rates. Some microbial agents also cause infections (this topic is addressed in Chapter 6).
The effects of climate change on moisture indoors are driven by several factors, including extreme weather events, local changes in temperature and humidity, and the adaptations that occupants make and mitigation strategies that they use in response to changed environmental conditions.
The US Global Change Research Program notes that increases in air temperatures and increased frequency and intensity of heavy downpours have already been observed in the United States and that likely future changes “include more intense hurricanes with related increases in wind, rain, and storm surges” (USGCRP, 2009). Extreme weather conditions may lead to breakdowns in building envelopes followed by sudden infiltration of water into indoor spaces. Dampness problems and water intrusion create conditions favorable to the growth of fungi and bacteria and may cause building materials to decay or corrode and lead to off-gassing of chemicals. In areas where the climate is warm and humid for more months of the year, air conditioning will be used more often. Well-designed and properly operating heating, ventilation, and air conditioning (HVAC) systems can ameliorate humid conditions; poorly designed or maintained systems may introduce moisture and create condensation on indoor surfaces.2 Mold-growth prevention and remediation may also introduce fungicides and other agents into the indoor environment, which can lead to adverse exposures of occupants.
Flooding as a result of extreme weather events can have profound health and economic effects. In 2010, there were 103 flood-related fatalities in the United States, a significantly higher number than the 10-year average of 71 measured between 2001 and 2010 (National Oceanic and Atmospheric Administration, 2011). In that same year, floods were part of six of the seven most costly insurance loss events in the United States; events that were responsible for $6.3 billion in losses (Swiss Re, 2011). Jonkman and colleagues (2009) estimate that two-thirds of the 771 known fatalities of Hurricane Katrina were the direct result of flooding and that additional fatalities were associated with flood-related circumstances including lack of access to potable water or medical services and exposure to extreme heat as a result of power outages.
Altered climatic conditions will not introduce new dampness problems into the indoor environment but may make existing problems more wide-
2 This topic is addressed in Chapter 7.