Although several days have passed since the Tianjin explosion, the work difficulty remains high as there are still many toxic substances at the explosion site. Recently, a neurotoxic gas has been discovered. So, what is this gas?
What is Neurotoxic Gas?
Neurotoxic agents are the main lethal military chemical agents used by certain foreign armies. They are called phosphorus-containing agents or organophosphate agents because their molecular structure contains phosphorus atoms. They belong to the same organic phosphorus compounds as organophosphorus pesticides. There are two types of neurotoxic agents:
1. G-class agents such as sarin, soman, and tabun. These agents are volatile and primarily enter the body through the respiratory tract. They have high toxicity, short latency period, quick action, and severe poisoning can lead to death within a short period of time if not promptly treated.
2. V-class agents such as VX and methylphosphonothioic acid. These agents have low volatility and their liquid droplets do not easily evaporate. They primarily enter the body through the skin, but can also cause respiratory tract poisoning in aerosol form. They have higher toxicity compared to G-class agents. After skin contamination, there is a certain latency period. If not promptly treated after symptoms occur, death can also occur within a short period of time.
Symptoms of Neurotoxic Gas Poisoning
Neurotoxic agent poisoning is generally classified into three levels: mild, moderate, and severe. The main symptoms are as follows:
Mild Poisoning
It is characterized by mushroom-like symptoms, mild central nervous system symptoms, and local nicotine-like symptoms. These include small pupils, blurred vision, chest tightness, mild difficulty breathing, runny nose, excessive salivation, nausea, excessive sweating, weakness, facial tremors, dizziness, headache, restlessness, and insomnia. The blood cholinesterase activity is 50-70% of the normal value.
Moderate Poisoning
Mushroom-like symptoms worsen, and obvious nicotine-like symptoms occur, such as significant difficulty breathing, wheezing, mild cyanosis, vomiting, abdominal pain, profuse sweating, muscle tremors throughout the body, unclear speech, weakness, ataxia, anxiety, depression, and delayed reaction. The blood cholinesterase is 30-50% of the normal value.
Severe Poisoning
The above symptoms become more severe, and central nervous system symptoms become prominent. The pupils become pinpoint, excessive salivation and sweating occur, abdominal pain, urinary and fecal incontinence, extreme difficulty in breathing or respiratory failure, obvious cyanosis, widespread muscle tremors, limb convulsions, followed by paroxysmal tonic-clonic seizures, coma, and finally generalized flaccid paralysis. Death occurs due to respiratory depression and circulatory failure. The blood cholinesterase activity is 0-30% of the normal value.
History of Neurotoxic Gas
Although chemical weapons were not used during World War II, German chemists accidentally discovered certain organophosphate salts that could kill insects while researching compounds used as insecticides. This gas can interfere with human neural activity and is therefore called "neurotoxic gas."
Mechanism of Neurotoxic Gas Poisoning
Acetylcholine is a neurotransmitter that is primarily responsible for transmitting information between neurons. When one neuron cell finishes transmitting information to the next neuron cell through its axon, which contains protruding vesicles, it releases acetylcholine. After acetylcholine completes information transmission, it undergoes hydrolysis.
Chemicals in neurotoxic gases inhibit the hydrolysis of acetylcholine, causing continuous transmission of information and keeping the muscles in an excited state. This continuous excitement prevents the muscles responsible for breathing from functioning properly, causing respiratory muscle paralysis (our breathing relies on the continuous contraction and expansion of muscles), ultimately leading to death.
Most Toxic Neurotoxic Gases
Neurotoxic gases are currently the most toxic gases in the world. The main ones are sarin, soman, tabun, and VX. They have extremely high toxicity, and even a small amount of inhaled gas can be lethal. The lethal doses for unprotected personnel are 190 mg/min/L for chlorine, 3.2 mg/min/L for phosgene, 0.4 mg/min/L for tabun, and only 0.1 mg/min/L for sarin.
Neurotoxic Gas at the Tianjin Explosion Site
Various hazardous chemicals in the explosion area could produce such substances. He said, "These substances can produce neurotoxic gases when they come into contact with water or alkaline substances. For example, sodium cyanide and some alkaline sulfides. In addition, some substances undergo chemical reactions during high-temperature explosions, producing toxic gases, such as dimethyl disulfide. Once inhaled, neurotoxic gases can interact with nerve cells, deactivate enzymes, and cause respiratory system and cardiac arrest, resulting in death."
How to Avoid Neurotoxic Gas
If the density of neurotoxic gas is high, evacuation should be done as soon as possible. If the concentration is not severely exceeded, protective measures should be taken to avoid contact with the body. Personnel working at the Tianjin explosion site must wear protective clothing to perform on-site cleanup.
