Health officials encourage people to stay inside during ozone-advisory days or periods of extreme heat. Their warnings suggest our home or office building may offer protection from the harmful consequences of climate change. Yet a groundbreaking report from the Institute of Medicine (IOM) concludes that, surprisingly, our indoor environment ― where we spend over 90 percent of our time ― is precisely where we’ll experience most of the adverse health effects of global warming.
The report’s findings suggest that alterations in indoor environmental quality induced by climate change are an important public-health problem, and the authors recommend that the U.S. Environmental Protection Agency spearhead efforts to make indoor environment and health issues an integral part of federal climate change research and action plans.1
Recently, a study published in Indoor Air by IOM report co-author William Nazaroff at UC Berkeley illustrated one of the ways that our indoor environment is influenced by the environment outside.2 Nazaroff and his research team measured ultrafine particles in six northern California classrooms. Outdoor concentrations were also measured at each school site. They found that average indoor particle concentrations when students were present in the classroom were within a comparable range of those outdoors. After deciphering patterns in their measurements, the study’s authors were able to conclude that most of the classroom particle exposure could be attributed to outdoor particles that had penetrated inside.
“Poor indoor environmental quality creates health problems and impairs the ability of occupants to work and learn,” IOM report authors say.3
Ventilation, therefore, plays a significant role in improving indoor environments. Higher ventilation rates are associated with fewer adverse health effects and with superior work and school performance, according to scientists at the Lawrence Berkeley Laboratory. In addition, evidence suggests that occupants of buildings with higher ventilation rates have lower rates of absence from work or school.4
“The issues of climate change bring to the forefront the need to be more efficient in the way that we use energy,” says Nazaroff. “There will likely be changes in buildings to reduce energy use. Those changes don’t automatically mean that they will make indoor environmental quality problems worse, but they could. For example, if we reduce ventilation rates with a goal of saving energy then pollution emitted indoors will rise to higher levels.”
Nazaroff points out that, “We see a higher incidence of a phenomenon called sick building syndrome in mechanically ventilated buildings compared to those that are naturally ventilated with operable windows. But until now, we haven’t paid enough attention to the hygiene of the ducting system – the fans and filters – in buildings that are mechanically ventilated.”
If we did a better job of managing the hygiene of ventilation systems, Nazaroff believes we could probably operate safely with less ventilation than we do today. And, in outdoor environments that are heavily polluted, “we can do a better job of filtering the pollution from the ventilation air, along with working to ensure we don’t have excessive indoor emission sources. If we can put all those elements together,” says Nazaroff, “we can reduce the carbon footprint and have healthful buildings.”
In a separate article, Nazaroff notes that approximately one-third of global, energy-related greenhouse gas emissions occur in buildings, according to an estimate based on year 2002 measurements.5 In developed countries, improvements with the largest potential include increasing the thermal performance of building envelopes with better insulation and windows and improving space-heating systems.6
In addition to indoor air pollution, the IOM report draws attention to shifts in pesticide exposure as occupants and building owners respond to infestations of pests like termites whose geographic ranges have changed due to climate change.
Problems of flooding pose additional risks to the indoor environment. Increased frequency and intensity of heavy downpours have already been observed in the United States, the report states.7
“As buildings become wet more often, we end up with mold and mildew problems that have indoor environmental consequences,” says Nazaroff. “In the case of Hurricane Katrina, there was additional fallout. Trailers used for emergency housing were later found to be emitting unsafe levels of formaldehyde. I can’t say that’s a consequence of climate change, but it is a consequence of an extreme weather event that is likely to become more frequent.”
Poor environmental conditions and indoor contaminants cost the U.S. economy tens of billions of dollars a year by worsening illnesses and allergic symptoms that affect productivity.8
The IOM report suggests that, if we consider the consequences of climate change adaptation and mitigation actions before they play out, it will yield benefits in health and avoid costs of medical care, remediation, and lost production.9
COEH member William Nazaroff is the Daniel Tellep Distinguished Professor and Vice-Chair for Academic Affairs for the Department of Civil and Environmental Engineering at UC Berkeley.
1,3,7,9IOM (Institute of Medicine). 2011. Climate Change, the Indoor Environment, and Health. Washington, DC: The National Academies Press.
2Mullen NA, Bhangar S, Hering SV, Kreisberg NM, Nazaroff W. Ultrafine particle concentrations and exposures in six elementary school classrooms in northern California.Indoor Air. 2011 Feb;21(1):77-87.
5ürge-Vorsatz D, Danny Harvey LD, Sevastianos M, Levine MD. Mitigating CO2 emissions from energy use in the world's buildings.Building Research and Information. 2007;35(4):379-98.
6Nazaroff WW. Climate change, building energy use, and indoor environmental quality.Indoor Air. 2008 Aug;18(4):259-60.
8Fisk WJ, Rosenfield AH. Estimates of improved productivity and health from better indoor environments. Indoor Air. 1997;7(3):158-72.
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