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Human Tolerance to Hot Climates

A. R. Lind

10.1002/cphy.cp090106

Source: Supplement 26: Handbook of Physiology, Reactions to Environmental Agents

Originally published: 1977

Published online: January 2011

Full Article on Wiley Online Library



Abstract

The sections in this article are:

1 Hot Climates
2 Physiological Factors affecting Heat Tolerance
3 Human Tolerance to Heat in Various Occupations
3.1 Prescriptive and Compensatory Zones of Climates
3.2 Findings Pertinent to the Prescriptive and Compensatory Zones from Other Studies
3.3 Intolerable Zone of Climates
4 Concluding Remarks
Figure 1. Figure 1.

Rectal temperature of one man who walked continuously for 1 h at 370 W in many different thermal environments. Results from selected evironments illustrate the principle of the Prescriptive Zone. ET, Effective Temperature of the different climates.
Figure 2. Figure 2.

Rectal temperatures of three men (•, ○, ⋄) after walking continuously for 1 h at 370 W in a wide range of environmental conditions.
Figure 3. Figure 3.

Rectal temperature of one man after he had walked continuously for 1 h at 230 (•), 370 (○), and 490 W (Δ) in a wide range of climates.
Figure 4. Figure 4.

Average rectal temperature of six younger (•) and six older (○) men at the end of each of four successive periods shovelling. The men worked and rested successively throughout an 8‐h period in five different climates. Results show that for both groups the three coolest climates (Effective Temperature 20, 26, and 28°C) were in the Prescriptive Zone, and all those results are pooled. In the hotter climates (Effective Temperatures 29.5 and 30.5°C) the older men had higher rectal temperatures than the younger men.
Figure 5. Figure 5.

Total number of subjects exposed in each climate and percentage of men who were adjudged to have failed in each climate, in the 1st hour (), 2nd hour (), and 3rd hour () of exposure to work in the heat. The four climates, A, B, C, and D, had Effective Temperatures of 21, 27, 28.9, and 31.1°C, respectively.
Figure 6. Figure 6.

Individual values of rectal temperature of those men who completed a 3‐h walk in each climate. Solid line is drawn through values in the lower quartile.
Figure 7. Figure 7.

Individual values for esophageal temperature in relation to oxygen uptake or external work load (left panel) and to oxygen uptake in percent of the individual's maximal oxygen uptake (right panel).

From Saltin & Hermansen 49
Figure 8. Figure 8.

Psychorometric chart with lines or points adduced from evidence from various laboratories (see text for references). Data are for seminude men working at 370 W: 1, upper limits of the Prescriptive Zone for unacclimatized men; 2, upper limits of the Prescriptive Zone for acclimatized men; 3, upper limits of zone where thermal equilibrium can just be maintained by acclimatized men. The zone between 2 and 3 represents the compensatory zone of climates for acclimatized men in circumstances as described in the text.
Figure 9. Figure 9.

Suggested model of environmental limits to be set for industrial work between 120 and 580 W for clothed, acclimatized men. The term ULPZ refers to the upper limit of the Prescriptive Zone and the Environment Driven Zone is the Compensatory Zone.

From Dukes‐Dubos & Henschel 13
Figure 10. Figure 10.

The symbols represent the average tolerance times of inactive men in experiments involving 2 to 10 men (about 100 men in all), as described in the text; the encircled symbols refer to experiments on highly acclimatized men 63. Line A, reciprocal of those average tolerance times; line B, reciprocal of the shortest tolerance times of any individual in those experiments.
Figure 11. Figure 11.

Average tolerance times of groups of 6 to 31 men working at 325–385 W, as described in the text. Line A, reciprocal of those average tolerance times; line B, reciprocal of the shortest tolerance times of any individual in those experiments.
Figure 12. Figure 12.

Median (line A) tolerance times of 6 (○), 18 (•), or 48 () men working at 475 W. The tips of the arrows show the shortest individual tolerance time for each group of men (line B). Line C represents an arbitrary reduction of 20% of the times shown by line B, as described in the text.


Figure 1.

Rectal temperature of one man who walked continuously for 1 h at 370 W in many different thermal environments. Results from selected evironments illustrate the principle of the Prescriptive Zone. ET, Effective Temperature of the different climates.



Figure 2.

Rectal temperatures of three men (•, ○, ⋄) after walking continuously for 1 h at 370 W in a wide range of environmental conditions.



Figure 3.

Rectal temperature of one man after he had walked continuously for 1 h at 230 (•), 370 (○), and 490 W (Δ) in a wide range of climates.



Figure 4.

Average rectal temperature of six younger (•) and six older (○) men at the end of each of four successive periods shovelling. The men worked and rested successively throughout an 8‐h period in five different climates. Results show that for both groups the three coolest climates (Effective Temperature 20, 26, and 28°C) were in the Prescriptive Zone, and all those results are pooled. In the hotter climates (Effective Temperatures 29.5 and 30.5°C) the older men had higher rectal temperatures than the younger men.



Figure 5.

Total number of subjects exposed in each climate and percentage of men who were adjudged to have failed in each climate, in the 1st hour (), 2nd hour (), and 3rd hour () of exposure to work in the heat. The four climates, A, B, C, and D, had Effective Temperatures of 21, 27, 28.9, and 31.1°C, respectively.



Figure 6.

Individual values of rectal temperature of those men who completed a 3‐h walk in each climate. Solid line is drawn through values in the lower quartile.



Figure 7.

Individual values for esophageal temperature in relation to oxygen uptake or external work load (left panel) and to oxygen uptake in percent of the individual's maximal oxygen uptake (right panel).

From Saltin & Hermansen 49


Figure 8.

Psychorometric chart with lines or points adduced from evidence from various laboratories (see text for references). Data are for seminude men working at 370 W: 1, upper limits of the Prescriptive Zone for unacclimatized men; 2, upper limits of the Prescriptive Zone for acclimatized men; 3, upper limits of zone where thermal equilibrium can just be maintained by acclimatized men. The zone between 2 and 3 represents the compensatory zone of climates for acclimatized men in circumstances as described in the text.



Figure 9.

Suggested model of environmental limits to be set for industrial work between 120 and 580 W for clothed, acclimatized men. The term ULPZ refers to the upper limit of the Prescriptive Zone and the Environment Driven Zone is the Compensatory Zone.

From Dukes‐Dubos & Henschel 13


Figure 10.

The symbols represent the average tolerance times of inactive men in experiments involving 2 to 10 men (about 100 men in all), as described in the text; the encircled symbols refer to experiments on highly acclimatized men 63. Line A, reciprocal of those average tolerance times; line B, reciprocal of the shortest tolerance times of any individual in those experiments.



Figure 11.

Average tolerance times of groups of 6 to 31 men working at 325–385 W, as described in the text. Line A, reciprocal of those average tolerance times; line B, reciprocal of the shortest tolerance times of any individual in those experiments.



Figure 12.

Median (line A) tolerance times of 6 (○), 18 (•), or 48 () men working at 475 W. The tips of the arrows show the shortest individual tolerance time for each group of men (line B). Line C represents an arbitrary reduction of 20% of the times shown by line B, as described in the text.

References
 1. Adam, J. M., F. P. Ellis, J. O. Irwin, M. L. Thomson, and J. S. Weiner. Physiological responses to hot environments of young European men in the tropics. I. A preliminary study to determine the effects of exposure for four hours twice weekly to varying combinations of air temperature, humidity and air movement. Med. Res. Council (London) R. N. P., Rep. 52: 721, 1952.
 2. Adolph, E. F. Physiology of Man in the Desert. New York: Interscience, 1947.
 3. Astrand, I. Aerobic work capacity in men and women with special reference to age. Acta. Physiol. Scand. Suppl. 169, 64–73, 1960.
 4. Bar‐or, O., H. M. Lundgren, and E. R. Buskirk. Heat tolerance of exercising obese and lean women. J. Appl. Physiol. 26: 403–409, 1969.
 5. Belding, H. S., and E. Kamon. Evaporative coefficients for prediction of safe limits in prolonged exposures to work under hot conditions. Federation Proc. 32: 1598–1601, 1973.
 6. Bell, C. R., and M. J. Crowder. Durations of safe exposure for men at work in high temperature environments. Ergonomics 14: 733–757, 1971.
 7. Bidlot, R., and P. Ledent. Travail dans les milieux a haute temperature. Que savons‐nous des limites de temperature humainement supportables? Comm. No. 28, Institut d'hygiene des Mines, Hasselt, Belgium, 1947.
 8. Bligh, J., and R. Moore (editors). Essays on Temperature Regulation. Amsterdam: North Holland, 1972.
 9. Blockley, W. V. A systematic study of the human sweat response to activity and environment in the compensable zone of thermal stress. Washington, D.C.: NASA, 1965. (Rep. CR‐65260)
 10. Blockley, W. V., J. W. McCutchan, J. Lyman, and C. L. Taylor. Human tolerance for high temperature aircraft environments. J. Aviation Med. 25: 515–522, 1954.
 11. Crockford, G. W., and J. Goudge. Dynamic insulation: an equation relating airflow, assembly thickness and conductance. Proc. Roy. Soc. Med. 63: 1012–1013, 1970.
 12. Crockford, G. W., R. F. Hellon, P. W. Humphreys, and A. R. Lind. An air‐ventilated suit for wear in very hot environments. Ergonomics, 4: 63–70, 1961.
 13. Dukes‐Dobos, F., and A. Henschel. Development of permissible heat exposure limits for occupational work. ASHRAE J. 15: 57–62, 1973.
 14. Eichna, L. W., W. F. Ashe, W. B. Bean, and W. B. Shelley. The upper limits of environmental heat and humidity tolerated by acclimatized men working in hot environments. J. Ind. Hyg. Toxicol. 27: 59–84, 1945.
 15. Ellis, F. P., H. M. Ferres, and A. R. Lind. The effect of water intake on sweat production in hot environments. J. Physiol., London 125: 61P, 1954.
 16. Ellis, F. P., H. M. Ferres, A. R. Lind, and P. S. B. Newling. The upper tolerable levels of warmth for acclimatized European men working in the tropics. Med. Res. Council (London) R. N. P. Rep. 53: 759, 1953.
 17. Haldane, J. S. Second Report to the Doncaster Coal Owners' Committee. Trans. Instit. Min. Engr., London 48: 555–569, 1914.
 18. Hardy, J. D., A. P. Gagge, and J. A. J. Stolwijk (editors). Physiological and Behavioral Temperature Regulation Springfield, Ill.: Thomas, 1970.
 19. Haymes, E. M., E. R. Buskirk, J. L. Hodgson, H. M. Lundegren, and W. C. Nicholas. Heat tolerance of exercising lean and heavy prepubertal girls. J. Appl. Physiol. 36: 566–571, 1974.
 20. Hertzman, A. B., and I. D. Ferguson. Failure in temperature regulation during progressive dehydration. Ohio: Wright Air Development Center, 1959. (Tech. Rep. No. 59‐398)
 21. Humphreys, P. W., A. R. Lind, and K. F. Sweetland. The energy expenditure of coal miners at work. Brit. J. Ind. Med. 19: 264–275, 1962.
 22. Iampietro, P. F., M. Mager, and E. B. Green. Some physiological changes accompanying tetany induced by exposure to hot, wet conditions. J. Appl. Physiol. 16: 409–416, 1961.
 23. Iampietro, P. F., and R. F. Goldman. Tolerance of men working in hot environments. J. Appl. Physiol. 20: 73–76, 1965.
 24. Jensen, R., and F. Dukes‐Dobos. Validation of proposed limits for exposure to industrial heat. [Cited by F. Dukes‐Dobos and A. Henschel .]
 25. Kerslake, D. McK. The Stress of Hot Environments. London: Cambridge University Press, 1972.
 26. Killick, E. M. Physiological response to breathing hot air. J. Hyg. 32: 332–339, 1932.
 27. Leithead, C. S., and A. R. Lind. Heat Stress and Heat Disorders. London: Cassell, 1964.
 28. Lind, A. R. A physiological criterion for setting thermal environmental limits for everyday work. J. Appl. Physiol. 18: 51–56, 1963.
 29. Lind, A. R. Physiological effects of continuous or intermittent work in the heat. J. Appl. Physiol. 18: 57–60, 1963.
 30. Lind, A. R., P. W. Humphreys, K. J. Collins, K. Foster, and K. F. Sweetland. Influence of age and daily duration of exposure on responses of men to work in the heat. J. Appl. Physiol. 28: 50–56, 1970.
 31. Lind, A. R. Effect of individual variation on upper limits of prescriptive zone of climates. J. Appl. Physiol. 28: 57–62, 1970.
 32. Lind, A. R., and D. E. Bass. Optimal exposure time for development of acclimatization to heat. Federation Proc. 22: 704–708, 1963.
 33. Lind, A. R., and R. F. Hellon. Assessment of physiological severity of hot climates. J. Appl. Physiol. 11: 35–39, 1957.
 34. Lind, A. R., R. F. Hellon, J. S. Weiner, and R. M. Jones. Tolerance of men to work in hot, saturated environments with reference to mines‐rescue operations. Brit. J. Ind. Med. 12: 296–303, 1955.
 35. Lind, A. R., C. S. Leithead, and G. W. McNicol. Cardiovascular changes during syncope induced by tilting men in the heat. J. Appl. Physiol. 25: 268–276, 1968.
 36. Lind, A. R., G. W. McNicol, and F. D. K. Liddell. Permissible tolerance times for rescue personnel wearing the Aerorlox, Simbal, Aerophor and Proto apparatus. National Coal Board. Rep. Ph. P/p(69)1. London: National Coal Board, 1969.
 37. MacPherson, R. K. (editor). Physiological Responses to Hot Environments. Med. Res. Council London: H. M. Stationery Office, 1960. (Sp. Rep. No. 298)
 38. McArdle, B., W. Dunham, H. E. Holling, W. S. S. Ladell, J. W. Scott, M. L. Thomson, and J. S. Weiner. The prediction of the physiological effects of warm and hot environments: the P4SR index. Med. Res. Council (London) R. N. P. Rep. 47: 391, 1947.
 39. McConnell, W. J., F. C. Houghten, and C. P. Yagloglou. Air motion —high temperatures and various humidities —reactions on human beings. Trans. Am. Soc. Htg. Vent. Engr. 30: 199–224, 1924.
 40. Macworth, N. H. Researches on the measurement of human performance. Med. Res. Council Spec. Rep. No. 268. London: H. M. Stationery Office, 1950.
 41. Nielsen, B., and M. Nielsen. Body temperature during work at different environmental temperatures. Acta Physiol. Scand. 56: 120–129, 1962.
 42. Nielsen, M. Die Regulation der Korpertemperatur bei Muskelarbeit. Skand. Arch. Physiol. 79: 193–230, 1938.
 43. Provins, K. A., R. F. Hellon, C. R. Bell, and R. W. Hiorns. Tolerance to heat of subjects engaged in sedentary work. Ergonomics 5: 93–97, 1962.
 44. Robinson, S. Physiological adjustments to heat. In: Physiology of Temperature Regulation and the Science of Clothing, edited by L. H. Newburgh. London: Saunders, 1949, p. 193–239.
 45. Robinson, S., E. S. Turrell, and S. D. Gerking. Physiologically equivalent conditions of air temperature and humidity. Am. J. Physiol. 143: 21–32, 1945.
 46. Rowell, L. B. Human cardiovascular adjustments to exercise and thermal stress. Physiol. Rev. 54: 75–159, 1974.
 47. Rowell, L. B., K. K. Kraning, II, J. W. Kennedy, and T. O. Evans. Central circulatory responses to work in dry heat before and after acclimatization. J. Appl. Physiol. 22: 509–518, 1967.
 48. Saltin, B. Aerobic work capacity and circulation at exercise in man. Acta. Physiol. Scand. Suppl. 230, 62: 1–51, 1964.
 49. Saltin, B., and L. Hermansen. Esophageal, rectal and muscle temperature during exercise. J. Appl. Physiol. 21: 1757–1762, 1966.
 50. Senay, L. C., Jr. Movement of water, protein and crystalloids between vascular and extravascular compartments in heat‐exposed men during dehydration and following limited relief of dehydration. J. Physiol., London 210: 617–635, 1970.
 51. Senay, L. C., Jr. Body fluids and temperature responses of heat exposed women before and after ovulation with and without rehydration. J. Physiol., London 232: 209–219, 1973.
 52. Senay, L. C., Jr., and M. L. Christensen. Changes in blood plasma during progressive dehydration. J. Appl. Physiol. 20: 1136–1140, 1965.
 53. Stolwijk, J. A. J., B. Saltin, and A. P. Gagge. Physiological factors associated with sweating during exercise. Aerospace Med. 39: 1101–1105, 1968.
 54. Tromp, S. W., and W. H. Weihe (editors). Proceedings of Symposium on Temperature Regulation, Dublin. Intern. J. Biometeriol. 15: 2–4, 1971.
 55. Veghte, J. H., and P. Webb. Body cooling and response to heat. J. Appl. Physiol. 16: 235–238, 1961.
 56. Wagner, J. A., S. Robinson, S. P. Tzankoff, and R. P. Marino. Heat tolerance and acclimatization to work in the heat in relation to age. J. Appl. Physiol. 33: 616–622, 1972.
 57. Webb, P. Pain limited heat exposure. In: Temperature: Its Measurement and Control in Science and Industry. New York: Reinhold, 1973, vol. 3, part 3, p. 245–250.
 58. Webb, P., and J. F. Annis. Biothermal responses to varied work programs in men kept thermally neutral by water cooled clothing. Washington, D.C.: NASA, 1967. (Rep. No. CR‐739)
 59. Winslow, C. E. A., and A. P. Gagge. Influence of physical work on physiological reactions to the thermal environment. Am. J. Physiol. 134: 664–681, 1941.
 60. World Health Organization. Health Factors Involved in Working Under Conditions of Heat Stress. Geneva: W.H.O., 1969. (W.H.O. Tech. Rep. Ser. No. 412)
 61. Wyndham, C. H. Tolerable limits of air conditions for men at work in hot mines. Ergonomics 5: 115–122, 1962.
 62. Wyndham, C. H. The physiology of exercise under heat stress. Ann. Rev. Physiol. 35: 193–220, 1973.
 63. Wyndham, C. H., C. G. Williams, J. F. Morrison, A. J. A. Heyns, and J. Siebert. Tolerance of very hot humid environments by highly acclimatized Bantu at rest. Brit. J. Ind. Med. 25: 22–39, 1968.
 64. Wyndham, C. H., N. B. Strydom, J. F. Morrison, F. D. Dutoit, and J. G. Kraan. Responses of unacclimatized men under stress of heat and work. J. Appl. Physiol. 6: 681–686, 1954.

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Article Title: Human Tolerance to Hot Climates
 

How to Cite

A. R. Lind. Human Tolerance to Hot Climates. Compr Physiol 2011, Supplement 26: Handbook of Physiology, Reactions to Environmental Agents: 93-109. First published in print 1977. doi: 10.1002/cphy.cp090106