Indoor air quality and cognitive health: a study in the tropics

Abstract

An average person spends 23 hours per day in an indoor environment. Evidence shows that poor air quality experience affects one’s health and productivity. However, little is known about how productivity is affected. Literature has shown that productivity is a subset of indoor air quality (IAQ) effects on human cognition. Hence the thesis examines the effects of IAQ pollutants (PM2.5, TVOC and CO2 (bio-effluent)) on human cognition (creativity, working memory, inhibitory control (attention and response inhibition), cognitive flexibility & control (creativity), speed of information processing, planning, and fluid intelligence (reasoning and problem-solving)) and brain responses via EEG, Serious Brick Play and PEBL cognitive test battery. The controlled study involved 90 adult participants (21-35 years) with various backgrounds tested with a series of activities with controlled lunch once (8 hours) weekly for 21 weeks (3 rounds of 7 weeks each) consecutively. The controlled exposure was achieved by employing particulate and molecular filters whilst changing the rate of fresh air intake to manipulate the IAQ pollutants. The environmental chamber was designed to mimic an office environment equipped with a working desk, chairs, desktop, a set of Lego bricks, an EEG headset, disposable earplugs, a mineral water bottle, and an activities instruction sheet. In addition, other IAQ parameters (carbon monoxide (CO), formaldehyde, ambient temperature, relative humidity, bacteria count levels, fungi count levels, and ozone (O3)) stated in SS 554 were monitored during the study. The short-term exposure to increasing levels of IAQ pollutants increases cognitive stress that affects working memory related to anxiety, increased in mental effort, delay in reaction time, increased perceived complexity of a task, and effects on cognitive flexibility & control and planning. Significant results such as creativity (affected by variation in TVOC) are shown to improve by 10.8%, planning (affected by variation in CO2) is shown to improve by 25.8%, and speed of information processing (affected by variation in PM2.5) is shown to improve by 272.7ms. The single-blind longitudinal study concluded that different aspects of IAQ affected various cognitive parameters. For an individual employee over the space of 1 year, the value of the increased performance is S$1.66. The short-term effects make it profitable over the space of many years.