In our country, shark fin has always been regarded as a noble food, one of the "Eight Treasures of the Sea." No lavish banquet is considered complete without shark fin, which is rich in nutrients. According to texts like "Pharmacological Studies," it is believed to nourish blood, qi, kidneys, lungs, and stimulate appetite.

Recent detailed investigations and analyses by researchers from countries such as Thailand, Australia, New Zealand, and Denmark have found that shark fins contain high levels of mercury, posing serious health risks to humans. Pregnant women, in particular, may face severe consequences such as miscarriage, stillbirth, and impaired brain and nerve cell development in the fetus if they consume excessive amounts. Mild cases may result in delayed attention, memory, language abilities, and other brain functions in children, while severe cases can lead to developmental delays, mental retardation, deformities, or even cerebral palsy and death. Scientists also warn that even if a mother consumes only a small amount of mercury, fetal development may still be delayed. Non-pregnant women of childbearing age who consume large amounts of methylmercury may also face adverse effects, including severe cases of infertility.

To explore the root causes of these serious consequences, I interviewed Mr. Liu Donglin, a national health and nutrition management trainer. He pointed out that the high mercury content in shark fins primarily stems from pollution in the sharks' marine environment. Experiments show that mercury in water can easily be converted by microorganisms into methylmercury, which has a high absorption rate, strong toxicity, and is highly soluble in water. Methylmercury can rapidly spread in water and accumulate in aquatic organisms, with sharks, being at the top of the food chain, accumulating the highest levels in their bodies.

According to Liu Donglin, mercury poisoning often occurs through mercury vapor. Due to its high diffusivity and liposolubility, mercury vapor enters the alveoli through the respiratory tract and is transported throughout the body via the bloodstream. Once in the brain, metallic mercury is oxidized into mercury ions, gradually accumulating in brain tissue and causing damage when levels become excessive. Another portion of mercury ions is transferred to the kidneys. Therefore, chronic mercury poisoning primarily manifests as neurological symptoms, such as headaches, dizziness, limb numbness and pain, muscle tremors, and motor dysfunction. Metallic mercury is minimally absorbed by the digestive tract and generally does not cause poisoning.

Methylmercury is easily absorbed in the human intestine and spreads throughout the body, with most of it accumulating in the liver and kidneys. About 15% of methylmercury is distributed in brain tissue, but brain damage occurs before other tissues, primarily affecting the cerebral cortex, cerebellum, and peripheral nerves. Thus, methylmercury poisoning mainly presents as neurological symptoms, including headaches, fatigue, difficulty concentrating, memory loss, and mental abnormalities.

Additionally, sensory abnormalities and language disorders may occur, such as numbness, tingling, and sensory disturbances around the mouth and extremities, which can spread to the arms, legs, and even the torso in severe cases. Speech may become unclear, slow, and incoherent. More severe cases can lead to motor dysfunction, clumsiness, unsteady gait, coordination issues, and tremors. Visual field narrowing and hearing impairments may also occur, manifesting as bilateral concentric visual field narrowing while central vision remains normal, or even tubular vision in severe cases. Central auditory disorders may result in an inability to hear sounds or understand speech. Japan's infamous "Minamata disease" is a well-known case of chronic methylmercury poisoning.

(Chen Renjie)

Source: http:/ / big5. china. com. cn/ cit……07- 06/ 21/ content_8422342. htm