Journal of Threatened Taxa | | 26 December 2022 | 14(12): 22337–22340


ISSN 0974-7907 (Online) | ISSN 0974-7893 (Print)

#8167 | Received 29 August 2022 | Final received 26 September 2022 | Finally accepted 09 November 2022



Mercury in tuna from the western equatorial Atlantic Ocean and health risk assessment


Ana Paula Madeira Di Beneditto 1*, Inácio Abreu Pestana 2*, Igor David da Costa 3, Marcelo Gomes de Almeida 4, Braulio Cherene Vaz de Oliveira 5 & Carlos Eduardo de Rezende 6 


1,2,4,5,6 Universidade Estadual do Norte Fluminense Darcy Ribeiro, CBB, Laboratório de Ciências Ambientais, Av. Alberto Lamego 2000, Campos dos Goytacazes, RJ, 28013-602, Brazil.

3 Universidade Federal Fluminense, Instituto do Noroeste Fluminense de Educação Superior, Av. João Jasbick, s/nº, Santo Antônio de Pádua, RJ, 28470-000, Brazil.

* These authors contributed equally to this work.

1 (corresponding author), 2, 3, 4, 5, 6




Editor: Anonymity requested.            Date of publication: 26 December 2022 (online & print)


Citation: Di Beneditto, A.P.M., I.A. Pestana, I.D. da Costa, M.G de Almeida, B.C.V. de Oliveira & C.E. de Rezende (2022). Mercury in tuna from the western equatorial Atlantic Ocean and health risk assessment. Journal of Threatened Taxa 14(12): 22337–22340.


Copyright: © Di Beneditto et al. 2022. Creative Commons Attribution 4.0 International License.  JoTT allows unrestricted use, reproduction, and distribution of this article in any medium by providing adequate credit to the author(s) and the source of publication.


Funding: Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (grants no. 302.598/2021-9 and 305.217/2017-8)Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) (grants no. E-26/200.797/2021, E-26/210.703/2021 and E-26/200.586/2022).


Competing interests: The authors declare no competing interests.


Acknowledgements:  We are indebted to Felipe Miranda and Aline Aquino for access to tuna specimens at Mercado Municipal Central Leste. This research was funded by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (grants no. 302.598/2021-9 and 305.217/2017-8) and Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) (grants no. E-26/200.797/2021, E-26/210.703/2021 and E-26/200.586/2022).




Abstract: This study analyses the mercury (Hg) concentration in the meat of Thunnus albacares and Thunnus obesus caught from the western equatorial Atlantic Ocean. The objective was to estimate the Hg intake via tuna ingestion and presents the possible health risk assessment. For T. albacares and T. obesus, the median concentration was 212 ng·g-1 and 475.1 ng·g-1 wet weight, respectively. The Hg concentrations were below the maximum tolerable limit established by international and Brazilian regulations for fishery products. The consumption would pose a risk for human populations that ingest more than 80 g·day-1. Regular monitoring of both human consumption rates and Hg levels in fish are recommended.


Keywords: Hg, human health, Thunnus albacares, Thunnus obesus.


Portuguese: Este estudo analisa a concentração de mercúrio (Hg) na carne de Thunnus albacares e T. obesus capturados em pescarias no Oceano Atlântico equatorial ocidental, estima a ingestão de Hg via ingestão de atum e apresenta a avaliação de risco à saúde. Para T. albacares e T. obesus, a mediana das concentrações foi 212 ng·g-1 e 475,1 ng·g-1 peso úmido, respectivamente. As concentrações de Hg ficaram abaixo do limite máximo tolerável estabelecido pelas regulamentações internacionais e brasileiras. O consumo representaria um risco para as populações humanas que ingerem mais de 80 g·dia-1.




In Brazil, the tuna fishery targeted mainly the yellowfin tuna T. albacares Bonnaterre, 1788) and the bigeye tuna T. obesus (Lowe, 1839), which are among the main tuna species caught worldwide (Guillotreau et al. 2017; Rodrigues et al. 2020). Tuna species are large and long-lived predatory fishes with wide distribution, becoming good bio monitors of contaminants, such as mercury (Hg) (Ferriss & Essington 2011; Jinadasa et al. 2019; Tseng et al. 2021). In the marine environment, >95% of the Hg in the meat of predatory fish is methylmercury, a potent neurotoxin (Lescord et al. 2018). This study analyzes the Hg concentration in tuna meat from western equatorial Atlantic Ocean, and estimates the Hg intake via tuna ingestion.

Tuna sampling was conducted in 2019 and 2020 at the fish market named Mercado Municipal Central Leste, located in São Paulo State, southeastern Brazil. The fish sampled at the market were caught from commercial fishery done by the fishing fleet of Areia Branca Harbor. This fishing fleet operates in the western equatorial Atlantic Ocean (off northern Brazil), in the vicinity of one of the oceanic buoys of PIRATA Program (“Pilot Moored Array in the Tropical Atlantic”). The fishing area is located in waters that are 4,000 m deep, at 0°, 35 °W, and 600 km offshore (international waters). The sample size for T. albacares was 32 individuals in 2019, and 18 individuals in 2020; and for T. obesus it was 26 and six individuals in 2019 and 2020, respectively. Sample of meat from the fish belly (5 g of wet weight) was removed from each individual at the fish market. The samples were brought to the laboratory and kept frozen (-20 °C) in dry sterile vials, freeze-dried and homogenized with a mortar and pestle (Table 1). Mercury determinations followed Bastos et al. (1998) and were conducted with an ICP-OES (Varian, Liberty II Model 720 ES, Australia) with a cold vapor accessory (VGA-77). The recovery values for the certified reference material (DORM-4) ranged 85─95 %. The coefficients of variation of the triplicate analyses were <10%. The results were calculated as ng·g-1 dry weight and converted to a wet weight basis. For T. albacares, the water loss after freeze-drying was 74±1%, and for T. obesus, it was 73±1%.

The maximum permissible limit for Hg in predatory fishes established by the World Health Organization ―WHO (FAO/WHO 1991) and Brazilian Government (ANVISA 2021), is 1 mg·kg-1 (or 1,000 ng·g-1) wet weight. The estimated daily intake proposed in Caldas et al. (2016) was used for the intake analysis: EDI = C·IR/BW, where EDI is the estimated dietary intake of Hg (µg·day-1·kg-1), C is the Hg concentration in the fish meat (µg·g-1 wet weight), IR is the intake rate in Brazil (27 g·day-1; Barone et al. 2017), and BW is the body weight (70 kg for a Brazilian adult). The provisional upper tolerable weekly intakes - PTWI limit for Hg is 1.6 µg·week-1·kg-1 or 0.57 µg·day-1·kg-1 (FAO/WHO 2003). We calculated the IR of tuna meat that would be necessary to reach the intake limit for Hg. We considered the median Hg concentration as a fixed variable and applied the EDI formula to estimate the IR needed to reach the intake limits established by the FAO/WHO (2003).

ANOVAs (aov function, base package; R Core Team 2022) were used to test the differences in Hg concentrations among the species and sampling years. Estimations of Hg intake due to tuna consumption by humans were conducted by Monte Carlo Method (Khitalishvili 2016) to incorporate the variability of each variable (Hg concentration in fish, human intake rate and body weight) in the final results.

Total Hg concentration varied between sampling years for T. albacares, and between the two tuna species (higher Hg concentrations in T. obesus) (Table 1). T. albacares sampled in 2020 was larger and heavier than in 2019, and the size difference was consistent with the Hg concentrations, reflecting Hg bioaccumulation during the fish growth (Lacerda et al. 2017). The enrichment of more bioavailable organic Hg complexes in deep waters, such as methylmercury, and the tuna foraging depths explain the interspecific differences in Hg concentrations (Choy et al. 2009; Ferriss & Essington 2011; Lacerda et al. 2017).

The Hg concentrations were below the maximum tolerable limits established by ANVISA (2021) and FAO/WHO (1991) for fishery products, except for five T. obesus whose concentrations were higher than the limit (1,000 ng g−1) (Figure 1A). The estimates for Hg intake due to tuna consumption were below the tolerable intake limit established by the FAO/WHO (Figure 1B). This result was expected since the Brazilian per capita intake of fishery products is half of the world intake (9.75 kg·year-1 x 20.5 kg·year-1) (Barone et al. 2017; FAO 2020).

Currently, Brazil exports whole large tuna to Indonesia, Vietnam and the United States ( Considering that whole large tuna are exported to other countries, it is important to conduct case-by-case health risk assessments. In this sense, tuna consumption from the western equatorial Atlantic Ocean would pose a risk for human populations that ingest more than 80 g·day-1 tuna meat (IR based on our most contaminated fish: T. obesus individuals caught in 2019). Both tuna species are safe for intake as seafood, at least in the present, but we recommend regular monitoring of both consumption rates and Hg levels, since the encouragement of seafood consumption has increased worldwide, as well the anthropic pollution that reaches the ocean basins.



Table 1. Sample size, fork length, weight and Hg concentration (wet and dry basis) in the muscle of Thunnus albacares and Thunnus obesus from the western equatorial Atlantic Ocean. The values are shown as the median ± interquartile range (minimum and maximum). Lowercase letters compare the variables between sampling years for the same species. Uppercase letters compare the variables between species and consider the data from both samplings.


T. albacares

T. obesus


2019 (n = 32)

2020 (n = 18)

2019 (n = 26)

2020(n = 6)

Fork length (cm)

123.5 ± 22.3a  (97–167)

139.5 ± 9.3b (129–176)

104 ± 38a (91–181)

104.5 ± 5.3a (101–111)

Weight (kg)

25.5 ± 19.6a (12.6–65.2)

39.5 ± 9.5b (29.3–76.1)

18.2 ± 20.7a (11.9–72.3)

18.5 ± 1.5a (16.9–20.4)


(ng·g-1 wet weight)

168.3 ± 80.2a (82.1–455.1)

309.5 ± 98.8b (103.2–570.3)

499 ± 195.9a (204.1–1347.5)

457.7 ± 51.9a (387.7–475.1)


(ng·g-1 dry weight)

636.6 ± 303.4a (310.6–1722)

1170.9 ± 373.9b (390.5–2157.6)

1840.5 ± 722.5a (752.8–4970.4)

1688.5 ± 191.4a (1430–1752.5)

Log [Hg

(ng·g-1 wet weight)]·kg-1

6.7 ± 2.5a (3.4–11.9)

7.2 ± 2.7b (3.5–19.1)

26.7 ± 8.4a (4.9–49.7)

23.4 ± 2.8a (20.2–28.1)

All samples

T. albacares

T. obesus

Fork length (cm)

132.5 ± 23.5A

104 ± 20B

Weight (kg)

32.4 ± 20A

18.2 ± 9.1B

Hg (ng·g-1 wet weight)

212 ± 149.6B

475.1 ± 107.8A

Hg (ng·g-1 dry weight)

802 ± 565.9B

1752.5 ± 397.7A



For figure - - click here for full PDF





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