Variability of Mercury Concentrations Across Species, Brand, and Tissue Type in Processed Commercial Seafood Products

Abstract

Mercury (Hg) is a global health concern due to its prevalence, persistence, and toxicity. Numerous studies have assessed Hg concentrations in seafood, but variability in reported concentrations highlights the need for continued monitoring and stricter regulations. We measured total Hg (tHg) in 148 pre-processed, packaged seafood products purchased in Raleigh, North Carolina, using thermal decomposition-gold amalgamation atomic absorption spectrophotometry. Products were grouped into three categories based on trophic ecology and physiology: (1) tuna, (2) other bony fish, and (3) shellfish and squid. Among tuna, albacore had the highest average tHg (396.4 ng/g ± 172.1), while yellowfin had the lowest (68.3 ng/g ± 64.7). Herring (54.0 ng/g ± 23.2) and crab (78.2 ng/g ± 24.1) had the highest concentrations in the other two groups. One can of albacore exceeded the FDA action level of 1 part per million (1.3 ppm or 1300 ng/g). Brand differences were significant for both albacore and light tuna, with Brand 1 consistently showing higher Hg levels. Comparisons to FDA data (1990-2012) suggest Hg concentrations in tuna have remained stable over the past two decades. This study underscores the variability of Hg concentrations across species and brands and the need for continued monitoring to protect consumers.

Keywords: canned food; fish; mercury; seafood; tuna.

Figure 1

tHg concentrations vary significantly across species. Total Hg concentrations, wet weight (WW), in (A) albacore tuna (n = 44), light tuna (n = 27), skipjack tuna (n = 11), and yellowfin tuna (n = 13), (B) anchovies (n = 3), herring (n = 6), mackerel (n = 4), salmon (n = 9), sardines (n = 7), and trout (n = 3), and (C) clams (n = 3), crab (n = 6), oysters (n = 6), scallops (n = 3), and squid (n = 3); one-way ANOVA, * p < 0.05, ** p < 0.01, *** p < 0.001. Maroon squares indicate average concentration as reported by Karimi et al., 2012 [22]. Graphs indicate mean, min, max.

Figure 2

tHG concentrations in this study differ across brands and meat types. One-way ANOVA of log₁₀-transformed tHg concentrations in (A) albacore tuna, (B) light tuna, (C) other bony fish, (D) t-test between herring from Brand 18 and Brand 15, One-way ANOVA in (E) shellfish and squid, and (F) t-test between crab white meat and lump meat; one-way ANOVA and t-test, * p < 0.05, ** p < 0.01, *** p < 0.001. Graphs indicate mean ± SD.

Figure 3

tHG concentrations in this study are comparable to those previously reported by the FDA. One-way ANOVA of log_(x+1)-transformed tHg concentrations in (A) albacore tuna and (B) light tuna; one-way ANOVA, * p < 0.05, *** p < 0.001. Data shown for the years 2000–2010 were compiled from the FDA’s previously published data set (black data points), while the data shown for 2022 represent the data analyzed in this study (red data point). Graphs indicate mean ± SD.