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As global temperatures rise, just how hot is too hot for human beings?

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As global temperatures rise, just how hot is too hot for human beings?
Copyright  euronews
By Jeremy Wilks

Global warming means Europe is facing more frequent and more intense heat waves - so what does it mean for your health? How hot is too hot? It's a complex issue.

Anyone can get too hot and dehydrated, but the health risks depend on who you are, where you live, and the time of year.

Firstly, people with chronic health conditions like cardio-respiratory disease, kidney disease, high blood pressure, diabetes, mental illness, and dementia need to be extra vigilant when the mercury rises.

Very young children, pregnant women and people doing physical work outside are also at risk.

Another factor is that our body actually acclimatizes to the heat over the summer, so a heatwave in late spring is harder to manage than a heatwave in mid-August.

Finally, there's where you're from. Someone who grew up in Rome or Athens is better adapted to deal with temperatures in the mid-30s than someone from Dublin or Helsinki.

It's hard to identify a temperature by which we would say it's too hot or we should issue a warning. It's not universal.
Francesca de'Donato
Heat and health specialist, Lazio Regional Health Service

So it's all relative.

“It's hard to identify a temperature by which we would say it's too hot or we should issue a warning,” says heat and health specialist Francesca de'Donato from Lazio Regional Health Service.

“It is not universal. So there isn't a universal definition of a heatwave. There isn't a universal level of temperature which would be most at risk for the whole of Europe or worldwide.”

JORGE GUERRERO/AFP or licensors
Wildfires raged in Spain earlier this year.JORGE GUERRERO/AFP or licensors

Where there is universal agreement is that humidity is a growing problem.

As the atmosphere gets warmer it can hold more water vapour, and when humidity and temperatures rise to a certain level the body's ability to cool down by sweating just doesn't work anymore.

Some places in the Persian Gulf, Pakistan, Mexico, and south-east Asia now pass this threshold sometimes.

For example, if it's 38 degrees Celsius with 75 per cent relative humidity then it's hot enough to be potentially fatal for some people.

According to scientists, as many as 3 billion people could be living in these kinds of conditions within 50 years.