Do not drink poison, Gertrude, or about toxic electronics

13:48
24.11.2024
jar_ohty
60

I have already written about radiation. About how not to blow up on a capacitor or battery - too. It remains to write about how not to get poisoned.

Electronic devices contain elements from almost the entire periodic table and a wide variety of chemical compounds. It is not surprising that some of them are hazardous to health, and some of them are seriously hazardous. In this article, I want to discuss the main toxic substances contained in electronic devices and the safety measures for handling them.

Toxic Periodic Table

The periodic table has become a kind of symbol of chemical danger in popular culture. "It contains the entire periodic table" is said about something that should not be eaten or drunk. We will not emulate characters who use the great chemist's name in this way, but will walk through the periodic system of elements, examining their toxic properties.

We will encounter elements that are inherently poisonous. Arsenic, for example, in any form, will always be poisonous to a greater or lesser extent. Compounds of barium, lead, mercury, thallium, as well as the metals themselves, will always be poisonous. Only those compounds that cannot be absorbed due to extremely low solubility will be relatively non-toxic. On the other hand, we will see elements such as carbon, nitrogen, phosphorus, sulfur. Among their compounds, there can be the strongest poisons, while other compounds are practically devoid of toxic properties. For example, white phosphorus is a poison, while phosphate salts can only be harmful in large doses, and a certain amount is necessary for life. Elemental sulfur is practically safe unless it is in a colloidal state, while hydrogen sulfide is extremely poisonous. Among carbon compounds, there are both botulinum toxin and our food (one form of elemental carbon, soot, was the first known carcinogen to humans). Even oxygen, the source of life, becomes a strong poison in the form of ozone, but here this toxicity is inherent not to oxygen as an element, but to the simple substance ozone, which is so chemically active that any organic substance will be destroyed upon contact with it.

We notice that the larger the atomic number, the more likely the next element will have toxic properties. The concept of "heavy metals" did not arise out of nowhere - by firmly binding to proteins, they irreversibly disable the enzymatic systems of cells and, accumulating, can act in very small doses. Nevertheless, this pattern sometimes fails. Beryllium, for example, is extremely toxic in the form of metal, oxide, and any compound. Lithium is also toxic, disrupting the well-established mechanism of sodium, potassium, and calcium channels in cell membranes. The same can be said about fluorine - the lightest and at the same time the most toxic halogen - both in the form of a simple substance (everyone who attended school chemistry lessons knows about the all-destructive properties of fluorine) and almost all compounds, except perhaps sulfur hexafluoride and some fluorinated hydrocarbons, including fluoropolymers. But bismuth - it would seem, it is the heaviest of the non-radioactive metals and should be at least as toxic as lead. But no, due to its amazing tendency to hydrolysis, it is almost incapable of being absorbed per os. This is used to treat stomach ulcers: the drug De-nol not only envelops the affected mucosa, protecting it from acid, but also kills Helicobacter, for the discovery of the role of which in the pathogenesis of stomach ulcers a Nobel Prize was awarded.

Here, speaking of toxicity, one must not forget that in addition to many toxic elements, there are also many that are absolutely essential for life. And it is surprising that these sets overlap significantly, illustrating the very saying of Theophrastus Paracelsus "everything is poison, and only the dose makes the poison a remedy"*⁾. Some of them are required by the body in exceptionally small quantities, so that those dealing with selenium or cobalt are more likely to be harmed by contact with them than to benefit, but nevertheless, the absence of these elements in the body leads to no less problems than their excess. But this does not mean that the body also needs microdoses of, say, mercury, thallium, or beryllium. A number of elements are simply not needed by the body. Not all of them are strong poisons: tin, zirconium, niobium, and tantalum, lanthanides, which have no biological role in the body, almost do not show toxic properties in the form of metals and simple compounds. But mercury, lead, and thallium, which also have no biological role, are strong cumulative poisons.

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*⁾ It should be noted here a common misconception: this saying does not sound like "everything is poison and everything is a remedy". Paracelsus did not believe that any poison can and should be a remedy in a small dose.

And I turn to perhaps the most famous "electronic poison", to which almost every radio amateur or electronics engineer is involuntarily exposed.

Lead

Lead belongs to those chemical elements that have been known to people since ancient times. The first lead products found during archaeological excavations of ancient Egypt and Mesopotamia date back to the third millennium BC, and throughout human history, lead has been widely used in almost all areas of human activity, from art and medicine to engineering and construction. Lead is a metal without which electronics could not do until recently. Mainly, lead is contained in solders and coatings on the surface of leads and printed conductors, whose task is to ensure solderability. In the past, the main solder used in electronics assembly was an alloy of 60-63% tin and 37-40% lead. To this day, this solder is the best in terms of properties — it is relatively low-melting (183°C) and at the same time crystallizes at a constant temperature in the form of a homogeneous fine-dispersed eutectic, has good adhesion to the main metals of conductors and has good mechanical properties (in particular, it is not brittle).

Lead is also contained in significant quantities in ferroelectric ceramics used in ceramic capacitors and piezoceramic transducers and filters, as well as in the glass of radio tubes and cathode-ray devices. Since these materials have fairly high hardness, strength, and chemical resistance, the lead content in them is not so significant from a toxicological point of view, as it is reliably enclosed inside these materials. Large quantities of lead are also used in batteries. Cheap, but heavy and not very durable lead-acid batteries with bound electrolyte are often used as a backup power source in UPS, alarm systems, etc. But the main amount of lead is contained in batteries in transport.

Mercury

For some reason, the mention of the toxicity of no other substance causes such discussions as when it comes to mercury. The number of people who consider the special, outstanding toxicity of mercury a myth, a horror story, and even a money scam is amazing. Perhaps this is due to the fact that every house had a mercury thermometer, and few people did not break it, and it seems that this did not lead to any emergency. People did not fall dead, no one evacuated the building, and a new thermometer was bought without presenting not only a permit to purchase weapons of mass destruction, but even a doctor's prescription.

And yet, mercury is poisonous, and very much so. The maximum allowable concentration (MAC) of mercury in residential areas is the lowest among all MACs, excluding beryllium and radioactive isotopes. In some countries, the MAC is only 30 nanograms per cubic meter (in our country, the MAC for residential areas is 0.0003 mg/m³— that is, 300 ng, ten times more). These 30 ng are just nine billion atoms in a cubic centimeter. Some kind of homeopathy, you might say. And yet, this "homeopathy" works. The secret, in general, is the same as with lead. Mercury in the form of vapors is easily and completely absorbed into the bloodstream in the lungs, and part of it, remaining in a non-ionized molecular state or turning into organomercury compounds, then passes through the blood-brain barrier into the nervous tissue and never leaves it, staying there for life. In a day, a person will inhale 3.6 micrograms of mercury with air at the MAC level, in a year — 1.3 mg, and in 50 years — 66 mg. Quite a significant amount. Of course, not all of this mercury will remain in the brain, but only a small part of it (but still significantly more than if mercury entered the body in the form of salts), but to permanently disable the target for the neurotransmitter on the postsynaptic membrane, exactly one atom of mercury is needed. And so, atom by atom, mercury destroys the information stored in the brain, breaks neural connections. A person who deals with mercury professionally, daily exposed to high concentrations of its vapors or soluble compounds without any protection, is immediately noticeable: such people are said to be "mad as a hatter." Mad hatter syndrome is the traditional name for severe chronic mercury poisoning, as it was representatives of this profession who had to deal with wool treated with mercury nitrate to make it better and more durable. People noticed that hat makers often looked like madmen: they were betrayed by a strange convulsive gait, trembling hands (characterized by intentional tremor — the hand begins to shake widely at the moment when it is about to reach its goal, for example, to take something), shyness, stuttering, poor memory. Gradually, as the symptoms deepen, the person loses coherence and logic in speech, loses skills, loses memory, and ultimately — their own personality. Surprisingly, even these changes are to some extent reversible if, at an early stage, contact with mercury is stopped and treatment aimed at removing mercury from the body and restoring the impaired functions of brain cells is started. But still, only in rare cases does the victim fully recover from the consequences of severe mercury poisoning, manifested by hatter syndrome.

"Hatters", however, were not only hat makers. Mercury has always been a universal remedy for prospectors who mined gold, and for jewelers and everyone who dealt with gold, and for medieval alchemists who considered it one of the main primordial elements of all things and consumed it for their experiments literally by the bucketful, and for physicists and chemists of the New Age. Mercury has always been indispensable as an ideal electrical contact, as a shutter for moving any moving parts inside a sealed (for example, vacuumed) part of the installation, and as an ideal, almost frictionless, bearing, as a liquid for filling thermometers, manometers and barometers, for obtaining high vacuum, as an electrode in electrochemistry, as an always horizontal mirror in optics (and R. Wood invented a mercury telescope in which the surface of the mercury acquired the shape of an ideal paraboloid when rotated). Huge amounts of liquid mercury were used in lighthouses: the rotating lantern floated in a bath of mercury, which made it easy to rotate it, despite its huge mass, so lighthouse keepers were no less crazy than hatters.

It is not surprising that many scientists and inventors of the past suffered from the consequences of inhaling its vapors. Among them was Isaac Newton, who at some point in time was quite unsystematically repeating alchemical experiments (during which he heated and evaporated significant amounts of mercury), and then fell ill with a mental illness, which was most likely the result of mercury poisoning. Modern studies of Newton's hair have shown that the mercury content in them is extremely high, which indicates that he inhaled enough mercury throughout his life. However, Newton was lucky — he survived, remained a genius, and lived to be 84 years old. Moissan's student, the German inorganic chemist Alfred Stock, became practically the discoverer of chronic mercury poisoning, studying its course on himself and his colleagues, who were constantly fiddling with mercury vacuum pumps, manometers, and other mercury devices. On this material, he first obtained evidence of the harmful effects of mercury vapors on health, and then suffered for half his life from the consequences of his "games" with mercury. And Karen Wetterhahn, not so long ago, on August 14, 1996, accidentally dropped dimethylmercury on her glove (!), and was fatally poisoned by this compound. At the same time, she began to experience any symptoms of this poisoning only five months after this incident, and three weeks later she fell into a vegetative state from which she never recovered.

On dimethylmercury and mercury organics in general, I would like to dwell in more detail. All forms of mercury are poisonous, of course. Some are less poisonous, such as poorly soluble calomel, some are more so, such as mercury (II) salts and especially mercury vapors. But its organic compounds, such as methylmercury and dimethylmercury, are especially poisonous. The extreme toxicity of methylmercury and dimethylmercury is due to their highest ability to concentrate in brain tissue, easily penetrating the blood-brain barrier. Mercury-organic compounds are extremely chemically stable, and once in the World Ocean (and when mercury in any form enters the water, it is fairly quickly converted to methylmercury due to bacterial activity), they concentrate in food chains, which leads to the fact that people who consume a lot of fish and seafood are at risk of poisoning by them. This risk is especially high in the vicinity of industrial enterprises that have discharged mercury waste into the water in the past, or continue to do so at present. In 1956, a mass poisoning occurred in the vicinity of the Japanese city of Minamata, which had the character of a real epidemic. Mainly the sick were residents of fishing villages who fished in Minamata Bay and mainly fed on it. The disease began with loss of sensation in the hands and feet, impaired vision and hearing, and then the patient lost the ability to perform fine precise movements due to tremors, it became difficult for him to walk. Many of the sick then began to have epileptic seizures, they lost consciousness and never regained consciousness. The survivors were left permanently disabled.

But these are all poisonings that develop in people who encounter a sufficiently large amount of mercury. When acute or severe chronic poisoning occurs, in addition to neurological symptoms, signs of renal syndrome also appear, as well as characteristic changes in the gums and eyes, and sometimes characteristic lung damage. Symptoms of poisoning with small doses of mercury — and household poisonings are usually just that — are quite nonspecific. They can be mistaken for "age-related" symptoms, the consequences of excessive drinking, overwork at work, and in our time — for the result of staying up late playing video games.

Mercury is an amazing metal. It is the only metal that is not only liquid at room temperature but also gaseous. Mercury vapor consists of diatomic molecules, which are only positively charged and immersed in an electron gas, at least partially consisting of liquid mercury, which explains its surprisingly low melting point. Mercury is capable of evaporating even through a layer of water and especially oil, passing into the solution, then diffusing through its thickness and evaporating again from the surface. The equilibrium vapor pressure of mercury over its surface at room temperature is about a thousandth of a millimeter of mercury. It seems insignificant, but in fact, it is a lot, considering its toxicity - 12 mg per cubic meter. This is 1200 times higher than the maximum allowable concentration in the workplace and half a million times more than the maximum allowable concentration for residential buildings and city streets. Therefore, spilled mercury, even if it is a few drops, is always a time bomb laid under the health of people living in this place. Mercury evaporates slowly; it will take hundreds of years for a gram of mercury to completely evaporate. And all this time, a ball of mercury that has rolled under the baseboard, which has escaped from a broken thermometer, will be able to maintain a mercury concentration in a poorly ventilated room close to the one-time maximum allowable concentration of the working area or even exceed it. If this ball breaks into thousands of microscopic droplets, as usually happens, the evaporation surface increases many times, and the concentration of mercury vapor will increase tens or even hundreds of times. At the same time, the decisive factor is not the amount of mercury, but its dispersion: a whole puddle of mercury lying compactly can give a lower concentration than a drop that has scattered into many microscopic droplets when it falls.

Therefore, any, even the smallest, mercury spill requires special attention. The affected area must be thoroughly examined to identify and remove all visible mercury, and then treat the places where invisible mercury may be present with reagents that convert mercury into relatively safe compounds. The most effective of these are polysulfides, the so-called liver of sulfur, in combination with bleach. This combination is part of the standard demercurization agents used by the Ministry of Emergency Situations. Ferric chloride is also effective, which needs to be diluted to a concentration of 20% and used to treat contaminated surfaces (10 liters of solution is enough for 20–30 m²), and then washed off with water the next day, but it leaves indelible brown stains and causes severe corrosion of metal objects. After demercurization, its effectiveness should be checked by measuring the concentration of mercury in the air of the room, which has not been ventilated for 12 hours. The measurement is carried out using special devices based on the absorption of mercury vapor by the resonance line of mercury at 254 nm. For this, you can try to contact the Ministry of Emergency Situations or the nearest sanitary and epidemiological station, but often their employees have to wait a very long time. The services of private companies can be very expensive (hence, apparently, the ideas about "mercury toxicity - a money scam"). But health is more important.

Cadmium

Cadmium is a "brother" of mercury. And it is similar to mercury in that it is easily volatile. Not as easily as mercury. A cadmium ingot lying in your drawer will not poison you. But if you get the idea to melt this ingot — you will inhale the vapors.

Cadmium is almost as toxic as mercury, but still a little less. Its toxicity is versatile. If the effect of mercury, excluding very large amounts, is mainly localized in the central nervous system, in the brain, then cadmium also destroys bones, damages kidneys, and disrupts hematopoiesis. It does not forget to affect the nervous system as well, and in addition, it is a carcinogen.

In the field of mass cadmium poisoning, as in the case of mercury, the Japanese distinguished themselves. "Itai-Itai disease" - under this name cadmium poisoning became known in Japan. The mining of polymetallic ores in Toyama Prefecture continued from the beginning of the 20th century and caused the contamination of groundwater and water bodies with many heavy metals, but it was cadmium that caused mass poisoning because contaminated water was used to irrigate rice fields. And rice has a special ability to concentrate cadmium.

A characteristic feature of cadmium poisoning is the disruption of calcium-phosphorus metabolism, which results in bone destruction. Those affected by cadmium contamination suffered from severe pain in the bones, joints, especially in the spine. Because of this, the name appeared, which in Japanese means a cry of pain. Along with this, the kidneys were affected and renal failure developed, and the "shutdown" of enzymes responsible for iron metabolism and disruption of bone marrow cell division processes led to severe anemia. The reason for all these phenomena caused by cadmium is common. It binds very strongly to many functional groups of protein molecules - not only sulfhydryl (as all heavy metals do), but also carboxyl and amino groups, causing denaturation and inactivation of almost all functional proteins and enzymes.

Finding cadmium in the surrounding world is not that difficult. Nickel-cadmium batteries were not so long ago the most common type of batteries besides lead ones. In addition to them, cadmium is also contained in the silver electrodes of silver-zinc batteries. This should be noted by those who have "scavenged" these batteries somewhere and decided to extract silver from them. Another source of cadmium danger also threatens precious metal hunters: the "silver" contacts of relays and other switching devices are often made from a pressed mixture of powdered silver with cadmium oxide - such a composite has high resistance to burning in an electric arc and accelerates its quenching due to the evaporation of cadmium oxide. When such silver contacts are used, cadmium burns in the air and gives off toxic smoke.

You can encounter cadmium without even knowing it, soldering some old Soviet board with components - components that are afraid of overheating were often soldered using POSK50-18 solder, which contains 18% cadmium and has a melting point of 145°C. And it is quite unexpected to find cadmium... in a children's constructor. In the USSR, they liked to cadmium-plate fasteners and hardware. A characteristic, but not absolute sign of this is the golden-iridescent sheen of the surface.

Other sources of cadmium include photoresistors, in which cadmium sulfide, selenide, or telluride are semiconductors sensitive to light. Cadmium-mercury telluride is a well-known material with a unique ability to change the bandgap width from zero to 1.5 eV depending on the mercury content, which makes it possible to create infrared radiation photodetectors with a wavelength of about 10-12 microns, significantly more sensitive than bolometric detectors usually used in this range, but requiring mandatory cooling to cryogenic temperatures. However, the amount of cadmium in them is usually small.

Beryllium

Amazing metal. Light to the extent that its plate floats on water (beryllium density 1.85, but due to non-wettability, its plate is held on the surface by capillary forces), strong as steel, transparent even to the softest X-rays, and... terribly poisonous.

When Louis Vauquelin discovered beryllium, he named it "glycinium". Having the standard practice of chemists of that time to taste all substances, he tasted it too. Beryllium salts turned out to be sweet to the taste. For a long time, they worked with beryllium without fear. They started talking about its toxicity when its compounds began to be used in industry, in large volumes, and many people were exposed to it. For the first time, such conditions arose in the production of fluorescent lamps, in which zinc and beryllium silicate were used as phosphors. It was enough to cut oneself with glass - and there were always plenty of fragments in such production - literally traces of beryllium from the skin got into the blood, and severe poisoning occurred. Accidents stopped only after the abandonment of beryllium-containing phosphors in favor of safer and cheaper halophosphate ones.

But the use of beryllium in X-ray technology and nuclear physics, in aviation and space technology, electronics and precision mechanics continued. The metal turned out to be indispensable. And... people got sick. They suffered from a strange disease that affected the lungs, from which it was almost impossible to protect themselves with any dust respirators, any measures to reduce dust formation. Beryllium caused lung damage even in cases where its concentration in the air was below the detection threshold of analytical instruments. And the most surprising thing: when beryllium entered the body not with inhaled air, but by other means, it still primarily affected the lungs.

Beryllium, like many other toxic metals, has a high affinity for many enzymes including alkaline phosphatases, lactate dehydrogenase, etc., inactivating them and thereby disrupting the functioning of various tissues and organs. But the main direction of beryllium's action, apparently, is different — it is associated with the activation of the immune system, which becomes sensitized to beryllium, and then begins to attack its own tissues containing even the slightest traces of it.

Often, patients with berylliosis end up... with a phthisiatrician. Beryllium is adept at skillfully simulating the symptoms of tuberculosis, up to positive skin tuberculin tests — the immune system, agitated by beryllium, fiercely attacks any irritant, giving a characteristic reaction including to tuberculin. And only when the attempt to culture Koch's bacillus from such a patient fails, do doctors, unaware that the person had contact with beryllium, sometimes suspect that the case is more unusual than ordinary tuberculosis. And often they treat it as tuberculosis, sarcoidosis, emphysema caused by smoking. Without much success, of course.

Currently, acute beryllium poisoning is almost never encountered in production. But chronic cases, alas, are plentiful. An unpleasant feature of beryllium is its delayed action. One can develop beryllium disease even 15 or 20 years after the last contact with beryllium, and this contact can be a single one. Moreover, when it comes to small amounts of beryllium, the severity of the disease, its duration, and the speed of manifestation no longer depend on its dose. Apparently, berylliosis can develop from virtually any amount of beryllium that has entered the body at least once.

The consequence of beryllium exposure is also the development of malignant tumors in the lungs and other organs.

Encountering beryllium in electronics is quite simple. This is especially true for simple Soviet military... in general, all that old electronic junk that many radio amateurs love to collect and which collectors of KMok and "yellow" are eager for. The latter are at the greatest risk because components containing beryllium are usually rich in gold. These are various types of HF and UHF transistors, which this fraternity calls "helicopters" and "bolts". Between the semiconductor crystal and the metal heat sink, there is a washer made of beryllium oxide, which has high thermal conductivity comparable to that of copper, and at the same time reliably and with minimal parasitic capacitance isolates the crystal from the heat sink. And when such a transistor begins to be picked and broken, and even more so boiled in acids to extract gold crumbs from it, they inevitably come into contact with beryllium ceramics, its dust, and its dissolution products containing beryllium salts, including in the form of aerosols. Beryllium oxide is also found in domestic equipment in the form of ceramic plates, which are used to isolate transistors from radiators. Moreover, somewhere there is thermal paste, absolutely similar to the well-known KPT-8, with one exception: it contains beryllium oxide!

You have probably seen metallic beryllium if you have dealt with X-ray tubes, especially those designed to obtain characteristic radiation (for example, X-ray structural tubes of the BSV type) and various soft X-ray detectors (Geiger counters, gas proportional counters, scintillation crystals, and semiconductor detectors). In a number of aviation gyroscopic compasses, a very precisely manufactured hollow sphere made of beryllium is used as the working body (rotor).

Even household appliances have been penetrated by beryllium — it is used to make diaphragms for the highest quality high- (and sometimes mid-) frequency dynamic heads of Hi-End acoustics, which allows reducing the mass of the moving system several times while maintaining the unparalleled rigidity of the dome. The speed of sound in beryllium is the highest among all metals and is 12 km/s, so the dome of the beryllium tweeter oscillates as a whole at all frequencies of the sound range, "driving" the dome resonances above the audible frequencies and making the frequency response within the sound range smooth, devoid of the characteristic jaggedness of speakers starting from a certain frequency, where the piston mode of the diffuser is replaced by the emission of sound by a bending wave propagating along the diffuser.

There is also beryllium bronze, from which springs of watch balances, stretch marks in pointer measuring heads, contacts in relays, switches and connectors are made, and... in huge editions at the end of the USSR and in the early post-Soviet years, chains, rings and various other jewelry "under gold" were made. Beryllium bronze is very similar in appearance to 585 gold and never tarnishes. The impact of beryllium on the health of those who made these products, not to mention those who wore them, was not thought about. However, due to the high chemical resistance of beryllium bronze and its low beryllium content, the danger to those who wore such products is rather hypothetical.

Completely exotic is triglycine fluoroberyllate, a ferroelectric and nonlinear optical material that promised a lot at one time, but soluble in water, even hygroscopic, which can theoretically be found in some experimental device as a space-time light modulator, an optical memory element, a pyroelectric infrared receiver, and the like.

The basic rules for handling beryllium in any form, if it gets into your hands, are not to touch it with your hands and not to do anything with it that could cause it to become dust or dissolve. By the way, beryllium oxide dissolves, albeit slowly, even in organic acids, so you should not take beryllium ceramics and metallic beryllium in your hands. You should also not try to drill, grind, break, or split them at home. The same, but in a milder form, applies to beryllium bronze. And you should not create deposits of beryllium-containing devices at home.

Regarding the latter, the following fact is indicative. My former boss, being a thrifty person, collected old X-ray tubes from all over the institute — BS, BSV types, Japanese ones... in general, wherever he found them. Why — no one but him knew, most of these tubes were dead. The tubes ended up filling two cabinets. And one fine day, occupational safety learned about this collection. An air analysis for beryllium was conducted, and beryllium was found in the air. With an excess of the maximum allowable concentration in the working area — small, but confident.

A few words about what beryllium and beryllium oxide ceramics look like. Beryllium is a gray, rather nondescript metal. In commercial products, it is sometimes subjected to color anodizing. The ceramics have a usual white or slightly grayish color. If you see pink ceramics, it is definitely not it, contrary to the common misconception that pink ceramics are beryllium.

There is an opinion that beryllium oxide powder was poured inside the metal cases of some transistors. Apparently, this is nothing more than a legend — this powder is most likely aerosil, which absorbs moisture and gases released during the sealing of the case, and also prevents metal splashes from getting on the crystal during welding.

Thallium — Agatha Christie's favorite poison

In my childhood, when I was 12 years old, I got my hands on a scintillation crystal from some kind of radiometric device. My mother's colleague, a geophysicist, saw me with it. The crystal was immediately and deftly taken from my hands, and I was given a preventive conversation in which thallium poisoning was described in detail and vividly. After that, to my surprise, the crystal was returned to me under a sworn promise that I would never disassemble or break it. He also gave me from his supplies something to which this crystal could be attached - a PMT-85 and a socket for it with a voltage divider soldered on its petals, and from memory, he drew a diagram of a simple converter for obtaining high voltage. Not so long ago, I found this sheet in old papers, but the design itself, based on a six-digit frequency meter on 176 series microcircuits, which I had previously assembled from a radio constructor, remained in the Kolyma village with the romantic name Dukat. But, however, I digressed. I still did not get poisoned with thallium then. And I was unlikely to be poisoned.

Thallium firmly took its place... in the criminal chronicle. For a long time, its main use was as a poison - for ants and rats. Thallium turned out to be the perfect murder weapon. Because the lethal dose of thallium salts is almost impossible to taste, because there is a noticeable time between poisoning and the onset of the first symptoms (from 12 to 24 hours), because the initial symptoms of this poisoning can resemble anything - from the flu to osteochondrosis, and before the characteristic thallium poisoning alopecia, the fatally poisoned person usually does not survive. Because thallium could only be found in the victim's blood in the past when the killer overdid it. And besides, thallium was easy to get.

In our country, where household poisons containing thallium were not available for sale, the typical source of thallium for murders and suicides was Clerici solution. This very heavy liquid, a solution of thallium malonate and formate with a density of up to 5 g/cm³, was widely used by geologists to determine the density of minerals — it was diluted to the point where the mineral being determined neither floated nor sank in it, and then its density was measured using a pycnometer — a measuring flask of precisely known volume, or — more roughly — simply by pouring it into a graduated cylinder and weighing it. Finding a few drops of such a liquid (especially already diluted) from acquaintances was usually not difficult.

Well, enough about murders. The symptoms of thallium poisoning are known to anyone who has read Agatha Christie. First, the stomach begins to hurt—12 to 24 hours later. Then come signs of nervous system damage—initially peripheral (pain at the fingertips, joint and bone aches, and other symptoms of thallium polyneuropathy, which are very similar to the onset of the flu), followed by central nervous system damage—seizures, epileptic attacks, ataxia, blindness, and altered consciousness, up to a comatose state. If the patient survives, their hair will fall out in a week or two (sometimes hair loss is the first symptom, which indicates mild poisoning). And then... for years, the person remains almost entirely without immunity. A kind of “chemical AIDS,” as it was once called. Reproductive function is also irreversibly affected. Thallium, like lead and mercury, easily accumulates in the body, and even very small doses over time lead to chronic poisoning. In this sense, it is an unremarkable heavy metal, with the difference being that it enters cells through the same pathways as potassium, significantly increasing its toxicity.

Where can you find thallium in electronics? There aren’t many such places: gamma-ray detectors based on scintillator crystals NaI(Tl) and CsI(Tl), as well as gas-discharge lamps—metal-halide and ultraviolet erythemal lamps for tanning. In scintillators, there is very little thallium—you’re more likely to get poisoned by iodine than thallium—but in metal-halide lamps, there is about as much thallium as mercury. And in tanning lamps, possibly even more. Enthusiasts of the unusual might stumble upon a detector for the mid-IR range, which, in addition to cadmium, mercury, and tellurium, also contains thallium—in the IR-transparent window made of KRS-6.

Arsenic and Antimony

I remember a newspaper headline from the heyday of the yellow press: “Mad Scientist Recreates Ancient Poison.” The headline promised that ancient evil, unleashed by this madman, would soon start wreaking havoc among Russians. The article, however, discussed the identification of the poison used to kill a courtier during the Romanov era. And that poison, of course, was arsenic.

Arsenic acts similarly to heavy metals. The same affinity for sulfur-containing amino acids, the same inactivation of enzymes. And the same neurotoxicity. The difference, due to the fact that arsenic is still a non-metal, is its tendency to form arsine and organic arsenic compounds. If the first is extremely poisonous, then some organoarsenic compounds (for example, arsenocholine) are much less toxic than elemental or white arsenic (arsenic trioxide). Cells try to use arsenic instead of phosphorus. It turns out badly.

Arsine, arsenic hydride, is the strongest poison, almost odorless even at a concentration that can kill in half an hour. It is formed when metals containing arsenic impurities are dissolved in acids, when ferrosilicon decomposes with water (again, arsenic impurities).

Antimony, according to Hasek, became known after "by morning all forty monks died in terrible agony": the abbot of the Stalhausen Monastery in Bavaria discovered this element as a result of alchemical experiments and, finding that pigs fatten from it, decided to fatten his thin monks as well. This, of course, is a legend, but people have known about the toxicity of antimony for almost as long as about antimony itself.

Antimony is very similar to arsenic, but on the one hand, it is somewhat less toxic with a single dose (especially when taken orally due to the strong tendency of antimony salts to hydrolyze), on the other hand, it even more resembles heavy metals in its action than arsenic, having a much greater tendency to accumulate in the body in small doses. As a result of their action, purulent-inflammatory lesions of the skin occur, the lungs and respiratory tract, liver, kidneys and gastrointestinal tract are affected, and sexual function is suppressed. Almost all organs suffer. And, like arsenic, antimony forms gaseous stibine, the toxicity of which exceeds all other antimony compounds.

In electronics, arsenic is used almost exclusively in the composition of A^IIIB^V semiconductors, such as gallium arsenide. In electronic components, the amount of arsenic is so negligible that normal people need not fear it, but gold prospectors are still at risk: when dissolved in acids, arsenic will inevitably turn into arsine. Antimony is present almost exclusively as an additive in solder, increasing its mechanical strength, and in negligible amounts as a doping additive in semiconductors and an activator in phosphors.

Selenium and Tellurium

The word "selenium" usually evokes two associations: selenium rectifiers and selenium dietary supplements, which are beneficial to health. Few people think about the toxicity of selenium, yet it is no less poisonous than arsenic. Selenium poisoning generally resembles arsenic poisoning. A characteristic feature of its course is the characteristic foul odor emanating from the victim's body, hair loss, and nail destruction, due to selenium competing with sulfur and disrupting the synthesis of sulfur-containing amino acids and, consequently, keratin, which is rich in them. Yes, there is also a benefit: microscopic doses of selenium are necessary for humans. However, cases of real selenium deficiency are few and far between, and the benefits of all these supplements for ordinary people are highly questionable. Selenium is primarily dangerous in the form of oxide, selenious and selenic acids, and soluble selenites and selenates. Elemental selenium is toxic only in the form of dust.

What is selenium in electronics and technology? Of course, selenium rectifiers are deep retro, but it is easy to encounter such a rectifier. When it fails, very poisonous smoke is produced, and in an old receiver, machine, battery charger, or other device with a selenium rectifier, everything can be covered with a poisonous deposit from this smoke if the selenium column previously failed in it. A qualitative reaction to selenium: place the suspicious deposit in a test tube with a drop of concentrated sulfuric acid and heat. If selenium is present, a green coloration appears.

Selenium is the basis of the photoreceptor drum coating in copiers and laser printers, as well as the information-carrying layer in rewritable optical discs.

Tellurium is less toxic than selenium. This is because, on the one hand, it is not capable of entering into the same biochemical reactions as sulfur, and on the other hand, once in the body, its compounds are immediately reduced to elemental tellurium. Often the consequence of tellurium poisoning, even in large doses, is one, but extremely unpleasant: the smell. Tellurium, reduced to elemental, is very slowly further reduced to volatile organic tellurium compounds and very unstable tellurium hydride, and these compounds have a disgusting smell, somewhere between garlic and rot. Nevertheless, with chronic intake of tellurium compounds into the body, especially through the respiratory organs, a complex of symptoms develops, including nausea, dryness of the skin and mucous membranes, weight loss, bronchitis, and the aforementioned nauseating smell emanating from the patient. This smell persists for months and years. In the old days, chemists poisoned with tellurium were evicted from Moscow.

Finding tellurium in electronics is much more difficult than selenium. These are mainly materials for far-infrared photodetectors - narrow-band semiconductors with a band gap width adjustable to zero. First of all, this is cadmium-mercury telluride. Lead-tin telluride is another similar narrow-band semiconductor that has not found significant application, although it was considered a promising far-infrared photodetector to replace cadmium-mercury telluride.

Less toxic, sometimes useful: copper, manganese, nickel, cobalt, and others.

Most people are more or less aware of the toxicity of lead. But the fact that handling a copper ingot without gloves is also generally not useful is rarely considered.

Copper belongs to those elements that are required for life in small quantities. Copper is the most important trace element, and if at least a milligram (or better 2-5 mg) of copper does not enter the body every day, its deficiency will develop, accompanied by fatigue, anemia, hair loss, and brain dysfunction. But copper deficiency is rare these days - it mainly occurs in patients who do not eat on their own and receive nutritional mixtures intravenously. But an excess of copper happens often. It is enough to accidentally take a few hundred milligrams of copper sulfate to cause acute copper poisoning, and if you swallow 2-3 grams, they will most likely kill you. And such a small amount as 10 mg (I remind you, this is only 2-5 times the daily requirement), taken every day, will eventually lead to copper accumulation and chronic poisoning. Stone carvers working with malachite, electricians, air conditioner installers, railway contact network repairmen, sculptors, and foundry workers often suffer from chronic copper poisoning if they do not use gloves and a respirator when working with copper and its alloys. The liver and kidneys mainly suffer from this poisoning, but in the end, almost the entire body is affected. Prolonged contact with copper, for example, wearing a copper bracelet (at one time it was fashionable, supposedly good for health) leads to skin discoloration with subsequent development of dermatitis.

Zinc is similar in this sense to copper, only the need for it is tens of times greater. Therefore, it is almost impossible for zinc to accumulate, and zinc poisoning is always acute. Most often, zinc poisoning occurs during casting - inhalation of zinc oxide aerosol formed during the combustion of zinc vapors leads to the so-called foundry fever. And sometimes the source of poisoning is well water raised by a galvanized bucket. Radio amateurs are mainly poisoned by zinc when soldering aluminum with HTS-2000 solder or similar, which is almost pure zinc. However, the toxicity of technical zinc is mainly determined not by the zinc itself, but by the impurities of cadmium and arsenic in it. The latter creates a danger of poisoning when preparing the so-called soldering acid on their own, since arsenic is released in its most dangerous form, in the form of arsine.

Cobalt and nickel are found in the practice of an electronics engineer in the form of coatings and components of special alloys. Poisoning with them in this state is extremely unlikely (although prolonged contact with the skin of nickel alloys often causes allergic dermatitis). It is only necessary to avoid dust during mechanical processing. Soluble compounds of these elements are highly toxic, carcinogenic, cause allergic reactions, and should be handled with extreme caution (for example, when applying electroplated coatings).

Manganese is also a metal without which there is no life. The need for manganese is the same as for copper, a few milligrams per day. With chronic or acute intake of a larger amount, manganese primarily causes manifestations of neurotoxicity - the so-called manganese encephalopathy. Its symptoms resemble Parkinson's disease and it is practically untreatable. Welders, forced to inhale smoke containing manganese mainly in the form of oxides, and drug addicts are particularly susceptible to this disease. Manganese is found in large quantities inside ordinary batteries, but in a very poorly soluble and therefore low-toxic form. But the well-known potassium permanganate, as well as soluble manganese salts - sulfate, chloride, etc. - with relatively low acute toxicity are very dangerous due to the long-term consequences of their entry into the body. In addition to brain damage, it also causes infertility.

Exotic: Gallium, Indium.

Indium and gallium are metals that few have seen in person, but we all hold them in our hands every day. Gallium is part of gallium arsenide and gallium nitride - semiconductors that are in almost every second, if not first, electronic device. And the mixed indium-tin-zinc oxide forms transparent conductive films, without which no liquid crystal or AMOLED screen can do.

Information on the toxicity of these elements is contradictory. Somewhere they are called low-toxic, and somewhere they are attributed toxicity at the level of mercury. But gradually accumulating data suggests that these elements should not be taken lightly. Thus, in the production of LCD displays, a professional disease "indium lung" is known - inflammatory-fibrotic changes in the lungs, accompanied by coughing, progressive impairment of gas exchange in the lungs, and the release of bloody mucus. The prognosis for the disease is very poor, most of the patients die. All this is very reminiscent of berylliosis, and it is quite likely that the situation with toxicity is approximately the same as with beryllium: there may be no safe levels of its content and intake into the body. After the discovery of "indium lungs" in Japan, the MAC of indium compounds was set at a very low level: 300 ng/m³, and this is in the air of the working area (for comparison, a similar MAC is set for mercury in the residential area). Indium-organic compounds are known to be extremely toxic. Small amounts of them can be formed when soldering with indium solders or pure indium when interacting with flux, which should be taken into account.

Gallium, according to some reports, also has toxicity comparable to the toxicity of mercury when administered parenterally, however, when administered per os, its toxicity is reduced by low bioavailability due to the hydrolysis of salts. In dust form, gallium compounds, entering the body, affect the lungs, immune system, and kidneys. Metallic gallium has the ability to easily oxidize in air and easily passes into a soluble state when in contact with skin secretions, and at the same time it is strongly "smeared" in molten form, so contact of gallium with the skin is dangerous. Gallium is a mutagen, but there is no evidence that it is a carcinogen.

Thus, when using gallium-indium alloys (so-called "liquid metal", used as a thermal interface and filler in thermometers, including medical ones) and indium-containing solders, special precautions should be taken, despite the fact that their labels will say "non-toxic" and "lead-free". At the same time, unlike mercury, there is no danger of exposure to the vapors of these metals -- they can be considered absolutely non-volatile (excluding the possibility of the formation of volatile indium and gallium organic compounds).

Gallium in its pure form is not particularly used in electronics, but it is a component of "liquid metal", a thermal interface with particularly high thermal conductivity compared to traditional thermal pastes, which, in addition to gallium, also includes indium and tin. Indium, in the form of a special low-temperature solder, is used in selective soldering, for example, for inter-board connections (for example, the well-known "sandwich" of two boards and a frame with contact pads on both sides in Apple smartphones). When tuning microwave devices, indium foil is used, utilizing its ability to weld to a metal surface at room temperature -- it only needs to be pressed hard. Indium foil is also sometimes used as a thermal interface, filling the gap between a powerful transistor or microcircuit and a radiator -- here its extreme softness, similar to plasticine, is used, as well as for sealing gaskets. The softness of indium is also used when it is necessary to solder something fragile with a sharply different CTE - the plasticity of indium sharply limits the load on the fragile crystal (soldering the heat spreader lid to processor crystals, mounting laser arrays). Another application of this property is the coating of contact pads on hard drive boards, to which needle-like mating contacts protruding from the hermetic case are pressed, for example, in old IBM/Hitachi hard drives. Finally, in old germanium pnp transistors and diodes, indium in the form of droplets was fused into the germanium crystal, forming p-conductivity regions.

Halogens and Halogen-Organic Compounds

Fluorine is all-destroying and all-destructive in its elemental form (even water burns in a fluorine environment!), it remains very toxic in the form of most salts — fluorides, and actually hydrofluoric acid — hydrogen fluoride. The fluoride ion firmly binds ions of such metals as calcium and iron, disrupting many processes in the body: from cellular respiration to nerve impulse transmission. Fluorides and hydrofluoric acid, once on the skin, quickly and deeply penetrate the skin, causing severe painful burns, and then are absorbed, causing general poisoning over a large area of damage, which often leaves no chance of saving a person even at the moment when they have not yet shown any symptoms.

At the same time, a small amount of fluorine is necessary for the formation of teeth, the inorganic part of the tissue of which consists of the mineral fluorapatite, which, unlike hydroxyapatite, which bones are made of, is much more chemically stable.

On the contrary, many hydrocarbons in which all hydrogen atoms are replaced by fluorine are very inert and biologically neutral compounds. A typical example of such a substance is polytetrafluoroethylene — fluoroplastic-4 or teflon-4. For its chemical resistance, it was nicknamed "organic platinum" — at room temperature, it is affected only by alkali metals. The same properties are possessed by a number of low-molecular-weight fully fluorinated hydrocarbons, as well as sulfur hexafluoride — SF6. But the products of their thermal decomposition contain a number of extremely toxic compounds, including molecular fluorine, which is somehow formed under these conditions! This should be remembered when using fluoroplastic film, the still popular MGTFE type wire, or coaxial cables with fluoroplastic insulation: they are thermally resistant enough not to melt with a soldering iron, but you can easily repeat Davy's feat if you overestimate the thermal resistance of the teflon film and heat it to 400 degrees Celsius or higher. It is unacceptable to use "burners" to remove insulation from MGTFE type wire without very good ventilation.

Chlorine is not as unconditionally poisonous as fluorine if it is not in a free state (in which it was used as a chemical warfare agent): sodium and potassium chlorides are essential vital components of the body's internal environment. Therefore, their toxicity can only be discussed with a large degree of conditionality. Sodium chloride can be "poisoned" in much the same way as water can be "poisoned". The body's homeostasis maintains a certain concentration of sodium chloride in the blood and tissue fluids — 0.9%, and the simultaneous intake of a large amount of salt causes compensatory phenomena aimed at maintaining this concentration at any cost. And the price of this with excessive salt consumption is an increase in blood pressure, edema, and stress on the kidneys in people who have problems with these organs. But hypochlorites, chlorates, and perchlorates are poisonous. Their toxicity, however, is not due to chlorine, but... oxygen. Its separation from these compounds occurs with the release of energy, and also in an atomic form. Atomic oxygen is extremely active and destroys any organic substance, thereby killing living organisms.

Chlorine in organic compounds in many (though not all) cases turns them into poisons. In each individual case, the reason for this is different. In some, the chlorine atom is easily detached from the organic molecule under the action of water, forming caustic hydrochloric acid - this is how various types of "tear gases" such as chloroacetophenone act, causing unbearable irritation of the mucous membranes of the eyes and respiratory tract, and at high concentrations - and the skin. Other compounds are able to donate a chlorine atom to other molecules, thereby damaging nucleic acid molecules and causing carcinogenic effects. Still others dissolve in the membranes of nerve cells, disrupting the processes of nerve impulse transmission. The mechanism of toxic action of many organochlorine compounds is unknown. Many of them tend to accumulate in the body, dissolving in lipids, penetrating through the respiratory organs and skin. Organochlorine compounds also include some of the most dangerous environmental pollutants - dioxins, effectively combining the ability of polyaromatic hydrocarbons to interfere with DNA synthesis processes, causing failures in them, and chlorinating activity.

Electronics engineers should remember the toxicity and harmfulness of organochlorine compounds when dealing with solvents containing methylene chloride, chloroform, carbon tetrachloride. Methylene chloride, for example, is a typical component of aerosol flux residue remover. Burning polyvinyl chloride insulation produces a whole range of volatile organochlorine compounds, including the infamous dioxins. It is reasonable to abandon this method of wire stripping at home.

And it is impossible not to mention polychlorinated biphenyls in connection with the fact that they are widely used in electrical engineering as components of insulating oils. A number of paper capacitors designed to operate in power circuits contain PCBs as an impregnation liquid. Among them, in addition to specifically industrial products designed to correct the power factor or accumulate energy in laser power supplies, there are also quite small parts. For example, LSE-type capacitors for fluorescent lamps produced in the USSR, and their counterparts produced in Czechoslovakia in characteristic cylindrical cases, reminiscent of large electrolytic capacitors. Such capacitors fully deserve the title "What should not be touched with hands", along with radioactive artifacts: the tightness of their cases after 50 years of operation and being in landfills most often leaves much to be desired.

Bromine... In its simple form, it is one of the scariest things you can hold in your hands. Bromine is always handled with fear. Bromine spilled on a glove destroys it in a few seconds, and when it gets on the skin, it almost instantly causes a deep, crippling burn, accompanied by necrosis of the skin, muscles, and sometimes even tendons and bones. And it is not easy not to spill it: it is very fluid. Bromine vapors are toxic, similar to gaseous chlorine, causing coughing, choking, inflammation of the respiratory tract at low concentrations, and at high concentrations, pulmonary edema and death.

And in the form of salts, bromides, bromine is just poison. There is no benefit to the body from bromine — only harm. Competing with chlorine, but "not getting through" the channels in the membranes, it disrupts the salt balance in the cells, which primarily affects the neurons, making their work and transmission of nerve impulses difficult. This is also the basis of the action of bromide salts as a cheap medicine for calming nervous and violent people. However, the consequences of long-term use of bromides are extremely negative: bromine, penetrating into the membranes of neurons, irreversibly damages them, which leads to a syndrome known as bromism. A couple of years ago on tekkix there was a good article about bromides and bromism, so I give the floor to its author.

And organic bromine compounds in their mass are poisons, carcinogens and... some of them are excellent flame retardants (substances that prevent combustion). In connection with which they are regularly present in plastics, wire insulation, electrical varnishes, cases of electronic components. Mainly old ones. Currently, the bromine content in them is strictly limited, however, alas, not in all countries. However, this is mainly important when electronics release "magic smoke" or when they end up in a landfill and from there — into a waste incinerator. It is difficult to get poisoned by plastic with flame retardants without gnawing on wire insulation for breakfast, lunch, and dinner.

There is nothing much to write about iodine. On the one hand, it is an essential trace element, on the other hand, of course, it is a poison, and it is quite easy to get poisoned by it in everyday life, especially by abusing the drawing of "iodine grids" on oneself and others, but what does this have to do with electronics? The only near-electronic component containing a significant amount of iodine is scintillation crystals based on NaI and CsI for gamma radiation detectors. And there is also a danger of iodine entering the body during the silvering process using iodide electrolyte. It is quite difficult to get acutely poisoned by iodine unless you drink undiluted iodine tincture or inhale vapors of iodine heated to over a hundred degrees, but for chronic poisoning, it is enough to receive half a milligram every day. In the body, iodine very actively changes forms, existing in the form of elemental iodine, iodide ion, and in the form of various iodorganic substances, which causes less diversity in the manifestations of iodine toxicity from its different forms compared to chlorine and bromine. Mainly, it overloads the thyroid gland, causing it to produce an excess of thyroid hormones, and high concentrations of elemental iodine have a cauterizing effect, killing the tissues in contact with it.

Lithium is another psychiatric poison along with bromine

At the beginning of the 20th century, the serious toxicity of lithium (as well as bromides) was not suspected. Robert Wood used a pinch of lithium chloride — "a completely safe substance, similar to ordinary salt in appearance and taste" (V. Seabrook), to "mark" leftovers in the student canteen, wanting to expose dishonest cooks. But as lithium began to be widely used in psychiatry (it perfectly curbs mania), it became clear: this metal is not so harmless. Its effect during long-term treatment affects the CNS, causing long-lasting symptoms — tremor, difficulty walking and balancing, drowsiness, and the kidneys, up to their complete failure, and the hormonal system, causing a decrease in the production of many hormones, and can even lead to sudden cardiac arrest. Lithium is a teratogen, when it enters the body during the formation of the fetus, it leads to severe deformities, and when used in the second half of pregnancy, it can cause low muscle tone and delayed mental development in the child. The reason for such diverse toxicity of lithium is that it easily penetrates both sodium and potassium channels, disrupting the entire homeostasis system "sodium-potassium-calcium". Such a versatile villain — no wonder it's the third number in the Mendeleev table. On the other hand, lithium's neighbor in the cell is beryllium.

Professional lithium poisoning is rare, as microdoses of lithium apparently do not cause poisoning and do not accumulate. Nevertheless, the MAC of lithium is set at the level of lead, as no one can guarantee that small doses still cause mild forms of poisoning, which, as in the case of lead and mercury, are mistaken for early "age-related" conditions.

Where can you get poisoned by lithium without taking it as a medicine? First of all, by dealing with batteries. And not just lithium-ion ones. Some amount of lithium hydroxide is usually added to the electrolyte of all alkaline batteries to increase its conductivity (the mobility of lithium ions is much higher than that of sodium or potassium). And the second source is... lubricants. The name "lithol" actually comes from lithium: its water-insoluble salts with fatty acids are used to thicken grease. When dealing with lithol, you should protect your skin from contact and avoid it.

Elemental lithium itself, in the form of a metal or a compound with graphite, causes severe burns when it comes into contact with moist skin. Remember this if you suddenly feel like disassembling a lithium battery or accumulator. The smoke from a burning lithium-ion battery is highly toxic mainly due to the aerosol of lithium oxide, inhalation of which causes severe burns to the respiratory tract, and then lithium intoxication, which is especially dangerous against the background of electrolyte imbalance characteristic of burn disease.

Precious poisons

Silver is known for its bactericidal properties, but rarely do people think about the fact that it is toxic to humans as well. Silver poisoning in humans is rare because soluble silver compounds precipitate to poorly soluble chloride and then are easily reduced to metal, and the metal itself is very inactive and noble, does not corrode, and does not dissolve in significant amounts in the absence of oxidizing acids - concentrated nitric and sulfuric acids. However, with prolonged intake of soluble silver or its dust into the body, a disease called argyria develops. It is characterized by the appearance of dark pigmentation of the skin and mucous membranes, as well as the eye membranes. The cause of pigmentation is the formation of finely dispersed silver and its sulfide, as well as the activation of protective mechanisms in the pigment cells of the skin, causing them to produce melanin. But argyria is not just a cosmetic problem: the accumulation of silver granules is also observed in the tissues of the kidneys, bone marrow, negatively affecting their functions (cases of agranulocytosis associated with the intake of large doses of silver have been noted), and others. The accumulation of silver in the transparent media of the eye leads to impaired vision, especially twilight vision.

Solutions of silver salts (primarily nitrate) have a sharply pronounced cauterizing effect on the skin and mucous membranes, so they, like solid soluble salts, should be handled with extreme care, using protective goggles and gloves. Ingestion of such substances leads to severe burns of internal organs, comparable to the result of swallowing mineral acids.

In the practice of a radio amateur or radio engineer, silver poses a threat only in the form of salts used in silvering, silver burning, etc. Metallic silver, as I mentioned above, is safe. Even when melted, it is not volatile enough to be toxicologically significant, and contact with the skin or even ingestion of its dust and shavings will not lead to significant absorption.

As a metal, gold is undoubtedly safe for the same reason as silver. Gold is exceptionally inert, and there are no conditions in the environment or within the body for metallic gold to dissolve into a noticeable concentration. However, in the form of salts, gold is significantly more dangerous than silver. Its toxicity and ability to accumulate are comparable to mercury, but the main target organs are not the nervous system, but the bone marrow, kidneys, and lymphatic system, as well as all organs containing constantly renewing cell masses. Gold is a general cellular poison that disrupts many processes in the cell, including reading the cell's genetic code, protein synthesis, and cell division. Gold suppresses the functioning of phagocytes, immune system cells that consume all foreign and unsuitable matter, making the body defenseless against infections.

However, we usually do not deal with gold salts — we do not play on the field of refiners. The situation is different with platinum metals. No printed circuit board with metallized holes can be made without palladium deposition. The independent production of such boards poses a serious health hazard: palladium (like other platinum metals) readily binds to DNA molecules, cross-linking their individual strands, making it a strong mutagen and carcinogen. Essentially, it is another poison without a safe dose, because any palladium atom that enters a cell will eventually settle on a DNA molecule, contributing to the likelihood of cancer or defects in offspring.

In elemental form, platinum metals, except for osmium, are absolutely safe, so there is no need to take any special precautions when handling electronic components containing them. However, it should be noted that all refining actions with them are not only illegal but also dangerous due to the formation of their soluble compounds, which can enter the body in microquantities and significantly shorten life expectancy.

The situation with osmium is special, and I will dwell on osmium in more detail.

Osmium among platinum metals is unique in that it oxidizes in air at room temperature to form volatile tetroxide. True, to a noticeable extent this occurs only with finely divided osmium black, but even compact metal slightly smells of osmium tetroxide. This is surprising also because osmium is the only platinum metal that does not dissolve in aqua regia at all.

And osmium tetroxide is a powerful poison. Even in very low concentrations, it first strongly irritates the eyes, simultaneously coloring the cornea black, and then causes pulmonary edema. In terms of oxidative ability, osmium tetroxide is second only to fluorine and ozone. It instantly turns a cell into a kind of scarecrow, cross-linking lipids of cell membranes and protein molecules, fixing the cell's structure in life, and at the same time "coloring" it with heavy osmium, which intensely absorbs the electron beam. It will do the same to your cells if you do not take special precautions.

But the chances of encountering osmium are slim if you are not a biologist. Osmium is used very limitedly, as its global production is about 250 kg per year. As it was written in some book on organic synthesis, "due to the toxicity and high cost of osmium tetroxide, it is used only in exceptional cases," and this generally applies to any use of osmium.

Speaking of high cost: the price of osmium is greatly exaggerated by popular rumor and the media. It is often possible to come across phrases about "the most expensive metal, which can only compete in price with californium," or to see specific figures from 10,000$ to 200,000$ and higher per gram. Meanwhile, according to the GOKHRAN of the Russian Federation, the price at the moment is 1$2.68 per gram. And the mentioned prices are characteristic of financial manipulations with the isotope osmium-187 at the turn of the "noughties" and "tens" years. The "promising" isotope, which almost surpassed "red mercury," turned out to be unnecessary for anyone except mass spectrometrists, and this bubble has long since burst, but those figures still wander from source to source.

***

This article cannot be considered an exhaustive review of the toxic properties of electronic components. I have overlooked rare earth elements, uranium and thorium, germanium, vanadium. I did not pay attention to the toxicity of precursors used in microelectronics to obtain ultra-pure silicon and CVD films. I did not mention organotin compounds, epoxy resins, formaldehyde, solder flux components, and much more. The article has already grown to a frightening size. Therefore, it is necessary to stop.

The conclusion from the above should be that safety in our business is of paramount importance. Without knowing the ford, it is necessary to venture into the unknown very carefully, having previously studied the question "what could be here" and protected oneself with personal protective equipment.