Culled from Securitas Volume #4, Issue #6 (November/December 2005)
The acute health effects of carbon dioxide vary with its concentration in the air and the length of time a person breathes the gas. The usual carbon dioxide content in fresh air is only 0.03%, and in exhaled air approximately 4.5%.
Persons (and animals) breathing 17-30% (or greater) carbon dioxide concentration for less than a minute will have sudden loss of controlled and purposeful activity, unconsciousness, convulsions, coma, and death, according to Environmental Protection Agency data (accessed December 8, 2005).
Carbon dioxide at these high concentrations has a direct effect on the central nervous system, and also displaces oxygen (usual amount by volume is 20.947% by volume) from the air, which leads to acute oxygen deprivation and suffocation (asphyxiation). This is the mechanism by which carbon dioxide fire extinguishers extinguish fires, i.e., they displace oxygen required by the fire (for more information [click here] -accessed December 8, 2005).
The nearly 1,700 Cameroonians and uncounted livestock and other animals who quickly succumbed to the carbon dioxide toxic clouds emitted from Lakes Monoun and Nyos in 1984 and 1986, respectively, were exposed to these very high levels of carbon dioxide (see accompanying article: “Killer Lakes of Cameroon”).
People exposed to lesser concentrations of carbon dioxide, say between 10 and 15% for one to several minutes, experience dizziness, drowsiness, severe muscle twitching, and sometimes unconsciousness. Exposure to 7-10% levels of carbon dioxide in the air for a few minutes and up to an hour for some people may result in mental clouding and confusion to the point of unconsciousness or near unconsciousness, and for other people, lesser symptoms including headache, increased heart rate, shortness of breath, dizziness, sweating, and rapid breathing. Speed of performance of reasoning task is significantly slowed at these higher levels of carbon dioxide concentration.
Mr. Joseph Nkwain, who survived the toxic carbon dioxide plume and whose interview is reproduced in the accompanying article, “Killer Lakes of Cameroon”, probably was exposed to fluctuating levels of carbon dioxide of between 7 and 15%, based on the symptoms he described. There is not a better clinical description of severe carbon dioxide toxicity than the one provided by Mr. Nkwain.
At carbon dioxide concentrations of 6% for 1-2 minutes, persons will have hearing and visual disturbances, at less than 16 minutes, headache and shortness of breath, and for several hours, tremors. At concentrations of 2-5% for minutes to hours, persons complain of headache, shortness of breath and sweating.
Joseph Nkwain's Story
A witness named Joseph Nkwain described the August 21, 1986 event to interpreter Dr. E. Shanklin on March 25, 1987. At the time of the catastrophe, Mr. Nkwain was at the village of Subum (about three miles from Lake Nyos) where 400 people perished and 400 lived. This is what he said:
“I was the first person to come out of the area. I was in Subum with my daughter who came to spend holidays with me. It was the evening [9:30 p.m.] of the 21st and we were sitting at the table reading, trying to help my small daughter with her studies. Then she went to bed and fell asleep; I also went to bed without noticing any sign of anything. We didn’t have any sign of anything.
“It was around midnight I didn’t even imagine the time when I started felling some heat. I felt as if rain was threatening to fall, so I got up from bed, got a bucket and went outside, expecting that rain would fall. Then I went back to the house and went back to sleep. I was in a very deep sleep. I felt as if it were becoming hot, you know when it is starting to be the rainy season, the first rain, we used to get some heat; yes; I felt that feeling that very night.
“Then I fell back to sleep; I heard some sound, something sounded like an airplane. I heard the sound. It went and bounced like this: boom. It was as if I was in a dream, I heard that noise as if I were dreaming…
“All of a sudden, my skin became very hot and I perceived something making some dry smell. I could not speak. I became unconscious. I could not open my mouth because then I smelled something terrible and could not speak. I just closed my mouth and remained silent.
“All of a sudden, I heard my daughter snoring in a terrible way, very abnormal. So I forced myself to stand up from the bed, I was already weak. I tried to see what was happening with my daughter and find out really what was smelling in the house. Id did not really know what the smell was, the smell was terrible. So just when I stood up, I fell. When crossing to my daughter's bed, in the middle of the floor, I collapsed and fell. I fell, I remained there, I didn’t stand up. I was there till nine o'clock in the morning, Friday morning. I don’t know whether I was sleeping, I don’t really know.
I was there until a friend of mine came and knocked at my door. The door was locked, he hit it very loudly, so much noise that he woke me. I heard it as if I was dreaming, I was surprised to see that my trousers were red, had some stains like honey. I saw some starch, some starchy mess on my body. My arms had some wounds…these are the wounds [he showed us circular scars ½ to ¾ inches in diameter on the right and left forearms]. I had some marks here. I didn’t really know how I got these wounds, where they came from. My face, too, had some wounds, these marks. So I managed, I stood up, opened the door. I was unable to speak. I wanted to speak, my breath would not come out. I sat in silence for some time, my friend was talking outside, asking me a question, my voice would not come out. I was breathing abnormally…My daughter was already dead. I didn’t know that she was dead, I thought she was still sleeping. When I drank that milk and water, it was around 11:30 a.m. I fell back to sleep. I went to my daughter’s bed, thinking that she was still sleeping.
I slept till it was 4:30 in the afternoon, almost getting to evening, on Friday. I slept with my daughter, not knowing that she was already dead. When I recovered, I really stood up at 4:30, with my clear senses. I really felt as if I was dreaming. I never knew what was happening until I went outside. Everywhere was quiet, I managed to go over to my neighbors’ houses. They were all dead. I tried my neighbors’ doors, they were bolted inside, I shouted through the window, I saw them lying.
The friend who came and knocked my door, I went to him and I saw him resting the same as I did. He was just lying on the bed, he told me that he cannot stand up, he was just resting. Everybody was asleep, those who survived. Myself, what I did was I went back. I saw that my daughter was already dead. It was ten minutes to five o’clock in the evening. I felt that I had a little strength; I decided to leave because there was no vehicle, since morning. The rest of my family was absent. So I decided to leave; I thought that, this thing must have happened all over and most my family was in Wum. If I am dying, I will die on the way.
I got my motorcycle; I rode. When I just started my motorcycle, I heard the sound [of the engine], it was quite normal.
“I wore my dresses, and wore my cap, I tied on some mask in case of any smell, I would not feel it much. A friend whose father died left with me to Wum…about [36 miles]. As I first arrived, I went to my boss [at WADA] I passed his door. Then he took me in his car, because I could not ride from there…I was unable to walk, even to talk. My hands were all frozen, when I reached the hospital, my body was completely weak…
“As I rode through from Subum, passing through Nyos, I didn’t see any sign of any living thing; the only [other] person was that friend I carried.” [At Nyos, 600 died, 6 lived.] (3)
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