Indoor Pollutant Emissions from Electronic Office Equipment
This page updated December 18, 2008
Chair’s Air Pollution Seminar
Wednesday, January 7, 2009
Indoor Pollutant Emissions
Thomas E. McKone, Ph.D.
recent studies have identified office equipment, such as computers and
printers, as key sources of indoor pollutants. But significant and
unexplained variability in reported emission rates among devices and
under differing conditions with the same device are often
encountered—resulting in uncertainty and confusion. We describe methods
and results from a recent research project to make standardized
emissions measurements of organic pollutants, ozone, and particulate
matter from a selected set of office equipment typically used in
residential and office environments. The project included a detailed
literature review and two experimental phases. We measured and
evaluated emissions for six categories of pollutants—volatile organic
compounds (VOCs), low-molecular-weight aldehydes, semi-volatile organic
compounds (SVOCs), siloxanes, ozone, and particulate matter (PM).
Both computers and printers produced detectable emissions of many VOCs; SVOCs, including polycyclic aromatic hydrocarbons, brominated flame retardants, and organophosphate flame retardants; and siloxanes. Many of the compounds emitted are on the Proposition 65 list of potentially harmful chemicals. The total number of identified VOCs, SVOCs, and siloxanes released from new and operating computers included 40 compounds and typically amounted to 300 to 500 µg/h of total chemical emissions. These emissions decreased as the computer “aged” (based on total operation hours). Turning the computer on and off intermittently had almost no impact on the decrease in emissions relative to continuous operation. The total number of identified VOCs, SVOCs, and siloxanes emitted by active printers included 30 compounds and amounted to 2,000 to 4,000 µg/h of total chemical emissions during active printing.
To provide context for our emission measurements, we used simple mass balance models (with 20 m3 and 100 m3 rooms and 0.2 ACH) to compare potential indoor concentrations to a range of health-protection guidelines. Most of our estimated exposures do not exceed these guidelines. The exceptions are formaldehyde emissions from computers for which our 20 m3 room-scale concentration estimate exceeds the California Chronic Reference Exposure Limit (CREL) and No Significant Risk Level (NSRL) for cancer, and dibutylphthalate emissions from printers for which our 20 m3 room-scale dose estimate exceeds the California Maximum Allowable Dose Level (MADL) for reproductive toxicity.
Laser printers emit large amounts of ultra-fine to fine particles, which are primarily due to a large burst (10 billion or more particles) released during each initial print. We found that the particle emissions rates were correlated with power consumption in laser printers. These emissions are likely the most important and still the least understood impacts that office equipment can have on the indoor environment.
The California Energy Commission was the primary funding source for this work. The Commission will use these measurements to assess the relationship between pollutants emitted from office equipment and ventilation requirements and energy usage. The Air Resources Board will use these data to better estimate source emissions contributing to the public’s indoor exposure to toxic air contaminants, and to better inform the public of ways to mitigate their exposure to such compounds.
Thomas E. McKone, Ph.D., is a senior staff scientist and deputy department head at the Lawrence Berkeley National Laboratory and an adjunct professor and researcher at the University of California, Berkeley School of Public Health. Dr. McKone's research interests include the development, use, and evaluation of models and data for human-health and ecological risk assessments; chemical transport and transformation in the environment; and the health and environmental impacts of energy, industrial, and agricultural systems. Dr. McKone served six years on the EPA Science Advisory Board and has been a member of numerous National Academy of Sciences committees and United Nations scientific committees. Dr. McKone was recently appointed by California Governor Arnold Schwarzenegger to the Scientific Guidance Panel for the California Environmental Contaminant Biomonitoring Program. Dr. McKone is a fellow of the Society for Risk Analysis and a former president of the International Society of Exposure Science (ISES). The ISES awarded him the 2003 Constance L. Mehlman Award for “contributions in exposure analysis research” that have provided “new approaches for the reduction or prevention of exposures” and have “helped shape national and state policies” and the 2008 Jerome J. Wesolowski award for outstanding contributions to the field of exposure assessment. Thomas McKone earned his Ph.D. in engineering from the University of California, Los Angeles.
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