Over the years there has been a sustained effort to portray human exposure to very high levels of CO2 as toxic. A new study undercuts these claims, as the decision-making performances of controlled-experiment participants were not impaired when exposed to CO2 concentrations as high as 15,000 ppm.
As a political activist, Al Gore has often referred to CO2 as a pollutant, even going so far as to characterize anthropogenic CO2 emissions as “global warming pollution”.
To that end, a study has just been published that suggests exposure to very high CO2 levels (1,500 ppm and 2,500 ppm) impaired the judgment and decision-making of airplane pilots (Allen et al., 2018), a result that reinforces the characterization of CO2 as a toxic gas.
And yet in another new study (Rodeheffer et al., 2018) it was determined that exposing submarine sailors to CO2 levels that reached 15,000 ppm did not impair their decision-making or overall cognitive functioning compared to sailors exposed to 600 ppm or 2,500 ppm.
In fact, sailors exposed to 15,000 ppm CO2 concentrations had better decision-making scores than sailors exposed to 2,500 ppm on 7 of the 9 measurement categories.
These findings undermine or at least cast doubt on claims that exposure to very high CO2 concentrations have a significant effect on human judgment or decision-making, which may assist in foiling efforts to portray CO2 as a toxin or pollutant.
Acute Exposure to Low-to-Moderate Carbon Dioxide
Levels and Submariner Decision Making
BACKGROUND: Submarines routinely operate with higher levels of ambient carbon dioxide (CO2) (i.e., 2000 – 5000 ppm) than what is typically considered normal (i.e., 400 – 600 ppm). Although significant cognitive impairments are rarely reported at these elevated CO2 levels, recent studies using the Strategic Management Simulation (SMS) test have found impairments in decision-making performance during acute CO2 exposure at levels as low as 1000 ppm. This is a potential concern for submarine operations, as personnel regularly make mission-critical decisions that affect the safety and efficiency of the vessel and its crew while exposed to similar levels of CO2. The objective of this study was to determine if submariner decision-making performance is impacted by acute exposure to levels of CO2 routinely present in the submarine atmosphere during sea patrols.
METHODS: Using a subject-blinded balanced design, 36 submarine-qualified sailors were randomly assigned to receive 1 of 3 CO2 exposure conditions (600, 2500, or 15,000 ppm). After a 45-min atmospheric acclimation period, participants completed an 80-min computer-administered SMS test as a measure of decision making.
RESULTS: There were no significant differences for any of the nine SMS measures of decision making between the CO2 exposure conditions.
DISCUSSION: In contrast to recent research demonstrating cognitive deficits on the SMS test in students and professional-grade office workers, we were unable to replicate this effect in a submariner population—even with acute CO2 exposures more than an order of magnitude greater than those used in previous studies that demonstrated such effects.