THE FOLLOWING ARTICLE APPEARED IN THE

JUNE 1997 ISSUE

THE POISON SLEUTHS

POISONING BY SILVER

-Dr. Anil Aggrawal

"Good morning doctor. Oh, my God, what are you doing today? Oh well, today you are examining an old man. What happened to him? His body appears to be grayish blue all over. Please explain"

"Good morning Tarun. The name of this person is Pyarelal, and he is 65 years old. He can not do much work now, and is mainly dependent on his son and daughter-in-law for his day-to-day needs. He however has a good bank balance which represents his life long savings. During his life time he had worked in relatively respectable positions."

"So why is he with you today?"

"Tarun, this makes an interesting story. He was quite unwanted by his son and daughter-in-law. His son is working in a private firm as an executive and his daughter-in-law is a chemist. For a few days he has discovered a grayish blue discoloration of his body, especially over the exposed parts of his body, and he contacted a local physician for this. He also complained of some tiredness, but besides this, he was alright. The local physician could not make much of his problem, so referred him to a specialist, and in turn this specialist referred this case to me."

"But you are a forensic medicine man. As far as I know, you deal with criminal cases only. How can you be helpful in this case?"

"You are right Tarun. I am a specialist in forensic medicine, and these specialists look at cases-live or dead- which are involved legally in some way. Well it goes like this. This specialist friend of mine thought that somebody might be trying to poison him slowly, and he consulted me on phone. When I had a look at this man, I thought he may be right. I enquired about his family life from Pyarelal and after talking to him for sometime, I became all the more convinced that it could indeed be a case of poisoning....."

"Do you mean to say that a man who develops bluish gray discoloration of his skin is getting slowly poisoned?"

"Not necessarily. There are other causes for this too, but my specialist friend had exhausted all those causes by various tests. Now only one possibility remained; slow poisoning by silver, a condition technically known as argyria, and that's why he referred this case to me. As you know, all cases of poisonings have some legality involved, so they are dealt with by forensic specialists. Before you start feeling uncomfortable with the word argyria, I must tell you that it comes from the Latin word for silver argentum. The chemical symbol Ag for silver has also come from the same Latin word. This condition was first described in 1816 by Johann Abraham Albers."

"So you decided Pyarelal was being poisoned. But by whom? and how?"

"Probably by his son or his daughter-in-law on whom he was a burden. They had an eye over his money too. Probably some silver salt was being mixed in his food. This rare and exotic poison was probably chosen because it is a relatively unknown poison, and it was probably thought by the culprits that doctors would find it impossible to detect it. But as you can see in a moment they had underestimated the capabilities of modern poison sleuths, who have an impressive array of facilities at their disposal. I asked him not to consume one day's food given to him by his daughter-in-law and instead submit it to me. He has done that today and I have submitted it to the lab for chemical analysis. While the test reports are awaited, let me tell you something about this rare but interesting poison."

"Oh, sure I would love to know about it. In fact I didn't even know silver was a poison"

"Well, in metallic form, it indeed is not. It is the chemical salts which are poisonous. Compounds of silver important from a toxicological standpoint are silver nitrate, silver lactate, silver picrate, silver acetate and the silver halides. Silver nitrate is a poisonous salt, also known as Lunar Caustic. Silver was likened to the moon by the ancient chemists on account of the latter's silvery color, hence the word Lunar. You would probably recall that Latin luna means moon. This term appears in the term "lunar month" which refers to the period during which the moon waxes and wanes completely once. This period as you know is equal to 28 days. This term also appears quite surprisingly in the word "lunatic". It is because ancient people thought that madness results from the effects of full moon. Even today, an excessively sentimental, dazed or a lunatic person is sometimes referred to as moonstruck."

"Interesting! And what is the origin of the term caustic?"

"The term caustic refers to the salt's caustic properties both as crystals and in aqueous solution. Silver has both medicinal and non-medicinal uses. Among the main non-medicinal uses are in jewelry, coins, silverware, tableware, and in manufacturing of mirrors and electrical wiring. You will probably recall that pure silver has the highest thermal and electrical conductivity of all metals. That is the basis for its use in electrical wiring."

"Yes, I do. And what are its main medicinal uses?"

"Tarun, silver and its salts have been used as medicines for various ailments throughout history. During the nineteenth century it was prescribed for the treatment of digestive disorders, including stomach ulcer. Later small sticks of compressed crystals of silver nitrate began to be used for cauterization, notably of throat lesions, because of its astringent properties...."

"Excuse me doctor. You have used certain terms which I don't quite understand. What is cauterization and what is meant by the term astringent?"

"Tarun, an astringent is a drug which precipitates proteins and causes contraction of tissues. The term comes from Latin astringere which means "to draw tight". Astringents have so little penetrability that only surface of cells is affected. Application of astringent often arrests secretions or discharge, so it is often applied to lesions which are discharging secretions. Precipitation of proteins also kills the cells. The idea of applying these drugs was also that it would kill any infective microorganisms lurking in the lesions, by precipitating proteins in their cells. The most popular astringents are salts of zinc and aluminum. Zinc sulfate (0.25%) is often recommended as an eye medication. Another common astringent is tannic acid. Cauterization is the destruction of tissues by the application of an astringent. Of course cauterization can be done by heat too. Warts can be cauterized by heat or by some astringent substance. There was a time when silver salts were popularly used for cauterization of warts."

"Oh, I see. Are these salts still used today for cauterization?"

"Not usually. This procedure carried a substantial risk of the silver nitrate stick getting broken and the patient swallowing -or worse- inhaling the detached fragment. Certain quacks in India still keep these sticks for such purposes. These sticks have been known to be used for the cauterization of infected umbilical stumps and in the treatment of nosebleeds too. They have been used in the treatment of warts as I told you earlier. Ayurvedic doctors are known to use Bhasmas (roughly equivalent to ashes) which contain various noble metals, of which silver may be one. Indian sweetmeat manufacturers often decorate sweetmeats with a paper thin sheet of silver, and consumers are known to consume sweetmeats along with it, but I am not aware of silver poisoning occurring by this means. Several other typical Indian preparations such as paan are also decorated in this way."

"Does silver nitrate have other medicinal uses too?"

"It is used as prophylaxis for ophthalmia neonatorum, which is an infective condition of the eyes in the newborn because of the gonorrhoea bacterium. Infants suffer from this condition when their mothers are known to be suffering from gonorrhoea. Silver nitrate is used in this condition, because of its known antiseptic effect against gonorrhoea bacteria. Dressings soaked in 0.5% silver nitrate have been extensively used in the treatment of burns. Topical use of silver nitrate in this way can produce poisoning although it is not common. Poisoning due to silver iodide nose drops has been reported. Silver is also used in dentistry for dental fillings. Silver salts, because of their germicidal properties, are also used as drinking water disinfectants. Such treated water may contain upto 50 mg/L of silver. Drinking water not treated with silver, usually contains extremely low concentrations of silver -up to 5 mg/L only."

"So silver is used for disinfecting water too. I didn't know that. I thought only chlorine is used for disinfecting water."

"Oh yes, silver indeed is used for disinfecting water. These days some companies are even marketing gadgets called "mobile electronic water purifiers" which work by generating silver ions. These are shaped like pens. The device is to be opened and dipped in water. In fact it has two silver electrodes and while in water, it is supposed to generate silver ions which in turn are supposed to kill microorganisms lurking in water. But as you know now, such disinfected water has more than the normal quantity of silver in it."

"Can one ingest silver accidentally too"

"Tarun, silver can be ingested accidentally in a most unexpected manner. To understand how it is possible, first of all I must tell you that sea water is known to contain silver in concentrations of 0.055-1.5 mg/L. Much higher concentrations have been reported in waste water effluents. For instance effluents entering southern California coastal basins have been known to contain silver in concentrations as high as 0.03 mg/L! Note that I am talking of milligrams here, not micrograms. Silver has been accumulated in concentrations of 14-20 mg/kg in bottom sediments in these areas. Molluscs ingesting this water accumulate seawater in their bodies. Molluscs collected from coastal areas of the North Sea have been reported to contain silver concentrations of up to 2.0 mg/kg. Ingestion of these molluscs as well as other marine food can thus lead to chronic silver poisoning!"

"Oh, that certainly is most unusual!"

"Exposure to silver can occur in other unusual ways too. For instance it can also occur from small amounts released from dental fillings and from eating out of utensils made of silver. Human activity has been known to increase silver concentration in the air. You perhaps know that a silver salt -silver iodide- is sometimes used to seed clouds precipitate rain artificially. The emission of silver iodide crystals during cloud seeding has been estimated to result in silver concentration in air of about 0.1 ng/m3. Silver concentrations in rainwater as a result of this process have been estimated to be between 0.04 pg/ml and 5 ng/ml. I must tell you that ng stands for nanogram and pg for picograms. 1 nanogram (ng) is equal to 10-9 g and 1 picogram (pg) is equal to 10-12 g. There is some amount of silver in tobacco too, but this is generally too low. Because of its high boiling point, most of the silver in cigarettes is not inhaled."

"This is quite interesting information about silver. But what happens to silver once it enters inside the body? I know this is not a normal constituent of the body, nor can the body make any use of it. Then how does it handle silver?"

"That's a good question Tarun. In humans, more than 50% of the body burden of silver goes in the liver. Elimination is mainly via faeces. The concentrations of silver in kidneys, liver and spleen of normal people have been reported to be about 0.4, 0.7 and 2.7 mg/kg respectively on a dry weight basis. This means that if these organs were dried into powder and then silver estimation done, one would get these figures. Normal concentrations in skin are 0.009 mg/g. This latter figure is on wet weight basis, i.e. estimation is done on the skin as such, without first converting it into dry powder. Daily excretion in urine is 0.006-0.015 mg/day and 0.02-0.11 in feces."

"Doctor, how much silver is needed to kill a person?"

"Tarun, fifty mg or more of collargol which is a silver salt has been reported to be lethal after intravenous injection for therapeutic purposes. Autopsy findings in such cases have included watery lungs, and destruction of bone marrow, liver and kidney. Silver nitrate has been used by quacks to induce criminal abortions. These are abortions done in a clandestine manner by quacks on girls who do not want a baby. Most of these girls are unmarried girls who contact these quack abortionists to get rid of unwanted pregnancies. They use all sorts of weird chemical compounds to get rid of these pregnancies. In a case which has been reported in medical literature, intrauterine administration of approximately 25 g of silver nitrate caused rapid death of the mother."

"And what is argyria?"

"The cases which I have mentioned above are cases of acute poisoning- cases in which silver is administered in one single big shot. Poisoning can occur in a chronic fashion, in which small doses of poison are administered slowly. In my earlier stories I told you about acute and chronic poisonings. Argyria is a chronic poisoning with silver. It is an interesting condition, which once seen is never forgotten. The patient- as in the case of Pyarelal- acquires a blue-grey color of the skin, especially over exposed areas. Silver bound to body proteins, is deposited widely in the body tissues. Internal body viscera may get discolored too. Pigmentation results partly from stimulation of melanin deposition but mainly from photoactivated reduction to metallic silver in the dermis- hence the distribution over areas exposed to light. It is like exposure of a photographic plate. The whole body -which has absorbed silver- becomes a kind of photographic plate which blackens on exposure to the sun."

"Can you prove this in the case of Pyarelal?"

"Yes certainly. In cases of argyrosis, microscopically detectable silver containing granules are found in the skin cells and particularly around the hair follicles and in the sebaceous and sweat glands. I have taken a skin sample from his neck area and have done electron microscopy on it. The dermis of this area showed irregular silver granules both inside as well as outside the skin cells. I also did a special investigation - neutron activation analysis. This technique can tell the exact amount of a chemical in a given sample. This technique showed that the silver concentration in his skin was 72 mg/g, far exceeding the normal 0.009 mg/g. You can plainly see that it represents an accumulation 8000 times normal. His total body content of silver is almost 8 g which is really quite high. In addition he shows a black colored line near the teeth, which is because of the deposition of silver there. It is called the silver line. I must tell you that although silver shines as a metal, in a colloidal state it appears black. That's the reason a photographic negative receiving more light becomes black. It is at these regions that silver halides are converted to colloidal silver by sunlight."

"That certainly is quite interesting. If silver is administered slowly to a person, how much silver needs to be introduced before the person suffers from argyria?"

"Tarun, it has been estimated that a total dose of about 1-8 g of silver is required by inhalation for argyrosis to occur. The dosage by ingestion seems a little higher; between 1 to 30 g of a soluble silver salt. Blond people are considered more susceptible than others. The reason for this is unknown. Argyrosis seemed to have become only of historical interest, but it has recently reappeared, especially in the West. Respaton an anti-smoking lozenge, available in the West from retail chemists since 1974, contains silver acetate and ammonium chloride. Another similar anti-smoking lozenge is Tabmint. Manufacturers of these lozenges claim that regular sucking of these lozenges can reduce one's desire to smoke. They recommend a maximum of 6 lozenges per day. Chronic use of these lozenges has caused argyria in several cases. The patient remains discolored for life and ironically the smoking habit for which he took all the trouble remains!"

"That is certainly most interesting. Can argyria occur in other ways too?"

"Tarun, repeated occupational handling of silver objects, especially if repeated minor injury is involved, may give rise to so called local argyria, which is bluish-gray discoloration of the skin at the exposed site. This condition is however considered harmless apart from aesthetic considerations."

"So it is now almost certain that Pyarelal was being given some silver salt in low concentrations by his son and daughter-in-law."

"Yes it is. Here comes the chemical analysis report of the food and milk submitted by Pyarelal. Oh it shows a rather high concentration of silver nitrate. So my worst fears have proved correct. His daughter-in-law was taking advantage of her position as a chemist and was regularly giving him silver nitrate in his milk and food- probably just a drop or two in his milk. But over the years this has caused silver poisoning in this poor fellow. We have all the evidence now. Let us go to the police and tell them the whole story."

"Sure we should. And thank you doctor for telling me about such an interesting poison. What are you going to tell me next time?"

"Tarun, next time I shall tell you about vanadium which as you shall see is a very important poison. "