More than five million people will die from a frightening cause: breathing.
Do you sometimes find yourself losing focus on the job? Is your thinking a little fuzzy? It could be something in the air – and you and your co-workers may be the source.
We all know that excess carbon dioxide in the atmosphere is bad. It’s a greenhouse gas that contributes to global warming, though it has no immediate harmful effects on people in concentrations that occur outdoors. Until recently, experts believed that indoor carbon dioxide — which is emitted, for example, when people exhale — also was harmless except at extremely high levels of 5,000 parts per million (ppm) or more.
New research, however, has prompted scientists to rethink this assumption.
Two studies, one published in 2012 and another last fall, suggest that indoor exposure to carbon dioxide can impair performance and decision-making. Although the research focused on workers, the findings pose troubling questions for people in many indoor environments, including schools, airplanes, autos and even homes.
“We spend 90 percent of our time indoors,” says Joseph Allen, an assistant professor of exposure assessment science at the Harvard T.H. Chan School of Public Health, lead author of the most recent study. “To get a sense of this, multiply your age by 0.9. That’s how many years you have spent indoors.”
Until now, research used CO2 measurements as a rough indicator of overall ventilation in buildings. Low ventilation rates allow concentrations of many pollutants — including CO2 — to build up, which experts have blamed for illnesses. This new research, however, suggests that even carbon dioxide may be causing problems.
“Does this mean that kids in a crowded and poorly ventilated classroom have impaired decision-making? Does it mean that kids taking a high-stakes test like the SAT might be impaired? We don’t know,” says Mark Mendell, one of the authors of the 2012 study, which was conducted by the Department of Energy’s Lawrence Berkeley National Laboratory. “But the results for the first time raise this question.”
The Berkeley Lab scientists decided to conduct their study after coming across two small Hungarian studies suggesting that indoor CO2 was harmful at levels lower than 5,000 ppm.
On nine scales of decision-making performance, participants in the Berkeley study showed significant reductions on six scales at CO2 levels of 1,000 ppm and large reductions on seven at 2,500 ppm. The most dramatic declines in performance, in which subjects were rated as “dysfunctional,” were for taking initiative and thinking strategically.
The Berkeley researchers, initially skeptical of the Hungarian studies, were flabbergasted by their findings. “We found astonishing, unbelievable effects with CO2 levels that were not that high,” Mendell says. “Our study suggested that even at 1,000 ppm there were some adverse effects on decision-making, and 2,500 produced ‘dysfunctional’ performance.”
Outdoor concentrations of CO2 in the air are around 400 ppm. Building operators have long tried to keep levels below 1,000 — as an indication of adequate general ventilation, not because they had concerns about CO2 itself. But concentrations often exceed that, especially in crowded rooms with poor ventilation, Mendell says. Indoor levels can reach several thousand parts per million, according to the Berkeley scientists, with concentrations in classrooms occasionally exceeding 3,000 ppm.
Illnesses apparently related to tight, energy-efficient new buildings received increasing attention beginning in the 1970s, with the emergence of “sick building syndrome,” a cluster of symptoms that include headaches, respiratory symptoms and difficulty concentrating. Experts identified indoor air pollutants as the likely source, but they didn’t suspect that carbon dioxide was part of the problem.
The Harvard study, which also involved researchers from SUNY Upstate Medical Center and Syracuse University, used similar testing methods as the Berkeley study, but it monitored participants over a longer period. It confirmed the 2012 results.
Twenty-four participants – architects, designers, programmers, engineers, creative marketing professionals and managers — spent six full workdays in an environmentally controlled office space, blinded to test conditions. All were exposed to the same conditions which varied each day.
The researchers studied the effects of different concentrations of air pollutants, including carbon dioxide. They also looked at performance under high and low rates of ventilation.
The subjects used a computer interface to make decisions about situations that match real-world challenges, from relatively simple tasks to highly complex problems.
On average, cognitive scores were 61 percent higher on days with low concentrations of pollutants, compared with the same participants’ scores when they spent time in a low-ventilation environment with elevated levels of pollutants, and 101 percent better on days with the most ventilation. In fact, participants scored highest in eight of nine test areas on the days with the greatest ventilation.
For seven of the nine areas of productive decision-making, the average scores decreased as the level of carbon dioxide grew higher. Compared with the two days of high ventilation, cognitive function scores were 15 percent lower on the day with moderate CO2 — about 945 ppm — and 50 percent lower on the day with CO2 concentrations around 1,400 ppm.
Worrisome, to be sure — but probably fixable. “There are things we can do, right now, to enhance indoor environmental quality and benefit human health, well-being and productivity,” Allen says. “This research has reinvigorated discussions with industry professionals on creating healthy indoor environments. People want buildings that make them healthy.”
The most obvious solution is to increase ventilation from the outside. But this will prove problematic if carbon dioxide levels continue to rise in the atmosphere. Also, it can be expensive: Outside air that comes inside must be warmed in the winter and cooled in the summer.
A recent paper by Allen and colleagues suggests that spending money to increase ventilation in office buildings would be very cost-effective for employers, estimating the cost of doubling indoor ventilation rates at $40 per person annually, against a productivity gain of $6,500 per person per year.
“The increased use of energy may be worthwhile, if it turns out to have important benefits for people in the workplace or the classroom, allowing them to think or perform better,” Mendell says.