Metal content in stranded pelagic vs deep-diving cetaceans in the Canary Islands

Trace elements concentration, tissue distribution, and associated health risks in wild and captive pantropical spotted dolphins (Stenella attenuata)

Trace element (TEs) concentrations are key indicators for evaluating the health status of cetaceans. However, there is currently no research on TEs levels and tissue distributions in captive dolphins. Investigating TEs in wild and captive dolphins could provide critical insights into the effects of diets and habitats on TEs accumulation and improve healthcare protocols for captive dolphins. This study investigated concentrations of six TEs (Hg, Cd, Cr, Se, Cu, and Zn) in seven tissues (skin, muscle, liver, spleen, lung, kidney, and intestine) of wild (n = 8) and captive (n = 6) Stenella attenuata. The findings indicated that most studied wild and captive individuals exhibited medium levels of Hg, Cd, and Cr globally, with low health risks. However, alarming concentrations, such as 306 μg/g Hg in captive individuals and 178 μg/g Cd in wild individuals, suggested localized contamination persists. Tissue distributions of TEs indicated that ingestion and inhalation were the predominant exposure routes for wild and captive dolphins. Additionally, positive correlations between Hg levels in skin and liver and Cd levels in skin and kidney indicated that skin could serve as a healthy indicator for captive dolphins. Consuming odontocete tissue, even from healthy individuals, poses potential health risks to humans.

First record of trace elements in cetaceans stranded along the Asturias Coastline, Northwest Spain: One great diversity area of marine mammals

The concentrations of cadmium (Cd), lead (Pb), arsenic (As), selenium (Se) and mercury (Hg) in the kidney, liver, brain and muscle of 20 individuals of cetaceans, stranded along the Asturias coastline between 2018 and 2020, have been studied. Species studied include fin whale (Balaenoptera physalus), striped dolphin (Stenella coeruleoalba), common dolphin (Delphinus delphis), bottlenose dolphin (Tursiops truncatus), harbour porpoise (Phocoena phocoena) and pygmy sperm whale. (Kogia breviceps). All trace elements analyzed were detected in all cetacean families. The most detected compound was Se in the kidney (90 %), closely followed by Hg in muscle (85 %), while the least detected metal was Pb in the kidney (5 %). The highest concentrations of Se (66.00 mg/kg), Hg (44.00 mg/kg) and As (2.00 mg/kg) were detected in the liver, followed by Cd (53.00 mg/kg) in the kidney and Pb (0.37 mg/kg) in the brain. The family that presented the highest concentrations of toxic metals was Delphinidae, compared to the family Balaenopteridae, which is explained by the feeding and behavioural habits of odontocetes. The concentrations found are lower than those detected in other areas of Spain and the Atlantic Ocean and lower than those considered responsible for toxic effects in cetaceans. In addition, low levels of metal contamination (IMP) were found in most samples, although in two individuals we cannot exclude effects at the renal level due to metal accumulation. The overall effect of biologically relevant variables on metal concentrations was assessed by generalised linear modelling (GLM) analysis, with tissue being the most influential variable on metal concentrations. In addition, the Hg:Se molar ratio was lower than 1 in most samples analyzed, so the detoxifying action of Se against Hg is confirmed. As it represents the first record of trace element analysis in cetaceans of this area, our study supplies useful data for the development of conservation strategies in the Cantabrian Sea, as well as provides valuable information for future research.

Tracing metals in Mediterranean and Atlantic Sardina pilchardus: Unveiling impacts on food safety

This study evaluates the concentration of metals and trace elements (Al, Cd, Cu, Fe, Li, Pb, Zn) in the muscle tissue of Sardina pilchardus from three northeast Atlantic localities (Lisbon, Canary Islands, Rabat) and two western Mediterranean sites (Málaga, Cartagena) to assess food safety and environmental impact. A total of 100 sardines were sampled between January and June 2019, with specimens collected, homogenized by size and weight, and analyzed for metal content using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). Results show significant geographical variation in metal concentrations, with Cartagena exhibiting the highest levels due to industrial and urban activities, while the Canary Islands had the lowest, likely influenced by geographical isolation and stringent environmental regulations. Intermediate levels were observed in Lisbon, Rabat, and Málaga, with Rabat ranking second highest. Importantly, none of the samples exceeded EU safety limits for lead (0.3 mg/kg) or cadmium (0.25 mg/kg), confirming their suitability for human consumption regarding metal content. These findings emphasize the role of local environmental and industrial factors in influencing metal bioaccumulation in marine ecosystems. Genetic and ecological dynamics, such as the Almería-Oran Front and the Canary Islands' isolation, likely contribute to these patterns. The study underscores the importance of continuous monitoring to safeguard food safety and marine ecosystem health. Despite Cartagena's elevated contamination levels, which pose a higher potential risk if sardine consumption is frequent, sardines from all locations remain within safety limits. Moving forward, research should prioritize long-term monitoring and explore genetic and ecological factors influencing bioaccumulation trends, contributing to sustainable management and effective pollution control measures. This highlights the interconnectedness of environmental health and human dietary safety, emphasizing the need for a proactive approach to monitoring marine contamination.

Long-term trends (2002-2016) reveal an increase of mercury levels along with the decline of several metal elements in striped dolphins (Stenella coeruleoalba) stranded in the North-West Mediterranean

The determination of 18 metals and metalloids was realized in 4 tissues of 62 Stenella coeruleoalba specimens stranded along the French Mediterranean coastline from 2010 to 2016. While most concentrations were comparable to mean worldwide levels, Hg levels were alarming (1190 μg g-1 dw, in average). The results were discussed together with previous measurements in the same area, from 2002 to 2009. The elements Ni and Pb (-81 % and -88 % in liver in 2010-16 compared to 2002-09), and Cd (-40 % in kidney in 2010-16 compared to 2002-09) as well as V (-79 % in liver in 2013-16 compared to 2010-12), showed promising decreasing trends, and the decrease of Zn and Cu levels below baseline values could indicate a global decreasing burden of metal contaminants. In contrary, Hg dramatically increased in dolphins since 2007 (+135 % in liver in 2010-16 compared to 2002-09), regardless of total length. On the other hand, Se levels increased only slightly since 2012, potentially not offering anymore an efficient protection against Hg, with mean Se-to-Hg molar ratios below unity in most tissues (0.26, 0.56, 1.81, and 0.57 in liver, kidney, lung and muscle, respectively).

Analysis of Toxic Element Levels and Health Risks in Different Soybean Species (Glycine max, Vigna radiata, Vigna angularis, Vigna mungo)

Background: Soybeans are a widely consumed legume, essential in Western diets and especially prominent in vegan and vegetarian nutrition. However, environmental contamination from anthropogenic sources, such as industrial emissions, wastewater, and pesticide use, has led to the accumulation of non-essential and toxic elements in legumes, potentially impacting human health. Method: This study quantified the levels of 11 potential toxic elements (Al, B, Ba, Cd, Co, Cr, Li, Ni, Pb, Sr, V) in 90 samples of four soybean species (Glycine max, Vigna radiata, Vigna angularis, Vigna mungo) using inductively coupled plasma optical emission spectrometry (ICP-OES). Results: Results showed that boron had the highest mean content (9.52 mg/kg ww), followed by aluminum (6.73 mg/kg ww). Among the toxic metals, cadmium was most concentrated in green soybeans (0.03 mg/kg ww), and black soybeans had the highest level of lead (0.07 mg/kg ww). Based on an average soybean consumption of 50 g/day, no immediate health risk was detected. However, lithium and nickel were present in substantial amounts, with lithium contributing 31.43-48.57% and nickel 6.81-39.56% of their respective provisional daily intake limits, especially from red soybeans (V. angularis). Conclusions: This study highlights the importance of monitoring toxic elements in soybeans and calls for stricter environmental management practices to minimize contamination, ensuring the safety of soy products as their global consumption rises.

Metal Levels in Striped Dolphins (Stenella coeruleoalba) and Common Dolphins (Delphinus delphis) Stranded along the Sicilian Coastlines of the Mediterranean Sea

Dolphins, top predators of the aquatic food chain, are used as sentinel species of marine pollution as they are sensitive to environmental changes and able to accumulate a large content of contaminants. Several EU directives promote study of marine mammalians as bio-indicators to evaluate the presence of contaminants in the aquatic environment, such as the Mediterranean Sea, which is rich in environmental pollutants due to its geographic and geo-morphological characteristics. The aim of this study was to evaluate the content of toxic and essential metals and metalloids (Hg, Pb, Cd, As, Se and Zn), through ICP-MS analysis, in organs/tissues (liver, muscle, lung, kidney and skin) of striped dolphins (Stenella coeruleoalba) and common dolphins (Delphinus delphis) stranded along the Sicilian coastlines of the Mediterranean Sea. The results confirm the exposure of dolphins to toxic metals and metalloids, with the highest Hg levels observed in skin and liver, although a low Metal Pollution Index (MPI) was found in all samples of both dolphin species. From a comparative analysis of trace metals and metalloids according to sex and state of development, the highest levels of Cd and As were found in females vs. males and adults vs. juveniles, except for Pb in both species, and significant differences were observed between the two species, size of specimens, and organs/tissues analyzed. The highest Hg levels were correlated to those of essential metals Se and Zn, expressed as molar ratios, to evaluate the potential synergic effect of these detoxifying elements against Hg toxicity. This study confirms the rule of Stenella coeruleoalba and Delphinus delphis as valid sentinel species of the Mediterranean Sea, to verify the trend of metals pollution in this aquatic environment and, consequently, the health of these marine species.

Metal and trace element concentrations in cetaceans worldwide: A review

This bibliographical review is a compilation of different scientific publications that reported data on metal concentrations in the muscle tissue of different species of cetaceans from seas and oceans around the world. Forty-nine scientific articles were selected, published over a fifteen-year period (2006-2021) with data on heavy metals and trace elements. The different groups of cetaceans considered in this study generally presented low concentrations of Cd and Pb. The same cannot be said of Hg. The highest concentrations of Hg were found in the groups of false killer whales. Similarly, the use of these groups of cetaceans as bioindicators of metal contamination shows that the Mediterranean Sea is one of the most metallically contaminated areas in the world. This may be due to the closed nature of the Mediterranean Sea and to the fact that it is also a highly populated and industrialized area.

Risk Assessment and Characterization in Tuna Species of the Canary Islands According to Their Metal Content

Bioaccumulation is the process by which living organisms accumulate substances, such as pesticides, heavy metals, and other pollutants, from their environment. These substances can accumulate in the organism’s tissues over time, leading to potential health risks. Bioaccumulation can occur in both aquatic and terrestrial ecosystems, and can have a significant impact on the health of both humans and wildlife. The objective of this study is to find out if the concentrations of metals in the tuna species of the Canary Islands are suitable for human consumption and if they pose a health risk. Fifteen samples of Acanthocybium solandri, Katsuwonus pelamis, Thunnus albacares, Thunnus obesus and Thunnus thynnus present in canaries were analyzed. Ten grams of muscle were taken from each specimen and the metals Al, Cd, Cr, Cu, Fe, Li, Ni, Pb and Zn were determined by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The tuna species that presented more metals with a higher concentration compared to the others was T. thynnus, reaching up to 100 times more than the other studied species in Fe content with 137.8 ± 100.9 mg/Kg, which may be due to the fact that it is the largest species that reaches ages of more than fifteen years. The species Thunnus thynnus should not be suitable for commercialization according to the current legislation on the concentrations of Cd in blue fish, since 75% of the specimens studied exceeded the concentration legislated for Cd. A total of 40% of the studied specimens of this this species exceeded the legislated values for the concentration of Pb in oily fish meat, so this species must be monitored to ensure that it does not pose a risk to human health.