Comparison of WBGT and PHS Heat Exposure Assessment Methods

Details

• Personal Author:
  Bernard, Thomas E. ; Ferrer A
• Description:
  Objective: Two methods for assessing heat stress in occupational settings are an empirical model based on the wet bulb globe temperature (WBGT) and the Predicted Heat Strain (PHS), which is a rational model based on biophysical models of heat exchange. Their purpose is to predict limiting thermal stress in order to be able to protect the exposed worker. The purpose of this effort was to compare decision outcomes based on PHS for a range of limiting WBGT conditions. That is, are they congruent exposure assessments. Methods: Exposure scenarios were developed using all the combinations of metabolic rate, relative humidity and air speed at three levels each; two levels of radiant heat and four levels of clothing. The temperatures for all scenarios were calculated using an Excel macro that adjusted the temperatures until the WBGTeff reached the TLV. Once all data was computed, there were 216 distinct scenarios that predicted a sustainable exposure to heat stress based on WBGT. These data were used to calculate the PHS. Results: Of the 216 scenarios, there were a total of 23 incongruent scenarios. These tended to occur with high metabolic rates and low air speeds. High evaporative resistance also contributed to the incongruent scenarios. In general, the agreement was excellent. Conclusion: Although both methods are useful in assessing industrial heat stress, the added parameters of the PHS model may be a better predictor of sustainable heat stress in certain occupational settings. In these scenarios the rational PHS model yielded duration limitations even in cases where, according to the WBGT model, work would still be sustainable. [Description provided by NIOSH]
• Subjects:
  Environmental Exposure Heat Stress Disorders Hot Temperature Humidity Occupational Health Risk Assessment Risk Factors Safety Temperature
• Keywords:
  Author Keywords: Heat Stress Exposure Assessment Exposure Levels Heat Exchange Heat Stress Metabolic Rate Models PHS Risk Factors Stress Thermal Effects WBGT

  More +
• Publisher:
  University of South Florida (USF)
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Abstract or Summary
• Place as Subject:
  Florida ; OSHA Region 4
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  11
• NIOSHTIC Number:
  nn:20064002
• Citation:
  Sunshine ERC Research Poster Session/USF Health Research Day, February 21-23, 2013, Tampa, Florida. Tampa, FL: University of South Florida (USF), 2013 Feb; :11
• Contact Point Address:
  Angel Ferrer, College of Public Health, University of South Florida
• Federal Fiscal Year:
  2013
• Performing Organization:
  Sunshine Education and Research Center, University of South Florida
• Peer Reviewed:
  False
• Start Date:
  20050701
• Source Full Name:
  Sunshine ERC Research Poster Session/USF Health Research Day, February 21-23, 2013, Tampa, Florida
• End Date:
  20290630
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:23dae571dc5721ad8c4a299eac7940d480fe2fa547c204abfbd4d5a5f386f7e1164731ca189707c8549f4bcd31d9030c07cac830b691d6473133fb93b65eef59
• Download URL:
  https://stacks.cdc.gov/view/cdc/222529/cdc_222529_DS1.pdf
• File Type:
  [PDF - 158.65 KB ]