Direct effects of heat

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• Direct effects of heat
• Tord Kjellstrom, NCEPH, ANU
• Short course on Climate Change and Health, ANU,
  Wed 1 Oct. 2003

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Effects of heat exposure

• Sweating, dehydration, salt loss
• Loss of ability to work intensively
• Loss of perceptual motor performance
• Increased accident risk
• Increased body temperature (gt38 degr C)
• Heat stroke
• Unconsciousness
• Death

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Vulnerability dependent on age

• Elderly people and infants affected more rapidly
  and are the main victims of heat stroke and death
• Focus on mortality in the elderly
• Adults are as working people affected their
  ability to do work is reduced and their accident
  risk is increased
• Focus on productivity and economic cost
• All ages are affected in their daily activities,
  e.g. exercise, feasibility of walking and
  bicycling
• Focus on wellbeing, interference with daily
  activities

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Heat wave mortality
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Seasonal variation of temperature in Darwin
Sydney (Shrestha and Kjellstrom, 2003)
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Seasonal variation of non-external mortality in
Sydney
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Seasonal variation of non-external mortality in
Darwin
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Daily Max Temp and mortality, SydneyX2, x4 and
x6 functions (from Krys Sadkowski, AIHW)
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Daily Max and Min Temp and mortality, Sydney
Max Temp, x6 function
Min temp, x6 function
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Scatter plots of monthly mortality against
monthly average of daily maximum temperature in
Sydney
65 yrs
0-64 yrs
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Relationship daily heat and mortality
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increase of daily mortality in relation to
temperature (maximum to the right and minimum to
the left)
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Updated Christchurch study, methods(Kjellstrom
and Shrestha, 2003)

• Daily data on PM10, max temp, min temp, Rh
• PM10 data adjusted for methods variations during
  period
• Daily data on mortality, 1988-1999, appr. 30,000
  deaths
• Multiple Poisson regression, APHEA protocol for
  seasonal adjustment both in winter and summer
  analysis
• Non-external, circulatory and respiratory deaths
• Autocorrelation and interaction terms, not
  significant

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Results non-external mortality increase () per
degree, Rh or 10 ug/m3 lag 0 (1 or 2 similar)
Figures in red, plt0.05
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Results mortality increase () per degree, or 10
ug/m3 lag 0 (1 or 2 similar)figures in red,
plt0.05
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Impacts of heat in industrial settings

• Factory output lower during hot season (studies
  from 1919-1927)
• Accident frequency higher at temp gt 25 C
• Perceptual motor task performance reduced at
  temp gt 30 C
• Mistakes increased gt 33 C less in experienced
  workers
• WORK ABILITY of time that a person can work
  at intended work intensity

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Impact of heat on labour productivity

• Activity what people do
• Performance activities achieve a goal
• Productivity performance in terms of system
  goal quantity or quality of product
  examination success at school number of
  customers served appropriately etc.

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Heat balance equation for humans
where M - the metabolic work rate W - the
rate of external working E - the rate of heat
loss by evaporation from the skin R - the rate
of heat transfer by radiation C - the rate of
heat transfer by convection from the skin Eres -
the rate of heat transfer by evaporation from
respiration Cres - the rate of heat transfer by
convection from respiration S - the rate of heat
storage in the body The energy generated in
the body by the metabolic activity (M) will
either be released as external movement (work) or
as heat i.e. M Heat Work. The rate of
effective external work is around 20 but in many
work situations is zero.
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Metabolic and environmental requirements to avoid
heat strain

• Keep core body temperature below 39 degrees C,
  and preferably below 38 degrees.
• Encourage sweating, drink lots relative humidity
  below 100
• Encourage convection, wind blowing on skin
• Avoid direct sunlight or close proximity to hot
  surfaces

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Heat stress indices

• WBGT 0.7 x T-wet 0.2 x T-globe 0.1 x T-dry
• Heat index or Apparent temperature
• T-app 2.7 0.99 x T-dry 0.016 x (T-dew)2
• Required sweat rate index (based on physiological
  measurements)
• Predicted heat strain model (for European
  standards development, 2002)
• Thermal Work Limit (Brake and Bates, 2002)
• T-dry gt 44 C or T-wet gt 32 C? No work
• MHPmax model (Nick Mann, 2002)

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ISO recommended maximum work duration in hot
environments, of time
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Conversion of ISO guidelines into work ability
curves 500 W 280 W/m2 (Kjellstrom, 2000)
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US Army advice for preventing heat illness

• When the WBGT reaches 26 C, caution level
• WBGT at 28 C, discretion needed for planning
  heavy exercise for unacclimatised personnel
• WBGT at 29 C, no strenuous exercise for
  unacclimatised personnel
• WBGT at 31 C, limited activity for all personnel
• WBGT at 32 C, physical training and strenuous
  exercise should be suspended for all personnel

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(No Transcript)
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Output from Nick Manns modelImpact of
temperature, absolute humidity and wind speed
2.2 kPa at 25 degrees 70 RH, 30 degrees 50,
35 degrees 40
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Work rates in different activities
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How long can you dig before MHPmax is reached and
core body temperature increases?
Nick Mann, 2002
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Work ability and labour productivity

• At high work intensity, the work ability reduces
  rapidly above 24 C (un-acclimatised) or 26 C
  (acclimatised)
• At the lowest work intensity the reduction starts
  at 29 and 30 C, respectively
• This will lead to less labour productivity, which
  may have to be compensated for by e.g. the
  workers working longer hours
• Lowered work ability may in economic terms be
  seen as disability

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A Haiphong shoe factory with 2900 young women
staff
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Heat impact on work ability in the shoe factory

• WINTER
• 7.30 start work
• 10 - 10.15 break
• 11.30 - 12.30 break
• 15 - 15.15 break
• until 17.00 8 hours work
• Finish at 18.00 - 20.00 at production target

• SUMMER
• 6.30 start work
• 10 - 10.30 break
• 11.30 - 13.00 break
• 15 - 15.30 break
• until 17.00 8 hours work
• Finish later because of heat ?
• At least one hour longer away from home.
• Bean-soup at breaks

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Calculation of DALYs/1000 persons due to 1 degree
C increase of heat at work

• Assuming that an increase of 1 degree C heat
  reduces daily work ability (WA) by 20 (typical
  value in previous figures)
• 2 months heat increase (EME), 4 months (India)
• Thus annual WA reduction (disability) 3.3
  in EME and 6.7 in India (Annual DALY 33 and
  67/1000 persons)

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Summary of DALYs due to selected risk factors
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Expected temperature increase due to Climate
Change

• Globally, 1.4 - 5.8 degrees C during this century
  (IPCC, 2001)
• An increase of 1 degree during a few months each
  year may therefore be a plausible assumption for
  working populations outdoors and in
  non-air-conditioned spaces within the next 50
  years
• Climate change effects on agriculture and
  industry include effects of heat on people
  working human input needed for economic output

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Conclusions

• The loss of work ability or labour productivity
  with increasing heat is significant, even after
  acclimatization
• If lost work ability is equated to
  disability-adjusted life years lost in economic
  terms, increasing heat contributes significantly
  to DALYs among working people
• The DALYs lost per degree C heat increase may be
  similar to the worst health risk factors (gt10 of
  all DALYs in a country)

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The HOTBODS projectHigh Occupational Temperature
Burden Of Disability Study

• Field studies in different countries of groups
  working at low, medium and high energy level in
  non-airconditioned workplaces
• Compare for hotter and colder periods
  climate/heat stress variables, physiological heat
  response, perceived fatigue and work output
  (economic productivity)
• Analyze impact of heathumidity on work
  productivity
• Estimate future impacts under climate change
  scenarios and adaptation methods to reduce impacts