): Pb 0.01, Cd 0.001, Cr 0.01, Hg 0.000003.

Hazard quotients (THQ for canned tuna and fresh fish species, worst-case scenario: EF=365 days/yr, IR=3.4 g/day canned tuna, 3.7 g/day fresh fish, BW=70 kg, ED=75 yr):

• Canned tuna: Hg HQ 0.0345-0.1889 (mean 0.0946), Cr HQ 0.0696-0.2615 (mean 0.1327), Cd HQ 0.00001-0.00003 (mean 0.00002), Pb HQ 0.00008-0.00027 (mean 0.00012); THQ 0.227
• Mako shark: THQ 0.545
• Yellowfin tuna (fresh): THQ 0.156
• Soupfin shark: THQ 0.397
• Swordfish: THQ 0.209
• All values <1.0; Hg dominates the HQ for all species

Regulatory comparison:

• Author-cited Mexican MPL for Hg in canned fish under NOM-028-SSA1-1993: 1.0 mg/kg; 2/48 samples exceeded (1.17 and 1.04 mg/kg)
• Author-cited Mexican MPL for Hg in fresh fish under NOM-027-SSA1-1993: 1.0 mg/kg; 60% of fresh-fish samples exceeded
• EU regulation (EC No. 1881/2006) Pb limit: 0.20 mg/kg; 2/48 canned tuna samples exceeded (0.322 and 0.289 mg/kg)
• EU Cd limit: 0.10 mg/kg; all samples below

Methods (brief)

Total mercury measured by cold vapor atomic absorption spectrometry (CVAAS), USEPA method 7471b, after microwave-assisted digestion. Pb, Cd, and Cr measured by graphite furnace atomic absorption spectroscopy (GFAAS), USEPA method 7010, after microwave-assisted digestion. Quality control: certified reference materials ERA 524 (Pb, Cd, Cr) and ERA 027 (Hg); recoveries 95–105% for QC standards, 85–102% for spikes. Note: mercury is measured as total Hg; no speciation between MeHg and inorganic Hg is performed. Consumption rate assumptions for hazard quotient calculation are derived from national per capita consumption data for Mexico (1.23 kg/yr canned tuna, 1.34 kg/yr fresh tuna equivalent), representing a worst-case scenario treating all fish species as if consumed at the fresh tuna rate.

Implications

Certification: The tHg data for canned tuna (mean 0.278 mg/kg, max 1.170 mg/kg ww) and yellowfin tuna fresh (mean 0.377 mg/kg) are measured as total Hg, not MeHg — relevant context when comparing against HMT&C MeHg thresholds. The Cr concentrations (canned tuna mean 0.167 mg/kg, up to 0.65 mg/kg) are substantially higher than reported in other studies; the authors note no MPL exists for Cr in Mexican or EU regulations for these matrices, but the values are worth flagging in any Cr monitoring context. Cd is very low across all samples.

Courses: Illustrates the species-dependent tHg gradient from canned yellowfin tuna (mean 0.278 mg/kg) through fresh yellowfin tuna (0.377 mg/kg) to shark species (mako 1.286 mg/kg) — useful for teaching biomagnification and species-selection as a contamination lever.

App: Provides canned tuna tHg range (0.005–1.170 mg/kg) and Pb range (0.07–0.32 mg/kg) from Mexico; the Cd data (max 0.007 mg/kg) confirms very low Cd burden in canned tuna across this dataset.

Wiki pages this source may touch

• canned-tuna
• tinned-fish
• fish
• shark
• seafood
• canned-fish
• fresh-fish
• seafood
• mercury-total
• lead
• cadmium
• chromium
• eu-1881-2006-contaminants-superseded
• eu-reg-2022-617-mercury-fish
• mx-nom-027-ssa1-1993-fresh-frozen-fish-superseded
• mx-nom-028-ssa1-1993-canned-fish-superseded
• mx-nom-242-ssa1-2009-fishery-products

Verification notes

• 2026-05-18 Codex merge-enhance: matched DOI/raw path to P0149, added DOI access URL and PDF SHA-256, corrected invalid species-level ingredient slugs to existing broader seafood slugs, replaced [[metals/mercury]] with total-mercury routing, and corrected the canned-tuna hazard-quotient line that had mislabeled the Cr HQ range as THQ.
• The source reports eight canned-tuna groups using anonymized codes only; this page aggregates the canned-tuna table to avoid turning anonymized group rows into a wiki-side product ranking.
• The paper cites NOM-027-SSA1-1993 and NOM-028-SSA1-1993 for Mexican MPL comparisons. Those rules had already been cancelled by the 2011 successor NOM-242-SSA1-2009, so this page preserves the author-cited benchmark while linking the current successor regulation separately.
• 2026-05-18 fresh-context audit: REVISE verdict; two minor findings applied (matrix vocabulary narrowed to fish; unsupported “acid” qualifier removed from microwave-assisted digestion wording); brand firewall and HMT&C firewall clean.

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.