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Use of swallowable core body temperature sensors and other measures for a heat stress evaluation of employees of a southwestern U.S. Park.

Krake A
American Industrial Hygiene Conference and Exposition, June 1-6, 2002, San Diego, California. Fairfax, VA: American Industrial Hygiene Association, 2002 Jun; :83
Because of working conditions of high heat stress and moderate to extreme physical exertion, the potential for the development of heat stress prompted southwestern U.S. park managers to request NIOSH assistance. In response, NIOSH investigators evaluated heat stress and strain among park service personnel using swallowable core body temperature (CBT) sensors, external heart rate monitors, and WBGT monitors. Pre- and post-shift weight comparisons were made and changes in blood chemistries were determined. In addition, job activities were analyzed according to metabolic heat production estimates. ACGIH suggests a maximum CBT of 101.3 degrees F for medically selected, acclimatized personnel and 100.4 degrees F for unselected, unacclimatized personnel. For individuals with normal cardiac performance, sustained heart rate (over several minutes) should not exceed 180 beats per minute (bpm) minus age. Chronic demands placed on the body were evaluated by calculating the average heart rate for the entire activity, which should not exceed 115 bpm. Finally, there is a greater risk of heat strain if profuse sweating is sustained over hours, so weight loss over a shift should not exceed 1.5% of body weight. NIOSH work/rest regimen tables were used to plot the estimated metabolic heat against the environmental heat measurements. On all but two days (of eight), WBGT temperatures exceeded 90 degrees F, with a high of 98.8 degrees F. Dry bulb temperatures exceeded 109 degrees F every day, with a high of 122.5 degrees F. Physiological sampling results indicated that every study participant experienced heat strain to some 1 degree. Most of the participants developed -1 mild dehydration during their activities, but] their electrolytes remained within normal limits. Body weight comparisons showed an average loss of 1.2% among participants. 1 Metabolic heat production estimate showed most activities were close to or exceeded the parameters of the NIOSH work/rest regimen. (Recommendations were made to develop heat stress management and illness surveillance systems.
Heat-stress; Workers; Work-environment; Heart-rate; Monitors; Physiological-testing; Sampling
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American Industrial Hygiene Conference and Exposition, June 1-6, 2002, San Diego, California
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division