Arsenic & Methyl-Mercury in Processed Shark Fins
Mercury itself is a naturally occurring element that is present throughout the environment from industrial activity from coal-fired electricity generation, smelting and the incineration of waste. The airborne mercury eventually finds its way into lakes, rivers and the ocean where microscopic organisms convert it methyl-mercury (MeHg). As it enters the marine food chain, it “bioaccumulates” in the larger predators. That is why older and larger fish, such as bluefin tuna and sharks have the highest levels of the highly-toxic form of mercury in their bodies.
A study published in Marine Pollution Bulletin has found that most processed shark fins in Hong Kong have mercury and methyl-mercury levels five to 10 times higher than the legal maximum amount of 0.5 parts per million, as specified by the Centre for Food Safety (CFS) in Hong Kong. Researchers at Florida International University tested shark fins from nine of the most common species used in shark fin soup, including blue sharks, silky sharks and hammerheads. High levels of acutely toxic inorganic arsenic BMDL were found in blue shark fins and hammerhead shark fins were found to carry the highest risk of mercury toxicity.
Although little is known about the impacts of methyl-mercury on sharks themselves, humans suffer serious health problems when they consume methyl-mercury-rich foods, particularly when consumed over time and infants of pregnant women who consume methyl-mercury are at risk of neurocognitive deficits and neuromotor disabilities.
The release of methyl-mercury in the industrial wastewater from the Chisso Corporation's chemical factory in Minamata city in Kumamoto prefecture, Japan, resulted in "Minamata Disease", subsequently recognized as methyl-mercury poisoning. By 2001, it had caused the deaths of 1,784 people in Japan. Tragically, it resulted in many severe birth defects among children.
Garcia Barcia L, Argiro J, Babcock EA, Cai Y, Shea SKH, Chapman DD. (2020) Mercury and arsenic in processed fins from nine of the most traded shark species in the Hong Kong and China dried seafood markets: The potential health risks of shark fin soup. Mar Pollut Bull 157:111281. https://doi.org/10.1016/j.marpolbul.2020.111281