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This study examines the water quality in the Yaqui Valley in Mexico, a semi-arid region impacted by mining, agriculture, and aquaculture. Contamination sources, health risks and ecological impacts are investigated. Freshwater was found to be contaminated by dissolved As, presumed to result from mining activities in the mountains. Drainage water revealed an overall contamination by dissolved As and by suspended particles enriched with Al, Fe and Mn, associated with runoff processes. Intermittent contamination of drainage water by Cu, K + , NO 3 - and PO 4 3- is attributed to the use of fertilizers or pesticides. In the coastal area, drainage water contains high concentrations of Na, Ca, SO 4 2- and Cl, related to salinization processes, as well as higher concentrations of dissolved As, related to solid/liquid interactions that are enhanced by salinization. This drainage water discharges into the bay, degrading the seawater quality and increasing ecological risks. Outputs of this study can serve as a reference for the protection of this economically important coastal ecosystem. Concerning health risks, this study demonstrates that groundwater is also contaminated by dissolved As, believed to be associated with transfers from the geological basement to the dissolved phase of water, and other major chemicals related to salinization processes. The findings indicate that ingesting the groundwater poses a significant risk to human health with a primary exposure risk associated with dissolved As, particularly among children. This study presents crucial data for the Yaqui population, water managers and researchers, and provides novel insights into the management and mitigation of the identified risks., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Barats reports financial support was provided by National Research Agency (ANR). Gonzalez-Perez reports financial support was provided by Consejo Nacional de Ciencia y Tecnología (CONACYT). If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

This study focuses on the "El Lavadero" tailings deposit, a mining environmental liability (MEL) located near the town of San Felipe de Jesús, Sonora, in northwest Mexico. The objective was to determine the total arsenic (As) content, its granulometric and geochemical distribution, as well as its mobilization capacity and bioavailability. The results from oxidized and unoxidized tailings showed low potential of hydrogen (pH) values (2.4-5.7) and high concentrations of total arsenic (8235-36,004 mg kg -1 ), predominantly in the finer granulometric fractions (< 0.05 mm). Arsenic also prevails in the finest fraction of agricultural soil (> 2 mm). These fine particles could present adverse environmental effects due to their potential to be transported by leaching and water suspension. In contrast, arsenic in the effluent sediments is primarily found in the coarser fraction (> 2 mm). A significant proportion of arsenic in the tailings (5-40%) was found in the non-residual geochemical fractions (I + II + III) (1106-7675 mg kg -1 ), indicating potential for mobilization and bioavailability. Depending on environmental conditions (redox potential and pH), arsenic can redissolve and exhibit high mobility in abiotic media, which may ultimately impact the environment and human health. Therefore, it is crucial to rehabilitate the "El Lavadero" MEL to prevent further environmental damage. This study provides useful information to understand some phenomena in other global mining environmental liabilities, such as mobilization and bioavailability of arsenic and its possible impact on the surrounding environment and biota, contributing to the worldwide research of ecosystems polluted by mining activity, especially in arid and semi-arid climates., Competing Interests: Declarations. Competing Interests: The authors have no relevant financial or non-financial interests to declare., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Aquatic ecosystems have been suffering deleterious effects due to the development of different economic activities. Metal(loid)s are one of the most persistent chemicals in environmental reservoirs, and may produce adverse effects on different organisms. Since fishes have been largely used in studies of metal(loid)s exposure, tilapia and largemouth bass were collected in three ecosystems from the Yaqui River Basin to measure the concentrations of metal(loid)s (chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), zinc (Zn) arsenic (As), mercury (Hg), and selenium (Se)) and some biomarkers (somatic indices, metallothionein expression and histopathological analysis) in tissues of both species. Metal(loid) concentrations varied seasonally among ecosystems in tissues of both species. The elements varied seasonally and spatially in tissues of both species, with a general distribution of liver > gills > gonads. Also, biomarkers showed variations indicative that the fish species were exposed to different environmental stressor conditions. The highest values of some biomarkers were in largemouth bass, possibly due to differences in their biological characteristics, mainly feeding habits. The multivariate analysis showed positive associations between metal(loid)s and biomarkers, which are usually associated to the use of these elements in metabolic and/or regulatory physiological processes. Both fish species presented histological damage at different levels, from SI types (changes that are reversible for organ structure) to SII types (changes that are more severe but may be repairable). Taken together, the results from this study suggest that the Yaqui River Basin is moderately impacted by metals and metalloids., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

In the present paper, we investigated the accumulation of six metals in tilapia (Oreochromis nilocticus) and largemouth bass (Micropterus salmoides) as indicators of the environmental pollution present at three constructed dams in the Yaqui River basin in Sonora, Mexico. The La Angostura (ANG), El Cajon de Onapa (ECO), and El Oviachic (OVI) dams are ecosystems under different degrees of anthropogenic stress. The collected fishes were dissected to obtain liver, gonad, stomach, gill, and muscle samples to determine the metal concentrations of Fe, Mn, Ni, Cu, Zn, and Cr. The results of a PERMANOVA showed that the concentrations of Fe, Cu, and Zn were significantly higher in tilapia liver, stomach, and gill tissues compared with those of the largemouth bass. Also, differences were detected between seasons, with the metal concentrations during the dry season being significantly higher than those of the rainy season (p < 0.001). The results of a principal component analysis showed an association between metals, tissues, and dams with significantly higher (p < 0.001) concentrations in tilapia from the ECO dam compared with those from the ANG and OVI dams. The general distribution of metals in the tissues was as follows: liver > stomach-gills > gonads > muscle. Variations in metal concentrations may be indicative of the different sources of anthropogenic stress in each ecosystem.

Marine ecosystems are subject to contamination by metals and metalloids and other elements and compounds that are emitted due to various human activities. These substances subsequently induce changes in marine biota after entering the marine environment. Marine organisms are frequently consumed worldwide because they constitute relatively cheap and accessible food items of high nutrient quality. The aim of this study was to estimate metal accumulation in frequently consumed marine species and to evaluate the associated health risks for particular population groups in a coastal region of northwestern Mexico. The marine species were consumed in different quantities between spring (from 0.29 kg year -1 for white clam, to 38.40 kg year -1 for blue crab) and autumn (from 0.34 kg year -1 for white clam, to 15.02 kg year -1 for leopard grouper). The general distribution of metal concentrations in the marine species (n = 13 in each season) evaluated in this study followed the trend of Fe > Zn > Cu > Mn > Cr with the highest metal concentrations detected during autumn. Although many metal concentrations were above the international standards of the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO), the hazard quotient (HQ) and hazard index (HI) values for the women in this study indicated that their health was not at risk due to the consumption of either fish or seafood. In contrast, the HQ and HI values determined for groups of men and children indicated that they are at risk due to the frequent consumption of most species evaluated in this study., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Water reservoirs are essential for regional economic development, as populations depend on them for agriculture irrigation, flood control, hydroelectric power generation, water supply for human consumption, and subsistence fishing activities. However, the reservoir environmental quality can be disturbed by enhanced sediment input and trace metal contamination, affecting human health as a consequence of contaminated water and fish consumption. With the purpose to understand the trends and extent of sediment accumulation and trace element contamination in the Oviachic reservoir (OV, northwestern Mexico) since its construction, the temporal variations of sediment accumulation, and As, Cr, Cu, Hg, Ni, Pb, and Zn concentrations, enrichment, and fluxes, were evaluated through the study of two 210 Pb-dated sediment cores. We assumed that siltation and trace element contamination were driven by the development of anthropogenic activities in the region within the past ~ 70 years. Elemental concentrations accounted from null to minor enrichment for most elements, but moderate to significant enrichment by Hg. Mercury, As, and Cu fluxes have notably increased since the past decade, most likely because of a combination of anthropogenic and natural processes, including catchment erosion, artisanal gold mining, and recent drought conditions in the region. Arsenic and Hg concentrations may pose deleterious risks to biota in the reservoir, and consequently to humans through fish consumption, for which further biological and toxicological tests are advisable. This study highlights the importance of using sediment dating to assess historical trends of metal contamination and identify possible sources, to support decision-making in programs addressed to reduce environmental and health risks in aquatic ecosystems.

Mercury and selenium were assessed in Mustelus henlei, which is a carnivorous predatory shark that is important for the coastal communities of the northern Mexican Pacific (NMP). Sixty-two individuals were sampled; muscle and liver were isolated and analyzed by atomic absorption spectrophotometry. The mean Hg concentrations (wet weight) obtained for muscle (0.08 ± 0.10 μg g -1 ) and liver (0.09 ± 0.26 μg g -1 ) were below the allowed limits (< 1.0 μg g -1 Hg). The average Se concentration was 0.03 ± 0.01 μg g -1 in muscle and 0.13 ± 0.05 μg g -1 in liver. The Se/Hg molar ratio of muscle was 1.83; however, the selenium health benefit value (HBV Se ) was of 0.08. We calculated that an adult man (70 kg), an adult woman (60 kg), and a child (16 kg) could consume 1595, 838, and 223 g/week of M. henlei muscle, respectively, without risks to health. In conclusion, the concentrations and molar ratio of Hg and Se in M. henlei muscle mean that consumption of this shark's meat does not represent neither a benefit nor a public health risk.

In this study, we elucidated the impacts of allochthonous organic matter (OM) and nutrients (N and P) inputs coming from agriculture and shrimp aquaculture activities on food web structure in a subtropical coastal lagoon located on the central-east of the Gulf of California. This coastal lagoon is highly influenced by OM and nutrients inputs by a large agriculture district and aquaculture development center in Mexico. We also selected a second coastal lagoon, without direct OM and nutrients inputs, considered as a 'pristine' ecosystem. We evaluated the quantity of OM, N and P in both ecosystems and reconstructed the food webs using isotopic tools of C and N from the base to top. We collected and analyzed autochthonous and allochthonous OM, and organisms including primary producers, and primary to tertiary consumers. Overall, specimens of the same species and/or functional groups showed higher δ 15 N values in the ecosystem receiving agriculture and shrimp aquaculture effluents than the pristine. Food webs were composed of four and five trophic levels, where fish and birds occupied the top-predator levels. Seasonal increases in OM and N and P quantities in lagoons affected by anthropogenic activities produced high δ 15 N values in primary producers and consumers., (Published by Elsevier B.V.)

The Tobari Lagoon, located in the central-east coast of the Gulf of California, receives effluents from the Yaqui Valley, one of the most extensive agricultural areas of México. The Tobari Lagoon also receives effluents from nearby shrimp farms and untreated municipal sewage. Surface sediment samples and six different species of filter feeders (Crassostrea corteziensis, Crassostrea gigas, Chione gnidia, Anadara tuberculosa, Chione fluctifraga, and Fistulobalanus dentivarians) were collected during the dry and the rainy seasons and analyzed to determine concentrations of cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn). Seasonal variations in metal concentrations in sediment were evident, especially for Cd, Cu, Hg, and Zn. The total and bioavailable concentrations of the five metals are not elevated in comparison to other areas around the world. The percentages of bioavailable respect to total concentrations of the metals varied from 0.6 % in Hg to 50.2 % for Cu. In the organisms, Hg showed the lowest concentrations (ranged from 0.22 to 0.65 μg/g) while Zn showed the highest (ranged from 36.6 to 1,702 μg/g). Linear correlations between the levels of Cu, Pb, and Zn in the soft tissues of C. fluctifraga and C. gnidia, and A. tuberculosa and C. gnidia were found. Seasonal and interspecies variations in the metal levels in filter feeders were found; F. dentivarians, C. corteziensis, and C. gigas exhibited the highest levels, could be used as biomonitors of metals contamination in this area.

The purpose of this research is to provide a comprehensive assessment of the concentration levels and spatial variability of cadmium (Cd), copper (Cu), mercury (Hg), lead (Pb) and zinc (Zn) in El Tobari Lagoon in surface sediments during two seasons for several geochemical variables that could explain the observed heavy metal variability. Seventy-two surface sediments samples were collected in 12 different sites of the El Tobari Lagoon. Sediment samples were dried and subjected to acid extraction using a microwave system and five metals (Cd, Cu, Hg, Pb and Zn) were measured using atomic adsorption spectrometry. A certificate sediment material and blanks were used as quality control purposes. The enrichment factor (EF) and the index of geoaccumulation (Igeo) were calculated as index of metals contamination for the sediments, using aluminum as the conservative element. The five metals examined in sediments from El Tobari Lagoon exhibited a linear correlation with Al as result of the large specific surface areas of these sediment components and the chemical affinities between them. The metals contents in sites of the El Tobari Lagoon were variable, and Cd, Cu and Hg presented a seasonal behavior. The enrichment factor and index of geoaccumulation analysis indicated that Cd and Hg exhibited a certain extent (EF for Cd ranged from 4.10 to 10.29; EF for Hg ranged from 2.77 to 12.89) of anthropogenic pollution, while Cu showed sporadic (EF ranged from 0.43 to 2.54) anthropogenic contamination. The highest concentrations of Cd, Cu and Hg were found in the sites that regularly received discharge effluents from agriculture and aquaculture.

This study investigates the presence of Cu, Zn, Cd, Pb, and Hg in 24 dietary supplements purchased in different health stores across the city of Hermosillo, located in the northwest of Mexico. Analysis of metals was done by microwave digestion and atomic absorption spectroscopy. The most abundant elements in dietary supplements were Cu (<0.19-137.85 microg/g) and Zn (<2.83-4785.71 microg/g), followed by Pb (<0.003-66.32 microg/g), Cd (<0.001-2.90 microg/g), and Hg (<0.24-0.85 microg/g). The estimated daily intakes of metals were below those recommended by WHO and the Institute of Medicine, showing that little risk from heavy metals is associated with the consumption of the dietary supplements analyzed. However, some products presented more than 10% of the tolerable daily intake of Pb, indicating that production processes should be improved.

In early April 2003, fishermen from Kino Bay Sonora alerted us about a massive die-off of fish and mollusks occurring at Kun Kaak Bay. Phytoplankton samples taken on 17 May 2003 reported the presence of a harmful algal bloom composed of Chatonella marina, Chatonella cf. ovata, Gymnodinium catenatum and Gymnodinium sanguineum. On 22 of May, we collected samples of water, sediment and organisms at the affected area. Physicochemical parameters and nutrients were measured in water samples from different depths. Sediment and benthic organisms were analyzed for Cd, Cu, Zn, Pb and Hg. We found concentrations of heavy metals higher than background levels for this area. Cadmium and Lead concentrations in sediment from the HAB area were up to 6x greater than background levels and Cd in mollusks was 8x greater than regulations allow. A relationship between elevated Cd and Pb concentrations in sediment and the survival of toxic dinoflagellates is suspected.

Although various studies have reported the bioaccumulation of metals in bivalves of commercial interest from the Gulf of California (GC), the risk associated with their consumption remains poorly understood. In this study, our own and bibliographic concentrations of 14 elements in 16 species of bivalves from 23 locations were used to investigate (1) the species-specific and regional accumulation of metals and arsenic in bivalves, (2) the human health risks by age and sex, and (3) the maximum allowable consumption rates (CRlim). The assessments were done according to the US Environmental Protection Agency guidelines. The results indicate that the bioaccumulation of elements varies markedly between groups (oysters > mussels > clams) and localities (higher on Sinaloa due to intense anthropogenic activities). However, consuming bivalves from the GC remains safe for human health. To prevent health effects for residents or consumers on the GC, we recommend (1) following the CRlim proposed herein; (2) monitoring levels of Cd, Pb, and As (inorganic) in bivalves, as the elements of top concern, mainly when are consumed by children; (3) calculating CRlim for more species and locations, including at least: As, Al, Cd, Cu, Fe, Mn, Pb, and Zn; and (4) determine the regional consumption rates of bivalves., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Trace metals have been found in sea turtle blood and tissues and may represent a threat to these endangered species. Essential trace metal (Cu, Zn Cd, Pb, As, and Hg) concentrations were determined in blood of adult female, post-nesting olive ridley turtles Lepidochelys olivacea (n = 35) on Ceuta beach, Sinaloa, Mexico. Essential metals (Zn and Cu) analyzed were found in higher concentrations than toxic metals (Cd and Pb), while As and Hg concentrations were below the limits of detection (0.01 μg g -1 ). Low Pb concentrations (0.09 μg g -1 ) were previously observed in sea turtles in the Gulf of California. There were no significant correlations found between curved carapace length (61.00-71.00 ± 2.29) vs metal concentrations (p > 0.05). Cd levels were relatively high when compared to other species and populations of sea turtles worldwide and Cd may represent the greatest risk for sea turtles in the Mexican Pacific. Such concentrations of Cd may pose a further risk to sea turtles through bioaccumulation from the nesting female to offspring which may affect embryo development.

In this study, the concentration of six metal(loid)s was examined in the fish Oreochromis aureus collected from El Comedero dam during a massive mortality event induced by a mine tailing spill. A major spill (~ 300,000 m3) of waste was released into the San Lorenzo River System following a rupture in the tailing dam of a mining plant in NW Mexico; consequently, the discharged material flowed into El Comedero dam. The accumulation of metal(oid)s in the tissues of O. aureus showed higher levels in the liver than in the guts and muscle. Concentrations in the liver were high (As, 1.1–1063; Cd, 8.9–392; Cu, 372–59,129; Hg, 0.46–19.79; Se, 8.7–748; and Zn, 116–820 μg g−1), revealing that these fish were exposed to high concentrations of these elements. The mortality of fish could have resulted from the combined effect of the six analyzed metal(loid)s, as well as other residues present in mine tailings. [ABSTRACT FROM AUTHOR]

Human consumption of the thornback guitarfish (Platyrhinoidis triseriata) is concentrated in coastal populations of the Pacific coast of Mexico as its meat is prized for its high quality. This study analyzes the distribution of mercury and selenium in the muscle and liver of Platyrhinoidis triseriata and the risk to human health associated with its consumption. In order to conduct these estimates, specimens were collected from the Eastern Pacific Ocean in 2015 and 2016 and found mean concentrations (µg g−1 wet weight) of mercury ranging from 0.02 to 0.58 in muscle and 0.10 to 0.31 in liver. Selenium ranged from 0.14 to 1.31 in muscle and from 0.93 to 4.52 in liver. Mercury levels in the muscle of P. triseriata were significantly correlated (positive correlation) with the total length of the specimens. The predominant prey of P. triseriata was the shrimp Pleuroncodes planipes and according to the biomagnification factor, only mercury was biomagnified. The risk to consumers associated with the simultaneous presence of mercury and selenium in the muscle and liver of rays under the selenium health benefit value approach indicated that consumption of P. triseriata from this area is beneficial to human health. [ABSTRACT FROM AUTHOR]

To balance the risks and benefits of fish consumption, selenium, fatty acids (DHA + EPA), and mercury in fishery products were determined. Analyzed products were canned tuna, frozen tuna (Thunnus albacares), smoked striped marlin (Tetrapturus audax), fresh Pacific sierra (Scomberomorus sierra), fresh dolphinfish (Coryphaena hippurus), fresh tilapia (Gerres cinereus), and fresh bullseye puffer (Sphoeroides annulatus). Mercury (μg g−1 wet weight) ranged from 0.01 (dolphinfish) to 0.23 (bullseye puffer); Se ranged from 0.12 to 0.25. EPA + DHA ranged from 1.16 to 10.72 mg g−1. Intake of EPA + DHA was comparable or above the recommended daily intake; Hg intake was below the reference dose but Se intake was below than recommended values for the different population groups. Considering the HBVSe, fishery products had positive values; i.e., they are healthy food items. According to the interaction of Hg and Se and the rate of fishery product consumption, the risk for consumers is below one percent. [ABSTRACT FROM AUTHOR]

During January 2013, a mining spill occurred in the Santa Maria mining region, releasing around 300,000 m 3 of tailings on Los Remedios river, which was transported through the San Lorenzo river and finally to El Comedero (EC) dam. Twenty months later, we examined the concentrations of Hg and Se in the muscle, liver, gills, and guts of three fish species (Cyprinus carpio, Oreochromis aureus, Micropterus salmoides) captured in the EC dam to assess the performance of the cleaning operations. A high Se concentration in the liver of all species (carp, 1.2 ± 0.4; tilapia, 3.9 ± 2.1; bass, 3.5 ± 1.1 µg g -1 ww) was consistently observed, while this behavior was only found in the blue tilapia for Hg (0.15 ± 0.11 µg g -1 ww). Tilapia (benthic-detritivorous) exhibited the highest Se concentrations compared to the carp (omnivore) and the largemouth bass (piscivore). In contrast, the largemouth bass had the highest Hg levels in the muscle compared with the other fishes. Such differences could be related to the different metabolism and feeding habits among species. Compared to a tilapia study carried out three months after the mine spill during a mortality event, a decrease was evident in the liver for Se and Hg by 7.2 and 4.7 times, respectively. This reveals that cleaning operations were more efficient for Se and less for Hg, and that a prolonged period was required for the partial recovery of the element levels in fish from sites impacted by mining. Considering the Mexican consumption scenarios for each fish species, it could be concluded that there will be no non-cancer risk by exposure to Hg or Se., (© 2023. The Author(s).)

Trace element (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd, As, Hg) concentrations were assessed in marine organisms (n = 52) sampled from the Magdalena Bay lagoon complex in Baja California Sur, Mexico, a pristine marine environment. The overall trend of metal concentrations (dry weight) in the organisms was found to be Fe > Zn > Cd > Cu > Mn > Pb > As > Hg > Ni > Cr > Co. Bivalve mollusks (53.83 mg kg−1) contained twofold higher levels of metals than the finfishes (20.77 mg kg−1). Calculated BioConcentration Factor (BCF) values showed that dissolved Mn is readily bioavailable to the organisms, whereas Biota Sediment Accumulation Factor (BSAF) indicated high values for Zn, Cu and Cd. Cd and As levels were observed to be increasing with the trophic levels. Toxic elements, namely Pb, Cd and As in the studied fish species were found to be higher than the values recommended for human seafood consumption. The study provides a comprehensive baseline report on trace element bioaccumulation in several marine organisms that will aid in developing effective conservation strategies of the highly biodiverse lagoon complex. [ABSTRACT FROM AUTHOR]

Mean Cd trend in the muscle of omnivorous (O), planktivorous (P), benthopelagic-carnivorous (BPC), and benthic carnivorous (BC) fish of one lagoon of NW Mexico was BPC > BC > P > O (0.89, 0.59, 0.55 and 0.24 μg g). That of Pb was P > BC > O > BPC (1.07, 0.48, 0.17 and 0.04 μg g). In the liver Cd was P > BPC > O > BC (5.09, 2.40, 2.07 and 1.95 μg g). Pb was P > O > BPC > BC (0.63, 0.40, 0.13 and 0.07 μg g). There were no differences in Cd and Pb contents due to feeding habits, and the correlations between metals and troph level were not significant ( p > 0.05 in all cases). [ABSTRACT FROM AUTHOR]

Exposure to lead (Pb) and mercury (Hg) remains a world public health problem, particularly for young children in developing countries. In Mexico, the main sources of exposure to Pb and Hg are wastes from human activities that increase the natural sources of these metals. Pb and Hg are highly toxic during development and maturation periods of the central nervous system (CNS); these effects are associated with the risk for neurodegenerative diseases. Mexico has numerous exposure sources to Pb and Hg; nevertheless, information on exposure in children is limited, particularly for Hg. Therefore, we conducted a review of the studies performed in children exposed to Pb and Hg. Data presented support that an important proportion of Mexican children have Pb levels above values associated with dangerous effects. On the other hand, studies on Hg-exposure are scarce, so we need more studies to estimate the magnitude of the problem and to determine exposure levels in Mexican children. Available data support the urgent need for coordinated actions among researchers, and health and environmental government authorities to implement education and nutritional campaigns, as well as to decrease exposure and effects of Pb and Hg. In addition, there must be a priority for the implementation of educational campaigns directed to the general population, but with emphasis in parents, education staff and health care providers to decrease both the risk of exposure of children to Pb and Hg and the effects of the exposure to these metals. [ABSTRACT FROM AUTHOR]

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 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. [ABSTRACT FROM AUTHOR]

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 μg g in C. gigas and 0.56 and 0.18 μg g 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. [ABSTRACT FROM AUTHOR]

This study examines seasonal variations in the concentrations of Cd, Cu, Pb, and Hg in experimentally cultured Crassostrea corteziensis, an oyster species known to have high resistance to physical and chemical stressors. The highest levels of Cd (4.92 mg/kg), Cu (3.45 mg/kg), and Pb (0.67 mg/kg) were detected in oyster samples collected during the summer, while Hg concentrations were similar (0.03 to 0.04 mg/kg) throughout all seasons. Results indicate that except for Cd, Crassostrea corteziensis accumulates metals to levels below those recommended by the US. FDA and the Mexican government. For Cd, its concentration correlates more strongly with the temperature of the oyster’s environment rather than to the oyster growth cycle. [ABSTRACT FROM AUTHOR]

Background: Elevated concentrations of mercury have been documented in fish in Lake Chapala in central Mexico, an area that is home to a large subsistence fishing community. However, neither the extent of human mercury exposure nor its sources and routes have been elucidated. Methods: Total mercury concentrations were measured in samples of fish from Lake Chapala; in sections of sediment cores from the delta of Rio Lerma, the major tributary to the lake; and in a series of suspended-particle samples collected at sites from the mouth of the Lerma to mid-Lake. A cross-sectional survey of 92 women ranging in age from 18-45 years was conducted in three communities along the Lake to investigate the relationship between fish consumption and hair mercury concentrations among women of child-bearing age. Results: Highest concentrations of mercury in fish samples were found in carp (mean 0.87 ppm). Sediment data suggest a pattern of moderate ongoing contamination. Analyses of particles filtered from the water column showed highest concentrations of mercury near the mouth of the Lerma. In the human study, 27.2% of women had >1 ppm hair mercury. On multivariable analysis, carp consumption and consumption of fish purchased or captured from Lake Chapala were both associated with significantly higher mean hair mercury concentrations. Conclusions: Our preliminary data indicate that, despite a moderate level of contamination in recent sediments and suspended particulate matter, carp in Lake Chapala contain mercury concentrations of concern for local fish consumers. Consumption of carp appears to contribute significantly to body burden in this population. Further studies of the consequences of prenatal exposure for child neurodevelopment are being initiated. [ABSTRACT FROM AUTHOR]