The health of astronauts at the International Space Station is being impacted at lower than expected Carbon dioxide (CO2) concentrations according to Dr David Alexander of NASA’s Johnson Space Centre who monitors the impact of O2, CO2 and other gases. Dr Alexander has authored a number of NASA studies in 2012 (investigated chronic exposure to elevated CO2 concentrations during long space flight) and 2014 (investigated the relationship between CO2 concentrations and reported headaches on the International Space Station).
Studies ... have also found that CO2 directly impacts human cognitive function and decision making
Medical staff who monitor astronauts are concerned that headaches may indicate higher intracranial pressure as a result of a CO2 induced increase in cerebral blood flow and the effects of microgravity on blood flow. The 2014 study looked at this effect in particular and found that higher intracranial pressure could lead to headache, impaired mental function and other central nervous system symptoms.
Studies from the Harvard School of Public Health and the Lawrence Berkeley National Laboratory have also found that CO2 directly impacts human cognitive function and decision making in a negative way in the range of 900-1000 parts per million (ppm), and possibly lower concentrations. The issue with these concentrations is that according to Climate Progress, many Americans and their children are exposed to concentrations of that order in classrooms, offices, homes, aircraft and their vehicles. Concentrations of that order will become increasingly difficult to mitigate if outdoor CO2 concentrations continue to increase. Both studies used a multi-variable assessment of human cognition and their respective findings were published in the peer reviewed Environmental Health Perspectives Journal.
A USEPA literature review noted that higher CO2 concentrations in inhaled air has a dramatic influence on the function of vital processes including breathing control, vascular dilation or constriction and body fluid pH. Our bodies compensate for higher CO2 concentrations in inhaled air to keep blood pH in a narrow range to prevent acidosis.
A more recent study led by Dr Joe Allen from Harvard University’s Healthy Buildings Program and Dr John Spengler, Harvard Professor of Environmental Health and Human Habitation used a lower CO2 baseline concentration than the previous Harvard Study. They found that cognitive scores dropped by just over 20% with a 400 ppm CO2 increase. The researchers found that crisis response, information usage and strategy (which require higher order cognitive function and decision making) were affected the most by increased CO2 concentrations.
In modern buildings where most people live and work, CO2 concentrations are commonly higher than outdoors (sometimes by as much as 200-400 ppm). If ventilation is inadequate and more people are crammed into the same size space, the difference between indoor and outdoor concentrations can be even greater. Building envelopes have become more tightly sealed in the last few decades and the exchange of indoor and fresh outdoor air has decreased, according to Allen and Spengler.
If you are wondering how all of this relates to climate policy, the answer is simple according to Climate Progress. At present global CO2 concentrations are at approximately 400 ppm and are rising at 2 ppm each year. While we can’t currently pinpoint the exact threshold beyond which human cognition measurably impacts human cognition, the studies to date report some level of impact below 930 ppm, and in some individuals, at much lower concentrations.
A Carnegie Mellon University study conducted for the US General Services Administration found a threshold as low as 600 ppm, based on measurements at more than 1200 workstations in 64 office buildings across the US. Occupant satisfaction with the overall indoor air quality was strongly linked to CO2 concentrations, and dramatically decreased at concentrations above 600 ppm.
Vivian Loftness, one of the world’s leading experts on health, productivity and the quality of the built environment has assembled the world’s most extensive databases of studies on the health and productivity gains that can be made from green building design. In her opinion, there are two main take-aways from these studies and her database. Firstly, ventilation and the use of outside air in buildings should be increased from a public health perspective. Secondly, we need to keep outdoor CO2 concentrations below 600 ppm, as after that the implications are extremely serious.
According to Climate Progress, a successful outcome at the Paris meeting in December can “buy” us up to a decade in the continual fight against a catastrophic global impact. Indoor CO2 concentrations should be more closely monitored and kept as close as possible to outdoor concentrations by using outdoor air. Cost effective strategies and technologies which can be used to achieve this already exist, and therefore increases in building energy consumption can be avoided.
As a scientist who has read many indoor air quality (sometimes called indoor environmental quality) and personal exposure studies, I am pleased to see that CO2 has been receiving greater attention from research institutions and NASA. I can recall survey after survey asking participants to evaluate the air quality at their workstation or in their office (including whether the ventilation/air circulation/flow was too little or too much) on a Likert scale, and variables such as temperature and humidity and pollutants such as volatile organic compounds (VOCs) and carbon dioxide being measured.
I’m not questioning these traditional approaches-of course they have enabled scientists to gain a better understanding of indoor air quality and personal exposures to pollutants in indoor environments. My point is that studies which effectively extend such traditional approaches and examine the effects of pollutants on cognitive function (required for many daily workplace tasks) add significant value. In the case of CO2, a better understanding of the health effects is extremely valuable.