ion efforts such as acclimatization programs (e.g., ensuring adequate heating and cooling systems, and improved insulation). The report also considered the reduction in extreme cold deaths expected in a warmer climate; approximately 100 fewer cold deaths per year were expected in the US by 2050, with no further reduction in cold deaths between 2050 and 2090 (Ebi et al. 2018)
The bottom line is that high and low temperature extremes affect vulnerable populations, such as the unwell, the poor, the young, and the elderly, among others. Understanding the extreme-temperature risk for the future requires additional in-depth study of the interaction between temperature-related deaths and socioeconomic factors. With additional information, we can avoid adverse policy outcomes and achieve effective adaptation strategies.
Human impacts from excessive heat
Heat affects humans in a variety of ways, impinging on multiple body systems. As depicted in Figure 3-2, elevated temperatures directly cause heat-related conditions ranging from muscle cramps to heat exhaustion to heat stroke, the latter of which is deadly if not treated promptly (Becker and Stewart 2011; Epstein and Yanovich 2019). In addition, elevated temperatures have been associated with increases in respiratory disease (Anderson et al. 2013; Ho et al. 2015); heart disease and strokes (Knowlton et al. 2009; Wang et al. 2016; Achebak et al. 2018); and fluid and electrolyte disorders, kidney disease, and kidney failure (Bobb et al. 2014; Ross et al. 2018; Sorensen and Garcia-Trabanino 2019). A study by Li et al. (2012) found evidence of a potential high-temperature threshold for several age groups (15–64 yr, 75–84 yr, and >85 yr) and specific heat-related causes for hospital admissions that included endocrine, genitourinary, and renal morbidities, as well as accidental injuries and intentional self-harm.
Elevated temperatures are also associated with increased risk of preterm labor (Auger et al. 2014; Ha et al. 2016; Avalos et al. 2017), as well as sudden infant death/sudden unexpected infant death syndromes (SIDS/SUID) (Jhun et al. 2017). Elevated temperatures also cause worsening mental health, as described in the Mental Health subsection later in Section 3.
The severity and duration of high temperatures influence the health impacts resulting from extreme heat. In addition, air pollution and population vulnerability (Basu 2009) compound these impacts. Vulnerability is also a function of the typical temperatures to which a population is exposed, plus the extent to which a population adapts (Curriero et al. 2002; Baccini et al. 2008; Ho et al. 2015).
Workers, especially those who work outdoors or in hot indoor environments, are at increased risk of heat stress and other heat-related disorders, occupational injuries, and reduced productivity at work (Levy and Roelofs 2019). Workers in the agricultural sector face increased risk of heat strain and dehydration due to repeated exposures to high air temperatures, arduous physical exertion, and limited fluid intake. These risk factors may result in acute kidney injury (Moyce et al. 2017), as well as increased heat-related traumatic injuries (Spector et al. 2016). Spector et al. (2016) suggest that efforts should be made to address heat-related illness and prevent occupational injury for high-risk populations exposed to high temperatures and high physical exertion.
The impacts of increased air temperature may increase workers’ exposure to hazardous chemicals and, thus, the adverse health effects of those chemicals (Spector et al. 2016). Global warming is also increasing ground-level ozone concentrations with adverse effects on outdoor workers (Levy and Roelofs 2019).
Assessing heat impacts specific to Montana
Multiple studies—covering wide ranges of temperature, time, and geographic area—have sought to assess the health impacts of extreme heat (e.g., Morabito et al. 2014; Zhang et al. 2014). Some studies estimate how heat-related mortality differs between rural and urban landscapes (reviewed by Ho et al. 2015). Other studies develop