Document Detail


Continuing the search for WBGT clothing adjustment factors.
MedLine Citation:
PMID:  10457638     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The original concept for the heat stress limits adopted by the American Conference of Governmental Industrial Hygienists (ACGIH) was that the threshold for heat stress can be marked by environmental conditions (WBGT) that are adjusted for metabolic rate. The underlying data were based on ordinary work clothes. The Physical Agents Committee promoted clothing adjustment factors within the industrial hygiene community through a revision in the TLVs for heat stress in 1990. As approved, there were adjustment factors for three other clothing ensembles. To extend and further understand adjustment factors, adjustments for commercially available clothing ensembles and prototype ensembles have been examined. The fundamental principle of the assignment of an adjustment factor to an ensemble begins with establishing critical environmental conditions in which test subjects were just able to maintain thermal equilibrium. Four or five subjects for each ensemble walked on a tread-mill inside a climatic chamber under controlled conditions of heat stress. During each test, heart rate and core temperature were continuously monitored. After a physiological steady-state was achieved, temperature and humidity were slowly increased to maintain relative humidity at 20 percent, 50 percent, or 70 percent. Metabolic rate was assessed by measuring the rate of oxygen consumption. Reviewing a trial, the critical conditions were noted as the time when thermal regulatory control was lost (called the inflection point and marked by a steady increase in core temperature). The climatic conditions at the inflection point were used to assign a critical WBGT. A WBGT representative of each ensemble was assigned through a weighted average of different protocols. Clothing adjustment factors representing an equivalent increase in WBGT were computed by noting the difference between the representative WBGT of the cotton work clothes and the other clothing ensembles. The results suggested adjustment factors with reference to ordinary work clothes from the least stress at -2.1 to 5.5 degrees C-WBGT. The adjustment factors were reasonably well predicted by a linear regression based on a computed value for total evaporative resistance (r2 = 0.92).
Authors:
D J O'Connor; T E Bernard
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Applied occupational and environmental hygiene     Volume:  14     ISSN:  1047-322X     ISO Abbreviation:  Appl Occup Environ Hyg     Publication Date:  1999 Feb 
Date Detail:
Created Date:  1999-09-17     Completed Date:  1999-09-17     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9103256     Medline TA:  Appl Occup Environ Hyg     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  119-25     Citation Subset:  IM    
Affiliation:
College of Public Health, University of South Florida, Tampa, USA.
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MeSH Terms
Descriptor/Qualifier:
Adult
Body Temperature
Female
Heat Stress Disorders / prevention & control*
Humans
Male
Occupational Diseases / prevention & control*
Occupational Exposure / adverse effects*
Protective Clothing / standards*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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