Working Through The Heat Wave

Daniel Martinez and Jose Garcia of Ossining Window Cleaners take a quick break from washing windows at the Hastings Library.

Working Through The Greenburgh Heat Wave (Greenburgh, N.Y.) - Window washers Daniel Martinez and Jose Gracia were happy to find a bit of relief from Wednesday's heat wave, ducking under a tree to reach the second floor windows at the Hastings Public Library. "Very hot, all day, all week," said Martinez, who works with Garcia for the Ossining Window Cleaning Co. "We are trying to get the work done in eight hours each day. We do high buildings too. Then you get some breeze." With the National Weather Service predicting at least three more days of plus-90 degree temperatures, the Westchester County Health Department has issued a county-wide heat advisory, which cautions people to drink plenty of water and avoid long periods in the direct heat unless necessary.

Mark Carlson a window cleaner & also a vendor at Target Field, works the crowd.

BEER HERE - The sun begins rising over Minnie and Paul about 5 a.m., arcing high above their center field perch and bathing Target Field in sunshine under a brilliant blue sky. The New York Yankees are in town and the ballpark will soon be buzzing with energy. For the next 14 hours, none of it will involve an actual baseball game. About 1,200 workers are deployed to scrub, stock, prep and prime the stadium, a routine the group performs before each main event -- 81 regular-season games.

Meanwhile, in the service level accessible only to employees, Mark Carlson is readying for battle among his fellow vendors. He stands 6 feet 7, with a reddish goatee and ruddy complexion that bear a striking resemblance to former slugger Mark McGwire. It is 6:20, and Carlson is about to learn what he will be selling and where. The 48-year-old window cleaner from Minnetonka started vending at Met Stadium at age 15 and is one of only six who have sold at all three Twins venues. Carlson said he has vended at more than 25 stadiums and arenas across the country, including Wrigley Field, Dodger Stadium, Lambeau Field and Candlestick Park.

About 100 vendors dressed in fluorescent shirts are milling around the assignment desk strategizing how best to make a buck. Beer generally is the most lucrative product to hawk but it also is the most expensive (typically $7.50 per bottle), sometimes making for less generous customers. Still, the weather is warm, and it is the night before the July 4 holiday. Carlson has no desire to lug Coke and ice cream. Seniority gives him preference, so Carlson opts for beer, peanuts, sunflower seeds and Cracker Jack. He marches toward a dispensary on the main concourse behind Section 121. He derides several colleagues who have dropped anchor and started selling to passers-by.

"This isn't why we're here," Carlson said. "That's like shooting fish in a barrel." Suddenly, Carlson realizes he has forgotten his knee brace at his locker, and he races back to retrieve it. Lugging 40 pounds of ice, snacks and cold beverages for more than 30 years takes its toll. He chooses to work the lower-deck boxes near the visitors' dugout. "The stairs aren't as steep. It's just a lot easier on my knees," he said. Carlson attaches empty beer bottles, his price buttons and several flashing trinkets to his shirt, shoulders his case and walks into his first section at 6:48 p.m. "Cold beer here! Cold beer! Cold beer! Gitchyer cold beer here!"

Jesse Green owner and operator of Sparkle King. Jesse above protecting himself from the sun. Serving the South Shore, South Coast, and Cape Cod Massachusetts.

Give me shelter…. One Window Cleaner’s Flight from the Sun - While cleaning windows in Cape Cod this last year, I have gotten into some risky behavior. You see, the moist salty air coming off the ocean feels so good on my skin that I end up not protecting myself as I should. So while my skin was turning a nice golden brown, I also was getting mildly burnt enough times to warrant a dirty look from any self respecting dermatologist.

Some may say that the solution is as simple as slathering yourself in SPF 50 sunblock. That’s great if you don’t sweat like I do…. buckets. And forget about the waterproof stuff, makes you feel like a cookie sheet getting greased to go in the oven.

Besides half the time, I just plain forget to put the sunblock on.

I needed a solution. My desperation increased as the temps rose into the mid nineties with the humidity to rival an equatorial jungle.

I turned once again to the shadowy world of performance enhancing clothing. I wanted to play it straight, to be all natural… but the lure of SPF rated high performance nylon weaves beckoned to me. “We will protect you, shield you from the molten rays, wick away your foul sweat and launder with relative ease” The fibers seemed to say. Or at least that’s what I heard in my heat stroke hallucination.

Like any junkie switching from one kick to another, I started tentatively and with great care…. first it was a hi-tech fishing shirt, and that seemed like enough. But then after awhile I suddenly needed fancy hiking pants, then somehow I ended up with an African safari hat. I don’t know where it will end. The next time you see me, you may mistake me for a river rafting guide.

I sometimes worry that my customers will panic. That they will assume my prices will start inching up. That I will have to charge double to afford all the swanky performance fibers that drape hang from me like linen on An Egyptian Pharaoh.

Thankfully my habit of not shaving very often keeps my appearance down to earth curbs that sort of panicked thinking.

So here I am writing this article from my hammock after work. I am tick free from my long pants. No scratches from rose bushes as I weasel my way through customer’s back yards. My neck is unscathed from my window cleaning gymnastics during the tropical heat blast, and most importantly, no heat induced hallucinations.

What is heat stress? "Heat stress" is the net (overall) heat burden on the body from the combination of the body heat generated while working, environmental sources (air temperature, humidity, air movement, radiation from the sun or hot surfaces/sources) and clothing requirements. [Reference: 2008 TLVs and BEIs: Threshold Limit Values for Chemical Substances and Physical Agents and Biological Exposure Indices. Cincinnati, Ohio: American Conference of Governmental Industrial Hygienists, 2008. p. 217.] Other heat-related terms are at the end of this document in the Glossary of Terms.

In foundries, steel mills, bakeries, smelters, glass factories, and furnaces, extremely hot or molten material is the main source of heat. In outdoor occupations, such as construction, road repair, open-pit mining and agriculture, summer sunshine is the main source of heat. In laundries, restaurant kitchens, and canneries, high humidity adds to the heat burden. In all instances, the cause of heat stress is a working environment which can potentially overwhelm the body's ability to deal with heat.

Most people feel comfortable when the air temperature is between 20°C and 27°C and the when relative humidity ranges from 35 to 60%. When air temperature or humidity is higher, people feel uncomfortable. Such situations do not cause harm as long as the body can adjust and cope with the additional heat. Very hot environments can overwhelm the body's coping mechanisms leading to a variety of serious and possibly fatal conditions.

This OSH Answers document contains information relating to the health effects of hot environments. Please see Working in Hot Environments - Control Measures for information about the prevention and control from heat related illnesses.

How does the human body react to hot environments?

The healthy human body maintains its internal temperature around 37°C. Variations, usually of less than 1°C, occur with the time of the day, level of physical activity or emotional state. A change of body temperature exceeding 1°C occurs only during illness or when environmental conditions surpass the body's ability to cope with extreme temperatures.

As the environment warms-up, the body tends to warm-up as well. The body's internal "thermostat" maintains a constant inner body temperature by pumping more blood to the skin and by increasing sweat production. In this way, the body increases the rate of heat loss to balance the heat burden created by the environment. In a very hot environment, the rate of "heat gain" exceeds the rate of "heat loss" and the body temperature begins to rise. A rise in the body temperature results in heat illnesses.

How does the body control heat gain and heat loss?

The main source of heat gain is the body's own internal heat. Called metabolic heat, it is generated within the body by the biochemical processes that keep us alive and by the energy we use in physical activity. The body exchanges heat with its surroundings mainly through radiation, convection, and evaporation of sweat.

Radiation is the process by which the body gains heat from surrounding hot objects, such as hot metal, furnaces or steam pipes, and loses heat to cold objects, such as chilled metallic surfaces, without contact with them. No radiant heat gain or loss occurs when the temperature of surrounding objects is the same as the skin temperature (about 35°C).

Convection is the process by which the body exchanges heat with the surrounding air. The body gains heat from hot air and loses heat to cold air which comes in contact with the skin. Convective heat exchange increases with increasing air speed and increased differences between air and skin temperature.

Evaporation of sweat from the skin cools the body. Evaporation proceeds more quickly and the cooling effect is more pronounced with high wind speeds and low relative humidity. In hot and humid workplaces, the cooling of the body due to sweat evaporation is limited by the capacity of the ambient air to accept additional moisture. In hot and dry workplaces, the cooling due to sweat evaporation is limited by the amount of sweat produced by the body.

The body also exchanges small amounts of heat by conduction and breathing. By conduction, the body gains or loses heat when it comes into direct contact with hot or cold objects. Breathing exchanges heat because the respiratory system warms the inhaled air. When exhaled, this warmed air carries away some of the body's heat. However, the amount of heat exchanged through conduction and breathing is normally small enough to be ignored in assessing the heat load on the body.

What are the effects of hot environments on the body?

When the air temperature or humidity rises above the optimal ranges for comfort, problems can arise. The first effects are subjective in nature - they relate to how you feel. Exposure to more heat stress can cause physical problems which impair workers' efficiency and may cause adverse health effects. (Short-term exposure / Long-term exposure).

Some of the problems and their symptoms experienced in the temperature range between a comfortable zone (20C - 27°C) and the highest tolerable limits (for most people) are summarized in Table 1.

In moderately hot environments, the body "goes to work" to get rid of excess heat so it can maintain its normal body temperature. The heart rate increases to pump more blood through outer body parts and skin so that excess heat is lost to the environment, and sweating occurs. These changes impose additional demands on the body. Changes in blood flow and excessive sweating reduce a person's ability to do physical and mental work. Manual work produces additional metabolic heat and adds to the body heat burden. When the environmental temperature rises above 30°C, it may interfere with the performance of mental tasks.

Heat can also lead to accidents resulting from the slipperiness of sweaty palms and to accidental contact with hot surfaces. As a worker moves from a cold to a hot environment, fogging of eye glasses can briefly obscure vision, presenting a safety hazard.

Several studies comparing the heat tolerances of men and women have concluded that women are generally less heat tolerant than men. While this difference seems to diminish when such comparisons take into account cardiovascular fitness, body size and acclimatization, women have a lower sweat rate than men of equal fitness, size and acclimatization. Laboratory experiments have shown that women may be more tolerant of heat under humid conditions, but slightly less tolerant than men under dry conditions.

What are the illnesses caused by heat exposure?

The risk of heat-related illness varies from person to person. A person’s general health also influences how well the person adapts to heat (and cold). Those with extra weight often have trouble in hot situations as the body has difficulty maintaining a good heat balance. Age (particularly for people about 45 years and older), poor general health, and a low level of fitness will make people more susceptible to feeling the extremes of heat.

Medical conditions can also increase how susceptible the body is. People with heart disease, high blood pressure, respiratory disease and uncontrolled diabetes may need to take special precautions. In addition, people with skin diseases and rashes may be more susceptible to heat.

Substances -- both prescription or otherwise -- can also have an impact on how people react to heat.

Heat exposure causes the following illnesses:

Heat edema is swelling which generally occurs among people who are not acclimatized to working in hot conditions. Swelling is often most noticeable in the ankles. Recovery occurs after a day or two in a cool environment.

Heat rashes are tiny red spots on the skin which cause a prickling sensation during heat exposure. The spots are the result of inflammation caused when the ducts of sweat glands become plugged.

Heat cramps are sharp pains in the muscles that may occur alone or be combined with one of the other heat stress disorders. The cause is salt imbalance resulting from the failure to replace salt lost with sweat. Cramps most often occur when people drink large amounts of water without sufficient salt (electrolyte) replacement.

Heat exhaustion is caused by loss of body water and salt through excessive sweating. Signs and symptoms of heat exhaustion include: heavy sweating, weakness, dizziness, visual disturbances, intense thirst, nausea, headache, vomiting, diarrhea, muscle cramps, breathlessness, palpitations, tingling and numbness of the hands and feet. Recovery occurs after resting in a cool area and consuming cool salted drinks.

Heat syncope is heat-induced giddiness and fainting induced by temporarily insufficient flow of blood to the brain while a person is standing. It occurs mostly among unacclimatized people. It is caused by the loss of body fluids through sweating, and by lowered blood pressure due to pooling of blood in the legs. Recovery is rapid after rest in a cool area.

Heat stroke and hyperpyrexia (elevated body temperature) are the most serious types of heat illnesses. Signs of heat stroke include body temperature often greater than 41°C, and complete or partial loss of consciousness. The signs of heat hyperpyrexia are similar except that the skin remains moist. Sweating is not a good symptom of heat stress as there are two types of heat stroke – “classical” where there is little or no sweating (usually occurs in children, persons who are chronically ill, and the elderly), and “exertional” where body temperature rises because of strenuous exercise or work and sweating is usually present.

Heat stroke and heat hyperpyrexia require immediate first aid and medical attention. Delayed treatment may result in damage to the brain, kidneys and heart. Treatment may involve removal of the victim's clothing and spraying the body with cold water. Fanning increases evaporation and further cools the body. Immersing the victim in cold water more efficiently cools the body but it can result in harmful overcooling which can interfere with vital brain functions so it must only be done under close medical supervision.

What are the illnesses caused by long-term (chronic) heat exposure?

Certain kidney, liver, heart, digestive system, central nervous system and skin illnesses are thought by some researchers to be linked to long-term heat exposure. However, the evidence supporting these associations is not conclusive.

Chronic heat exhaustion, sleep disturbances and susceptibility to minor injuries and sicknesses have all been attributed to the possible effects of prolonged exposure to heat.

The lens of the eye is particularly vulnerable to radiation produced by red-hot metallic objects (infrared radiation) because it has no heat sensors and lacks blood vessels to carry heat away. Glass blowers and furnace-men have developed cataracts after many years of exposure to radiation from hot objects. Foundry workers, blacksmiths and oven operators are also exposed to possibly eye-damaging infrared radiation.

A possible link between heat exposure and reproductive problems has been suggested. Data from laboratory experiments on animals have shown that heat stress may adversely affect the reproductive function of males and females. Exposure of males resulted in reduced rate of conception. Exposure of females caused disruption of the reproductive cycle until they became acclimatized to heat. When animals are simultaneously exposed to heat and toxic chemicals, the influence of heat exposure seems to accelerate the chemical reactivity.

In men, repeatedly raising testicular temperature 3 to 5°C decreases sperm counts. There is no conclusive evidence of reduced fertility among heat-exposed women. There are no adequate data from which conclusions can be drawn regarding the reproductive effects of occupational heat exposure at currently accepted exposure limits.

Laboratory study of warm-blooded animals has shown that exposure of the pregnant females to hyperthermia may result in a high incidence of embryo deaths and malformations of the head and the central nervous system (CNS). There is no conclusive evidence of teratogenic effects of hyperthermia in humans. The NIOSH criteria document (1986) recommends that a pregnant worker's body temperature should not exceed 39-39.5°C during the first trimester of pregnancy.

(Reference: Occupational exposure to hot environments. Revised Criteria. Cincinnati, Ohio: National Institute for Occupational Safety and Health, 1986)

What are some of the terms used in this document (Glossary of Terms)?

 

Acclimatization - Physiological changes which occur in response to several days of heat exposure and make the body accustomed to a hot environment.

Convection - Process of heat exchange between the body and the surrounding air or fluid as a result of bulk flow of that air or fluid.

Dehydration - Loss or deficiency of water in body tissues caused by sweating, vomiting or diarrhea. Symptoms include excessive thirst, nausea, and exhaustion.

Heat cramps - Painful and often incapacitating cramps in muscles. Heat cramps are caused by depletion of salt in the body as a result of heavy sweating, and ingestion of water without replacing salt.

Heat exhaustion - Weakness, lassitude, dizziness, visual disturbance, feeling of intense thirst and heat, nausea, vomiting, palpitations, tingling and numbness of extremities after exposure to a hot environment.

Heat hyperpyrexia - Rise in body temperature with moist skin and mental dysfunction, caused by exposure to an extremely hot environment.

Heat rash (prickly heat or milliaria) - An itchy rash of small raised red spots on the face, neck, back, chest and thighs caused by a hot and moist environment.

Heat strain - Physiological and behavioural responses of the body as a result of heat exposure.

Heat stroke - Acute illness caused by overexposure to heat. Symptoms are dry, hot skin, high body temperature (usually over 105F) and mental dysfunction.

Heat syncope - Temporary loss of consciousness induced by insufficient flow of blood to the brain. Recovery is normally prompt and without any long-term ill effects.

Metabolic rate - Rate of energy (heat) production of the body which varies with the level of activity.

Natural Wet Bulb Temperature - Air temperature measured using a thermometer in which the bulb is covered with wet cotton wick and cooled by the natural movement of air.

Nausea - The feeling that one is about to vomit as experienced in seasickness.

Prickly heat - See Heat rash.

Radiation (heat) - Transfer of heat between hot and cold bodies without contact between them.

Relative humidity - The ratio of the water vapour content of air to the maximum possible water vapour content of air at the same temperature and air pressure.