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Toxicological interactions between carbon monoxide and carbon dioxide
B C Levin1, M Paabo, J L Gurman
1National Bureau of Standards, Gaithersburg, Maryland 20899.
Toxicology
|December 1, 1987
Summary
Carbon monoxide (CO) and carbon dioxide (CO2) exposure can be lethal, especially when combined. These gases exhibit synergistic toxicity, increasing carboxyhemoglobin formation and causing prolonged acidosis.
Area of Science:
- Toxicology
- Environmental Health
- Occupational Safety
Background:
- Carbon monoxide (CO) and carbon dioxide (CO2) are common combustion byproducts.
- Understanding their individual and combined toxic effects is crucial for safety assessments.
Purpose of the Study:
- To investigate the synergistic toxicity of combined carbon monoxide (CO) and carbon dioxide (CO2) exposures.
- To determine the impact of these gases on carboxyhemoglobin formation, acidosis, and mortality in rats.
Main Methods:
- Fischer 344 male rats were exposed to varying concentrations of CO and CO2, individually and in combination.
- Carboxyhemoglobin (COHb) levels, acid-base balance, and mortality were monitored.
- Combustion of 11 materials was analyzed to assess the role of CO and CO2 in real-world scenarios.
Main Results:
- CO alone had LC50 values of 4600-5000 ppm, while CO2 alone did not cause incapacitation or fatal injury.
- Combined CO and CO2 exposures resulted in deaths during and up to 24 hours post-exposure.
- The combination of 2500 ppm CO and 5% CO2 increased COHb formation rate by 1.5 times and led to greater acidosis and longer recovery.
- A mathematical model indicated a synergistic interaction between CO and CO2.
Conclusions:
- CO and CO2 exhibit synergistic toxicity, with combined exposure being more dangerous than individual exposure.
- CO is a primary toxicant in some combustion scenarios, while combined CO and CO2 are implicated in others.
- Further research on additional fire gases is needed to fully explain combustion-related deaths.