Press Releases

2000 Releases

Increased Sick Leave Associated with Decreased Ventilation in Office Buildings

For immediate release: November 14, 2000

Boston, MA--Office employees who work in areas that receive less fresh air from outside are more likely to call in sick than their colleagues who breathe higher levels of outside air, according to a new study by researchers at the Harvard School of Public Health (HSPH) and the Polaroid Corporation. The absences cost US companies billions of dollars each year, say the researchers in their paper, "Risk of Sick Leave Associated with Outdoor Air Supply Rate, Humidification, and Occupant Complaints," published in the current issue of Indoor Air.

In 1994, the researchers measured ventilation rates in 40 buildings owned by the Polaroid Corporation in Massachusetts with 115 independently ventilated work areas. They divided air supply into two categories: moderate (supply at 25 cubic feet per minute per person) and high (supply at 50 cubic feet per minute per person). They then analyzed sick leave taken by 3,720 employees and noted in which areas the absent employees worked. From the 3,720 employees, the researchers focused on 600 office workers because they were less likely to be exposed to irritants than those employed in manufacturing areas.

The researchers used sick leave records only of employees not on long-term disability. After controlling for factors such as age, gender, and number of times employees took off when they were not ill--such as vacation days--the researchers found that office workers employed in moderately ventilated areas were 53 percent more likely to take time off due to illness than their colleagues in highly ventilated areas. They further reported that increasing ventilation may have prevented 35 percent of the absences among workers in moderately ventilated areas.

The increased absences may result from the transmission of cold and flu viruses and other irritants that are not removed in ventilation systems with moderate air flow, said Dr. Donald Milton, associate professor in the Department of Environmental Health at HSPH and lead author of the paper. He added that employees who come to work ill and then spread airborne infections may exacerbate the situation.

In the study, the potentially preventable employee absences cost the company an average of $480 per worker per year. When the researchers extrapolated the data and applied the numbers to the US working population as a whole, they estimated that American companies lose as much as $22.8 billion each year to lost productivity resulting from poor ventilation.

Milton said that the estimated losses by the companies may be curtailed by increasing air circulation in buildings. But, he added, net savings depend on energy costs, which have risen in the past year and are expected to continue to increase during the next decade as oil reserves are depleted. Companies may want to search for alternative means of cleaning the air they recycle in their buildings, said Milton.

"I think over the next 10 to 15 years it will be important to know why we see this association between ventilation and sick leave," said Milton. "We need to figure out what we can do as energy costs go up that is cost effective but still protects the health and productivity of workers."

Further experimental study is needed to confirm and explain the results of the paper, said Milton, who added that he is looking for companies that are interested in partnering with him to conduct similar studies.

An abstract of the study is available at

The study was funded by grants from the Centers for Disease Control and Prevention/National Institute for Occupational Safety and Health, the National Institute of Environmental Health Sciences Occupational and Environmental Center, and the National Institute of Standards and Technology. 

For further information, please contact:

Robin Herman
Office of Communications
Harvard School of Public Health
677 Huntington Avenue
Boston, MA 02115
Phone: 617-432-4752