Recreational Activities and Athletic Competitions

Of the unacclimatized lowlanders traveling to high altitude, the largest numbers are clearly those engaged in recreational and athletic endeavors. It has been estimated, for example, that in 2013, more than 100 million people visited regions at high altitude (Burtscher et al. 2013). By way of other examples, the number of tourists entering Tibet increased from 2.5 million in 2006 to more than 15 million in 2014, (National Bureau of Statistics of China 2018), while in the western United States, 87 million people visit Colorado on an annual basis with more than one-third visiting a mountain resort (Colorado Tourism Office 2018) and more than 590,000 people alone visiting the summit of Pikes Peak (4301 m) (Pikes Peak—America’s Mountain 2019).

One of the highest profile groups of high altitude travelers are individuals engaged in trekking and mountain climbing in various regions of the world. For example, steadily increasing numbers of people have visited the Sagarmatha National Park in the Mount Everest region in the past two decades including more than 53,000 people in 2019 alone (Sagamartha National Park Office 2020) (Figure 5.1). In 2019, the Himalayan Database reported that more than 660 people summited Everest from the Nepal side and an additional 216 summited from the Northeast Ridge in Tibet (Figure 5.2). With these increasing numbers have come increasing risk for climbers. In the spring of 2019, for example, crowding high on the mountain during the narrow summit window was of major concern, as climbers waited in long queues to reach the summit of Everest, and a total of 11 people died.

One particular area of high altitude recreational activities that has seen a surge of interest in recent years is athletic events conducted at high altitude. This includes events such as the Everest Marathon, which starts at Everest base camp (5365 m) on May 29th each year in celebration of Tenzing Norgay Sherpa and Sir Edmund Hillary’s first successful climb of the mountain on May 29, 1953. Numerous other events exist, including, but not limited to, the Leadville 100 running and mountain bike races in Leadville, Colorado; the Western States 100 ultramarathon in the Sierra Nevada Mountains, California; the 171-km Ultra-Trail du Mont Blanc, which utilizes the Tour du Mont Blanc and runs through Switzerland, Italy, and France; and the Patrouille des Glaciers ski mountaineering race in the Swiss Alps.

Regardless of the particular activity in which they are engaged, all of these recreational high altitude travelers, as well as the groups discussed in the remainder of this chapter, are at risk for developing one of several forms of acute altitude illness—acute mountain sickness (AMS), high altitude cerebral edema (HACE), and high altitude pulmonary edema (HAPE). The clinical aspects, pathophysiology, and management of these problems are described in greater detail in Chapters 20–22, while issues faced by travelers with underlying medical conditions are considered in Chapter 25. Athletes engaged in races such as those mentioned earlier must face the additional challenge of decreases in exercise capacity at high altitude and resolve questions such as how long to spend at high altitude prior to their planned athletic event. These issues are considered further in Chapter 18.

Religious Pilgrimages

While much of the attention regarding nonoccupational travel to high altitude is focused on trekkers and climbers, far greater numbers of people participate in religious pilgrimages to various high altitude locations on an annual basis and have been doing so since well before trekking and climbing began in various regions of the world (Basnyat 2006; 2014). Although precise information is lacking, it has been estimated that more than 2 million people travel to elevations between 3100 m and 4600 m as part of at least seven major and several other lesser festivals in the Himalaya with the largest being in Badrinath (3100 m) and Kedarnath (3500 m), India, between May and October. These two festivals attract an estimated 1 million and 600,000 people, respectively, each year (Basnyat 2014). Many pilgrims try to participate in as many of these pilgrimages as possible over their lifetimes as they serve as important opportunities for spiritual fulfillment and a path to salvation.

At the same time, these pilgrimages pose significant physical challenges to the participants and, in many cases, a threat to health and physical well-being. In addition to infection control issues related to overcrowding and poor hygienic conditions, many participants ascend to high elevation at overly rapid rates, which significantly increases the risk of the acute altitude illnesses described in Chapters 20–22 (Basnyat et al. 2000; MacInnis et al. 2013). This problem is exacerbated by a general lack of awareness of acute altitude illness, underlying health problems and poor physical fitness among many pilgrims, as well as the fact that fasting is a common practice during the pilgrimages (Basnyat 2014). A further problem is that many pilgrims believe that physical suffering is an integral part of the experience and may even value completion of the pilgrimage over protecting their physical well-being. With increasing recognition of these problems, efforts have been made by groups such as the Himalayan Rescue Association (HRA) in Nepal to educate pilgrims and health care providers about the importance of pretravel counseling, how best to protect themselves during the pilgrimage itself, and how to set up and staff clinics, such as the temporary HRA clinic at Lake Gosainkunda (4300 m) during the August pilgrimage to that location.

Railway and Road Travel

Even if they are not engaged in recreational or religious activities or athletic competition, some unacclimatized lowlanders are acutely exposed to hypobaric hypoxia in the course of rail travel including the central railway of Peru, which crosses the Andean crest at Ticlio at an altitude of 4800 m and the more recently completed railway from Golmud in Qinghai Province, China (2810 m), to Lhasa, Tibet (3656 m). The latter is more than 1100 km in length with more than three-quarters of the distance above 4000 m altitude. In fact, the track crosses some of the highest ranges on the Tibetan plateau, the highest altitude being just over 5000 m. Travel along the railway poses risks of acute altitude illness among the train’s passengers (Wu et al. 2010) while the more than 100,000 construction workers reported to have been employed during construction also faced a significant burden of these and other medical problems (Wu et al. 2007a; 2009). One of the most challenging problems was constructing the tunnels at very high altitudes, for example the Fenghuoshan Tunnel at an altitude of 4905 m. Excavations were done with hand drills and the physical demands on the workers were enormous. To partially relieve the hypoxia, large volumes of high concentration oxygen were produced by generators located outside the tunnel, and the gas was pumped to the workface through a large pipe. It was reported that this increased the inspired PO₂ by as much as 15 mmHg, which would have reduced the equivalent altitude by about 1200 m. Another remarkable challenge was the Mount Kunlun Tunnel at an altitude of 4660 m, which is 1686 m long and believed to be the longest tunnel through permafrost in the world.

Road building is also increasing in many mountainous regions previously only accessible by air or trekking such as northern India and parts of Nepal. While road access is helpful from a socioeconomic standpoint, as it increases the speed of travel and facilitates faster and cheaper transport of supplies to these regions, it also raises the risk that individuals ascend to higher elevations at too rapid a rate and, as a result, face an increased risk of acute altitude illness. For example, after completion of a road from Besisahar (760 m) to Manang (3540 m) in the Annapurna region of Nepal in December 2014, a greater number of individuals were diagnosed with acute altitude illness at the HRA clinic in Manang when compared to a several-year period before road completion with the number of patients with acute altitude illness increasing in tandem with the number of people arriving in Nepal by motor vehicle (Figure 5.3) (Reisman et al. 2017). To meet the public health challenges posed by this situation, it will be necessary to increase efforts to educate the people traveling by road and also to build medical infrastructure in these areas seeing increasing numbers of travelers.

Mining

Mining activities have been conducted at high altitudes for many centuries. Chinese sources suggest that Tibetans worked as high as 6000 m in the Tanggula range of central Tibet mining quartz; chromate mines were also found in central Tibet (Ward 1990). The open cast mines at Thok Jalung (thok is Tibetan for gold) were investigated in 1867 by Nain Singh, one of the early clandestine native explorers of the Survey of India (Waller 1990). In several areas of the South American Andes, there is evidence that mining activities were carried out by the Incas before the Spanish conquest. The Spanish conquistadors founded the imperial city of Potosí (4060 m) in Bolivia, the site of an enormous silver mine, in the 1540s. Today, many mines are still located above 4000 m in Tibet and South America. In the former, for example, copper and gold are mined in the Shetongmon, Gyama, and Yulong districts as China expands its quest for resources (Lafitte 2011), while 10 mines are located between 4800 m and 5000 m in Peru, Bolivia, and Chile from which a variety of minerals are extracted including copper, gold, lead, molybdenum silver, tin, and zinc (Arendal 2020).

A large amount of infrastructure is necessary in communities proximate to a mine, including schools, medical facilities, and meeting halls, all of which increases the expenses of the mine. In some locales, notably in South America where low and high altitude regions are often close geographically, these considerations have led some mining operations to develop a commuting pattern where the families live at or near sea level and the miners commute to the mine itself where they spend a period of 7–10 days. In Tibet, on the other hand, due to the extent of the Tibetan plateau, commuting on a frequent basis is difficult. Miners must either reside on a permanent basis or at least for much longer periods of residence reaching into months and years. Thus the “commuting” approach to working at high altitude applies only to areas where descent to low altitudes is practical, safe, cheap, and quickly achieved.

An example of the commuting pattern is provided by the Collahuasi mine, a very large, open-cut copper mine in northern Chile. The working areas of the mine are at altitudes of 4400–4600 m, although the mining camp where the miners sleep is at 3800 m. There are currently several thousand people working at the mine, which makes it one of the largest copper mines in the world. The miners’ families live at sea level in Iquique in accommodations supplied by the mining company. Within a few hours, the miners are transported to the mine by special buses, which ride on roads built by the mining company. Miners typically spend seven days at the mine, where they work for up to 12 hours per day, and then sleep in the mining camp at an altitude of 3800 m. At the end of seven days, they are transported by bus down to Iquique, where they spend the next seven days with their families. This 7 × 7 schedule is not universally employed in the high altitude mines that use commuting, as periods of work lasting from 10 to 21 days have also been used.

Telescopes

In contrast to mining, the practice of siting telescopes at high altitude is a considerably more recent phenomenon. There are several advantages in placing telescopes at high altitudes. One is improvements in image quality due to the fact that the instrument is above much of earth’s atmosphere, which otherwise absorbs some of the optical and radio waves. Another advantage is that in some areas, such as the Chajnantor plateau, the atmosphere is extremely dry and absorption of radio waves by water vapor is therefore much less. Finally, remote mountain sites tend to have little light or radio wave pollution, although this advantage can also be achieved in other remote areas at lower altitudes. Two of the major telescopes are described next.

Chajnantor

Another major telescope site is Llano de Chajnantor in northern Chile’s Atacama Desert. This area is easily accessible by road from San Pedro de Atacama (altitude 2440 m), the first part of which is an international highway leading from Chile to Bolivia and Argentina. The drive from San Pedro de Atacama to Chajnantor takes about 1 hour, making it one of the few places in the world where it is possible to reach an altitude of 5000 m so quickly by road. In addition to the ease of accessing the facility, another advantage of the site is the fact that it sits in the rain shadow of the Andes Mountains and the Chilean Coastal Range, making it one of the driest places on earth. The barometric pressure at the site, altitude 5050 m, is about 420 mmHg, with an inspired PO₂ of only 78 mmHg.

There are two major telescope projects at this site. The first is the Atacama Large Millimeter/submillimeter Array (ALMA), a large project jointly run by the National Radio Astronomy Observatory (NRAO) (United States) and the European Southern Observatory (Figure 5.4). ALMA uses 66 high-precision dish antennas, including 54 12-m antennas and 12 7-m antennas, amounting to a total collecting area of more than 71,000 square feet (NRAO 2020). The second major project is the Atacama Pathfinder Experiment (APEX), a 12-m diameter antenna located at 5100 m and jointly run by the Max Planck Institute for Radioastronomy (Germany), the Onsala Space Observatory (Sweden), and the European Southern Observatory.

Military Operations

The most noteworthy military campaign at high altitude is the conflict between India and Pakistan over the Jammu-Kashmir region, in which large numbers of soldiers have been stationed at altitudes up to 7000 m for substantial periods of time. Many of these soldiers come from low elevations within these countries, and as a result are at risk for acute forms of altitude illness and problems associated with more prolonged stays. Classic early work on the risks to human health during acute exposure to very high altitudes was provided by Singh et al. (1969), while further accounts of the issues faced by the soldiers have been provided by Anand et al. (1990). Their work included one of the first descriptions of “adult subacute mountain sickness,” a particular form of altitude illness marked by the development of right heart failure and peripheral edema (Anand et al. 1990). Other problems have also been noted among these soldiers including a high incidence of stroke (Jha et al. 2002). Additional military operations have been conducted at high altitudes, including the Soviet and later United States-NATO conflicts in Afghanistan. The pattern of exposure to high altitude varies significantly from conflict to conflict. Whereas soldiers in the India-Pakistan conflict reside for months at a time at high elevation, soldiers in the Afghanistan theater and other locations may reside at bases at moderate elevation but deploy in a rapid fashion to higher elevation for various operations.