Poisons: both drugs and poisons
This type of chemical refers to the accumulation of a certain amount after entering the body, which can have biochemical or biophysical effects on body fluids and organs, disrupt or destroy the normal physiological functions of the body, cause temporary or persistent pathological changes in certain organs and systems, and even life-threatening items. Oral intake of LD50 ≤ 500mg/kg for solids, LD50 ≤ 2000mg/kg for liquids; contact with the skin for 24 hours, LD50 ≤ 1000mg/kg for half lethal; dust, smoke and vapor inhalation of LC50 ≤ 10mg/L for solids or liquids.
The toxicity of different drugs varies. The toxicity of drugs is usually divided into acute toxicity and chronic toxicity.
Acute toxicity refers to the toxic effect of a certain amount of poison on an animal at one time. The magnitude of acute toxicity is often expressed by "half lethal dose" (LD50). It refers to the dose that can kill 50% of a group of tested animals (rabbits, white mice, etc.), and its unit is mg/kg body weight. For example, the oral half lethal dose (LD5o) of rats with sodium cyanide is 6.4mg/kg; the lower the half lethal dose of drugs, the greater its acute toxicity. However, the magnitude of chronic toxicity of drugs cannot be judged based on the value of half lethal dose alone. Due to the presence of certain drugs, although their half-lethal dose is higher (i.e., their acute toxicity is lower), a small amount of long-term ingestion is characterized by higher chronic toxicity due to factors such as their accumulative effect.
The pesticides listed in the "Dangerous Goods List" are also drugs. The toxicity of poisons is determined by a variety of factors, the main influencing factors are as follows.
1. Chemical composition and chemical structure
This is the fundamental factor that determines the toxicity of an item, and its influencing factors are described below.
(1) The degree of saturation of organic compounds, such as acetylene, which is more toxic than ethylene, and ethylene, which is more toxic than ethane.
(2) The number of carbon atoms of the hydrocarbon group on the molecule, such as methyl phosphorus, is 50% less toxic than ethyl phosphorus.
(3) The amount of nitro in nitro compounds increases and the toxicity increases. If halogen atoms are introduced into nitro compounds, the toxicity increases with the increase of halogen atoms.
(4) The positions of nitro groups on the benzene ring (interposition, para-position, ortho-position) are different, and their toxicity varies greatly.
2. Solubility Most poisons are more water-soluble or fat-soluble
The greater the solubility of poisons in water, the greater their toxicity. Because items that are soluble in water are more easily absorbed by the human body and cause poisoning. For example, barium chloride is soluble in water, which is harmful to the human body; while barium sulfate is insoluble in water and fat, so it is non-toxic. However, some poisons are insoluble in water but soluble in fat, and such substances are prone to certain toxicity to the human body.
3. The faster the volatile poison evaporates, the more likely it is to cause poisoning
Generally, the lower the boiling point of a substance, the more volatile it is, and the higher the concentration in the air, the more likely it is to be poisoned. The higher the ambient temperature, the faster the evaporation of volatile poisons, which increases the concentration in the air and easily causes poisoning.
4. Dispersion
The smaller the particles of solid poisons, the greater the dispersion, especially some poisonous particles that can be suspended in the air, which are easily inhaled into the alveoli and absorbed to cause poisoning. Small poisonous dust particles can easily penetrate the poorly packaged packaging and spread into the air, especially when the packaging is slightly damaged, it is more likely to spread and be inhaled to cause poisoning.
5. Examples of poisons
Poisons are divided into two categories: highly toxic drugs and poisons.
At present, the determination of the toxicity determination limits of highly toxic chemicals in our country mainly includes standard documents such as GB/T 15098-1994, GB 15258-1999 and ministerial standard GA 57-1993. The determination limits of the three standards are not the same; but they are all based on the "United Nations Recommendations on the Transport of Dangerous Goods" (Big Orange Book). The book divides "toxic substances" into three levels, and determines the judgment limits of three poisoning routes: oral toxicity, skin contact toxicity, inhalation of dust and smoke or vapor toxicity. In 2001, seven United Nations agencies, including the World Health Organization, the International Labour Organization, and the United Nations Environment Programme, jointly launched and recommended the Global Harmonized System of Classification and Labelling of Chemicals (GHS), which sets out the toxicity classification standards for toxic chemicals.
In order to strengthen the management of toxic chemicals, the State Administration of Work Safety is currently working with relevant state departments to study and formulate a unified breakdown and catalogue of highly toxic drugs and poisons.
(1) Serious drugs According to the 170 Convention, the United Nations Recommendations on the Transport of Dangerous Goods (Big Orange Book), and the Globally Harmonized System of Classification and Labelling of Chemicals (GHS), the definition of serious drugs: chemicals with very severe toxic hazards and cannibalism. Including synthetic chemicals and their mixtures (including pesticides) and natural toxins.
The determination limit is based on the secondary toxicity index in GHS: rat test, oral LD50 ≤ 50mg/kg, percutaneous LD50 ≤ 200mg/kg, inhalation LC50 ≤ 500 × 10-6 (gas) or 2.0mg/L (vapor) or 0.5mg/L (dust, fog).
(2) Poisons Classification of Dangerous Chemicals Class 6 All drugs except highly toxic drugs are poisons.
There are many varieties of drugs, which can be divided into inorganic and organic categories according to their chemical composition.
1) Sodium cyanide
Alias: Shannai; Shannai Sodium, Molecular Formula: NaCN
Physical and chemical properties: white powdery crystals, usually processed into coal balls, pellets or blocks; easily soluble in water, the aqueous solution is alkaline; slightly soluble in ethanol, ether, benzene; deliquescent and corrosive; density 1.60 (water is 1); used for refining precious metals such as gold and silver, electroplating and quenching, and also used in plastics, pesticides, medicine, dyes and other organic synthesis industries.
Hazardous characteristics: highly toxic, easily absorbed through the skin, and easily invaded the human body when exposed to skin wounds, causing death; the oral lethal dose (LD50) of rats is 6.4mg/kg; the maximum allowable concentration in the air of the workshop (calculated by hydrogen cyanide) is 0.3mg/m3; it does not burn itself, but in case of humid air or contact with acids, it will release highly toxic and flammable hydrogen cyanide gas, which reacts strongly with nitrates, nitrites, and chlorates, and there is a risk of explosion.
Fire extinguishing agent: dry powder, sand; acid-base and carbon dioxide fire extinguishing agents are prohibited; firefighters should wear gas masks and full-body fire suits.
Precautions for storage and transportation: The container must be sealed, and it should be specially stored in a special warehouse. It should be managed according to the "five pairs" management system; it should not be mixed with acid storage and transportation; it should be kept away from edible materials, general merchandise and flammable items; in addition to wearing protective equipment, handling workers should not eat without washing their hands and faces during or after the operation. Lost products should be collected as much as possible to reduce poisoning factors; if it cannot be collected, bleach powder can be used to add 15 times water to make a slurry (to keep alkaline or neutral) for cleaning and decomposition; ferrous sulfate can also be used to react into relatively non-toxic ferrous cyanide.
2) arsenic trioxide
Alias: arsenic; arsenous acid; white arsenic Molecular formula: As2O3
Physical and chemical properties: odorless, tasteless white powder; slightly soluble in water, soluble in ethanol, acids, alkalis and glycerol; relative density 3.86 (water is 1); used in glass, enamel, pigment industry and pesticides, leather preservatives, etc.
Hazardous characteristics: highly toxic, with only a half lethal dose (LD5o) of 14.6mg/kg in rats; the maximum allowable concentration of workshop air is 0.3mg/m3; although this product will not burn, it will produce highly toxic gases in the event of a fire due to the sublimation at 193 ° C.
Extinguishing agent: water, dry powder, sand.
Precautions for storage and transportation: containers must be sealed, and it is advisable to store them in a dry and clean warehouse, away from heat sources, and managed according to the "five pairs" management system; they should be stored separately from food additives, acids, and alkalis; they should be handled lightly and lightly to prevent packaging damage and dust from flying; workers should not eat without washing their hands and faces during or after the operation; loose goods should be collected and utilized as much as possible to reduce poisoning factors; in the event of a fire, firefighters should wear gas masks.
