How to help workers stand the heat

According to the NIOSH publication Working in Hot Environments, the frequency of accidents in hot environments is higher than in more moderate environmental conditions: “Working in a hot environment lowers the mental alertness and physical performance of an individual. Increased body temperature and physical discomfort promote irritability, anger and other emotional states which sometimes cause workers to overlook safety procedures or to divert attention from hazardous tasks.”

If the workers you need to protect can’t get out of the kitchen, what can you do to reduce their risk of heat-related illnesses?

“Well, it’s the same answer we get for everything else—good planning and recognition that you are facing that kind of a hazard,” says Phillip Bishop, professor of kinesiology and director of the Human Performance Laboratory at the University of Alabama.

Kris Bancroft, an OEHS consultant with Tiger Safety Consultants, Dayton, Tenn., agrees, “Preventing the incidence of heat stress requires knowledge, planning, worker acclimatization, training and the use of some engineering and administrative controls. These factors should be considered when designing a heat stress prevention program.”

Know Your Ingredients
A worker can react to heat in a variety of ways, and it is important to recognize all of them. Even conditions that might not be deadly by themselves can cause serious problems. Bancroft shares this story: “In the mid-’90s, a worker employed by a landscaping business was planting bushes at a golf course in south Florida. It was reported that he left his work and walked over to a pond, where he bent over to splash water on his face. He subsequently collapsed and fell into the water. The cause of death was listed as ‘drowning.’”

He continues, “Subsequent to the event, there was no record of the worker’s core body temperature, enzyme levels in the blood or autopsy to determine the presence of aneurysm, yet the statements of the co-workers indicated that the worker was experiencing some degree of difficulty with the heat.”
Preheating

Although IHs and other health and safety professionals are certainly aware of heat-related conditions, it can be helpful to review “Heat Disorders and Health Effects” in the OSHA Technical Manual (see “Hot Web Resources,”). The manual is clear when it describes factors leading to heat-related injuries: Everything from age, weight, degree of physical fitness, degree of acclimatization, metabolism, use of alcohol or drugs, preexisting medical conditions, type of clothing worn and prior heat injury can all affect a worker’s sensitivity to heat. Because of all these factors, it is not easy to predict which workers will be affected —and how they will be affected.

Environmental factors can also come into play. Radiant heat, air movement, conduction and relative humidity are considerations that should be taken into effect. And don’t forget PPE; for instance, a self-contained breathing apparatus can increase the possibility of heat stress due to its weight. Totally encapsulating chemical protection suits can also add to the problem.

“Anything encapsulating—welding gear or other PPE—[makes it] much harder to recognize the symptoms [of heat stress],” says Bishop. “You can’t see your workers very well in this gear.”
He added that it can be difficult to have workers monitor themselves, because often workers aren’t aware of their own body temperature and don’t realize they are having heat-related problems.

Keeping an Eye on the Oven
The ACGIH TLV® for heat stress states, “Excessive heat strain may be marked by … body core temperature greater than 38.5 C (101.3 F) for medically selected and acclimatized personnel; or greater than 38 C (100.4 F) in unselected, unacclimatized workers.” And according to the OSHA Technical Manual, monitoring workers is one of several important steps to reduce heat stress. So how can you tell if a worker is overheated? The answer is awareness.

Daniel Webster, president of Quest Technologies in Oconomowoc, Wis., offers a solution for monitoring heat stress. “With or without protective clothing, the accepted area method for assessment of how much work can be done without danger of heat stress calls for a WBGT (wet bulb globe temperature) monitor.”

Webster points out that there is no perfect solution to the heat stress problem. While they cannot take into consideration several personal factors, WBGT monitors have been successful in the past. “If one needs a good way to assess [personal] factors as well, it would be wise to turn to a personal heat stress monitor,” he says.

But Bishop warns that his lab’s studies show that not all personal monitors are 100 percent effective, and they can lead to a false sense of security. “Our studies are that you get some false negatives,” he says.

HQ Inc. in Palmetto, Fla., manufactures one such personal monitor, the CorTemp system. HQ Product Manager Susan Smith says that their ingestible monitor has “been used for years in research and medicine, but it also has great benefits for industrial [environments]. It is highly convenient, highly accurate and highly safe. It gets to the core of the problem, literally.”

These ingestible monitors are relatively inexpensive, but the cost adds up over time. Also, not all workers want to swallow a radio transmitter. Other personal heat monitors are also available, including ear sensors, heart rate monitors and skin temperature monitors.

While agreeing that personal heat monitors can help, Bishop still cautions health and safety professionals to not totally rely on the technology. “[Personal heat monitors are] a good idea, but we haven’t quite mastered it yet,” he says.

Adding Cool Ingredients
OSHA recognizes five major types of engineering controls to reduce heat stress: Ventilation, air cooling, fans, shielding and insulation.

“Put up shades, radiant shielding [such as] a tarp or a barrier, make sure all the workers are acclimated and make sure they are hydrated,” says Bishop.

To ensure adequate hydration, OSHA suggests that workers get one cup of cool, nonalcoholic fluid every 20 minutes when working in hot conditions. The agency also adds that ample amounts of liquid should be placed close to the work area. In some cases, it might be possible for workers to carry their own supply. “One thing the military is doing [is] wearing the Camelbaks®,” says Bishop (see below for one soldier’s perspective on heat stress). “Portable hydrators can have a lot of industrial applications.”

Choose your hydrating fluid carefully. “The problem with water is the thirst sensation is resolved very quickly,” notes Bishop. If people don’t feel thirsty, they may stop drinking and not stay sufficiently hydrated. “If [people] drink other fluids that are higher in electrolytes, they will drink a lot more.”

There is also a flip side: You can drink too much water. “One of the problems that is not widely recognized is that you can get hyponatremia—low blood sodium, a serious medical situation itself,” Bishop says.

Another way to decrease the risk of heat stress is to design and apply a program to acclimatize workers by exposing them to a hot environment for progressively longer periods. NIOSH says that for workers who have had previous experience in jobs with risk of heat stress, the regimen should be 50 percent exposure on day one, 60 percent on day two, 80 percent on day three and 100 percent on day four. For new workers, the regimen should be 20 percent on day one, with a 20 percent increase in exposure each additional day.

But Bishop urges caution when trying such a program. “The biggest challenge is you have huge variability in the population,” he says. “We used to say, here is the prescription, apply this to everybody. If you follow it, you end up resting people who really don’t need to rest, and if you ignore it, then some of your workers will do fine and some of your workers will get heat injuries.”

Adding to Bishop’s comment, Webster says, “[Employers] might be able to obtain more accuracy about a particular human being by equipping that person with a personal heat stress monitor. They might get more work out of a person using this means than using what a WBGT monitor might recommend. The problem comes in the shortcomings of all the different personal methods, and the severe downside—possible heat stroke and death—that can result if the instrument is not calibrated, worn properly, misapplied, its warnings ignored, etc.”

Webster adds, “Personal monitors can be very useful if a new, unacclimatized employee is admitted to a worksite and there is cause to want to personally monitor the person for a time until they acclimate. … In the case of people operating in full body suits, they are the only way to assess the individual thermal condition of each person.

“If you are an employer faced with OSHA compliance, I would use WBGT measurements,” Webster says. “With these, you can figure work-rest regimens that are safe for most people.”

OSHA also recommends that you should:
• Reduce the physical demands of work, such as excessive lifting or digging with heavy objects
• Provide recovery areas, such as air-conditioned enclosures and rooms
• Use shifts like the early morning or the cool part of the day, or night work
• Use intermittent rest periods with water breaks
• Use relief workers
• Use worker pacing
• Assign extra workers and limit worker occupancy, or the number of workers present, especially in confined or enclosed spaces

Some high-tech solutions to heat stress are now available, such as thermally conditioned clothing with a self-contained air conditioner, ice vests, wet clothing, water-cooled garments and circulating air. But not all employers can afford such products. In these cases, Bancroft offers a low-cost solution that just about everyone can implement. “The time that a worker may perform a given task while wearing personal protective equipment must be adjusted—reduced—to the point where the worker is not placed at risk.”

Bancroft adds that work/rest cycles should be based on information gathered on each individual’s capability for enduring hot environments, the physical demands of the work and the environmental conditions in which the work is to be performed. Bishop and Webster agree and add that protective clothing should also be considered.

Out of the Frying Pan …
For the most part, cooling technologies and strategies are useful and help prevent heat stress and other heat-related problems. But it’s important to balance the benefits against the potential drawbacks.
Bancroft says that sweatbands, water misting devices and cooling vests may offer some aid to the worker in hot environments, but that their use should be carefully considered.

“For instance,” he says, “would a sweatband increase the possibility of electrical shock to the worker who used such a device? Could a water-misting device increase the possibility of a slip/fall injury? Would a cooling device inhibit body movement to the point where the worker could not do the required task or still have the agility to get out of harm’s way?”

Bishop says while personal cooling and zone cooling are effective, the expense may be prohibitive to some, and there are hazards associated with using a tethered personal cooling system. “You aren’t going to be very mobile,” says Bishop.

Even alternating work and rest can cause problems. “If you are in a contaminated area and we have to unsuit you, decontaminate you, resuit you, etc. … you risk exposure to the hazard. If it’s very hot, then you may not cool at all during the rest periods,” says Bishop.

Too Many Cooks Won’t Spoil a Thing
Education is key to reducing heat-related injuries. But learning the causes and solutions isn’t enough. It is also important to educate the workers themselves. NIOSH says that a good heat stress-training program should include:
• Knowledge of the hazards of heat stress
• Recognition of predisposing factors, danger signs and symptoms
• Awareness of first-aid procedures for, and the potential health effects of, heat stroke
• Employee responsibilities in avoiding heat stress
• Dangers of using drugs, including therapeutic ones, and alcohol in hot work environments
• Use of protective clothing and equipment
• Purpose and coverage of environmental and medical surveillance programs and the advantages of worker participation in such programs

“Continuing education is probably the best of all possible ways to enable the worker to understand that we must also deal effectively with the hazards associated with hot work,” says Bancroft. “Dealing effectively with hot working conditions—preventing heat stress—will enable us to stay on the job and be optimally effective in getting the job done, and it will enable us to enjoy the fruits of our labors in good health.”

Anticipating health and safety issues and taking action to prevent them is a long-term and profitable investment for companies. For more information on industrial hygiene and methods for promoting health and safety in the workplace, as well as a listing of industrial hygiene consultants, please visit the American Industrial Hygiene Association website at www.aiha.org.

Hot Web Resources
A variety of resources on heat stress and other heat-related hazards are available online. Here is a sample:
• “Working Outdoors” can be downloaded from OSHA’s Web site at www.osha.gov. This new OSHA fact sheet offers advice on ways to protect against exposure to ultraviolet radiation, extreme heat, Lyme disease and the West Nile virus. The publication also offers links for teenagers working at summer jobs.
• OSHA’s “Heat Stress Card” can also be downloaded at www.osha.gov. The card lists tips to prevent heat-related deaths and injuries and includes warning signs and symptoms. The laminated card, available in English and Spanish, is free to employers to distribute to workers.

• The OSHA Technical Manual, available online at www.osha.gov/dts/osta/otm/otm_toc.html, has a section on “Heat Disorders and Health Effects.”

• The publication Working in Hot Environments is available on NIOSH’s Web site at www.cdc.gov/niosh/hotenvt.html.

• Kris Bancroft, an OEHS consultant, has posted several articles on heat stress at http://home.sprintmail.com/~chiron/heat_stress.html. He can also be contacted by e-mail at [email protected].

• Oklahoma State University offers an online safety library featuring heat stress at www.pp.okstate.edu/ehs/links/heat.htm.

• Additional heat stress links can be found at www.garlic.com/~pburnett/heatlist.htm.

Combating Heat Stress in Baghdad
It might be 120 F in the shade in Iraq, but it’s a sure bet that it’s 140 F under someone’s helmet. Wearing body armor and Kevlar®, troops in the Persian Gulf region face heat stress on a daily basis. In fact, just before speaking to Synergist staff about heat stress in the region, Corp. Nathan Bowman, a medic in the 124th infantry stationed in Baghdad, had assisted an Iraqi woman who collapsed due to heat stress.

“Every time you go outside, you have to be ready for a heat casualty,” says Bowman.

To keep troops safe, medics and other personnel like Bowman keep an eye on their comrades to make sure they don’t become heat casualties. The troops receive regular shipments of water and are encouraged to drink a minimum amount of water a day, depending on their physical activity and working environment. But Bowman works to get them to drink more. “You have to keep water in their systems,” he says.

He also carries around a meat thermometer to show them just how hot they are getting. Bowman sticks the thermometer between their helmets and their heads to take a measurement.

“When it’s 120 degrees, the Kevlar cooks their heads,” says Bowman. “It can be 140 degrees under a helmet.”

The troops are also given adequate breaks from the sun. After spending time outside, they are required to spend a certain amount of time inside—similar to the way many civilian health and safety professionals require workers in hot environments to take breaks in cool areas.

Some of the troops use technology such as CamelBaks® that allow them to carry water on their backs and drink at will while keeping their hands free. Medics like Bowman also carry extra water and oral rehydration packs and are ready to give fluids intravenously as a last resort. However, other technologies that might prove useful, such as cooling vests, are impractical because they don’t have the resources in the field to support the technology.

Bowman has his own strategy for keeping his comrades safe: “You have to play ‘mother’ with them,” he says.

Mason is associate editor for The Synergist, the journal of the American Industrial Hygiene Association.