Farmworker-Relevant Heat Exposure in Different Crop and Shade Conditions

Details

• Personal Author:
  Blancas M ; Briggs NL ; Cardoso T ; Flores M ; Flunker JC ; Reeb-Whitaker C ; Schoonover, Todd ; Spector JT
• Description:
  Objectives: Agricultural workers are at risk of heat-related illness, which is preventable. Few field studies have compared farmworker-relevant heat exposure in different conditions. We examined heat exposure over time in different potential shade and work locations to inform future occupational heat prevention approaches. Methods: We assessed heat exposure in Eastern Washington State (WA) cherry and grape fields in August 2022. QUESTemp monitors recorded Wet Bulb Globe Temperature (WBGT) and Black Globe Temperature (BGT) every 10 min from approximately 07:00-14:00 for three days in the center of crop rows (mid-row), under portable shade structures (shade), and in open field (open) locations. Linear mixed effects regression (LMER) models compared WBGT and BGT among field locations. Hourly time-weighted average WBGT and comparisons with occupational exposure limits (OELs) were computed for different hypothetical work-rest cycles during the hottest sampling hours, assuming different worker effort levels, rest locations (mid-row versus shade), and acclimatization statuses. Results: Across all crops and locations during the study period, the mean/SD air temperature was 31 degrees C (88 degrees F)/3.9 degrees C (6.9 degrees F), with a maximum temperature of 39 degrees C (102 degrees F) and a mean/SD relative humidity of 30%/9.6%. LMER models suggested no significant difference in mid-row versus open WBGT but significantly lower WBGT in shade versus open locations for both cherries (main effect -5.14: 95% confidence interval [CI] -6.97,-3.32) and grapes (-6.20: 95%CI -7.73,-4.67), though this difference diminished over the course of the day. BGT was significantly higher in the mid-row than the shade (cherries main effect 14.33: 95%CI 9.52,19.13 and grapes 17.10: 95%CI 13.44,20.75). During the hottest sampling hour, the exceedances of OELs were reduced with assumptions of increased shaded break lengths, reduced effort level, and acclimatization. Conclusions: Shade canopies, but not the crops studied, provided significant reductions in heat exposure. We observed increased protection from heat assuming longer shaded breaks and reduced effort levels. Results highlight the need for additional field research on the effectiveness, feasibility, and acceptability of different shade types and work-rest cycles to guide employer optimization of best practices for worker protections, including acclimatization before high heat, sufficient shaded rest time, reduced effort levels as the day warms, and avoiding work in peak heat. [Description provided by NIOSH]
• Subjects:
  Agriculture Farmers Heat Stress Disorders Hot Temperature Occupational Health Safety Temperature
• Keywords:
  Agricultural Workers Author Keywords: Heat Stress Farmworker Farm Workers Field Study Heat Exposure Heat Stress Outdoor Workers Rest Periods Shade Temperature Effects

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• ISSN:
  1059-924X
• Document Type:
  Text
• Funding:
  Cooperative Agreement
• Genre:
  Journal Article
• Place as Subject:
  San Francisco Region [OSHA] ; Washington
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  29
• Issue:
  4
• NIOSHTIC Number:
  nn:20069809
• Citation:
  J Agromedicine 2024 Oct; 29(4):547-560
• Contact Point Address:
  June T. Spector, Department of Labor and Industries, Safety & Health Assessment and Research for Prevention (SHARP) Program, PO Box 44330, Olympia, WA 98504-4330
• Email:
  spel235@lni.wa.gov
• Federal Fiscal Year:
  2025
• NORA Priority Area:
  Agriculture, Forestry and Fishing
• Performing Organization:
  University of Washington
• Peer Reviewed:
  True
• Start Date:
  20010930
• Source Full Name:
  Journal of Agromedicine
• End Date:
  20270929
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:7f5b303804ee2b8e6774c117baed91e6c1d26248bf8ed3816307f2b9487aa6fb763984d54799177a8901a36f6ae39b9998a90ba300f330df66dc89b504e4a403
• Download URL:
  https://stacks.cdc.gov/view/cdc/208164/cdc_208164_DS1.pdf
• File Type:
  [PDF - 4.70 MB ]