Climate Change, the Indoor Environment, and Health
Amid the considerable research on how climate change may affect public health, one subject has received relatively little attention—the impact of climate change on indoor environments and thereby on the health of people who live, work, study, or play in them. No government or private body has lead responsibility for investigating this question, and the lack of leadership is hindering action on identifying potential hazards, formulating solutions, and setting research and policy priorities.
Against this backdrop, the U.S. Environmental Protection Agency (EPA) asked the Institute of Medicine to convene an expert committee to summarize the current state of scientific understanding of the effects of climate change on indoor air and public health and to offer priorities for action.
Health Problems Here—and May Worsen
The committee’s report, Climate Change, the Indoor Environment, and Health, points to extensive research on how climate change affects the outdoor environment, how the outdoor environment affects indoor environments under different climate conditions, and how indoor environments affect occupant health, among other related topics. But facing a dearth of research specifically directed at how these factors interact, the committee analyzed and synthesized information from the various independent lines of research.
The committee concludes that climate change influences indoor environmental quality, warranting attention and action. The committee based its conclusion on three key findings:
- Poor indoor environmental quality is creating health problems today and impairs the ability of occupants to work and learn. By one estimate, poor indoor conditions cost the nation’s economy tens of billions of dollars a year in exacerbation of illnesses and allergenic symptoms and in lost productivity.
- Climate change may worsen existing indoor environmental problems and introduce new problems.
- There are opportunities to improve public health while mitigating or adapting to alterations in indoor environmental quality induced by climate change.
Problematic Exposures Identified
To help in targeting research, the committee identified five major types of climate-induced indoor environmental problems.
Indoor air quality . Indoor environments can be contaminated by chemical, organic, and particulate pollutants that migrate from outdoors or that result from gas stoves and other indoor emission sources, such as building materials, radon, and environmental tobacco smoke. Climate change can affect these factors in various ways. For example, changes in the outdoor concentrations of a pollutant due to alterations in atmospheric chemistry or atmospheric circulation will affect indoor concentrations. Measures to reduce energy use in buildings, such as lowering ventilation rates may cause higher exposures to pollutants emitted from indoor sources. The expected increased use of air conditioning, if accompanied by reduced ventilation, could increase the concentrations of pollutants emitted from indoor sources. Additionally, power outages—caused by heat waves or other extreme weather events—could lead to the use of portable electricity generators that burn fossil fuels and emit poisonous carbon monoxide.
Dampness, moisture, and flooding . Extreme weather conditions associated with climate change may lead to more frequent breakdowns in building envelopes—the physical barrier between outdoor and indoor spaces—followed by infiltration of water into indoor spaces. Dampness and water intrusion create conditions that encourage the growth of fungi and bacteria and may cause building materials to decay or corrode, leading in turn to chemical emissions. Poorly designed or maintained heating, ventilation, and air- conditioning systems may introduce moisture and create condensation on indoor surfaces. Humid conditions can, however, be improved by well-designed and properly operating systems. Mold-growth prevention and remediation activities also may introduce fungicides and other agents into the indoor environment.
Infectious agents and pests . Weather fluctuations and climate variability influence the incidence of many infectious diseases. Climate change may affect the evolution and emergence of infectious diseases, for example, by affecting the geographic range of disease vectors. The ecologic niches for pests will change in response to climate change, leading to changed patterns of exposure and, possibly, increased use of pesticides in some locations.
Thermal stress . Extreme heat and cold have several well-documented adverse health effects. High relative humidity exacerbates these effects in hot conditions. An increased frequency of extreme weather events may result in more frequent power outages that expose persons to potentially dangerous conditions indoors. The elderly, those in poor health, the poor, and those who live in cities are more vulnerable to both exposure to temperature extremes and the effects of exposure. Those populations experience excessive temperatures almost exclusively in indoor environments.
Building ventilation, weatherization, and energy use . Leaky buildings are common and cause energy loss, moisture problems, and migration of contaminants. Poor ventilation is associated with occupant health problems or lower productivity. Climate change may make ventilation problems more common or more severe by prompting the implementation of energy-efficiency (weatherization) measures that limit the exchange of indoor air with outdoor air. The introduction of new materials and weatherization techniques also may lead to unexpected exposures and health risks.