500
The largest organ in the human body is the skin. One of the skin's functions is to help regulate the amount of body heat that flows in and out of the body. When it is cold, we cover the skin with extra layers of clothing to slow down the outward flow of heat. When it is hot, evaporation of sweat cools us down. However, if you are a heavy smoker, your skin is unable to efficiently undergo this process, resulting in often improper body heat.
b.) Heavy smoking ages skin very quickly.