Do carbon dioxide, volatile organic compounds and atmospheric pressure affect the cognitive performance of occupants in indoor environments? Results of a large-scale experiment with simulated flights.

BACKGROUND Indoor air quality, especially carbon dioxide (CO2) and volatile organic compounds (VOCs), has been linked to cognitive impairment in previous studies, even below guideline levels. Most previous studies employed small cross-over designs and varied only one indoor air factor. OBJECTIVE This study aimed to investigate the influence of various combinations of indoor air parameters at typical and elevated levels on cognitive performance. METHODS We conducted a randomized controlled trial with 398 healthy adults aged 18-69 years. Participants were randomly assigned to 11 groups and exposed to different combinations of pure CO2 (1200, 2750, 4200 ppm), atmospheric pressure (940, 755 hPa), and a VOC mixture of selected compounds at low, medium, and high concentrations. Eight different cognitive domains were assessed with established tests. RESULTS Participants rated air quality as good to very good at the end of exposure in all groups. Analyses of variance with pairwise comparisons showed effects of exposure in 2 out of 8 cognitive domains (concentration and figural working memory). None of the observed differences were systematically aligned with the air quality conditions. CONCLUSION Our study provides no evidence that short-term exposure to various combinations of CO2 (up to 4200 ppm), TVOCs (up to 2100 μg/m3), and atmospheric pressure up to 8000 ft. elevation had any systematic negative effects on the cognitive abilities of healthy adults. The TVOC results should be viewed with caution, as a specific mixture was used, and other mixtures may occur in other indoor environments. Rigorously designed studies with longer exposure times are recommended.