Study: Ozone, Filters Linked to Sick Building Symptoms
of researchers at the U.S. Department of Energy's Lawrence Berkeley
(Calif.) National Laboratory has found evidence that the prevalence of
building-related symptoms increases with increasing outdoor
concentrations of the pollutant ozone. They also have discovered that
the type of air filter that some buildings use in their ventilation
systems may also play a role in the prevalence of symptoms.
Building-related symptoms (BRS), more commonly known as sick
building syndrome, are health symptoms reported by office workers that
improve when they leave the workplace. The symptoms can include
irritation of the eyes, nose, throat, respiratory tract, and skin, as
well as headache and fatigue.
This is the first epidemiological evidence from a field study of a
link between ambient ozone levels and BRS. It is also the first field
evidence linking BRS to a specific filtration technology used in large
The study was conducted by Michael Apte, Ian Buchanan, Mark Mendell,
and Anna Mirer of Berkeley Lab's Environmental Energy Technologies
Division in collaboration with EPA, which collected the data.
Results originated from the team's analysis of data from an EPA
study called BASE (Building Assessment Survey and Evaluation), in which
100 U.S. office buildings were studied for one week each in either the
summer or winter between 1994 and 1998. That study included surveys of
office workers and their self-reported health conditions, weather and
workplace data, and environmental conditions in and around the
(No data on indoor or outdoor ozone levels was collected during the
EPA's BASE study. Ozone data used in this analysis was obtained from
the historical records of ambient air quality monitoring stations near
the BASE buildings during the same time periods as the BASE buildings
According to Apte, "Based on patterns of associations between
building-related symptoms and certain volatile organic compounds
indoors, we hypothesized that increasing levels of outdoor ozone would
lead to higher prevalence of building-related symptoms among the
occupants within a building."
Their analysis of the BASE data shows that the prevalence of upper
respiratory symptoms in a building increases linearly with increasing
concentration of outdoor ozone. It also shows that the indoor
concentrations of formaldehyde, acetaldehyde, and organic acids
including pentanal, hexanal and nonanal increased with increasing
outdoor ozone. All of these are known sensory irritants, and
formaldehyde is a known carcinogen.
In a second paper, the researchers report on how different types of
building air filters can affect the prevalence of BRS symptoms. Data
from a subset of buildings in the BASE study showed strong statistical
connections between a certain type of air filter and increased BRS.
The team found that the combination of higher outdoor ozone levels
and the use of a polyester or other synthetic filter correlates with a
statistically significant increase in the prevalence of BRS compared to
other types of air filters. This filter showed a significant
association with lower and upper respiratory symptoms, cough, sore
eyes, fatigue, and headache.
The research suggests that replacing the polyester/synthetic filter
could have a major positive impact, reducing BRS prevalence by up to 75
percent in buildings with high outdoor ozone concentrations, and by up
to 39 percent in lower ozone environments. "The study estimated that
removing both risk factors -- higher ozone in outdoor air and
polyester/synthetic filters -- could reduce BRS by 26 to 62 percent,"
Apte notes that the results of both studies require further
verification. "This research is a first step, and it needs to be
replicated in other studies with a statistical design specifically to
address the ozone-symptom association and with accurate information on
filters and ozone levels. The strongest studies would involve
controlled interventions on these two factors," he says.
Two papers describing the results will be published in the journal Indoor Air. The work was funded by the Centers for Disease Control--National Institute for Occupational Safety and Health.