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Toxicology

Carbon Dioxide

Greenhouse gases are those that can absorb and emit infrared radiation,^[1] but not radiation in or near the visible spectrum. In order, the most abundant greenhouse gases in Earth's atmosphere are:

Water vapor (H�2O)

Carbon dioxide (CO�2)

Methane (CH�4)

Nitrous oxide (N�2O)

Ozone (O�3)

CFCs

Atmospheric concentrations of greenhouse gases are determined by the balance between sources (emissions of the gas from human activities and natural systems) and sinks (the removal of the gas from the atmosphere by conversion to a different chemical compound).^[12] The proportion of an emission remaining in the atmosphere after a specified time is the "airborne fraction" (AF). More precisely, the annual AF is the ratio of the atmospheric increase in a given year to that year's total emissions. For CO�2 the AF over the last 50 years (1956–2006) has been increasing at 0.25 ± 0.21%/year

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Carbon Dioxide

Also called Carbonic acid or Carbonic anhydride/ CO2
It is colourless, odourless gas and heavier than air
It constitutes 0.04 % of atmospheric air
5% CO2 is used as respiratory stimulant,
It is used in mineral water, cold drinks, and found in wines.
It is used in fire extinguishers

A. Nitrogen - 78% - Dilutes oxygen and prevents rapid burning at the earth's surface. Living things need it to make proteins. Nitrogen cannot be used directly from the air. The Nitrogen Cycle is nature's way of supplying the needed nitrogen for living things. �B. Oxygen - 21% - Used by all living things. Essential for respiration. It is necessary for combustion or burning. �C. Argon - 0.9% - Used in light bulbs.�D. Carbon Dioxide - 0.03% - Plants use it to make oxygen. Acts as a blanket and prevents the escape of heat into outer space. Scientists are afraid that the buring of fossil fuels such as coal and oil are adding more carbon dioxide to the atmosphere. �E. Water Vapor - 0.0 to 4.0% - Essential for life processes. Also prevents heat loss from the earth. �F. Trace gases - gases found only in very small amounts. They include neon, helium, krypton, and xenon.

The common name given to the atmospheric gases used in breathing and photosynthesis is air. By volume, dry air contains 78.09%nitrogen, 20.95% oxygen,^[1] 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Although air content and atmospheric pressurevary at different layers, air suitable for the survival of terrestrial plants and terrestrial animals currently is only known to be found in Earth'stroposphere (0-12 Km of earth) and artificial atmospheres.

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Carbon dioxide Bubbles in Soft Drink

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Sources of generation of CO2 in nature

Respiration by all living beings,
Fermentation,
Putrefaction,
Limekilns due to breakdown of carbonates
Combustion leading to formation of Choke damp or after damp in coal mines

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Causes of Poisoning by CO2

Being heavier than air high level may be found in

Bottom of old wells,
Damp cellars,
Mine shafts,
Brewer’s vats,
Grain pits,
Ship’s holds

CO2 given accidently instead of O2 during anaesthesia

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Clinical Picture

Sign & Symptoms

Rise in CO2 level in surrounding air causes heaviness in head, throbbing headache, giddiness,
10% CO2 causes hyperpnoea, tinnitus, mental confusion, muscular tremor, sweating, visual disturbances, and loss of consciousness
25-30% has direct toxic effect on nerve cells causing immediate loss of consciousness, convulsion, and death due to respiratory failure
60-80% directly toxic to higher centers of brain also causes spasm of the glottis, immediate loss of consciousness and death from suffocation.

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Concentration of

CO2 in air

Green 1 %

Blue 3%

Violet 5%

Red 8%

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Treatment

Remove from the place of intoxication
If respiration has stopped Artificial respiration and give oxygen
Tham (2-amino-2hydroxymethyl-1, 3-propanediol) (tromethamine injection), an amine buffer to be given I.V.
Maintain blood pressure and temperature
Cover with blanket give hot coffee, milk and/ or brandy
Never allow people to enter a well in which lantern extinguishes if lowered. Pump in fresh air by lowering a tube up to bottom

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Post-mortem appearance

Face pale minimal cyanosis in fast death at high concentration
Signs of Asphyxial Death in slow death

Pupil dilated
Central and Peripheral cyanosis
Tardieu's Spots on mucous membranes like conjunctiva, mouth pleura, pericardium, peritoneum etc.
All internal organs congested
Blood dark coloured and fluid
Left side of Heart Empty, Right side Full

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Medico- Legal Aspects

Poisoning mostly Accidental
Inhalation of High Concentration of CO2 can damage cognitive abilities permanently
In old wells containing high concentration of CO2 reduced O2 level was also detected.
Cases reported where during anaesthesia instead of oxygen CO2 was administered accidently