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.

Changes in metal contents in shrimp cultured in NW Mexico (2000-2010).

This study shows the concentrations of Cd, Cu, Pb, and Zn in the muscle and hepatopancreas of Pacific white shrimps, Litopenaeus vannamei, cultured during 2010 in 26 commercial farms of the three main producer states of the Mexican NW, Sonora, Sinaloa, and Nayarit and compares the results to those obtained in 2000 using samples collected in16 farms of the same states. No significant changes were detected in Cd concentrations, but the 2010 Zn levels were significantly higher in all states in the hepatopancreas and in Sinaloa in the case of the muscle. Cu showed a tendency to higher hepatopancreas values in 2010, but differences were significant only in Sonora and for the global mean value. In contrast, Pb was one order of magnitude lower in both organs in 2010, possibly because of the almost 15 years since leaded gasoline was discontinued in Mexico.

Metal contents of four commercial fish species of NW Mexico.

The metal contents in tissues of fish species: M. cephalus, Diapterus sp., Scomberomorus sierra and Oreochromis aureus, were determined in order to evaluate if their consumption might become a health risk. The liver and gills of M. cephalus and Diapterus sp. had the highest values of Cu, Fe and Pb. In the muscle, there were no interspecific differences in the Cd, Cu and Pb contents (0.27-0.32, 0.96-1.30 and 2.12-2.80 microg/g dw, respectively). Cd and Pb may be of concern, since their mean contents in the edible muscle of the four species are higher than the limits of the European Community.

Toxicity of metal mixtures to the Pacific white shrimp Litopenaeus vannamei postlarvae.

According to the literature, the safe level of a toxic substance for any given organism may be calculated from its median lethal concentration multiplied by a suitable application factor (AF: usually 0.1 and 0.01). The medial lethal concentrations for Litopenaeus vannamei postlarvae exposed to the mixtures in equitoxic proportions of Cd-Hg, Hg-Zn and Hg-Pb were close to one order of magnitude lower than the values calculated from individual toxicity tests, indicating a synergistic effect, while the mixture Cd-Zn showed an antagonistic effect. Exposure to the mixture of Cu, Fe, Mn, Zn, Cd, Hg and Pb caused 63.3% and 100% mortality after 21 and 13 days for 0.05 and 0.1 AF, showing that environmental safe concentrations of toxicants should not be calculated from individual toxicity tests.

Cadmium, copper, lead and zinc contents of the mangrove oyster, Crassostrea corteziensis, of seven coastal lagoons of NW Mexico.

The ranges of concentrations of Cd, Cu, Pb and Zn of the soft tissues of C. corteziensis collected in seven coastal lagoons of NW Mexico were 1.55-7.45, 17.50-166.36, 4.13-9.49 and 245.34-2,304.12 microg/g (dry weight), respectively. Their distributions were not consistent and there were no seasonal trends, indicating different point sources of the metals in each lagoon. The mean Cd and Pb concentrations were 5.34 and 6.30 microg/g (dry weight), which are higher than the values indicative of polluted areas. Our data indicate that only the levels of Cd are a possible health risk in six of these lagoons, and only in the case of regular local consumers. In one, Cu and Zn reach levels of concern.

Metal content of the gulf of California blue shrimp Litopenaeus stylirostris (Stimpson).

The blue shrimp Litopenaeus stylirostris is the main target species of the Gulf of California shrimping fleet, and its heavy metal content might be of concern for human health because of the increasing contamination of the Gulf. The Cd content of shrimp caught by commercial trawlers ranged from 0.38 to 1.05 microg/g and the mean value was significantly lower in the northern fishing grounds. Pb ranged from 3.19 to 9.59 microg/g and was significantly higher in the northern area. There were no significant geographic difference in the case of Cu and Zn (respective means = 25.4 and 57.8 microg/g). The mean values of all metals show that none is of particular concern for human health.

Trace metal concentrations and their distribution in the lobster Panulirus inflatus (Bouvier, 1895) from the Mexican Pacific coast.

The concentration and distribution of Fe, Mn, Ni, Cu, Co, Cd, Cr and Zn among the tissues of female and male lobster Panulirus inflatus from the Pacific coast of México were determined. Distinct inter-tissue and intersize differences in metal concentrations were observed. In general, highest Zn concentrations were found in viscera while highest Cu levels occurred in the gill and gonadal material. The highest Mn, Ni, Cr and Co concentrations were observed in exoskeleton and highest in eggs and gills. Cadmium was undetectable (<0.05 microg g(-1)) in most tissues, only muscle and viscera contained low but detectable amounts. A positive relationship between size and metal concentration was observed only for Zn contained in the muscle of females and males, for Zn contained in the gonad of females, for Mn contained in the gonad of males and for Cu associated with muscle of males. These results are discussed with regard to trace metal concentrations found in temperate and tropical regions.