Mercury and selenium in oysters Saccostrea palmula and Crassostrea corteziensis from coastal lagoons of the southeastern Gulf of California: molar ratio and risk assessment on human health

Total mercury (Hg) and selenium (Se) contents were determined in oysters Saccostrea palmula and Crassostrea corteziensis soft tissues from four coastal lagoons of the southeastern Gulf of California. The annual Hg mean concentrations for S. palmula (0.09 ± 0.04 µg g- 1, wet weight) and C. corteziensis (0.08 ± 0.04 µg g- 1) were similar (p ˃ 0.05) among the lagoons and did not exceed the limit established by the Norma Oficial Mexicana and World Health Organization (< 1.0 µg g- 1 Hg). On the other hand, the annual mean concentrations of Se for S. palmula (3.34 ± 0.96 µg g- 1) and C. corteziensis (2.79 ± 0.89 µg g- 1) were higher (p < 0.05) in El Colorado lagoon. The Se/Hg molar ratios were above 1; the positive selenium health benefit value index suggested that Se load in oysters could reduce the Hg potential toxic effect. The hazard quotient for Hg in both species was below 1. Therefore, the consumption of oysters does not represent a risk due to Hg ingestion.

Assessing Human Health Risks Associated with Consumption of Metal Content in Shrimp from NW Mexico

Shrimp of Farfantepenaeus californiensis (78 groups) and Litopenaeus stylirostris (14 groups) were caught in the northwestern fishing zones in Mexico during the 2014-2015 fishing season (September-February); both shrimp species have high commercial value. Muscle, hepatopancreas and exoskeleton were analyzed to determine their metal contents. For F. californiensis, the highest Cd, Pb and Zn contents were determined in specimens caught off the State of Baja California Sur (BCS) with 22.4 ± 8.9 (hepatopancreas), 2.83 ± 4.63 (muscle), and 748.5 ± 1567 (muscle) µg/g, in the regions off Mulegé, Los Cabos and Los Cabos, respectively. For L. stylirostris, the fishing zone of Comundú (BCS) showed higher Cd (12.3 ± 11.5 µg/g), Cu (569.1 ± 646.5 µg/g) and Zn (549.7 ± 400.7 µg/g) contents; all values were determined in the hepatopancreas. Regarding the hazard quotient and total hazard quotient calculated in this study, the consumption of marine shrimp caught off NW Mexico does not represent a risk to human health (both < 1).

Total mercury in muscles and liver of Mugil spp. from three coastal lagoons of NW Mexico: concentrations and risk assessment

Total mercury (Hg) concentrations were determined by atomic absorption spectrophotometry in muscles and liver of composite samples of Mugil cephalus and M. curema collected during November 2013 and in January, April, and July 2014 from the coastal lagoons Altata-Ensenada del Pabellón (AEP), Ceuta (CEU), and Teacapán-Agua Brava (TAG) of Sinaloa State. The mean Hg contents and information on local consumption were used to assess the possible risk caused by fish ingestion. Mean total mercury levels in the muscles ranged from 0.11 to 0.39 μg/g, while the range for liver was 0.12-3.91 μg/g. The mean Hg content of the liver was significantly (p < 0.001) higher than that of the muscles only in samples collected from AEP. Although total Hg levels in the muscles were lower than the official permissible limit, the HQ values for methyl mercury calculated for the younger age classes of one fishing community were >1, indicating a possible risk for some fishing communities of the Mexican Pacific coast.

Mercury and selenium concentrations in marine shrimps of NW Mexico: health risk assessment

We determined total Hg and Se contents of hepatopancreas, exoskeleton, and muscle, and the Se:Hg molar ratios in the muscle of shrimps Farfantepenaeus californiensis and Litopenaeus stylirostris caught in NE Pacific Mexican waters. Total Hg mean values in muscle, hepatopancreas, and exoskeleton were 0.31 ± 0.26, 0.28 ± 0.29, and 0.24 ± 0.06 μg g^-1, and 0.46 ± 0.46, 0.41 ± .034, and 0.24 ± 0.06 μg g^-1 for F. californiensis and L. stylirostris, respectively. In all tissues, the mean concentrations of Se tended to be close to one order of magnitude higher than the respective Hg values. In F. californiensis, the hepatopancreas of the larger commercial size had significantly (p < 0.05) higher Hg content than smaller sizes, but correlations size-Hg concentration calculated for each tissue of either species were not significant. The Hg content of the muscle of all commercial sizes of both species was lower than the permissible limit and their Se:Hg ratios in all sizes were higher than 1, indicating low risk for human consumption.

Bioavailability of cadmium, copper, mercury, lead, and zinc in subtropical coastal lagoons from the southeast Gulf of California using mangrove oysters (Crassostrea corteziensis and Crassostrea palmula)

Cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn) were assessed in the edible tissues of Crassrotrea corteziensis oysters collected during the rainy and dry seasons in 27 sites from 8 coastal lagoons of the southeast Gulf of California. In addition, C. palmula oysters were sampled at 9 sites from the same mangrove roots where C. corteziensis oysters were collected. Metal analyses were performed by flame atomic absorption spectrophotometry (Cd, Cu, and Zn), graphite furnace (Pb), and cold vapor detection (Hg). The obtained mean levels were (µg g(-1) dry weight) as follows: Cd 6.05 ± 2.77, Cu 60.0 ± 33.4, Hg 0.38 ± 0.17, Pb 1.11 ± 0.63, and Zn 777 ± 528 µg g(-1). For all metals except Hg, the concentrations were greater during dry season than during rainy seasons. The high levels, particularly that for Cd, were related to upwelling along the eastern Gulf of California. High Hg levels in the rainy season were associated with the transport of materials from the watershed to the lagoon. Shrimp farming, agriculture, and other sources were considered as potential sources to explain the differences in metal bioavailability in the 8 lagoons. The mean concentrations of Cd (Santa María-La Reforma lagoon), Cu [San Ignacio-Navachiste-El Macapule (SINM), Urías (URI), and Altata-Ensenada del Pabellón lagoons], and zinc (Zn) (URI, Santa María-Ohuira-Topolobampo, El Colorado, and SINM lagoons) during the dry season were greater than the maximum permissible limits. C. palmula collected in 8 sites where they were present simultaneously with C. corteziensis had consistently greater metal levels than C. corteziensis, but correlation analyses showed a high and significant (P < 0.05) correlation between metal concentrations in both species. The correlation equations obtained are useful where the same species is not distributed and is necessary to compare results from distinct regions.

Cadmium, copper, lead and zinc in cultured oysters under two contrasting climatic conditions in coastal lagoons from SE Gulf of California, Mexico

In order to determine the metal concentrations in cultured oysters from four coastal lagoons from SE Gulf of California, several individuals of Crassostrea gigas and C. corteziensis were collected and their cadmium, copper, lead and zinc levels were measured by atomic absorption spectrometry after acid digestion. The concentration of metals in oyster soft tissue was Zn > Cu > Cd > Pb. In two lagoons, Cd concentrations (10.1-13.5 μg g(-1) dw) exceeded the maximum level allowed according to the Official Mexican Standard (NOM-031-SSA1-1993), which is equivalent to the WHO recommended Cd levels in organisms used for human consumption.

Mercury in cultured oysters (Crassostrea gigas Thunberg, 1793 and C. corteziensis Hertlein, 1951) from four coastal lagoons of the SE Gulf of California, Mexico

In order to determine the mercury concentrations in cultured oysters from coastal lagoons (SE Gulf of California), several individuals of Crassostrea gigas and C. corteziensis were collected and their mercury levels were measured with a cold vapor analyzer. The mean concentrations during the rainy and dry seasons, respectively, were 0.70 and 0.15 microg g(-1) in C. gigas and 0.56 and 0.18 microg g(-1) in C. corteziensis. During the rainy season, elevated mercury contents are apparently related to terrigen transport from the watershed, while during the dry season, the moderate levels are related to upwellings.