Thermoregulation Heat gain, storage and loss Heat strain and related illnesses Risk factors for heat strain Risk assessment and control
“reaksi fisik dan fisiologi tenaga kerja terhadap temperatur sekitar lingkungan yang berada diluar zone nyaman manusia (pekerja)”
Zone nyaman pekerja didasarkan pada standar: - ASHRAE –American Society of Refrigeration, Heating, and Air-Conditioning Engineers. - ASHRAE standard 55-1981 outlines human comfort zones based on temperature and humidity.
Kesetimbangan Panas External Heat Source Cooling Internal Heat Source (Muscular Activity) H
Normal body temperature Kondisi optimal tubuh manusia akan mempertahankan suhu tubuh 37°C
- Proses dimana tubuh beradaptasi pada variasi suhu dilingkungan sekitar. Proses ini akan berlangsung selama kurang lebih 3 minggu Menurunnya berat badan 1.5% karena dehydration
Hypothalamus – organ utama di otak yang mengatur/menyesuaikan suhu tubuh dengan mengendalikan hormons, dengan cara: - Meningkatkan denyut jantung - Berkeringat - Meningkatnya aliran darah di permukaan kulit
Aliran darah akan mendinginkan permukaan tubuh dari panas yang berlebihan melalui permukaan kulit.
Ada 4 cara pelepasan panas: Convection Radiation Evaporation Conduction
Internal dan eksternal 70-80% kerja otot - metabolic heat
Heat Rash (prickly heat): Sebab: tersumbatnya pori-pori dan saluran keringat. Gejala: kulit memerah, gatal, nyeri dan iritasi. First Aid: Menjaga kebersihan, mengeringkan keringat, pakaian longgar, konsult ke dokter bila sakit berlanjut. Seriousness: Ringan/Relatively minor.
Radiation Burns (Sunburn) Cause: radiasi UV yg diserap kulit. Symptoms: kulit mengering, lebam, kerusakan jaringan kulit. First Aid: Menutup kulit yang terkena, menggunakan krim anti UV (sunscreen). Membungkus bagian kulit yang terbakar. Seriousness: Minor to relatively serious.
Transient Heat Fatigue: Cause: kehilangan cairan yang mengurangi sirkulasi. Symptoms: Kelelahan umum (tiredness or fatigue) First Aid: Memperbanyak minuman dan beristirahat. Seriousness: Dampak singkat.
Heat Syncope: Cause: mengumpulnya darah kebagian extremities bawah dan menyebabkan berkurangnya supply darah ke otak. Symptoms: Syncope berarti “pingsan” First Aid: korban ditidurkan terlentang dengan kaki dinaikkan horisontal. Bila sadar diberikan minuman. Seriousness: Korban butuh satu/dua hari untuk sembuh, hingga mampu beraklimatisasi.
Heat Cramps: Cause: hilangnnya cairan elektrolit dalam darah menyebabkan kram pada otot. Symptoms: Otot cramp, bagian anggota badan dan perut. First Aid: Minum cairan elektrolit dan istirahat. Seriousness: membutuhkan istirahat.
Heat Exhaustion: Cause: Kurangnya cairan seluruh tubuh membuat dilatasi pembuluh darah berlebihan. Symptoms: Mual, pusing, lemah, sakit kepala, kabur pandangan, profuse sweating, cold/wet (clammy) grayish skin, tidak sadar, coma dan meninggal.
Heat Exhaustion (continued) : First Aid: pertolongan ditempat yang dingin, a face down position, minuman, segera dibawa ke unit UGD. Seriousness: Sangat serius
Heat Stroke: Cause: Kerusakan pada sytem pengaturan panas tubuh (hypothalamus), fails and sweating stops. Symptoms: dingin, gelisah tidak bisa istirahat, irritasi, muka merah, disorientation, hot/dry skin (not always), collapse, unconsciousness, kejang and death.
Heat Stroke (continued) : First Aid: segera dibawa ke UGD. Seriousness: Heat Stroke is a MEDICAL EMERGENCY.
Indirect Heat-Related Health Effects: Menurunkan kinerja Potensi kecelakaan Masalah Reproduksi Heart/Lung Strain
Predisposing Factors: very small body size poor nutrition overweight over 40 years old (the older the more sensitive) previous heat illness heart disease high blood pressure diabetes skin disease liver, kidney, and lung problems
Accurate temperature measurement is crucial for determining thermal stress. WBGT (Wet Bulb Globe Temperature) is the accepted method for determining true temperature Accounts for air currents, relative humidity, solar load
Heat Stress Monitor takes readings from, and calculates WGBT by: -Dry Bulb Thermometer -Wet Bulb Thermometer -Globe Temperature
For indoor or shaded environments: WBGT = 0.7 x T nwb + 0.3 x T g T nwb = natural wet-bulb temperature T g = globe temperature For direct sunlight exposure: WBGT = 0.7 x T nwb + 0.2 x T g + 0.1 x T db T db = dry-bulb temperature
Using the reading from the thermostat on the west wall, convert that temperature to WBGT using the following info: -WB = 64.1 F -GT = Temperature reading from thermostat
Step 1 : Convert F temps to C -5/9 (temp F) –32 = temp C *5/9 (64F) –32 = 17.77C *5/9 (thermostat F) –32 = ?
Verification of readings : Using WB temp and WBGT from monitor, calculate the corresponding GT, which should agree with the thermostat…if it’s accurate. * GT = (WBGT – 0.7(WB))/0.3 * convert temp to F - 9/5(Temp C) + 32 = Temp F
WBGT is used by Industrial Hygienists to determine the workload requirements/restrictions for work areas, using Heat Stress/Strain TLV.
Engineering controls Administrative controls Personal protective equipment
- Use machinery instead of people where applicable - Take steps to cool building or worksite - Use thermal barriers (mylar reflective surfaces) - More?
-Conduct training on Heat stress/strain -Work during coolest part of day -Co-worker observation -Implement work/rest schedule -More?
How Much Water is Enough? More than you want just to satisfy your thirst Sources of water are: 1. Fluids - 1 cup or 8 oz = 240 mL every 20 min 2. Foods - fruit & veggies are 90% water Why 10-15°C? … to maximize the amount you drink (not too cold, not luke warm) Does it need to be delivered to the work station? … depends on workplace logistics …
What to drink: Electrolyte drinks (e.g. Gatorade) are usually not needed for typical North American diet (can be used for first aid). Stay away from caffeinated, carbonated, diet drinks, and alcohol as they take water out of your body. Water is the best; juices and/or no caffeine sport drinks are also good (juices contain energy restoring glucose).
% weight loss fluid loss time*effect & symptoms (* timing may vary based on intensity of work and heat/humidity) 1%0.75 L1 hr unnoticed (at 1.5% weight loss you are considered dehydrated) 2%1.5 L2-3 hrs loss of endurance, start to feel thirsty, feel hot, uncomfortable 3%2.25 L3-4 hrs loss of strength, loss of energy, moderate discomfort 4%3 L4-5 hrs cramps, headaches, extreme discomfort 5-6%3.5-4 L5-6 hrs heat exhaustion, nausea, faint 7+%5+ L7+ hrs heat stroke, collapse, unconsciousness
Fans: Purpose of a cooling fan is primarily to increase the rate of sweat evaporation but it also cools by convection if the air is cooler than the skin Fan coolers may interfere with local exhaust ventilation for contaminant control, therefore be careful in where they are placed
Fans, cont’d: The lower the relative humidity the better the evaporation the more effective the cooling If the relative humidity is close to 100% the fan will no longer increase evaporation of sweat The closer the air temperature is to skin temperature (35-36°C) the less effective the cooling if the air temperature exceeds skin temperature then the fan may even heat up the body (like a convection oven)!
Notice the ACGIH Heat Stress/Strain TLV’s take into account the workload as well as the work/rest cycle. Also to note that the TLV’s make a few assumptions regarding acclimatization, clothing, water and salt intake, as well as the ability of most workers to work continuously at 38C.
Light: standing with light work at machine/bench using mostly arms; using table saw Moderate: walking about with moderate lifting or pushing; scrubbing in a standing position Heavy: shoveling dry sand; cutting with a hand saw Very Heavy: shoveling wet sand
The following correction factors for the WBGT should be used:
Heat Stress/Strain measurements (WBGT) should be taken prior to work being performed, to allow for measures to be taken to protect exposed individuals. Anticipated workload, work/rest cycle, clothing should be taken into account in determination. If work/rest cycle is not constant, time- weighted average should be used in determination.
Take readings: Select a representative spot to place your thermometer(s) and/or hygrometer Designate someone to take readings on an hourly basis (on the hour) and record them If activities are altered in response to the heat (slow down, more breaks, water distribution) record the details including the time and the degree If heat stress health conditions appear record time and describe symptoms and situation
Things you can check: Look for typical heat strain symptoms; feeling over-heated, fatigue, headache, nausea, weakness, dark concentrated urine, etc. Sweat that drips off your body no longer allows for cooling by evaporation; thus, unless there’s another medical reason for it, this is a sign that your body is heating up Check your pulse; heat stress is unlikely if your pulse rate is under 100 beats per minute after 1 minute rest.
Just as high temperatures have far- reaching effects on the body, cold temperatures present their own challenges to the thermal regulation of the human body. Let’s examine what the effects of cold temperatures are, what health effects cold temperatures present, and methods for treatment of cold-related injuries.
As we see, the four causes of heat loss in a hypothermic environment are convection, radiation, evaporation, and conduction. The large difference is that in hypothermic environments, you are trying to retain heat, instead of releasing it to the environment.
Determining the risk of cold-injuries is done using the following formula: Heat Retention + Heat Production > Cold Factors or Heat Retention + Heat Production < Cold Factors
- Heat Retention: - Size/shape (Eskimo vs. Masai) - Insulation (Clothing type/# of layers) - Fat (Used as insulation) - Shell (Blood in core of body) These are positive factors. Increase of any or all of these factors decreases risk of injury.
- Cold Factors: - Temperature - Humidity - Wind The total of these represents the challenge to the thermo-regulation of the human body. If Retention + Production < Cold Factors, Hypothermic condition could develop.
“a decrease in the core body temperature to a level at which normal muscular and neurological functions are impaired” – Medicine for Mountaineers Hypothermia is possible at any temperature under 98.6 degrees, if the right conditions exist (lack of insulation, increased heat loss, etc.)
“Umbles” – Stumbles, Mumbles, Fumbles, and Grumbles Shows decreased physical and mental capacity.
Mild Hypothermia: - core temperature 98.6 – 96 F - non-voluntary shivering -complex motor functions impossible -vasoconstriction to periphery
Moderate Hypothermia: - core temperature 95 – 93 F - loss of fine motor coordination - slurred speech - violent shivering - paradoxical undressing - apathetic attitude
Severe Hypothermia: - core temperature 92 – 86 F or below - shivering in waves (violent then pause) - person curled in fetal position to conserve heat - muscle rigidity develops - pale skin/dilated pupils - reduced pulse
-at 90 degrees F, the person goes into hibernation, slowing heart rate and respiration, shunting blood to peripheral tissues. -at 86 degrees F or below, the person looks dead, but is still alive…barely. Severe Hypothermia is LIFE THREATENING!
Although hypothermia is well known, there are other cold injuries. -Frostnip -Frostbite -Immersion foot (trench foot)
Frostnip is the freezing of upper layers of the skin. Characterized by: - white, waxy skin. - general numbness Frostnip is generally reversible and does no major tissue damage.
Gently warm area by blowing warm air on it or by placing it near a warm body part. DO NOT rub the area! Rubbing can rupture frozen cells, causing extensive damage. Frostnip is a warning sign of possible frostbite*
Frostbite is a freezing of the surface and deep layers of tissue. Characterized by: - white, and feels “woody” - numbness, possible anesthesia - deep frostbite can affect bone and muscle - purple/black color is from ruptured blood vessels
Immerse affected area in 105 – 110 degree F water until thawing is complete. - part will be extremely painful Wrap affected part in sterile gauze Affected part should not be used for anything - keep part from refreezing
Immersion foot is caused by prolonged exposure of the feet to wet, cool conditions. Characterized by: - yellowish, smelly feet - possibly numb - sloughing of skin tissue/itching *Immersion foot may cause permanent damage to foot tissues, leaving person susceptible to cold injuries in future.