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Extreme heat poses extreme risks for outdoor workers

Working outdoors during extreme heat is a growing concern for Southwestern cities like Las Vegas, where summer temperatures are rising each year. However, the risks of working outdoors in extreme heat are not distributed evenly. Female workers are facing disproportionate impacts, and more experienced outdoor workers are at higher risk than those with fewer years on the job. 

In a new study led by the Desert Research Institute, scientists have investigated how extreme heat is impacting the workforce in three of the hottest cities in North America – Las Vegas, Los Angeles, and Phoenix. The results share important findings for policymakers and employers across the US. 

Heat index data combines temperature and humidity as a measure of how people feel the heat. To assess the relationship between extreme heat and workplace heat-related illness, the study compared occupational injuries and illnesses from 2011-2018 with heat index data. 

This type of analysis has not been completed in the past, which allowed the research team to identify interesting social implications. 

The experts found a significant increase in heat index at two of the three locations (Phoenix and Las Vegas) during the study period. In these locations, average heat index values for June to August increased from “extreme caution” in 2012 to “danger” by 2018. Over the same period, the number of nonfatal heat-related workplace injuries and illnesses increased steadily, climbing above the national average in 2018. 

“Our data indicate that the increases in heat are happening alongside increases in the number of nonfatal occupational injuries across these three states,” said lead author Erick Bandala. “Every year we are seeing increased heat waves and higher temperatures, and all of the people who work outside in the streets or in gardens or agriculture are exposed to this.” 

Next, the team wanted to learn about the number of male and female workers affected. At the beginning of the study in 2011, 26 to 50 percent of the people affected were female. By 2018, 42 to 86 percent of the people affected were female. 

This could be a result of more women entering the outdoor workforce, or, it could be related to the vulnerability of women to certain heat-related effects, like hyponatremia — a condition that develops when too much plain water is consumed under high heat conditions and sodium levels in blood get too low. 

“As the number of female workers exposed to extreme temperatures increases, there is an increasing need to consider the effect of gender and use different approaches to recommend prevention measures as hormonal factors and cycles that can be exacerbated during exposure to extreme heat,” said study co-author Dr. Kebret Kebede, an associate professor of Biology at Nevada State College.

The researchers also examined the length of an employee’s service and found that those who had more than five years of experience were at greater risk than those with less than one year. This may be due to a reduced perception of risk, or could be a cumulative effect of years of chronic heat exposure.

In severe cases, heat-related illness or injury can cause extensive damage to all tissues and organs, disrupting the central nervous system, blood-clotting mechanisms, and liver and kidney functions. In these cases, lengthy recoveries are keeping many outdoor workers away from work for more than 30 days. 

“These lengthy recovery times are a significant problem for workers and their families, many of whom are living day-to-day,” said Bandala. “When we have these extreme heat conditions coming every year and a lot of people working outside, we need to know what are the consequences of these problems, and we need the people to know about the risk so that they take proper precautions.”

The team hopes that their results will be useful to policymakers to protect outdoor workers by adopting regulation to address heat illness. The need for public policy is clear to alleviate health and the economic impacts of rising temperatures. 

The experts also hope that the information will inform outdoor workers to stay safe during extreme heat, and employers who rely on a healthy workforce to keep their businesses operating. In the future, the team hopes to continue research to better support people who are most vulnerable to the impacts of extreme heat. 

The study is published in the International Journal of Environmental Science and Technology.

By Katherine Bucko, Staff Writer

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