Abstract

There have been many laboratory studies of the effect of heat on the health of individuals in sport, at work or in the military. However, epidemiological studies are needed to develop impact assessment of climate change. In this presentation we outline the development and use of population-exposure risk functions for different heat effects.

The first risk function is for heat discomfort based on the predicted mean vote with 10% population feeling discomfort at WBGT=21C and with 90% affected at 29C.

The second population risk function is for heat exhaustion which we derive by using epidemiological data from the US military. 10% of the population is affected by heat exhaustion at WBGT=31C increasing up to 90% of the population affected at a WBGT=38C.

The most severe population risk is heat stroke for which we use hospital data to calculate 10% of the population affected by heat stroke at WBGT=41C and 90% of the population at WBGT=44C.

These health effects of heat create different durations of ill health, with serious heat stroke causing prolonged periods of dis-ability. Based on climate modelling and our risk functions the number of people affected globally can be calculated. For heat stroke, few persons working in the shade at 300W metabolic rate, will currently suffer from heat levels that can cause heat stroke. By 2085 half a million workers (at 300W) will be exposed to heat levels that cause heat stroke. As for becoming totally exhausted (and unable to work) while working at 300W in the sun, currently that stands at about 124 million worldwide, but in 2085 that number will jump to 835 million.

Additional epidemiological studies are utilised to validate these risk estimates at local and national level.