Published online by Cambridge University Press: 20 May 2010
HUMAN BIOCLIMATOLOGY
The high altitude environment is one of severe stress for humans. Air pressure is reduced from its sea level value by 30 percent at 3000 m and almost 50 percent at 5000 m (see Table 2.2, 32) and, on average, air temperatures decrease from sea level to the same elevations by about 18 and 30℃, respectively. Other factors include low humidity and increased ultraviolet radiation. Visitors to high altitudes, above about 3000 m, generally notice the oxygen deficiency as a slight breathlessness, especially when undergoing any exertion, and they frequently experience sleep-disordered breathing and/or apnea. Beneficial effects of altitude have also been noted among asthma sufferers due to reduced levels of air pollution and allergens (Hackett, 2001).
The consequences for permanent residents of high altitudes are quite different, however, since they acquire long-term acclimatization. In fact, low temperatures, snow cover and, therefore, limited food resources rather than oxygen deficiency are the dominant controls of human occupancy in the high mountains (Grover, 1974). We will consider first some basic physiological aspects relating to mountain environments in terms of short-term visitors.
Physiological factors and responses
Oxygen deficiency
The difficulties of breathing and symptoms of mountain sickness experienced by early travelers crossing high mountain passes is reported in many historical documents, but scientific explanations only began to be proposed in the late eighteenth century (Houston, 2001).
To save this book to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.