UC Cooperative Extension helps farm employers and workers meet challenges of heat stress

Heat stress often affects people before they notice it.

As a new law hits the books this summer to prevent heat-related illnesses in California workplaces, UC Cooperative Extension agricultural personnel management specialist Howard Rosenberg of UC Berkeley is ready with resources and information to support farmers in complying with the new standards.

Last summer, a handful of well-publicized heat-related deaths of farmworkers prompted lawmakers in Sacramento to adopt an emergency regulation to protect outdoor workers from the heat. In June, that regulation became permanent law, requiring employers to provide a quart of water per hour to their outdoor workers, a shaded area and time to rest there when necessary, and training in heat illness prevention.

But fighting heat stress is nothing new to Rosenberg, dubbed “Dr. Heat” by colleagues for his years of effort applying principles from physiology research to Californians working hard in hot environments.

“For every widely reported tragedy, there are thousands of workers hampered by excess heat,” Rosenberg said. “Everyone knows it’s hot outside, but few people realize how heat builds inside them and how much harm it’s doing.”

Early symptoms of heat illness – fatigue, irritability, loss of concentration or coordination – might result in a miscalibrated chemical mix, an injury due to mishandling a tool, bruised fruit, butchered vines, or conflicts between co-workers or in families, Rosenberg said. Other symptoms, like fainting or blurred vision from sweat in the eyes, could have tragic effects.

“A momentary loss of consciousness itself is not a lasting problem,” Rosenberg said, “unless the person is driving a tractor or standing on top of a ladder.”

Rosenberg takes on heat stress

Preventing heat-related discomfort, impaired performance and accidents, as well as heat illnesses that threaten workers’ lives, has become a focus of Rosenberg’s program, joining more traditional labor management topics, such as employee compensation, recruitment, retention and supervision.

Rosenberg was first drawn to the topic by the makers of CamelBak “hydration systems,” a soft water bottle carried on the back or around the waist that features a long tube to make frequent drinking effortless. When a CamelBak salesman asked if workers had water in the fields, Rosenberg said farmers generally provide water in “Igloo” insulated jugs. The next questions both stumped and intrigued Rosenberg: “Are they drinking it? How much and how often?”

Though not formally trained as a physiologist, Rosenberg began looking for answers and embarked on a journey that has led to his becoming a sought-after expert on dealing with heat stress.

A key to coping with heat stress is drinking enough water to replenish fluid the body loses in cooling itself, he said. When the body is working hard, its internal furnace is raging, raising core temperature from the inside.

“Our own metabolism is the prime source of the heat that stresses us,” Rosenberg said.

Radiant heat from the sun adds to the load, and hot ambient air slows down the natural release of heat. The body’s first response to heat build-up is sending more blood to its extremities and outer layers, from which heat can flow into the environment. If faster cooling is needed, sweat glands kick in, drawing fluid from the blood to carry heat through pores onto the skin surface.

With less water in the bloodstream, capacity for further cooling decreases. The heart has to pump harder to circulate thicker blood bringing nutrients and oxygen to muscles, the brain, and other vital organs.

“Drinking to replace the water lost as sweat is crucial. Waiting for a sensation of thirst is a notoriously lousy way of deciding when to drink,” Rosenberg said. “People are better off when they drink on the basis of what they know about the body, rather than simply how they feel.”

Rosenberg draws an analogy from crop irrigation systems.

“Drip is usually more effective than flood,” he said. “Drinking eight ounces of water every 15 minutes is better than chugging a whole quart at the end of an hour’s work on a long row.”

Acclimatization a key to preventing heat illnesses

Getting used to the heat is also an important factor in preventing heat illnesses, Rosenberg said. In 25 serious cases of heat illness investigated by the California Occupational Safety and Health Administration last year, water was available, but most victims were dehydrated. Four out of five sufferers were in their first week on the job; nearly half fell ill the first day on the job. None had been trained about acclimatization. Most of the illnesses were not recognized until they were in an advanced state. Victims’ mean body temperature was 104 degrees, 76 percent fainted, 38 percent were hospitalized beyond the emergency room and 54 percent died.

At a recent heat stress presentation by Rosenberg, employers wondered how to handle the issue of acclimatization.

“We hire them because we need them now,” said Ken Hernandez, the human resource manager for Tulare River Ranch, a custom calf/dairy operation.

“It’s a good idea to start by working only a part of the day and gradually increasing both work time and effort over the first week,” Rosenberg said. “And it always helps to schedule the most strenuous jobs for cooler times of day. If the work must go on full bore, be especially alert for early signs of heat illness when the weather is very hot or humid.”

David Aquino, the vice president of human relations for SunWorld, a Bakersfield table grape producer, said another concern for employers is pre-existing conditions workers bring with them to the job.

“Sunday is a big night for pachangas (parties) among Hispanics, especially the young single guys that make up a lot of our workforce. Guys will come in Monday morning hung-over. They’re already dehydrated,” Aquino said. “Or they may be obese, have diabetes or are just not feeling well that day. We’ve always dealt with heat stress. Now we will modify our program to comply with the new regulations.”

Rosenberg is helping employers tackle the challenge of getting workers to do what scientists have learned is good for them.

“Many workers are inundated with signs, slogans and exhortations. I came to the conclusion early on that most pitches about drinking water were falling on deaf ears, because they were short on ‘the why.’” Rosenberg said. “Some employers might say, ‘Do it or you’re fired,’ others might implore, ‘Do it because I’m asking you to.’ I say, do it because it makes sense. I encourage growers and supervisors to tell workers, ‘Here’s what happens, here’s how your body works, you decide.’”

Rosenberg has been traveling around California, giving employers information and resources to use in explaining to workers how to control heat stress and why those strategies work.

Training resources are available for California farmers

The first panel of Rosenberg's bilingual fold-out card for informing farmworkers about heat stress.

In partnership with the California Farm Bureau Federation and with support from the USDA Western Center for Risk Management Education, he has compiled key points concisely in Spanish and English on a pocket-sized fold-out card and printed 200,000 copies for distribution to California’s outdoor agricultural labor force. Farm Bureau is coordinating distribution by offering free supplies of cards to agricultural employers statewide. To order copies, contact Danielle Rau at drau@cfbf.com, (800) 698-3276, Ext. 5596.

Rosenberg has also put a vast collection of practical material on heat stress online at his Agricultural Personnel Management Program Web site, http://apmp.berkeley.edu. Included are links to the new regulation, information on complying with the new laws, training aids, a pdf version of the field education card, articles and heat stress references. All the materials are offered free to help employers protect their workers and businesses from the damaging effects of heat stress.

(July 2006)

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