Heat resistant

first_img Previous Article Next Article Heat resistantOn 1 Jul 2004 in Military, Personnel Today Comments are closed. Related posts:center_img Howto identify the rationale with which to support the frequency and type ofhealth monitoring of employees, in relation to heat exposure in their workingrolesIthas long been known that working in the heat can compromise health and safetyand lead directly or indirectly to worker injury and death.1 Theaim of this article is to identify the frequency, type and rationale behind theproposals for the monitoring of employees exposed to heat, rather than, as iscurrently the case, the sole focus being based on risk attached to individuals’working roles. Thecurrent occupational hygienic limit values for heat stress are based on acutereactions to heat stress rather than to the effects of chronic heat exposure. Theobjective is to encourage an active, specialist and operationalmultidisciplinary team to formalise safer systems of work and to identifyresearch opportunities that employers could pursue to provide a benchmark forstandardised practice. This should be addressed from the organisational, macroand micro working climate, for it to be successful.2 Workingroles Heatexposure is a risk involved in many job roles and in relation to thesurrounding environment, such as for outdoor workers/labourers, miners, foundryworkers, armed services personnel and front-line public sector emergencyservices. This is mainly due to the increased use of personal protectiveequipment (PPE); for example firefighters’ uniforms, police officers’stab-proof vests and ambulance crews’ overalls, all worn to protect employeesfrom personal harm; whether weapons, flame; biological or chemical spillage. Thebody can maintain its core temperature between 36.5ûC and 37.5ûC. Heat isproduced by the body’s muscular activity, metabolic reactions and endocrineactivities, and is removed by the mechanisms of convection, conduction,radiation and evaporation. Problems occur when this core temperature rises dueto the external environmental temperature or over-exertion. When the ‘removalsystems’ fail and the body’s temperature rises above 40ûC, it can causeirreversible damage to the body’s organs.3,4 Acuteheat exposure Arise in heat exposure causes the following signs and symptoms, in varyingdegrees, depending on the individuals’ health, working role, the PPE worn, typeand duration of exposure: –Irritability, discomfort –Lowered work performance –Heat rash –Heat cramp –Heat exhaustion –Heat stroke –Heat syncope (sudden dizziness) –Heat tetany (muscle spasms, respiratory problems) –Heat oedema (swelling due to fluid build-up) –Sunburn –Heat cataracts.3,5,6 Heatstroke is a medical emergency and, according to Williams, it is most common inthose who are un-acclimatised, obese, dehydrated, inappropriately dressed andwho have consumed alcohol.3 Fiveorgan systems are affected: –The brain –Haemostatic system (blood clotting control mechanism) –Liver –Kidneys –Muscle.4 Heatinjury Inthe Army’s defence council instructions on the prevention and treatment of heatillness, it identified that heat exhaustion and heat stroke should be seen as aheat illness, meaning that individuals become incapacitated as a result of arise in body temperature.5 This is because it can often be difficult todetermine the difference between the signs and symptoms of heat exhaustion andheat stroke, and an incorrect diagnosis may lead to a poorer outcome for theheat-exposed individual. Susceptibility varies widely in terms of: –Temperature duration threshold at which the injury occurs –The systems affected –Severity of which a given system is affected –Duration of the latent period following heat exposure before an injuryprogresses. Inshort, there is no elevated temperature-duration threshold below which heatinjury will never occur, and all cases of heat illness should be admittedpromptly to hospital for observation for at least 24 hours.7 Inorder to determine the type, frequency and requirement for medical screening tobe carried out, research needs to be undertaken to identify the long-termeffects of heat exposure in specific work roles. Chronicheat exposure Therehas been very little research into chronic heat exposure, except for researchinvolving small animals.8, 9,11,12 Acouple of studies that identified human reactions to heat included a study byHobbesland, Kjuus and Thelle, who investigated the increased mortality fromsudden death in 12 Norwegian ferro-alloy plant workers. Hypertension-relateddiseases were found to be associated with the common furnace work conditions(heat, psychosocial stress, shift-work, noise and carbon monoxide), found inmany industrial settings.13 Sainiet al attempted to identify the initial human body adaptation to chronicpassive heat exposure using a series of nocturnal blood collections.14 Bloodcollections monitored growth hormones, prolactin, thyrotropin and plasma reninactivity from 12 males over 11 days in a heat controlled climate. It was notedthat after five days, those exposed to a higher temperature had stimulatedplasma renin activity, but this had little affect on pituitary hormones. Thosekept at a steady lower temperature of 32ûC throughout the tests experienced nochange in hormone profiles. Theconclusion was that the main endocrine system involved in acclimatisation topassive heat exposure is the renin angiotensin system, due to its counteractiveprocessing against salt and water loss. Asidefrom the physiological reaction to heat in humans, other considerations need tobe addressed which can disturb the body’s natural heat balance.13,14 Forexample: –Excessive physical exertion –Hot weather and high humidity –Inadequate fluid intake/hydration level –Infections and medical conditions –Wearing heavy dark clothing on hot days/clothing which inhibits adequate heatloss –Extremes of age/older workers –Inappropriate environments, such as unventilated, tin-roof factories –Lack of acclimatisation –Low blood sugar/lack of food –Direct external environment/summer weather –Recent alcohol consumption –Obesity. 3,15,16,17 Anotherconsideration should be that some medications can impair heat loss, including: –Cardiac drugs –Oral hypoglycaemics –Antidepressants/antipsychotics –Anticholinergics –Antihistamines –Antiparkinsonians –Neuroleptics (chlorpromazine) –Benzodiazepines –Barbiturates –Diuretics –Hallucinogens –Cocaine. 18 DiscussionHeatstress in workplaces should be considered at an individual, organisational andmacro level. 16 Therisk at an individual level can be difficult to determine, due to differingorganisational demands, occupational status, individual health, shift patterns,and workload. On a macro level, there is an effect on economic climate toworkplace objectives, community provision, service procurement and serviceavailability.2 Anindividual may be seen as being at greater risk where there is less routineheat exposure, causing a reduced ability to acclimatise to the working role.Acclimatisation can take between three to 14 days depending on the health,gender and overall fitness of the individual adapting to the heat.18 Educationof the worker is very important in this situation as they need to know thatthey are placing increased demands on their bodies after a holiday, longweekend or period of illness.3,19 TheArmy has been at the forefront of risk management with heat exposure and usesthe standard index of the Wet Bulb Globe Temperature (WBGT) as a guide for itsown workers. It uses an acclimatisation regimen to prevent heat stress, whereby,for a soldier to be acclimatised, he/she should have taken regular exercise forlonger than 10 days in the same environment as the proposed activity.5,6 Meetingsshould take place with the workforce, according to their perception of the mostdemanding aspect of their job,19 and specialists should set the maximalpermissible limits for work duration. This is because it has been identifiedthat the actual heat strain experienced by workers does not necessarilycorrelate with the current ISO 7933 standards for heat stress.1,20 The riskassessment should take into account the working conditions, job demands andcurrent in-house workplace policies, and national legislative standards.1,2 Hansonand Gravelling, in their research in UK coal mines, identified a potentialproblem where high temperatures and humidity levels were ‘the norm’.21 Onesolution to this was their production of a code of practice to reduce theminers’ physiological symptoms of heat stress, as it was noted that as well asincreasing the amount of fluids available in relation to their sweat loss, theminers core temperatures increased with basic effective temperatures. Itwas concluded that action should be taken to reduce the risk of heat strainwhere their basic effective temperatures were routinely more than 27ûC.20 Asimple approach can be adopted in the workplace, based on education onhydration, provision of readily available water fountains/fluid containers anda canteen with water-rich foods, such as mousses and yoghurts, which cancontribute 1,000ml towards daily fluid intake, including approximately 300mlgenerated through the metabolism of dietary protein, fat and carbohydrate.21 Afurther, more complex individual risk assessment is presented by Malley, whoadvises a prescriptive weight/fluid balance maintenance system forfirefighters, whereby they pass water in the morning at the beginning of a dayshift, then weigh him/herself and re-hydrate as necessary. For each pound (lb)of water weight lost, there should be a replacement of 16 fluid ounces ofwater.22 Pre-hydrationis the key, according to Pribut, who advised that hydration should occur up to45 minutes prior to exercise in a hot environment, with a cupful of waterconsumed every 10 to 15 minutes.16 Forexercise from between 60 to 90 minutes in duration, sport replacement drinksshould be used post-exercise, because the electrolytes and carbohydrates theycontain assists the individuals in their recovery period. However,Professor World identified that many sports drinks contain added salt and heidentifies that salt intake in food is normally adequate to meet the body’srequirements.18 OHpractitioners must therefore be mindful of each individual’s pre-existingmedical conditions when advising on the content of re-hydration fluids. Regularreviews of healthcare maintenance and detection of illness through healthscreening have increased the likelihood of detecting workers’ underlyingmedical conditions earlier. Medicalconditions such as diabetes, hypertension, heart disease, anorexia nervosa,bulimea, obesity, alcoholism and fever may cause an enhanced reaction to heatstress.3,18 And some medications can further impair the body’s ability totolerate heat and adapt to hot environments. The patient may become toodehydrated to sweat and the core body temperature will rise leading to heatstroke.17 Organisationscould produce a procedural note to accompany the risk assessment as part of aneducation package, identifying how a recovery rate from exposure to hotenvironments can be assisted before, during and after a working day. Thisshould have identified the structure and diversity of the workforce, includingthe age, cultures and genders, (as women tend to be less tolerant to heatexposure due to their different physiological make-up), but is not related tofitness to undertake the work role.6 Hydrationcharts provide simple education material and assist the worker in undertakingan individual daily risk assessment system. Most authors indicate thatre-hydration should take place on a regular basis throughout the heat exposurein the working day, with the following issues addressed: –Drink cool, not cold fluids, try to avoid hot fluids –Make sure diluted beverages contain less than 8 per cent glucose –Continue to drink six to eight fluid ounces of water every 10 to 15minutes.17,19 Ifpossible, those workers who have to work in emergency situations, wearing PPE,should be allowed to adopt a procedure in which they: –Re-hydrate away from the hot environment –Do not consume solid food immediately post-incident –Do not continue working at a relatively high exertion level (exceeding 75 percent of maximum aerobic ability). 17,19,23,24,25 Thehigh temperatures individuals work in causes heart rates to increase. Coretemperatures increase approximately 1ûC when wearing PPE, which furtherincreases by 0.5ûC in the recovery period on completion of the task. If PPE isnot removed at this point, there is a greater risk of heat exhaustion than atthe start of a rest period. Writtenpolicies should acknowledge the need for formal education of workers, thebenefits and limitations of PPE and a recovery period and safe environment awayfrom the heat and therefore danger, to reduce the accumulation of physiologicalstrain, in which to remove protective clothing.3,26,27,28,29 Thesesix measurements are critical when identifying heat stress risk: –Air temperature –Radiant temperature –Air velocity –Humidity –Clothing properties –Metabolic rate.1 Adynamic risk assessment on each individual would be advantageous prior toworking in heat, and also for those returning to heat exposed work, especiallyfor new workers, keen to prove their work capability, who may inadvertentlyincrease their susceptibility to cardiovascular and psychological strain inheat if they continue to work.30 Long-termstrategy Initiatea test research programme (as advised by Professor World), using theCockcroft-Gault equation to establish any relation to the long-term effects ofheat exposure. Allow OH practitioners to continue to define the risk affordedto their employees and therefore establish the frequency and type of medicalsto be undertaken. Alongitudinal study could involve using a set of similar individuals in relationto their work role in the same occupation, in relation to the amount ofhistorical working life, heat exposure, for example, those with regular heatexposure – at least twice per week on a regular basis and the other group withintermittent exposure. Eachpairing would be divided according to the following criteria, as near aspossible, in relation to: –Age –Weight –Gender –Height –General smoking habits –Alcohol consumption –Length of service in working role –Blood pressure readings –Number of heat exposures –Professional records (of heat exposure rather than personal recollection). Bloodtests would be taken for urea and electrolytes in addition to an electro-cardiogram for the potential relationship with the chronic effects of heatexposure on the circulatory system, to determine the effect of the exposure onthe body systems. Inconclusion, industries in which the workforce is at a level of risk due toheat-induced illness should provide care from an organisational, macro andmicro level. Further research is required to determine the exact requirementfor monitoring of workers who are exposed to heat in their workplace and whohave additional risk factors, which can disrupt the body’s natural heatbalance. Above all, personal initiative, experience, assessment or advice fromall team members should all contribute to the decision.32 –Lindsey Wood BA (Hons) Humanities, OHND, RGN Withthanks to: Lt.Col. M World, professor of military medicine, Queen ElizabethHospital, Renal Unit; Phil Castleton, West Midlands Fire and Rescue Service;Andy Tait, Leicestershire Fire and Rescue Service; Steve Rose, of the DyslexiaAdvice Resource Centre; Paul Fernley, occupational health nurse; and Dr PhilipHamilton, Fire Brigade medical adviser Recommendations for employers– Develop a strategy/policy/procedure and code of practicein the workplace, which involves scope (nature of work role, use of PPE andequipment), validity (does the method relate to the strain on the individualworker) and easy application in the workplace (not too complicated andappropriate to their workplace)1– Assess heat strain to determine the maximum allowableexposure duration in relation to tolerance time. Sweat rate, evaporationefficiency, water loss; increase in core temperature, work rate, restinterface, range of duties, use of combinations of clothing and surroundingenvironment– Provide training by OH practitioners explaining the signsand symptoms of heat induced illnesses– Active education and presentation materials on hydrationand nutrition on how to plan for the day. Provision of water containers forcarriage and storage at work/in vehicles as necessary– Use of hydration charts for individual hydration status– Monitoring and use of heat exposure records– Post heat exposure checklist – Fitness programme (according to age)– Validate present form of PPE and raise awareness of thelimitations of PPE– Investigate and research innovations in PPE wear, such asan ice, freon, water or air-cooled vests 27, 31– Use a virtual-reality computer-based training programmefor practice, to avoid heat exposure in real-life training scenarios– On site health surveillance every six months, for thefirst year, by an OH practitioner, with further frequency determined by theinitial test results, to include:– Health questionnaire (based on a healthy lifestyleapproach)– Blood pressure– Cholesterol test (for those at a greater risk ofcardiovascular disease)– Weight– Urine analysis for proteinuria, haematuria, specificgravity (SG) results (to monitor the concentration and diluting power of thekidneys and also recognising any dehydration), to be used as an additionaleducation tool31– Review of time sheet/heat exposure– Medical for the over-40s– Assessment of general health and medication side-effects.References1. Parsons and Bethea (2002). The Development of aPractical Heat Stress Assessment Methodology for use in UK Industry. Preparedby Loughborough University for the HSE. Research report 008. 2. Whittaker S C (2001). The Management of SicknessAbsence. 420-424. www.occenvmed.com 3. Williams N (1993). Working in a Hot Environment.Occupational Health. August. 275-277. 4. Edwards C, Bouchier I, Haslett C and Chilvers E. (1995)Davidsons Principles and Practice of Medicine. London: Churchill Livingstone.5. Harrington J M and Gill F S (1998). Occupational Health.ISBN 0-632-04832-8. 6. Defence Council Instructions. Joint Service. Ministry ofDefence. (1996) Heat Illness in the Armed Forces: Prevention and Treatment.(59): 1-11.7. Lt. Col. World M J, (1995). Policy for treatment of theAdverse Effects of Heat in Military Patients 1-3.8. Dukes – Dobas, F N. (1981). Hazards of Heat Exposure. AReview. Scandinavian Journal of Work and Environmental Health. (2): 73-83.9. Tohoku J. (1998) Effects of mild chronic heat exposureon the concentrations of thiobarbituric acid reactive substances, glutathione,and selenium, and glutathione peroxidase activity in the mouse liver. Exp. Med,185 (2): 79-87.10. Temim S, Chagneau A M, Peresson R, Tesseraud S. (2000)Chronic Heat exposure alters protein turnover of three different skeletalmuscles in finishing broiler chickens fed 20 per cent or 25 per cent proteindiets. Journal of Nutrition. 130 (4): 813-819.11. Geraert P A, Padilha, J C, Guillaumin S. (1996).Metabolic and Endocrine changes Induced by Chronic Heat Exposure in BroilerChickens: Biological and Endocrinological Variables. British Journal ofNutrition. 75 (2): 205-216.12. Samuels S E, McAllister T A, Thompson J  R (2000). Skeletal and Heart Muscle ProteinTurnover during Long Term Exposure to High Environmental Temperatures in YoungRats.  Canadian Journal of PhysiologicalPharmacology. 78 (7): 557-564.13. Hobbesland A, Kjuus H and Thelle D S (1997). Mortalityfrom Cardiovascular Diseases and Sudden Death in Ferro-alloy Plants.Scandinavian Journal of Work, Environment and Health. 23 (5): 334-34114. Saini J, Brandenberger G, Libert J P, Frollenius M(1993). Nocturnal Pituitary Hormone and Renin Profiles during Chronic HeatExposure. Journal of Applied Physiology. 75 (1): 294-300.15. Extremes of Temperature. Hypothermia and Heat InducedIllness (Hyperthermia) (2002) www.members.ozemail.co.au/tarong/extremes.htm16. Priburt S M, Dr. (2002). Running in the Heat: 2000Version. Dr Stephen M Priburt’s Sports Pages. (www.drpribut.com/sports)17. Shade B R (1996). Heat Injuries. Emergency. 18-24.18. Micromedex Inc, 1999. Drug Induced Hyperpyrexia andHeat Stroke. Vol. 100. Exp. 30 June 1999. (From West Midlands Drug InformationService, Good Hope Hospital, Sutton Coldfield)19. Faff J and Tutak T (1989). Physiological Responses toWorking with Fire Fighting Equipment in the Heat in relation to SubjectiveFatigue. Ergonomics. (32) 6: 629-638.20. Stirling, M, Leicestershire Fire and Rescue Service21. Hanson M A (1999). Physiological Monitoring of HeatStress in UK Coal Mines. Institute of Occupational Medicine. Edinburgh. HSE Abstracts2000/2001.22. Thirsty Work. Information for Medical Professionals. 4-623. Malley K S (1995) Heat Stress: Part 2. MaximumHydration. Firehouse. 112-113.24. Smith D L, Manning, T S, Petruzzello S J (2001). Effectof Strenuous Live Fire Drills on Cardiovascular and Psychological Responses ofRecruit Firefighters. 44 (3):  244-254.25. Orfinger B (2002). Disaster Relief.org. ScientistStudies Health Risks for Firefighters at Ground Zero and Elsewhere. 17May. (www.disasterrelief.org/Disasters/011105firerx/)26.  US Departmentof Labour. (2002) Occupational Health and Safety Administration. Heat Stress.(Heat Stress Card) OSHA Technical Website. Section III: Chapter 4.  (www.osha-slc.gov.)27. Lusa S, Louhevaara V, Smolander J, Pohjonen T, UusimakiH and Korhoned O (1993). Thermal effects of Fire – ProtectiveEquipment during Job Related Exercise Protocol. Safe Journal. (23) 1: 36-39.28. Carter J B, Banister E W and Morrison J B (1997). TheEffectiveness of Rest Conditions in the Prevention of Heat Stress. FireEngineering. 67-70.29. Clark, D L, Dr, Smith D F and Denise L (1998). HeatStress in the Training Environment. Fire Engineering. 151 (3) 163-164.30. Yakin, Heather, 1999. Firefighters wonder if gear issafe. The Times Herald-Record. 28 September. 1-3.31.  BayerDiagnostics. Urine Analysis. The Essential Information. Bayer plc. Berkshire.32.  Home Office. HMFire Services Inspectorate. Chief Officers Letter. 2000. DCOL. 6 April. London.29-37.Learning for lifeCPD Heat stress1. At present, occupational hygiene limits for heat stress are based on? a) Acute reactions b) Chronic reactions c) Long-term exposure d) The temperature 2. The body’s core temperature should be maintained at between: a) 35-38C b) 30 -40C c) 36-38C d) 36.5-37.5C 3. Heat is removed from the body by: a) Evaporation, emission, convection b) Convection, conduction, emission c) Convection, conduction, evaporation d) Evaporation, conduction, emission 4. All cases of heat stress should be admitted to hospital for at least: a) 24 hours b) 12 hours c) 1 week d) 5 days 5. Research carried out by Saini et al showed that those exposed to hightemperatures for five days had what sort of effect on the pituitary hormones? a) Little effect b) No effect c) A marked effect d) A rise in 6. Which of the following medications was NOT listed as improving heatloss? a) Diuretics b) Barbiturates c) HRT d) Antidepressants 7. Acclimatisation can take: a) 1-2 days b) 3-14 days c) 14-21 days d) 6 weeks 8. What factors affect acclimatisation? a) Age, gender, fitness b) Health, gender, fitness c) Health, age, gender d) Age, health, fitness 9. The standard index WBGT stands for: a) Washed bulb globe temperature b) Wet bulb gulf thermometer c) Wet bulb globe thermometer d) Wet bulb globe temperature 10. Pribut advises that for pre-hydration before exercise in a hotenvironment, a cupful of water should be consumed: a) One hour before b) 20-30 mins before c) Every 10-15 minutes for 45 minutes before d) 30-40 minutes before Answers & Feedback 1) a – If you got this answer wrong, you must really go back and revise yourknowledge of the body’s temperature control mechanisms. 2) d 3. c – this is basic physics – so maybe hunt out your GCSE books or do a bitof revising! It is important to understand what each one means. 4) a 5) a – It may be worth revising your knowledge of pituitary hormones orgetting a copy of this research. 6) c – However, it does help to control hot flushes! 7) b – This answer is a debatable and it may be worth reading some otherresearch on this topic, but it certainly explains why when you are just gettingused to the hot weather on holiday, it’s time to come home! 8) b 9) d – See the Resources page to find out where you get more informationabout this important index. 10) c – This fact is well worth knowing for those of you planning on doinglots of physical activity this summer. Features list 2021 – submitting content to Personnel TodayOn this page you will find details of how to submit content to Personnel Today. We do not publish a…last_img read more