Mercury thermometers are used to determine body temperature and are an integral part of a home medicine cabinet. The advantage of the device is its high accuracy - up to 0.01 degrees. The downside is the toxicity of the liquid metal and its health hazard. Mercury poisoning from a thermometer is common in medical practice.
How does mercury poisoning occur?
Mercury poisoning is a condition of the body caused by ingestion of mercury vapor or the substance itself into the respiratory tract through the gastrointestinal tract, as well as mercury compounds.
When the concentration of mercury is more than 0.25 milligrams per cubic meter, various problems with the respiratory system begin to develop; at higher densities, almost all other internal organs and systems of the body are affected.
In human blood, an excessive concentration of mercury is considered to be 35 ng/ml or more, in urine – 150 μg/l. Experts believe that children and women are most susceptible to mercury vapor.
Both organic and inorganic mercury can cause poisoning. Elemental or inorganic mercury is used in sphygmomanometers, thermometers, and materials for making fillings. Mercury salts are used in the production of certain medicines, plastics, and food products. Organic mercury can be found in cosmetics, paints, foods and medicines.
Mercury salts are often methylated in bacteria, which leads to contamination of the environment with this metal and its deposition in living organisms, for example, in fish. Further, it turns out that by eating such poisoned fish, a person poisons his body.
Inorganic mercury vapor enters the human body along with the air and settles in the lungs. Afterwards, through the pulmonary alveoli they penetrate into the circulatory system and are carried with the blood to all internal organs and systems. The absorption of this metal by the gastrointestinal tract is very small. Elemental mercury is excreted from the human body in feces and urine. Quite a bit of it comes back out with the help of the lungs. Its half-life is approximately two months.
Inorganic mercury and its compounds that enter the human body with food cause the greatest harm to the digestive system: it corrodes the mucous membranes of the stomach and intestines, due to which it spreads throughout the body. Mercury salts settle mostly in the kidneys, the rest of them affect the liver, spleen, intestines, lungs, skin, bone marrow and blood. It is also excreted through the urinary system and feces. In such cases, its half-life is about forty days.
Organic methylated mercury and its compounds enter the body mainly orally - through the mouth. It is usually quickly absorbed in the intestines, as well as through the pores of the skin. Such mercury is also dangerous because it easily penetrates the placental and blood-brain barriers, as well as into breast milk. Due to its binding to blood proteins, methylated mercury is distributed throughout the body, settling mostly in the circulatory system, kidneys and central nervous system. Organic metal is excreted from the human body with urine. The half-life reaches seventy days.
Toxic dose for humans
The toxic dose of a toxic substance depends on the individual characteristics of the person, the age of the victim, the route of entry of mercury into the body, and the duration of exposure to the poison. Separately, one should take into account the form in which the liquid metal was at the time it entered the body.
Table 1. Lethal doses of mercury
| Form of mercury | Lethal dose | |
| In an adult | In children | |
| In inorganic compounds | 10–42 mg/kg | 10–42 mg/kg |
| In organic compounds | 10–60 mg/kg | 10–60 mg/kg |
| Metal in the form of vapors | 2.5 g | |
| Oral Compounds | From 0.1–0.3 g to 3 g | |
Chronic intoxication develops when the concentration of toxic metal vapors in the air is from 0.001 to 0.005 mg/m3. For acute inhalation injury, the MPC is 0.13–0.80 mg/m3.
Symptoms of mercury poisoning
The first symptoms indicating mercury poisoning begin to appear when the concentration of this metal in the blood is more than 500 ng/ml and in the urine more than 600 μg/ml. There are acute and chronic mercury poisoning.
Signs characteristic of acute metal poisoning:
- severe cough, asthma attacks, catarrh of the upper respiratory tract;
- sore throat when swallowing, shortness of breath, chest pain, pneumonia;
- headaches and dizziness, body tremors;
- increased excitability;
- increased body temperature up to 40 degrees, chills;
- severe fluid loss leading to dehydration;
- abdominal pain, nausea, tenesmus, vomiting and bloody diarrhea;
- bleeding gums, gingivitis;
- metallic taste in the mouth, profuse salivation.
The manifestation of signs of chronic mercury poisoning is called mercurialism. The phenomenon of micromercurialism is also known, in which a person exhibits some signs of mercury poisoning when exposed to slightly small doses of the metal for five to ten years.
Signs of incipient mercurialism are:
- general weakness, apathy, severe fatigue;
- frequent urination, severe swelling of the limbs;
- nausea, vomiting, loss of appetite;
- decreased taste, sense of smell, skin sensitivity;
- stomatitis, gingivitis, tooth loss;
- excessive salivation, increased sweating;
- tremor of the limbs, turning into trembling throughout the body;
- skin rashes, hyperkeratosis and hypertrichosis of the skin, dermatitis;
- photophobia, increased excitability, insomnia or drowsiness, decreased intellectual abilities, irritability, headaches and dizziness;
- heart rhythm disturbances, low blood pressure, acrodynia or pink disease.
Pathogenesis
When inhaling air that contains mercury vapor in a concentration of up to 0.25 mg/m³, the metal is retained and accumulates in the lung parenchyma. If the concentration is higher, then the toxin can be absorbed by intact human skin, especially its inorganic compounds. After entering the lungs, up to 100% of inhaled mercury enters the bloodstream and circulates in the form of albuminates. A small amount of cations is absorbed into the gastrointestinal tract - 0.01% of the total mass of ingested metal, but after its destructive effect on the mucous membranes, this figure increases. After transformation in the body tissues, the metal becomes fat-soluble and is able to penetrate the gametoencephalic and placental barriers. Accumulation occurs predominantly in the kidneys, causing necrosis or nephrotic syndrome , but can also be found in the liver, central nervous system, red blood cells, bone marrow, spleen, intestines and skin.
When oxidized to compounds with divalent mercury, which easily binds to the sulfhydryl groups of proteins, it becomes limitedly mobile. For the excretion of elemental mercury in urine or feces, salivary, sweat and mammary glands, a minimum of 80-120 days is required.
The toxic effect of mercury is reduced to local irritant, enterotoxic, nephrotoxic and neurotoxic effects. It is explained by its affinity for thiol group enzymes and blocking of sulfide groups of tissue proteins. Disorder of enzymatic processes occurs in all tissues and organs, disrupting the synthesis of proteins in the blood plasma, liver, regulatory functions of the neuroendocrine system, cortical-subcortical relationships and autonomic functions. In the digestive and respiratory system, inflammation and signs of hematemesis, pain, tenesmus, as well as interstitial pneumonitis and, as a result, respiratory failure occur . On the part of the skin, hypersensitivity reactions may occur in the form of erythema , generalized rash , hyperkeratosis and scaly dermatitis .
Organic mercury compounds (for example, dimethylmercury ) are more toxic than inorganic ones, because they are neurotoxins and have high lipophilicity and the ability to interact effectively with the body's enzymatic system.
Complications and consequences of mercury poisoning
Mercury poisoning does not leave its mark on the body and, without proper treatment, in most cases leads to serious complications and unforeseen consequences, which are expressed in:
- delirium;
- paralysis;
- respiratory failure;
- coma and death.
If a pregnant woman inhales high concentrations of mercury vapor, this does not go away without consequences for the unborn baby. In severe cases, this leads to atrophy of the cerebellum or cerebral cortex and the development of cerebral palsy in the fetus.
Postpartum poisoning with mercury vapor or mercury compounds in some cases leads to:
- headaches;
- hearing, speech and vision impairment;
- impaired movement coordination;
- paresthesia and paralysis;
- memory loss;
- stupor, coma and death.
It happens that some of these symptoms remain with the poisoned person for the rest of his life.
General information
Mercury poisoning or mercurialism is a pathological condition caused by excessive intake of mercury vapor or its compounds into the body.
Mercury, or hydrargyrum, is a transition metal that is a contaminant with cumulative and extremely toxic properties (hazard class 1), especially in the form of vapors. Chronic poisoning with mercury vapor or compounds is called mercurialism. It is the vapors that are considered more dangerous, but from the liquid state it can gradually evaporate even at room temperature and oxidize into divalent mercury.
Historical reference
The toxic properties of mercury have been known since ancient times. Then it was used, among other things, as a poison for deliberate poisoning, although the toxicity of metallic mercury for a long time was not given importance, especially to its compounds such as:
- calomel - mercury (I) chloride , is a rare mineral that was used for the manufacture of calomel electrodes and as a catalyst for organic reactions, in medicine it was a well-known antimicrobial agent for the treatment of blenorrhea and venereal diseases , then modern drugs came to replace it;
- cinnabar - mercury (II) sulfide was used as a red paint for icon painting, as an antibiotic , for example, for syphilis ;
- mercuric chloride (II) was necessary for obtaining other mercury salts and impregnating wood.
Mercury began to be widely used in production during the Middle Ages, when it was used to make gold and silver mirrors (as part of an alloy with other metals - amalgams ), antiseptics, and felt hats. Then they started talking about the occupational disease of the “old hatters,” who were distinguished by their eccentricity and suffered from tremors .
Causes of mercury poisoning
Sources of mercury poisoning are:
- mercury lamps;
- mercury thermometers;
- fluorescent gas-discharge energy-saving lamps;
- mercury-zinc batteries;
- dental fillings with amalgam;
- medications: mercuzal, calomel, sublimate;
- industrial combustion of gas or coal in large quantities;
- fish or shellfish living in environmentally polluted waters;
- places of natural origin of mercury.
Classification
Depending on the dose of metallotoxin received and the duration of its effect on the human body, acute or chronic poisoning may occur.
Mercury poisoning from a thermometer
For the development of severe poisoning, the amount of mercury from an ordinary broken medical thermometer is enough. The toxicological effect is not only on the respiratory tract, but also on the structures of the nervous system, liver, kidneys, and gastrointestinal tract.
Timely cleansing of the room (demercurization) of mercury from a thermometer can protect a person from serious danger. To do this, you should quickly but carefully collect all the mercury balls on the surface. Effective tools for this include damp paper towels, pipettes, brushes, or wide tape. Corners and recesses in the floor can be problematic for cleaning. Collected mercury should absolutely not be thrown into household waste landfills; it must be placed in 2 zip-lock bags and call the unified dispatch service on duty to find out where this toxic waste can be disposed of. You should also ventilate the room for 24 hours. The first symptoms when treating a room may immediately appear as metal sensations in the mouth, nausea and weakness; try not to deeply inhale metal vapors and use personal protective equipment.
Chronic mercury poisoning
If the amount of mercury ingested over a long period of time does not exceed the sanitary norm, it causes chronic poisoning. The clinical picture differs depending on the health of the body and the state of the nervous system.
A separate type of chronic poisoning is micromercurialism , which occurs under the influence of small doses of mercury for 5 or more years.
Minamata disease
The syndrome that develops from intoxication with the organic compound of mercury, methylmercury, is called Minamata disease in honor of the environmental disaster in this Japanese city of the same name in 1956. Chisso's emissions released inorganic mercury into the bay, which was metabolized and accumulated in benthic organisms, especially fish and shellfish, the main source of food for the surrounding fishing villages.
The affected individuals experienced disturbances in the nervous system, in particular motor skills, speech, hearing and vision deteriorated, paresthesia in the limbs and even paralysis . Over time, consciousness was impaired, neurasthenia , and pathogenesis ended in death in 35% of cases.
First aid for mercury poisoning
If a person has signs of acute mercury vapor poisoning, it is necessary:
- Remove the injured person from the affected area.
- Make him drink several glasses of salted water or a weak solution of potassium permanganate.
- Induce vomiting mechanically.
- Rinse your throat with a weak solution of manganese.
- Give a few glasses of water again.
- Give the victim "Unitiol" - a universal remedy that is an antidote for heavy metal poisoning. Activated carbon in this case is useless and its use will not affect the patient’s condition in any way.
- Give the poisoned person laxatives.
After providing first aid, it is necessary to transport the injured person to a medical facility for further treatment.
All treatment of a person poisoned by heavy metals, in particular mercury, comes down to removing them from the victim’s body as quickly as possible. For this purpose, complex medications with active dithiol groups are used. If renal failure is detected, it is advisable to prescribe hemodialysis or peritoneal dialysis.
Symptomatic treatment is also often used to improve the patient's condition.
Why is mercury from a thermometer dangerous?
Children are taught that mercury is a harmful compound at an early age. But many adults do not believe in the danger of a thermometer, since the amount of mercury there is insignificant.
Reasons for careful handling of the measuring instrument:
- small size - a microcrack may form on the glass, toxic metal vapors will have a negative effect for a long time;
- fluidity - small balls of sublimate easily pass into any cracks in boards or cracks in walls. Therefore, during demercurization of the premises, they are easy to miss;
- ability to accumulate in walls, wood.
In addition, a child can hide the fact that the thermometer has been damaged for fear of punishment.
It is extremely difficult to get acute poisoning from liquid metal fumes at home. Long-term chronic intoxication will be present.
The symptoms of such poisoning are similar to those of various diseases; they appear gradually and the victim does not associate the broken thermometer with his condition. And dying due to pathologies that developed against the background of long-term mercury intoxication is a very likely outcome.
Prevention of poisoning by mercury vapors and compounds
To prevent this type of poisoning, it is necessary to observe safety measures.
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When working at industrial enterprises in conditions of possible poisoning by mercury vapor, you should rinse your mouth daily with a solution of potassium permanganate or potassium chlorate. Keep the mercury thermometer away from children. It is best to replace mercury thermometers with safer ones: electronic or infrared. Stop using energy-saving mercury lamps and replace them with more energy-efficient LED lamps. Do not eat fish and shellfish caught in polluted waters. Do not leave a child unattended while measuring their temperature with a mercury thermometer. Do not self-medicate and take medications prescribed by your doctor.
During pregnancy
Even in small quantities, mercury can cause serious health problems for the baby and pose a threat to the normal intrauterine prenatal development of the fetus. The toxic effect affects the functional abilities of the nervous, digestive and immune systems, disrupts the functioning of the lungs, kidneys, skin and eyes. Many children experience cerebral palsy due to atrophy of the cortical structures of the brain and cerebellum, as well as functional immaturity and disorders of the excretory system.
If an expectant mother consumes fish or shellfish contaminated with methylmercury, it may have a significant teratogenic effect on her fetus. At risk are certain groups of the population that live off fishing. Residents of Brazil, Canada, Colombia, China and Greenland are most susceptible to chronic mercury poisoning. In these countries, approximately 0.15-1.7% of children suffer from various types of cognitive impairment, including mild mental retardation, due to increased consumption of mercury-containing fish. Unfortunately, even heat treatment is not able to destroy mercury in food products.
