SICK BUILDING: When ground-level ozone known as smog increases outside, so do the number of sick workers inside office buildings.
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Smog caused by ground-level ozone isn't just an outdoor air problem. A new study shows that when the irritant's level rises outside, the number of people inside suffering from so-called "sick building syndrome" also increases. (Ozone, an air-polluting oxygen molecule (O₃), forms when sunlight strikes motor vehicle tailpipe emissions.)

"We found that outdoor air pollution, ozone, is associated with symptoms of lower-respiratory and upper-respiratory stress that occur in buildings to workers," says environmental health scientist Michael Apte of Lawrence Berkeley National Laboratory in California, who analyzed U.S. Environmental Protection Agency (EPA) data gathered on office air quality across the country. "These symptoms are prevalent at fairly high levels throughout the U.S. and are similar in other parts of the world."

Sick building syndrome is a term used to describe a broad range of ailments, including dry eye, congestion, difficulty breathing, fatigue and headaches that strike workers inside office buildings but disappear when they leave the premises. Previous studies have shown that individuals may exhibit such symptoms when irritating chemicals and particles are found in the air and that ventilation with clean air can help alleviate or prevent the problem.

The EPA from 1994 to 1998 tested indoor air quality and surveyed office workers in 100 buildings in 37 cities—from the smoggiest to the cleanest—across the country. Nearly all of the buildings had mechanical ventilation systems rather than windows or other natural means of circulating air. Officials measured air quality across a broad range of seasonal conditions, from an office in North Dakota on a –18-degree Fahrenheit (–28-degree Celsius) day to a workplace in Arizona on a 108-degree F (42-degree C) day.

The EPA found that, on average, even in buildings with no special history of sickness, nearly 19 percent of workers surveyed complained of dry eye, 21 percent felt congested on the job, 4 percent complained of difficulty breathing, more than 19 percent felt fatigued, and more than 15 percent reported having headaches while at work.

Apte and his colleagues compared the EPA office data with the agency's measures of local atmospheric ozone levels to determine whether they were linked. Their findings, published in the journal Indoor Air: the number of workers suffering symptoms indoors increased with the amount of smog outside—even at levels below the national limit of 80 parts per billion of ozone in air over an eight-hour period set by the EPA.

"Our body is telling us that there is something irritating in the air," Apte says. "People in the work condition are under all kinds of stress, but it does seem to be a real physical response."

The researchers found that the type of air filter used in a building's ventilation system was also tied to the number of ill people. "There is a six times greater likelihood that these symptoms will occur if you have both higher ozone levels and the polyester or synthetic filters," Apte says, "than if you are in lower ozone levels and using a fiberglass filter."

No specific cause for sick building syndrome has been identified, but Apte speculates that the symptoms are due to unstable ozone molecules chemically interacting with the wide range of materials found in an office building, beginning with the polyester air filter. "Glass is really a very inert material," Apte says of the fiberglass filters. "On the other hand, polyester is a polymer and it's got a lot of bonds in there that are capable of being broken up by ozone."