US media reported that on February 3, local time, a train carrying the toxic chemical vinyl chloride caused a fire after it derailed in eastern Ohio, USA. It is reported that 10 carriages were loaded with toxic chemicals, of which 5 carriages loaded with compressed vinyl chloride pressure relief devices stopped working.
To avoid catastrophic consequences, local emergency departments carried out a "controlled release" of toxic gases on board, discharging vinyl chloride into a pre-prepared tunnel and detonating it. The footage shows the scene of the accident filled with smoke and fire, and the incident triggered the evacuation of residents within a radius of several kilometers due to the threat of deadly gas.
What is vinyl chloride?
Chloroethylene, also known as vinyl chloride, chemical formula is C2H3Cl, is an organic compound, colorless, easy to liquefy, aromatic odor gas, can become liquid when pressurized.
Vinyl chloride is flammable and explosive, and when mixed with air, the explosion limit is 4%~21%. Its freezing point -159.7 °C, boiling point -13.9 °C, flash point -78 °C, more explosive under pressure, storage and transportation should pay attention to the sealing and nitrogen sealing of the container, and a small amount of polymerization inhibitor should be added.
Occupational vinyl chloride poisoning is mainly seen in workers who produce and use vinyl chloride monomer. Vinyl chloride has been identified as a chemical carcinogen.
(Image source: Tencent Medical Codex)
What are the consequences of exposure to vinyl chloride?
Absorption route: vinyl chloride vapor mainly enters the body from the respiratory tract; When its liquid contaminates the skin, it can also be absorbed by the skin.
Distribution: Most of the vinyl chloride entering the body is excreted in its original form by the respiratory tract, and a small part can be distributed in the skin, liver, kidneys and other organs.
Metabolism: Vinyl chloride is mainly metabolized by the liver in the body. After inhalation at low concentrations, it is metabolized in the liver by the alcohol dehydrogenase pathway; After inhalation at high concentration, after saturation by the alcohol dehydrogenase pathway, epoxidation by the action of liver microsomal mixed functional oxidase to generate vinyl chloride oxide, which is unstable and rearranged into chloroacetaldehyde.
Excretion: Most of the vinyl chloride absorbed through the respiratory tract is excreted from the respiratory tract in its original form, and a small part is excreted in urine after metabolism.
Toxicity: After short-term inhalation of high concentration of vinyl chloride, it has anesthetic effect on the central nervous system, manifested as dizziness, fatigue, nausea, lethargy and other symptoms, and in severe cases, it will cause unconsciousness, coma and even death.
Long-term exposure will cause varying degrees of damage to the human central and peripheral nervous system, digestion, respiratory, hematopoietic, endocrine, reproductive and other systems.
Vinyl chloride is a strong mutagen and chemical carcinogen. Hepatic angiosarcoma caused by vinyl chloride belongs to the statutory occupational tumor category. Studies have found that the incidence of lung, lymphoid tissue and brain tumors in vinyl chloride workers is increased, which deserves attention.
In the village called East Palestine, Ohio, local residents told interviewers: "Even indoors, it can smell it, it's a headache." "Is this physical discomfort of the local population a poisoning?
How to diagnose and grade acute and chronic vinyl chloride poisoning?
For the diagnosis of vinyl chloride poisoning, refer to the diagnostic criteria for occupational vinyl chloride poisoning (GBZ90-2017):
Vinyl chloride contact reaction: dizziness, headache, nausea, chest tightness, fatigue and other symptoms after inhalation of high concentration of vinyl chloride gas in a short period of time, no consciousness disorder, and symptoms reduced or disappeared within 24h~48h after disengagement.
Acute vinyl chloride poisoning: inhalation of high concentrations of vinyl chloride gas in a short period of time, clinical manifestations mainly of central nervous system damage, may be accompanied by liver and other organ system damage, combined with laboratory test results and workplace occupational hygiene investigation, comprehensive analysis, exclusion of similar diseases caused by other causes, can confirm the diagnosis.
Chronic vinyl chloride poisoning: long-term exposure to vinyl chloride gas, clinical manifestations mainly of liver and/or spleen damage, Raynaud's phenomenon and acral osteolysis, combined with laboratory test results and workplace occupational hygiene investigation, comprehensive analysis, exclusion of similar diseases caused by other causes, can confirm the diagnosis.
Is there a specific antidote to vinyl chloride poisoning? How is it treated?
There is no specific antidote for vinyl chloride poisoning.
Treatment principle: poisoned patients need to get rid of toxic contact early, remove contaminated clothing, and rinse the skin with running water or soapy water. For the occurrence of different target organ damage, corresponding symptomatic and supportive treatment is given.
According to foreign media reports, in the farms outside the evacuation area, some animals have shown symptoms of poisoning, fish have been found dead in rivers in nearby areas, and some residents have eye discomfort, headache, nausea and other symptoms after returning to their residences, and many residents are worried about the situation at the scene.
What chemicals does vinyl chloride combustion produce?
Is it harmful to the environment and human body?
The products of complete combustion of vinyl chloride are hydrogen chloride, carbon dioxide and water, a large amount of hydrogen chloride penetrates into the land, dissolves in water, forms hydrochloric acid and causes land acidification, affecting the development of agriculture and animal husbandry; Incomplete combustion of vinyl chloride forms toxic carbon monoxide, phosgene and dioxins, a highly toxic gas that was used as a chemical weapon in World War I; Dioxins are biotoxic organic compounds that can exist underground for many years.
Faced with the unknowable risks to the environment and human body caused by vinyl chloride leakage and combustion, some local residents chose to flee the country and consider returning after the situation became clearer. The local EPA will continue to be involved in overseeing the long-term cleanup of the spill, which could take years.
(Some pictures from the Internet)