Effects of Carbon Dioxide With and Without Bioeffluents on humans

Carbon dioxide (CO2) has traditionally been assumed innocuous at the typical levels indoors, and merely an indicator of metabolic emissions from humans (bioeffluents). Recent studies suggest that exposure to pure CO2 at concentrations of 2,500 to 4,000 ppm, the levels that occur periodically indoors, can have negative effects on mental performance in form of reduced ability for making decisions, typing and proofreading. Present study aimed to examine further these effects. Twenty-five human subjects were exposed to elevated CO2 with and without bioeffluents in a chamber. The exposure levels were as follows: background exposure with CO2 at 500 ppm, exposure to pure CO2 (without bioeffluents) at 1,000 and 3,000 ppm, exposure to metabolically generated CO2 (with bioeffluents) at 1,000 and 3,000 ppm. Each exposure lasted 4.25 hours and their order was balanced. Subjects rated perceived air quality and acute health symptoms. They performed several cognitive tasks. Their physiological responses were monitored. No effects were seen during exposures to elevated levels of pure CO2 (without bioeffluents). Exposures to elevated levels of bioeffluents (with CO2) reduced significantly perceived air quality assessed upon entering the chamber, increased significantly intensity of neurobehavioral symptoms, and reduced mental performance of addition in terms of lowering the speed and increasing error rates the latter two effects particularly so when metabolic CO2 was at 3,000 ppm. Physiological measurements and the performance of Tsai-Partington test suggested that exposures to bioeffluents increased arousal/stress and this result together with the stronger intensity of neurologic symptoms and complaints could be the underlying mechanisms of reduced performance. Present results confirm the expected negative effects of exposure to elevated levels of bioeffluents thereby providing basis for ventilation requirements. The effects of exposures to pure CO2 up to 3,000 ppm seem to be imperceptible and undetectable by the used cognitive tests, but the role of CO2 in the mixture with bioeffluents shall not be underestimated and further examined.