A new Harvard study to be published in Environmental Health Perspective demonstrates that higher concentrations of carbon dioxide (CO2) and volatile organic compounds (VOCs) can negatively impact brain function. The study, “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” led by Harvard Professor Joseph Allen, embedded office workers in a controlled environment at the Willis H. Carrier Total Indoor Environmental Quality laboratory at the University of Syracuse Center of Excellence. Over the span of 6 days, workers spent time in a typical cubical-based work environment where they were exposed to varying levels of carbon dioxide and VOCs. At the end of each day, the testers were asked to take a computerized test of their decision-making skills. The baseline condition, which is what most office workers experience daily, was termed “Conventional”, while a “Green” day indicated reduced VOCs, and the “Green+ day” also included reduced CO2 levels achieved by increasing outdoor air mixing. The study reported, “On average, cognitive scores were 61% higher on the Green building day and 101% higher on the two Green+ building days than on the Conventional building day.” This study is remarkable in its implication that employee work performance is strongly impacted by the office’s indoor air quality. The authors suggest that this work translates to the home environment, and more work could be done to examine specific impacts at home.
I want to comment on the study design and its implications. For background, NASA scientists have documented the increase in ambient carbon dioxide levels related to global warming. It was just this year, 2015, when global CO2 levels hit 400 parts per million (ppm), up from about 275 ppm in 1950. In the study above, the Conventional day assumed 945 ppm in a standard work environment. However, many “stuffy” work environments often experience 1,400 ppm. The Green+ day assumed 550 ppm, which is because a lot of outdoor air was being circulated in the space. Keep in mind that the total CO2 number is a combination of outside air blending with air exhaled from human beings who are occupying the space. Tighter spaces have slower rates of outdoor air, and thus have higher CO2 concentrations. Spaces that are less tight have more outdoor air, and lower CO2 levels. However, this assumption only holds true so long as outdoor air CO2 levels are low! As outdoor CO2 levels increase, it becomes more difficult to keep indoor CO2 levels low.
This study shows quite clearly that brain function (along the 9 measures of cognitive responses measured) reduces as CO2 levels increase. In fact, the authors determined that a 400 ppm increase in CO2 reduced cognitive function by 21%. The significant rise in ambient CO2 means that humans today are breathing significantly more CO2 than we did 75 years ago. As science has shown CO2 to be a major contributor to global warming, the government’s response to global warming has included a large emphasis on energy efficiency. By reducing demand for energy, we reduce pollution created by power plants. But there is a side effect of this policy. In the context of reducing heating and cooling energy, the solution includes not only more efficient appliances, but also tightening buildings to keep conditioned air in the building longer. These policies have helped save energy. But the less understood impact has been a worsening of indoor air quality as buildings become too tight. There are many pollutants including CO2 and VOCs that become more concentrated in tight buildings.
The good news here is that we know how to solve this problem. By adding mechanical ventilation with energy recovery, we can ensure that CO2 and other pollutant levels are kept low while allowing us to save significant amounts of energy. We note that current ventilation standards allow for exhaust-only ventilation, which uses bathroom exhaust fans on timers to bring in fresh air by pulling conditioned air out of the house. We view this as wasting energy. While exhaust-only ventilation is cheaper to implement, it is a bad policy from an energy conservation and global warming perspective. The main point here is that we can no longer be laser-focused on maximizing energy savings. Instead, we have to acknowledge that maximizing energy efficiency in buildings requires us to invest in mechanical ventilation at the same time.
Currently, consumers, business owners, and even the HVAC industry are mostly unaware that energy efficiency and indoor air quality are a trade-off. So while smart ventilation and energy efficiency strategies are being mandated by new building codes (newer codes are better than older codes), millions of consumers and businesses are retrofitting their homes and businesses in unhealthy ways. The government can help educate the public to consider mechanical ventilation as part of any retrofit strategy. Until this happens, both consumers and office workers are at risk of seeing their indoor air quality deteriorate in the quest for energy efficiency. Thus, while the global warming debate has been focused on impacts to agriculture, sea levels, and other environmental impacts, we have been missing an important factor – global warming is raising CO2 levels, which is probably making us dumber too.