Airtight buildings threaten cognitive function

People working in well-ventilated offices with below-average levels of indoor pollutants and carbon dioxide function significantly better than those working in offices with typical levels, according to a new study published in Environmental Health Perspectives.

Indoor pollution in airtight buildings can reduce cognitive ability.

Researchers from the Harvard T.H. Chan School of Public Health in Boston, MA - looked at the effect of "green" versus "non-green" buildings and found that indoor working environments could adversely affect cognitive function, whereas improved air quality could greatly increase the cognitive function performance of workers.

Since the 1970s, energy-efficient design has led to increasingly airtight buildings, with potential for poor indoor environmental quality. Air exchange rates in homes have decreased from approximately one air change per hour (ACH) in 1970 to 0.1-0.2 ACH in new homes.

Lower commercial ventilation requirements in the early 1980s led to "sick building syndrome," with significant annual costs and productivity losses due to health symptoms attributable to indoor environment factors, such as humidity, ventilation rate and chemical-emitting materials.

Design credits favor energy over health

In response, "green" building rating systems were introduced to reduce the environmental footprint of buildings and improve health by giving design credits to buildings adopting green design, operation and maintenance.

Although the credits cover ventilation, filtration, chemical and pollutant sources, they mainly focus on energy efficiency and environmental performance.

Green buildings gain credits for lower concentrations of particles, nitrogen dioxide, volatile organic compounds (VOCs) and allergens; but carbon dioxide CO₂ and air exchange rate are generally omitted due to the focus on energy efficiency.

Fast facts about indoor pollutants

• Sources of VOCs include pesticides, paints, air fresheners, fabric conditioners and cleaners
• VOCs may cause headaches, eye and respiratory infections, central nervous system, liver and kidney damage and cancer
• To avoid ill effects, use products with VOCs outdoors and always check safety labels.

The current study aimed to identify the specific attributes of green building design that influence cognitive function, an objective measure of productivity.

Researchers assessed the decision-making performance of 24 participants from various professions, while working in a controlled office environment.

For 6 days, while performing their normal work, participants were exposed to various simulated building conditions: conventional conditions with relatively high concentrations of VOCs, such as those emitted from common materials in offices; green conditions with low VOC concentrations; "green+" conditions with enhanced ventilation; and conditions with artificially elevated levels of CO₂, independent of ventilation.

In a double-blind study, participants performed their normal work activities 3 days a week, from 9 am-3 pm, for 2 consecutive weeks in randomly assigned cubicles in one of two nearly identical office environments.

At 3 pm each day, they performed 1.5-hour cognitive tests using Strategic Management Simulation (SMS) software designed to test the effectiveness of management-level employees through assessments of higher-order decision-making. Scores for nine cognitive factors were given, based on responses to the simulation.

Compared with those working in conventional environments, cognitive performance scores for those in the green+ environments were, on average, double; scores for those in the green environments were 61% higher.

Particularly affected were the areas of crisis response (97% higher scores in green conditions and 131% higher in green+), strategy (183% and 288% higher) and information usage (172% and 299% higher).

Need to address CO₂ levels

CO₂ is not normally considered a direct indoor pollutant, but for 7 out of 9 cognitive functions tested, average scores decreased as CO₂ levels approached 950 ppm (parts per million), levels officially considered acceptable, and typical of many indoor environments. For example, 66% of 120 classrooms in Texas measured CO₂ over 1000 ppm, reportedly causing student absences.

This study reflected typical indoor office environments. Researchers call for investigations of other environments, such as homes, schools and airplanes, where lower cognitive function and decision-making could have significant impacts on productivity, learning and safety.

The researchers spend 90% of our time indoors and 90% of the cost of a building are the occupants, yet indoor environmental quality and its impact on health and productivity are often an afterthought. These results suggest that even modest improvements to indoor environmental quality may have a profound impact on the decision-making performance of workers.

References:

1.  Associations of cognitive function scores with carbon dioxide, ventilation, and volatile organic compound exposures in office workers: a controlled exposure study of green and conventional office environments, Joseph G. Allen et al., Environmental Health Perspectives, doi.org/10.1289/ehp.1510037, published 26 October 2015.
2.  Harvard T.H. Chan School of Public Health news release, accessed 28 October 2015 via EurekAlert.
3.  Additional source: National AG Safety Database (NASD), Questions about indoor air quality?, accessed 28 October 2015.