News | Tuesday, 20th October 2020

Shark meat high in pollutants is being consumed unintentionally and risking human health, says research

Mislabelling in the supply chain could mean shark meat is consumed more commonly than we think

Shark meat could be posing a significant risk to human health due to high concentrations of pollutants found in the tissue of different species – and consumers around the globe might be unsuspectingly eating contaminated shark meat as a result of mislabelling in the supply chain, scientists have warned.

Researchers from Manchester Metropolitan University say concentrations of harmful pollutants such as mercury accumulate in the tissue of shark species over time, and when eaten by humans can be harmful to health.  

This is cause for concern as sharks are frequently caught and sold for human consumption either legally or illegally. While pollutant concentrations are higher in sharks as they accumulate through the food chain.

The team also warned that shark meat consumption could be more common than we think due to mislabelling, which sees shark meat sold as ‘cod’, ‘white fish’ and other regularly eaten fish – which look almost identical when gutted and filleted – and then distributed around the globe.

As a result, people could be eating harmful shark meat without knowing. 

Dr David Megson, Senior Lecturer in Chemistry and Environmental Forensics at Manchester Metropolitan, said: “When people consider the risks sharks pose on them, most will think about attacks when swimming.

“But what this research shows is that we might actually be more at risk from eating shark, then them eating us.

“In many cultures and areas of the world, shark meat is eaten intentionally, but what people are unaware of is that shark meat can also enter our food chain unintentionally due to dangerous mislabelling practises.”

The research shows that the consumption of shark is likely to pose a significant risk on human health as levels of pollutants, including mercury and dichlorodiphenyltrichloroethane (DDT), exceed the recommended safe limits.

Food Fraud

For the study, researchers carried out a systematic literature review, which analysed studies already completed on chemical pollutants found in the tissue of sharks, rays and skates. 

They discovered that the most common pollutants found in these species were mercury, cadmium, polychlorinated biphenyls (PCBs) and DDT, which can all be linked to serious health issues in humans.

Mercury has been linked to heart disease, impaired fine motor skills and fertility issues and high DDT exposure can cause problems with the nervous system and liver.

They also learnt that larger sharks, including great white sharks, thresher sharks, tiger sharks, bull sharks and great hammerheads, were among those with the highest concentrations.

Scientists also found that it did not matter which ocean or part of the world the sharks came from, all had high levels of pollutants in their tissue.

Guuske Tiktak, a PhD student from Manchester Metropolitan University and lead researcher on the study, said that species with highest level of pollutants are the ones most likely to be eaten as they are the main targets for the fin trade.

Up to 73 million shark species are killed each year as part of the controversial shark fin trade, which sees species captured and killed for their fins in order to make shark fin soup.

Guuske said: “Our findings are a real concern for communities around the world that eat shark regularly as part of their diet, and as these individuals are most at risk of pollutant exposure, it is crucial that they are aware of these threats.

 “But it is also a serious concern for the rest of us as a lot of shark meat trading goes undetected.

“This occurs on a global scale and shark meat has even been found in UK fish and chip shop labelled as cod.”

Environmental Negligence

Scientists explained that years of environmental negligence was to blame for their findings.

Pesticides, fossil fuels and metals have been entering oceans through waterways and rainfall for centuries. They contaminate food sources such as algae, which is then eaten by fish and other marine life.

Pollutant exposure then goes up the food chain, with bigger fish eating smaller species, creating higher concentrations, while sharks also offload pollutants to their offspring. 

Guuske said: “Relatively little is known about the risks that pollutants pose to sharks and we may not see the effects for generations as sharks are caught in such high numbers, it’s difficult to monitor.

“But it is crucial that we understand the risk of pollutant exposure in these species as this in combination with threats from overfishing, habitat loss and climate change, could mean that we lose many of these vulnerable species over time.”