Evaluation of Occupational Exposure Limits for Heat Stress in Outdoor Workers — United States, 2011–2016

Abstract

© 2018, Department of Health and Human Services. All rights reserved. What is already known about this topic? Recommended heat stress occupational exposure limits are based primarily on wet bulb globe temperature (WBGT), workload, and acclimatization status. These limits have not been validated at outdoor worksites. What is added by this report? Among 25 outdoor occupational heat-related illnesses, WBGT-based occupational exposure limits were exceeded for all 14 fatalities and for eight of 11 nonfatal illnesses. Six fatalities occurred when the Heat Index was <91°F (32.8°C). What are the implications for public health practice? Whenever heat stress exceeds occupational exposure limits, workers should be protected by acclimatization programs, training about symptom recognition and first aid, and provision of rest breaks, shade, and water. A Heat Index of 85°F (29.4°C) could be used as a screening threshold to prevent heat-related illness.