Microclimates and heat islands:

Transcription

1 Microclimates and heat islands: Climate change exacerbates occupational heat exposures Dr Liz Hanna Tord Kjellstrom, Keith Dear, Tony McMichael Bruno Lemke, Clem Davis, James Hall Australian National University National Centre for Epidemiology & Population Health

2 Rising heat : Occupational health issue Outline A warmer world Heat as a health hazard Physiological and productivity impacts Occupational heat exposures - microclimates

3 Global Warming Projections Source: IPCC (2001) Climate change 2001: Impacts, adaptation and vulnerability. A Report of Working Group II

4 Decadal T o C Northern Hemisphere Source: James Hansen (2012) NASA Climate Variability and Climate Change: The New Climate Dice

5 Heat records Heat records Heat records

6 HOT??? Just the beginning?

7 The problem with heat Heat as a health hazard Physiology 101

8 Heat limited human tolerance Humans inhabit ambient temps < 0 o C > 45 o C Controlled Temp preferences [A/C] o C Core temp small tolerance range o C < 35.5 o C.... Hypothermia > 38.0 o C.... Hyperthermia Future Human thermal tolerance???? James Hansen: Heat events 3σ from norm now occurring on 10% land surface (was 1%)... can expect 5 σ

9 Thermoregulation Circulatory: Distribution of temperatures within the body and division of the body into core and shell (skin) during exposure to (a) cold and (b) warm environments.

10 Heat gain Heat Balance Hypothalamus (thermostat) Heat absorption Heat generation Environment 1.1 o C / hr Metabolism Hormonal Pyrogens Muscular activity 1 o C / 5-6mins

11 Heat Balance Hypothalamus (thermostat) Heat gain Heat Loss Heat absorption Environment 1.1 o C / hr 1 o C / 5-6mins Heat generation Metabolism Hormonal Pyrogens Muscular activity Exchange Radiation Conduction Convection Evaporation Insensible Shunting Faeces Urine Expiration Selective perfusion

12 Mechanisms of heat exchange to the environment Radiation, Conduction, Convection Efficacy influenced by clothes, air movement, ambient T o C (Ta) Evaporation Main mechanism when Ta ~ core T (T re = rectal T) Vaporisation of 1g of water removes 0.6kcal of heat In high humidity evaporation less effective Maximal sweat losses of 1600mL/h ++++ Results in electrolyte imbalance

13 Exercise: Muscular activity is inefficient 75% - 80% of energy produced via muscular work is heat Work can increase heat production 10-fold Muscular heat conducted to core via bloodstream Without thermoregulation, under normal movement Temp gain 1 o C / 5-6mins Exercise limit = mins When working heat MUST be dissipated In hot environments this becomes a challenge

14 Exercise: strains the heart Evaporation = primary heat loss mechanism To heat loss blood flow through skin Blood flow to working muscles is several times greater than blood flow to skin Creates competing demands on circulation Perfuse the skin vs perfuse the muscles Loss of fluids & electrolytes due to sweating T re rises when doing light work in 30 o C & during heavier work in 25 o C Dr Liz Hanna Australian National University

15 Responses to overheating Boost heat loss efforts Cutaneous vasodilatation Sweating eccrine glands all over body Respiration Response to cut heat production Anorexia Apathy and inertia, fatigue Productivity implications Dr Liz Hanna Australian National University

16 Effect of WBGT on work output Heavy Work Light Work Dr Liz Hanna Australian National University Kjellstrom, et al 2009

17 Heat Related Disorders Heat cramps: Painful skeletal muscular spasms Heat exhaustion: Fatigue, nausea, headache, giddiness, fainting Skin clammy & moist, pale, goose flesh Pulse rapid & thready, BP low, T re < 39.5 o C Concentrated or restricted urine output Heat Stress = medical emergency Hot dry skin, red mottled, or blue Circulatory collapse, shock T re > 40 o C Organ failure acute renal failure Confusion... Convulsions... Coma... Death Dr Liz Hanna Australian National University

18 Pathophysiology Excessive heat denatures proteins Destabilise phospholipids & lipoproteins & liquefies membrane lipids..... We leak.... Low circulatory volume Increased cardiac effort Cardiovascular collapse..... Hypo perfusion.... Multi-organ failure

19 Admission ICD codes Cardiac incompetence Poor perfusion organ failure - AMI Vascular Renal Acute renal failure dark to nil urine Cerebro Cognitive / coordination / consciousness /coma Other GIT nausea / vomiting Muscular - fatigue / lethargy Skin shutdown / cessation of sweating (heat loss) Dr Liz Hanna Australian National University

20 The Wet Bulb Globe Temperature (WBGT) Standard, ISO 7243 Used in Occupational Health and Safety guidelines for working in hot environments

21 WBGT Alert comparisons Athletes IAAF Medical manual US Army Research Institute of Environmental Medicine

22 The Wet Bulb Globe Temperature (WBGT) Standard, ISO 7243 Used in Occupational Health and Safety guidelines for working in hot environments Caution - cancel or postpone Cancel

23 The Wet Bulb Globe Temperature (WBGT) Standard, ISO 7243 Used in Occupational Health and Safety guidelines for working in hot environments Caution - cancel or postpone Cancel

24 The Wet Bulb Globe Temperature (WBGT) Standard, ISO 7243 Used in Occupational Health and Safety guidelines for working in hot environments Caution - cancel or postpone Cancel

25 WBGT Lascar Data Loggers Our Gill Screen & Black Globe 3M Quest Temp 36

26 WBGT Wet Bulb Globe Temperature OHS standard measure of heat experienced by humans Weighted average of air, globe and natural wet bulb temperatures

27

28 Equipment Design and Testing Australian National University - NCEPH Canberra Airport

29

30 Testing Reflected Heat 35 Air Temperature (degrees C) (5 gills at NCEPH 2 nd -7 th March 2013) 5 Gill Screen QT36

31 NCEPH Urban Heat Island Air Temperature measured at NCEPH and the Airport QT36 Dry Bulb (NCEPH) Adjusted Gill screen (NCEPH) BoM (Canberra Air Port) /3/2013 9:00 1/3/ :00 1/3/ :00 1/3/ :00 1/3/ :00 1/4/2013 0:00 1/4/2013 3:00 1/4/2013 6:00 1/4/2013 9:00 1/4/ :00 1/4/ :00 1/4/ :00 1/4/ :00 1/5/2013 0:00 1/5/2013 3:00 1/5/2013 6:00 1/5/2013 9:00 1/5/ :00 1/5/ :00 1/5/ :00 Temperature (degrees C)

32 100 Relative Humidity data Gill screen V BoM Data (collected 3/1/13) Gill screen (5 minute data) BoM (half hourly data) Humidity (%) :00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 10:0011:0012:0013:0014:0015:0016:0017:0018:0019:0020:0021:0022:0023:00 0:00 Time of Day

33 Broken Hill Concrete

34 Heat Measuring Equip on-site Data Logger in Gill Screen Data Logger in Black Globe

35 Broken Hill Airport Feb 7 th 2013, 14:58 T 39.2 o C

36 Urban heat Island in Canberra 45 Air temperatures in Canberra measured with Gill screens BoM Canberra Worksite NCEPH courtyard /3/ :00 1/3/ :00 1/3/ :00 1/3/ :00 1/4/2013 0:00 1/4/2013 3:00 1/4/2013 6:00 1/4/2013 9:00 1/4/ :00 1/4/ :00 1/4/ :00 1/4/ :00 1/5/2013 0:00 1/5/2013 3:00 1/5/2013 6:00 1/5/2013 9:00 1/5/ :00 Air Temperature ( C) Date / Time

37 Mildura worksites v BoM

38 Temperatures in Car

39 White car parked in Canberra T e m p e r a t u r e o C 16th Jan 2013 BoM Tmax 31.3 o C Dr Liz Hanna Australian National University 17 th Jan 2013 BoM Tmax 35.9 o C

40 Heat island effect Heat exposures BoM Up to 7-8 degrees C Persists throughout the day Exacerbates heat load & reduces wind cooling Not only near high density dwellings Variable depending on local conditions, cloud, shade, trees... Higher when near a brick buildings Car Temperatures up to 70 o C

41 Implications for occupational health When approaching critical thermal environments BoM data cannot always be assumed to reflect the actual heat exposures on-site Cheap portable on-site heat measuring CAN be achieved.. Heat protective policies required,... locally relevant & evidence- based

42 Thank You Liz.

43 Angry Summer: Climate Commission

44

45 Estimated heat loss at rest and during exercise at 70% VO 2 max

46 Australian capital cities Number of days over 35 C