Researchers Evaluate Most Effective Methods of Preventing Heat Stress and Illness in Workers

CHPPR Investigator and Southwest Center for Occupational and Environmental Health Program Director Brett Perkison, MD, MPH, is leading a new study to evaluate the effectiveness of cooling vests in protecting construction workers from heat stress. This research is part of a broader effort to develop better practices for protecting at-risk workers from heat-related illness.

“Our aim is to combat heat stress early, before the harm becomes irreversible,” said Dr. Perkison.

With global temperatures soaring to record highs, heat exposure is becoming a serious health concern for vulnerable populations like construction workers. Heat hazards not only endanger workers’ lives but also impact employers through decreased productivity and increased costs. Comprehensive heat stress prevention programs are essential, yet there is a lack of studies on the effectiveness of individual components and no federal standard for heat stress prevention.

Dr. Perkison’s new study assesses the effectiveness of cooling vests in reducing heat strain on workers, as well as the capacity of personal sensing monitor devices to measure and detect heat strain. The primary measurement of heat strain was heart rate variability (HRV) or the change in the degree that the heart rate goes up and down. There has been some evidence shown in laboratory settings that early symptoms of heat stress can be detected by a decrease in an individual’s HRV. Participating construction workers in at rural construction site just east of Houston were divided into two groups, with one group wearing both cooling vests and monitoring devices for a day and the second wearing only the monitoring devices. The cooling vests consisted of a loose-fitting vest with pockets on the inside of the vest. Quick freezing liquid gel packs from a freezer were placed in the lining just prior to the workers going out into the outdoor workplace for the afternoon. On the second day, the groups switched with the one previously not wearing the cooling vest the day before now wearing the vest and vice versa. All participants also completed questionnaires about their experiences regarding the perception of feeling hot at the end of the shift.

Preliminary results show that cooling vests effectively reduced both heat strain as measured by the monitor’s HRV and by a change in the perception of heat stress by the individual. This perception lessened greatly after the first hour when the gel packs heated up to in temperature. The study suggests that heart rate variability, as measured by the monitoring devices, can serve as an effective indicator of the onset of heat stress and that cooling vests can be used to alleviate these symptoms if the gel packs are replaced on a regular basis.

This study is part of Dr. Perkison and his team’s ongoing work to combat heat stress among workers. In April, he published a paper in the Journal of Occupational and Environmental Medicine on the impact of removing a medical surveillance program from an effective heat illness prevention program in Central Texas. This observational study found that while a standardized heat illness prevention program significantly reduced heat-related illnesses, the removal of the surveillance portion led to a renewed increase in illness rates. These results suggest that medical surveillance programs are crucial in reducing heat-related illnesses.

“These two small studies illustrate the need for effective heat stress programs to have multiple ways to effectively reduce the risks of developing heat stress symptoms,” said Perkison, “as well as the need to utilize effective personal monitoring technology to identify those individuals are developing heat stress symptoms early on in order to treat them easily and effectively. Eventually, we want to develop a study that encompasses all of this into one big heat stress program and to figure out the optimal way of protecting outdoor workers in the face of steadily increasing temperatures each summer.”

To learn more, visit the Southwest Center for Occupational and Environmental Health Research and Practice page.