Ability of Thermal Work Limit (TWL) to assess sustainable heat stress exposures.

Details

• Personal Author:
  Ashley CD ; Bernard, Thomas E. ; Kapanowski D
• Description:
  Thermal Work Limit (TWL) recommends a maximum metabolic rate for a given environmental condition, clothing ensemble, and acclimatization state so that thermal equilibrium can be sustained at or below the limiting metabolic rate. The purpose of this paper was to assess the ability of TWL to recommend maximum sustainable levels of heat stress using an existing database of progressive heat stress trials using four levels of clothing (woven clothing, particle barrier, water barrier, and vapor barrier), three levels of relative humidity, and three levels of metabolic rate. Each trial had a compensable and an uncompensable observation plus and observation at the transition point from compensable to uncompensable. Each observation was classified as a case (steady increase in rectal temperature) or non-case (steady rectal temperature). The data were used to compare the difference between the observed metabolic rate (Mobs) and the limiting metabolic rate of TWL (i.e., deltaLimitTWL = Mobs - TWL), where deltaLimitTWL > 0 was above the TWL limit. The sensitivity and specificity for each of the four clothing ensembles were about 0.96 and about 0.20, respectively. Logistic regression for all the data found that deltaLimitTWL, clothing, metabolic rate, and water vapor pressure were significant predictors of outcome. The ln(odds) equations for each clothing ensemble predicted a probability of an uncompensable exposure. The probability of an uncompensable outcome (case) when deltaLimitTWL = 0 was 0.14 for work clothes and particle barrier, and 0.22 for water barrier and vapor barrier. The probability of a case at deltaLimitTWL = 0 was greater than the probability of a case for the wet bulb globe temperature-based exposure limits where the probability of a case was 0.01. That is, the TWL was less restrictive than WBGT but with higher risk. [Description provided by NIOSH]
• Subjects:
  Heat Stress Disorders Hot Temperature Humidity Occupational Health Personal Protective Equipment Protective Clothing Safety
• Keywords:
  Author Keywords: Clothing; Exposure Assessment; Validity Heat Exposure; Heat Stress; Body Temperature; Thermoregulation; Protective Clothing; Hot Environments; Heat Acclimatization; Relative Humidity;
• ISSN:
  2398-7308
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  Florida ; OSHA Region 4
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  66
• Issue:
  8
• NIOSHTIC Number:
  nn:20065119
• Citation:
  Ann Work Expo Health 2022 Oct; 66(8):1081-1085
• Contact Point Address:
  Thomas E. Bernard, University of South Florida College of Public Health, Tampa, FL 33612, USA
• Email:
  tbernard@health.usf.edu
• Federal Fiscal Year:
  2023
• Performing Organization:
  Sunshine Education and Research Center, University of South Florida
• Peer Reviewed:
  True
• Start Date:
  20050701
• Source Full Name:
  Annals of Work Exposures and Health
• End Date:
  20290630
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:58ce550fc3d13a17faa8d01069df5be731032a61ef547a35ea1bcf82ff7aedeb2330b3b76c2915aabc43ff6f4389d4eb5bb533fc073e7bdbfa80562c86f403fc
• Download URL:
  https://stacks.cdc.gov/view/cdc/248607/cdc_248607_DS1.pdf
• File Type:
  [PDF - 190.22 KB ]