Scientists studied seven types of deep-sea sharks living near the Canary Islands to understand how much toxic metal they’re absorbing from the ocean. They tested 51 sharks and found that some species accumulated dangerous levels of metals like cadmium and lead in their muscle tissue. Some sharks had so much cadmium and lead that they exceeded safety limits for eating seafood. The research shows that deep-sea sharks are like living pollution detectors, and their high metal levels warn us about ocean contamination near volcanic areas. This matters because some people eat shark meat, and these metals could pose health risks.

The Quick Take

  • What they studied: How much toxic metals (like cadmium, lead, and zinc) are stored in the bodies of different deep-sea shark species living 400 to 1,100 meters below the ocean surface
  • Who participated: 51 deep-sea sharks representing 7 different species caught near the Canary Islands off the coast of Africa
  • Key finding: Some shark species, particularly Deania quadrispinosa and D. profundorum, accumulated very high levels of toxic metals. Several individual sharks had cadmium and lead levels that exceeded international food safety limits, meaning they would be unsafe to eat
  • What it means for you: If you live in areas where shark meat is eaten or sold, this research suggests checking where it comes from and being cautious about consumption. For most people in developed countries, this is unlikely to affect you directly, but it shows ocean pollution is reaching even the deepest parts of the sea

The Research Details

Scientists collected muscle tissue samples from 51 deep-sea sharks representing seven different species living at depths between 400 and 1,100 meters near the Canary Islands. They used a laboratory technique called inductively coupled plasma optical emission spectrometry to measure eight different metals in the shark tissue: aluminum, boron, cadmium, copper, iron, nickel, lead, and zinc. This technique is like a super-sensitive scale that can detect even tiny amounts of metals in the samples.

The researchers then compared the metal levels between different shark species to see which ones accumulated the most. They also looked at whether the depth where sharks lived, their evolutionary family tree, or their eating habits affected how much metal they stored in their bodies. This allowed them to understand what factors make certain sharks more likely to accumulate toxic metals.

Deep-sea sharks are perfect ‘pollution detectors’ because they live in remote areas where we don’t have many other ways to measure ocean contamination. By studying what metals are in their bodies, scientists can learn about pollution patterns in the deep ocean. The study design is important because it compares multiple shark species, which helps us understand whether some sharks are naturally better or worse at filtering out toxins, or whether their environment is the main factor determining metal levels.

This study is a solid scientific investigation published in a respected marine science journal. The researchers used a precise laboratory method to measure metals, and they studied enough sharks (51 specimens) to see clear patterns. However, the study only looked at sharks from one region (Canary Islands), so we can’t be sure if these patterns apply to deep-sea sharks in other parts of the world. The study is observational, meaning the researchers measured what was already there rather than conducting an experiment, which limits what we can conclude about causes.

What the Results Show

The research revealed striking differences between shark species. Two species—Deania quadrispinosa and D. profundorum—showed the highest metal accumulation, with aluminum levels up to 32 mg/kg, zinc up to 35 mg/kg, and cadmium up to 0.29 mg/kg. In contrast, Apristurus laurussonii consistently showed the lowest metal concentrations across all eight metals tested.

Most importantly, several individual sharks exceeded international food safety limits. The international limit for cadmium in seafood is 0.05 mg/kg, and for lead it’s 0.30 mg/kg. Some sharks in this study had cadmium levels nearly six times higher than the safety limit. This is concerning because it means eating these sharks could expose people to dangerous levels of toxic metals.

The pattern of metal accumulation appeared to be related to where the sharks lived (their depth) and their evolutionary family history, suggesting that some shark species are genetically predisposed to accumulate more metals. Interestingly, what the sharks ate (their feeding mode) didn’t seem to strongly influence how much metal they stored.

The researchers found that metal accumulation patterns clustered by depth and evolutionary lineage, meaning sharks that are more closely related evolutionarily tended to have similar metal levels, and sharks living at similar depths showed comparable contamination patterns. This suggests that both inherited traits and environmental factors influence how much metal sharks accumulate. The study also documented marked metal enrichment along the volcanic slopes near the Canary Islands, indicating that volcanic geology in the region may contribute to higher metal levels in the surrounding ocean.

This research builds on previous work showing that sharks are sensitive to ocean contamination. However, this is one of the first detailed studies comparing metal accumulation across multiple deep-sea shark species. Previous research on sharks has often focused on surface-dwelling species, so this study fills an important gap by showing that deep-sea sharks also accumulate concerning levels of toxic metals. The findings align with broader research showing that deep-sea organisms can accumulate pollutants despite living far from human activity.

The study only examined sharks from one geographic region (Canary Islands), so we don’t know if these patterns apply to deep-sea sharks elsewhere in the world. The researchers didn’t measure metals in other deep-sea animals or in the water itself, so we can’t fully understand the source of the contamination. Additionally, the study is a snapshot in time—we don’t know if metal levels are increasing, decreasing, or staying the same over years or decades. Finally, the study measured metals in muscle tissue, but we don’t know how much metal is in other shark organs or whether the levels measured would actually cause health problems in humans who eat the sharks.

The Bottom Line

If shark meat is available in your region: (1) Source matters—try to purchase shark from regulated fisheries rather than uncontrolled sources, (2) Limit consumption frequency—eating shark occasionally rather than regularly reduces exposure to accumulated metals, (3) Avoid deep-sea shark species when possible, as they appear to accumulate higher metal levels. These recommendations have moderate confidence because they’re based on one regional study, though the findings align with general food safety principles. For most people in developed countries where shark consumption is rare, this research doesn’t require immediate action.

This research is most relevant to: (1) People in coastal communities where shark meat is regularly consumed or traded, (2) Fisheries managers and regulators who set seafood safety standards, (3) Environmental scientists monitoring ocean pollution, (4) Seafood importers and sellers. People in most developed countries where shark consumption is uncommon should be aware of these findings but don’t need to change behavior. Pregnant women and young children should be especially cautious about shark consumption due to their greater sensitivity to heavy metals.

If you reduce shark consumption, you would likely see decreasing metal levels in your body within weeks to months, as your body gradually eliminates accumulated metals. However, if you’ve consumed shark meat regularly for years, it may take several months to a year to significantly reduce metal burden. The ocean pollution itself will take much longer to improve—likely decades—even if we stop adding metals today, because metals persist in the environment for a very long time.

Want to Apply This Research?

  • Track seafood consumption by type and source: Log each time you eat shark or other seafood, noting the species (if known), where it came from, and portion size. This helps you monitor your exposure to potentially contaminated sources and identify patterns in your diet.
  • Set a goal to identify and substitute deep-sea shark products with safer seafood alternatives. Use the app to research which fish species are lower in accumulated metals and create a shopping list of alternatives. Track how often you successfully choose safer options.
  • Create a monthly seafood safety check-in where you review your shark and deep-sea fish consumption. Set alerts if you notice increasing frequency of shark consumption, and use the app to research the source and safety profile of any shark products you consider buying. Over time, this builds awareness of your exposure risk.

This research describes metal contamination in deep-sea sharks near the Canary Islands and should not be considered medical advice. If you have consumed shark meat regularly and are concerned about heavy metal exposure, consult your healthcare provider about testing and monitoring. This study is observational and shows correlation between shark species and metal levels, not proven cause-and-effect. Individual shark metal levels vary, and this study doesn’t assess actual health risks from consuming specific sharks. Pregnant women, nursing mothers, young children, and people with kidney disease should consult healthcare providers before consuming any shark products. Always follow local and international seafood safety guidelines from regulatory authorities like the FDA or EFSA.