無機砷 Inorganic Arsenic (iAs)
Inorganic Arsenic
*Inorganic arsenic is a toxic metalloid element that is widely present in the environment, including water, air, soil, and food. Its effects on living organisms depend mainly on the dose and exposure duration, exhibiting both acute and chronic toxicity.
*Normal Range: < 3.5 µg/L
*Metabolism and Absorption of Inorganic Arsenic
Inorganic arsenic primarily exists in two oxidation states: arsenate (As⁵⁺) and arsenite (As³⁺). It enters the human body through the digestive tract, respiratory system, and skin. After absorption, it undergoes hepatic metabolism, where it is methylated into relatively less toxic organic arsenic compounds, such as monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). Finally, it is excreted through the kidneys.
*Major Physiological Effects and Toxicity
-Disruption of Cellular Energy Metabolism:
Arsenate (As⁵⁺) interferes with phosphate metabolism and competitively inhibits the production of ATP (adenosine triphosphate) in cells, leading to energy depletion and impaired cellular function.
-Inhibition of Enzyme Activity and Protein Function:
Arsenite (As³⁺) binds to sulfhydryl (-SH) groups in proteins and enzymes, disrupting essential cellular functions. For example, it interferes with lipoic acid and inhibits pyruvate dehydrogenase, thereby obstructing energy metabolism.
-Oxidative Stress and DNA Damage:
Arsenic promotes the generation of reactive oxygen species (ROS), leading to oxidative stress, DNA damage, protein denaturation, and cell apoptosis, which may increase the risk of cancer.
-Interference with Signal Transduction and Gene Expression:
Inorganic arsenic affects intracellular signaling pathways (such as MAPK and NF-κB), which influence gene expression and may lead to abnormal cell division and an increased risk of carcinogenesis.
-Impact on the Immune System and Endocrine Function:
Arsenic may suppress immune cell function, leading to immune system dysregulation and increased susceptibility to infections. It also affects the endocrine system, such as thyroid function, potentially causing hypothyroidism.
*Health Effects of Inorganic Arsenic
-Acute Arsenic Poisoning (High-Dose Exposure):
Symptoms include nausea, vomiting, diarrhea, abdominal pain, muscle cramps, shock, arrhythmia, and, in severe cases, death.
-Chronic Arsenic Poisoning (Long-Term Low-Dose Exposure):
Potential effects include: skin lesions (pigmentation changes, hyperkeratosis), neurotoxicity (peripheral neuropathy, memory impairment), cardiovascular diseases (hypertension, atherosclerosis), increased cancer risk (skin cancer, lung cancer, bladder cancer, etc.)
*Prevention and Reduction of Arsenic Exposure
-Avoid drinking arsenic-contaminated groundwater by using filtration systems or switching to alternative water sources.
-Reduce consumption of arsenic-contaminated food, such as high-arsenic rice and seafood.
-Personal protective measures should be taken when working in arsenic-polluted environments, such as wearing appropriate protective equipment.
*Conclusion
Inorganic arsenic has multiple physiological effects, primarily disrupting energy metabolism, inducing oxidative stress, interfering with enzyme activity, and altering gene expression. Long-term exposure may lead to various chronic diseases and even cancer. Therefore, it is essential to be mindful of environmental and dietary sources of arsenic to minimize exposure to arsenic-contaminated substances.
*Inorganic arsenic is a toxic metalloid element that is widely present in the environment, including water, air, soil, and food. Its effects on living organisms depend mainly on the dose and exposure duration, exhibiting both acute and chronic toxicity.
*Normal Range: < 3.5 µg/L
*Metabolism and Absorption of Inorganic Arsenic
Inorganic arsenic primarily exists in two oxidation states: arsenate (As⁵⁺) and arsenite (As³⁺). It enters the human body through the digestive tract, respiratory system, and skin. After absorption, it undergoes hepatic metabolism, where it is methylated into relatively less toxic organic arsenic compounds, such as monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). Finally, it is excreted through the kidneys.
*Major Physiological Effects and Toxicity
-Disruption of Cellular Energy Metabolism:
Arsenate (As⁵⁺) interferes with phosphate metabolism and competitively inhibits the production of ATP (adenosine triphosphate) in cells, leading to energy depletion and impaired cellular function.
-Inhibition of Enzyme Activity and Protein Function:
Arsenite (As³⁺) binds to sulfhydryl (-SH) groups in proteins and enzymes, disrupting essential cellular functions. For example, it interferes with lipoic acid and inhibits pyruvate dehydrogenase, thereby obstructing energy metabolism.
-Oxidative Stress and DNA Damage:
Arsenic promotes the generation of reactive oxygen species (ROS), leading to oxidative stress, DNA damage, protein denaturation, and cell apoptosis, which may increase the risk of cancer.
-Interference with Signal Transduction and Gene Expression:
Inorganic arsenic affects intracellular signaling pathways (such as MAPK and NF-κB), which influence gene expression and may lead to abnormal cell division and an increased risk of carcinogenesis.
-Impact on the Immune System and Endocrine Function:
Arsenic may suppress immune cell function, leading to immune system dysregulation and increased susceptibility to infections. It also affects the endocrine system, such as thyroid function, potentially causing hypothyroidism.
*Health Effects of Inorganic Arsenic
-Acute Arsenic Poisoning (High-Dose Exposure):
Symptoms include nausea, vomiting, diarrhea, abdominal pain, muscle cramps, shock, arrhythmia, and, in severe cases, death.
-Chronic Arsenic Poisoning (Long-Term Low-Dose Exposure):
Potential effects include: skin lesions (pigmentation changes, hyperkeratosis), neurotoxicity (peripheral neuropathy, memory impairment), cardiovascular diseases (hypertension, atherosclerosis), increased cancer risk (skin cancer, lung cancer, bladder cancer, etc.)
*Prevention and Reduction of Arsenic Exposure
-Avoid drinking arsenic-contaminated groundwater by using filtration systems or switching to alternative water sources.
-Reduce consumption of arsenic-contaminated food, such as high-arsenic rice and seafood.
-Personal protective measures should be taken when working in arsenic-polluted environments, such as wearing appropriate protective equipment.
*Conclusion
Inorganic arsenic has multiple physiological effects, primarily disrupting energy metabolism, inducing oxidative stress, interfering with enzyme activity, and altering gene expression. Long-term exposure may lead to various chronic diseases and even cancer. Therefore, it is essential to be mindful of environmental and dietary sources of arsenic to minimize exposure to arsenic-contaminated substances.