Exposure was a medical condition resulting from prolonged time spent in contact with temperatures of high or low extremes, causing such conditions as sunburn or hypothermia, or radiation.
According to Sub-commander T'Pol, the radiation on Terra Nova was less than eight hundred millirads so a few hours of exposure shouldn't pose a risk to a landing party. (ENT: "Terra Nova")
In 2266, the landing party left behind on Alfa 177 suffered from exposure. (TOS: "The Enemy Within")
The hostile atmosphere of the Delta Quadrant planet nicknamed "Planet Hell" made death by exposure a possibility. (VOY: "Parturition")
After finding Bruce Maddox in captivity on Freecloud, Jean-Luc Picard visually diagnosed him as having suffered from exposure and dehydration. (PIC: "Stardust City Rag")