Smog Outdoors Saps Worker Productivity Indoors

Dog days in the call center

The study analyzed data from almost 5,000 employees that worked in call centers for Ctrip, China’s largest travel agency. Because each worker is compensated in part based on the volume of calls and orders, each worker tracks the number of calls handled per shift and the amount of time that he or she spent on breaks. Researchers compared this productivity data to daily air pollution levels and found that workers were 5%–6% more productive when air pollution levels are rated as good (defined as an air pollution index, or API, of 0–50) versus when they are rated as unhealthy (API of 150–200).

What’s more, some measures of productivity took a hit when air quality levels exceeded just 100 API, contradicting current guidance that suggests impacts to the general population (as opposed to sensitive populations, such as asthmatics) don’t occur until the API is over 150.

As the researchers deconstructed the data, they found that the productivity hits were mainly caused by workers taking longer breaks, not because they spent longer on each phone call. 

Your brain on air pollution

The culprit, the researchers suggest, is likely very small particulate matter (PM₁₀). Although the API in China takes into account three criteria pollutants, the pollutant with the highest index on a given day determines the score. In Shanghai and Nantong where the study was conducted, PM₁₀ is the pollutant with the highest index 95% of the time, according to the researchers.

This outdoor air pollutant is formed when airborne solid and liquid particles emitted from power plants, industries, and automobiles react together, but it can easily penetrate indoors. One report from JLL and PureLiving estimates that 75% of PM₁₀ finds its way into our buildings from the outside. And then, it is so small that it can pass beyond the lung barrier, enter the bloodstream, and become embedded deep in the brain stem. Greater exposure to these particles is associated with lower intelligence and diminished performance over a range of cognitive domains, so it makes sense that short-term exposures might cause the mind to grow weary faster, say the researchers. That explains why productivity so closely correlated with air quality—the workers weren’t being lazy; they physically needed more breaks for their brains.

Claiming causality

The authors argue that their study setup allows them to “credibly isolate the causal effect” that air pollution has on worker productivity—something that previous study authors have been reluctant to claim. That’s because this study takes into account potential confounders like:

• Discretion over labor supply—the workers have little control over which days they come to work, so the possibility that the most productive chose not to work on high pollution days can be ruled out.
• Variation in demand—the firm serves clients throughout China, so it is not likely that pollution levels local to the call center influence client demand for services.
• Stress of traffic—traffic is potentially a strong confounder because it can directly reduce productivity by creating emotional stress and making employees late for work—and it also may coincide with bad air quality days. The researchers discounted this possibility by consulting a previous experiment at Ctrip that measured productivity when employees worked from home. The correlation between avoiding traffic and productivity was negative and statistically significant at conventional levels, indicating traffic was not likely confounding the productivity effects the researchers had observed.  

Adding up the cost

This lost productivity comes at a cost, according to the researchers. If the same effect is applied to all service-sector workers in China, for example, a 10-unit reduction in national pollution levels would bring in US$2.2 billion per year. Or, applied to Los Angeles, bringing air quality into compliance (API of 0–50) would grow service sector productivity by $374 million.