Heat

Nautilus -   With blistering heat waves on the rise , scientists are pondering the pressing question: Exactly how much ambient heat can the human body tolerate? The conventional belief among researchers has been that humans can withstand temperatures up to 35 degrees Centigrade (or 95 degrees Fahrenheit) without suffering major consequences like heat strokes or heart attacks.

But in a new study published in the Proceedings of the National Academy of Sciences, Penn State University researchers challenge that limit. They say it doesn’t take into account factors that amplify heat’s effects. For example, many such estimates rely on the dry heat-tolerance level. Dry heat—that is, heat with little to no moisture in the air—is easier for humans to withstand. That’s because humidity—the level of water vapor in the air—affects how human bodies cool off, says graduate student Qinqin Kong, one of the study co-authors. Our bodies regulate temperature in a few different ways. Our skin naturally releases some heat into the air, for one. And wind or a light breeze on a hot summer day can whisk even more heat away. But sweating is best, Kong says.