THE FOLLOWING ARTICLE APPEARED IN THE

JANUARY 1998 ISSUE

THE POISON SLEUTHS

DEATH BY PHOSGENE

-Dr. Anil Aggrawal

"Good morning doctor. Oh, my God, what are you doing today? You have the dead body of a young man today. His eyes look suffused. What happened to him? Please tell me."

"Good morning Tarun. The name of this 36 year old man is Manhar. He is a welder by profession and was working for the last five years as a welder in Messers Arihant Welders Ltd. Welders as you know work with hot torches, and seal metallic objects. He used to weld metallic pipes in a small confined space in basement. Yesterday he was suffering from common cold, but he reached his workplace at 9 am as usual and started welding pipes in the basement. After sometime, a cup of tea and some snacks were sent to him by the management as he was having common cold. This was not a usual practice, but as he was ill and the management wanted quick work on that day, this sympathetic gesture was made. He took tea and snacks and got back to work. Soon he started feeling as if his throat was dry and burning. His eyes began itching, and there was a copious outflow of tears. He took it merely to be an aggravation of his common cold symptoms, and kept on working. Soon however he started coughing violently. Still he did not take things seriously. He took some water to soothe his throat and continued working. When the cough became unbearable, he came up and told about this experience to the manager on duty. He asked him to relax on a side chair. Soon thereafter he died."

"Oh, sure enough this is a mysterious death. What do you think happened in this case?"

"A few facts about Manhar would be in order before I proceed with this story. Manhar was a Union leader, and for the last three months was fighting with the management for better working conditions and salary. I have talked to the Union and its other leaders. They all hold Manhar in great respect. They have come out with a most outrageous suggestion, and in fact that is part of the reason, why his body is with me today."

"What have they suggested doctor? Please let me know."

"Well, the Union leaders think that the management has secretly poisoned Manhar. There is no secret of the fact that the management did want to sack Manhar, the moment he took up the cause of workers. But they couldn't do so, because the Union threatened to go on strike. Since then the Management was thinking of various ways and means of doing away with him. The Union leaders- as well as the family members -think that the management sent poisonous tea and snacks to Manhar on that fateful day. Manhar was naive enough to think that the Management was being friendly to him, and took the tea. The fact that Manhar started having symptoms of throat irritation, redness of eyes and coughing immediately thereafter has lent strength to their suspicion."

"Well come to think of doctor, even I think that he might have been poisoned."

"Tarun, I have made a habit of examining the scene of crime always before starting the autopsy. So before starting the autopsy on this case, I asked police to take me to the place where he was working. I was surprised to find that he was working in a really cramped place in the basement. The place had a rather musty odour.

"Perhaps you are suggesting that he died of suffocation. But he was working there daily for the last five years, and nothing happened to him!"

"Yes that's right. But I looked around and found some strange looking cans there. I enquired about these cans and was told by the Management staff, that they contained dry-cleaning fluid. They were soon going to expand into dry-cleaning business and for this purpose had bought dry-cleaning fluid and had stored the cans there. Some of the cans were lying open...."

"Sorry to interrupt you doctor, but is this observation of any help in this murder investigation?"

"Oh yes, surely it is. When you look at all the facts, you can pinpoint the probable cause of his death."

"Sorry doctor. I can't make any head or tail of the facts you have just mentioned."

"Tarun dry-cleaning fluid usually contain chlorinated solvents, such as carbon tetrachloride or tricholoroethylene. I investigated about the contents of that dry cleaning fluid and found out that it contained tricholoroethylene. It is a well known fact that welding in a poorly ventilated, confined space in the presence of chlorinated solvents can cause phosgene to form rapidly in lethal concentrations. After I found the dry cleaning cans there, and saw how cramped the place was, I immediately came to the conclusion that Manhar must have died of phosgene poisoning. There were some additional pointers to my hunch. In the first place the place had a musty odour much like the actual smell of phosgene...."

"But Manhar never noticed the smell. If phosgene was forming, he must have noticed it."

"Phosgene is not a particularly offensive smelling gas. Its odour has been described as musty, resembling that of fresh mown hay or green corn. Of course, in high concentrations phosgene is rather pungent and mildly irritating, but Manhar was having severe cold on that day and it is quite possible that he couldn't notice the smell because of his cold. In addition to the smell, the other things, that go in favor of phosgene poisoning are the peculiar symptoms that he displayed...."

"Oh, well, I am getting the idea. You certainly are a clever doctor. But let us begin from the beginning. Tell me something about phosgene first, so I could follow you better"

"Tarun, Phosgene is a colorless gas, about 3.43 times heavier than air. It liquefies at 80 C. Phosgene is an acidic chloride and its chemical formula is COCl2 . It is known by several other names. Some of these are Carbonic dichloride, carbonyl chloride, carbon oxychloride, and chloroformyl chloride. It has a musty odor resembling fresh mown hay or green corn as I have already told you. Because of these peculiar properties, and especially the fact that it is heavier than air, it was used extensively in gas warfare in World War I, and caused 80 per cent of the deaths by gas in that conflict. Fortunately, gas warfare was sparingly used in World War II, otherwise the casualties could have been much more. A curious fact is that smokers report a flat, metallic taste when smoking in the presence of phosgene. Phosgene does not occur naturally and was first synthesized by Sir Humphry Davy in 1812 by means of passing carbon monoxide and chlorine through charcoal. It was quite natural for a curious mind to do such an experiment, because these two were the most poisonous gases known at that time, and one would have thought, he could perhaps create a deadlier gas by mixing the two chemically. In a way, he succeeded too, because phosgene is in fact deadlier than both the other gases. According to most estimates, Carbon monoxide can prove fatal if inhaled in a concentration of 1000 ppm for sometime....."

"Sorry to interrupt you doctor, but would you tell me the meaning of ppm?"

"Sure, ppm is an abbreviation of parts per million. When we talk of the toxicity of gases, we usually talk in terms of ppm. If I mix 1 cc of a poisonous gas with ordinary air in such a way that the final volume of the mixture turns out to be 1 million cc, the concentration of the poisonous gas in that mixture would be referred to as 1 ppm. Of course you can understand that to make the final mixture to be 1 million cc, I would have to use 999,999 cc of ordinary air. Similarly if I mix 1000 cc of a poisonous gas with 999,000 cc of air, the resulting mixture would measure 1 million cc and the concentration of poisonous gas in that mixture would be 1000 ppm."

"Oh, that is quite clear doctor. So you were telling me about the lethality of certain gases."

"Yes, I told you about the lethality of Carbon monoxide. For chlorine the fatal concentration has been estimated to be somewhat lesser; about 400 ppm, but phosgene kills rapidly in as low concentration as 50 ppm. Its lethality is compounded by the fact, that it is not a particularly irritating gas, being only mildly irritating and that too in high concentrations. Because of this curious fact, the victim does not make any attempt to run away from the gas, as he would do if he were exposed to, say, chlorine. This is what happened in Manhar's case. In fact phosgene is such a dangerous gas that cylinders of phosgene are not normally supplied by the manufacturers unless they have satisfied themselves that the purchaser and his premises are satisfactory."

"But why would anyone want to buy such a deadly gas doctor?"

"Tarun, Phosgene is an important industrial chemical being used in the synthesis or manufacture of isocyanates, polyurethane, polycarbonate resins, aniline dyes, pharmaceuticals, plastics, and insecticides. It is also used in the "Uranium enrichment" process. Because of its wide use in industry, there is always a danger of workers getting dangerously exposed to it. Currently it is generally agreed that a Maximum Allowable Concentration (MAC) of phosgene should be 1.0 ppm of gas, which means that during a 10 hour continuous working period, there should be no more than 0.1 ppm of the gas in the environment (0.1 ppm x 10 hours = 1 ppm). Phosgene can form by burning of several compounds, most important of which is polyurethane. This is the chemical with which furniture upholsteries are made. In December, 1987, in Tampa, Florida, an individual was filling an air mattress with a hair dryer when the mattress exploded, burned and released phosgene into the apartment. This occurred because the mattress was made of polyurethane. This gas represents one of the many hazards to fire-fighting personnel and fire victims for similar reasons. Welding in a poorly ventilated, confined space in the presence of chlorinated solvents or other halides can cause phosgene to form rapidly in lethal concentrations as I have already told you. You would be surprised to know that phosgene was also implicated in the Bhopal tragedy that occurred in our country in December 1984..."

"Yes, that certainly surprises me doctor. Because I was under the impression that the gas responsible for the tragedy was Methyl Isocyanate (MIC)."

"Oh, sure it was. But that was just one of the main gases involved. MIC in turn is made from phosgene and methylamine and is used as an intermediate product in the manufacture of carbamate insecticide Carbaryl, or Sevin, the chemical which Union Carbide used to make. On that fateful day nearly 50,000 pounds of stored MIC was released in vapor and liquid forms over a period of 2 hours. Because of the hypothesized reactions that took place within the storage tank and in the surrounding atmosphere, it is thought that MIC, phosgene, and hydrogen cyanide all played a significant role in this disaster."

"That's certainly a good addition to my knowledge doctor. Tell me doctor, how does phosgene kill?"

"Tarun, phosgene damages the body in several ways. It slowly hydrolyzes in mucus membrane water to produce carbon dioxide and hydrochloric acid. Because this hydrolysis tends to occur slowly, phosgene is less irritating to the mucous membrane of the upper airway and eyes and therefore penetrates more deeply into the lungs. Formation of hydrochloric acid within the lungs causes damage to lung cells. This causes water to ooze out of the blood into the lungs. This in turn causes lungs to become water logged, a condition medically known as pulmonary edema. This is a very important and conspicuous finding in deaths due to phosgene. I have examined Manhar's lungs, and they are severely water logged. Hydrochloric acid can also cause red blood cells to break down, a process medically known as hemolysis. This usually occurs at high concentrations. There are other complex reactions too, which cause severe kidney and liver damage."

"Doctor, earlier you said that Manhar's symptoms also led you to conclude phosgene poisoning. Can you tell me what are the symptoms experienced in phosgene poisoning."

"Oh sure. In concentrations of 3 ppm, phosgene causes dryness and burning of the throat. At 4 ppm, it causes eye irritation, redness of eyes, and watering of eyes. At 5-10 ppm, it causes coughing. Exposure to 25 ppm for 30 minutes is very dangerous, and even brief exposures to 50 ppm or greater is rapidly fatal. You will remember that Manhar displayed roughly the same symptoms. 80% of mortalities occur within 48 hours of the initial exposure, which may be considered as its fatal period. There are no specific diagnostic tests for phosgene exposure. A detailed and meticulous history and crime scene examination is the only likey thing to help. And that certainly has helped me. Come let us tell the police that the management is innocent. They have not given any poison to Manhar. But certainly they were careless to keep those cans in the basement. The management may be charged for being careless, but certainly the charge of murder can not be proved."

"Oh, how very clever of you doctor. This was a most interesting discussion. Tell me what are you going to tell me the next time?"

"Tarun, next time, I would tell you about a very deadly poison- Sodium Monofluoroacetate, commonly known as SMFA."