Let’s face it, any job becomes more difficult when it’s hot. Add protective clothing, heavy exertion, a little humidity and performing basic tasks can become downright dangerous.

Heavy exertion in the heat is second only to major blood loss in the stress it places on the body. A person performing moderate work in an ambient temperature above 80 F wearing protective clothing can reach critical temperatures in as little as 20 minutes.

Once core body temperature rises, physical and mental functions become impaired and potential risk from heat related injury increases dramatically. And, with each heat related injury the body becomes more susceptible to re-injury.

Costs in time and money related to heat illness injury can be significant. According to the National Weather Service Forecast Office in Shreveport, LA, between 1975 and 2004, heat accounted for 38 percent of all weather-related fatalities. Heat illness is such a serious issue that California OSHA recently passed a Heat Illness Pre­vention Emergency Regulation applying to all outdoor places of employment in Cali­fornia when environmental risk factors for heat illness are present.

The good news is ALL heat related in­juries are preventable. But it’s important to know the signs and conditions that can lead to heat illness. Environmental risk factors to consider include the wet bulb globe tem­perature (WGBT) index, which takes into account air temperature, relative humidity and wind velocity. In addition it’s impor­tant to know workload, protective clothing and equipment worn by employees and the time to complete the task to get a compre­hensive picture of potential risk.

In general, it should be assumed that there is a significant risk of heat illness for employees working in a Heat Index of 80ºF or above. In fact the risk of injury can dou­ble with an increase of just three degrees in the heat index above 80. The Heat Index assumes people are wearing light summer clothing. When workers use heavier cloth­ing or some types of personal protective equipment, the body’s ability to lose heat is compromised and the risk of heat illness becomes significant at a lower Heat Index.

Chemical Protective clothing such as HAZMAT suits can put a worker at risk of heat illness even when temperatures are mild. The importance of prevention cannot be overstated and it is up to the employer to develop effective procedures for identi­fying, evaluating and controlling the risk factors in their workplaces. Evaluate each situation to determine heat illness risk. De­velop an assessment template to determine risk accounting for all factors including worker fitness, WGBT, clothing, work load and duration to complete the task. This should be your guide for planning to man­age heat exposure appropriately.

The Body’s Temperature Regulating Process

The human body functions best in a nar­row range between 96.8ºF and 100.4 F. Working in thermally stressful conditions, heat illness symptoms of mental fatigue, cramping, exhaustion can easily escalate into much more serious conditions of nau­sea, vomiting, loss of coordination, con­sciousness and into heat stroke.

The body uses two different mechanisms for cooling. First, blood is diffused to vari­ous portions of the body including the hands, feet, face and skin for conductive and convective cooling. Heart rate and stroke volume are increased to maintain pressure in the circulatory system. If suffi­cient cooling does not occur, the body then begins to sweat to facilitate evaporation. If the environment is equal to or greater than the body temperature, or work rate is greater than the ability to lose heat, core body temperature will continue to rise as the body stores excess heat

Too Hot to Handle

As temperature and heart rate continue to increase, more and more energy is used to dissipate heat and precious resources such as water and micronutrients are lost. Fluid loss from sweating further compro­mises the body’s ability to dissipate heat leading to dehydration. As the body’s core temperature rises above 100.4ºF, a number of heat related illnesses can occur including loss of endurance, cramping, loss of cognitive functions, fatigue and with con­tinued rise escalate to heat stroke and even death.

Heat Illnesses, Know the Signs:

•           Headache;

•           Muscle Cramping;

•           Nausea;

•           Vomiting;

•           Loss of Coordination; and

•           Fainting

If not recognized and dealt with imme­diately these symptoms can lead to more serious problems associated with Heat Stroke including:

•           Confusion;

•           Seizures;

•           Body Temperature of 104 degrees Fahrenheit or more; and

•           Death.

Prevention is the key

A good heat stress prevention plan in­cludes daily assessment of conditions, work tasks, work loads, convenient break loca­tions out of the heat, adequate supplies of water and education of all workers to rec­ognize the signs of heat stress in themselves and their fellow workers.

When risk of heat stress is high:

•           Alternate Work Rest periods more frequently;

•           Provide adequate

Have you ever wondered how a large furry animal stays cool during the hot sum­mer months? A recent discovery by Stan­ford University Biologists found unique structures in all mammals specifically adapted for heat dissipation. Called arteri­ovenous anastemoses (AVA’s) and venous plexus, these structures allow heavily insu­lated mammals to lose large amounts of heat from very small areas of exposed skin.

In humans these structures are located in the palms of the hands, soles of the feet and non-hairy portions of the face and ears. Like the thermostat and radiator of a car, these structures carry large amounts of hot blood very close to the skin sur­face. And, like a car, represent a direct cooling line to the engine or core of the body. The Stanford researchers found they could greatly enhance the natural cooling system by applying an optimal (not too hot and not too cold) tempera­ture and slight negative pressure to the lo­cations where the AVA’s and venous plexus are located.

By lowering the core body temperature with this technique blood flow and energy needed to eliminate heat at the skin sur­face can be delivered to the working mus­cles and core organs lowering temperature quickly and preventing heat illness. Or, if temperature is already ele­vated, the technique can help a person quickly recover from heat stress or illness

cooling the body core two to five times faster than other methods. This can be ex­tremely important in situations where some­one is approaching heat stroke.

If used preventively, core cooling can slow the rise in core temperature allow­ing an individual to work more safely. And used at the end of work shift, core cooling can help facilitate a more com­plete recovery, improving, comfort min­utes, hours and days after exposure to an extreme environment.

What’s the Big Difference?

The topical cooling methods most widely used can make you feel cooler. This is because our body’s sensors are lo­cated at the skin’s surface. Unfortu­nately, applying something cold to the skin’s surface may also cause a vasocon­striction, or reduced blood flow to the skin. This reduces the skin’s ability to dis­sipate heat and could actually result in a temporary increase in core temperature. An example of this phenomenon is when you’re hot and seek comfort in a cool shower. After the shower, drying off and dressing, we frequently begin to perspire profusely. This is caused by vasoconstric­tion and a temporary rise in core tempera­ture and is the body’s natural response to cooling the skin.

Cooling the body’s core is quite differ­ent. New methods utilize optimal tempera­tures and negative pressure to enhance blood flow to the AVA’s and venous plexus preventing vasoconstriction (reduced blood flow). Although humans don’t have inter­nal sensors that allow us to feel cooling at the body’s core, feelings of improved men­tal clarity, increased energy, reduced mental and physical fatigue are common.

Craig Heller, Ph.D., a Stanford re­searcher who has done extensive research on body core cooling explains, “While tra­ditional cooling methods make the victim feel cooler on the outside, they are not ef­fective in extracting heat form the body’s core organs. In fact, laboratory testing demonstrates that these methods may make matters worse. When cold is applied to the body’s surface, it can trigger constriction of the skin’s blood vessels which interferes with cooling.”

Stay Cool, Stay Safe

Maintain a safe and healthy work envi­ronment. Know the risks and signs of heat stress, heat illness and heat stroke. Have ad­equate sources of water for workers. Pro­vide shade or locations out of the heat for breaks. Assess the heat index and associ­ated risks frequently during the hot season. And, have procedures and proper equip­ment in place to provide active cooling to deal with any heat event so that you can re­spond quickly before heat stress escalates into something serious.

Additional information about Heat Stress is available at the OSHA website www.osha.gov/SLTC/heatstress/recog-nition.html. FSM

Mark Smith is Executive Vice Presi­dent of AVAcore Technologies Inc. And its Director of R&D.