The number of moles on a person seems to be an indication of their exposure to the sun. It is a colourless gas that has a very pungent odour. It exists naturally at low concentrations in the stratosphere where it absorbs ultraviolet radiation. In the troposphere it exists naturally at extremely low concentrations. But these concentrations increase when sunlight acts on various gases, coming mainly from vehicle exhausts, and ozone then becomes a pollutant in the troposphere.
Ozone is a highly corrosive gas and is poisonous to most organisms.
A small non-cancerous growth in the eye, arising from the outer layer of the eyeball. It is associated with long-term exposure to sunlight. Most pterygia are easily removed. These are harmless areas of slightly changed pigmentation, not as distinct as freckles or moles. Although not cancerous, they are a sign of skin damage by ultraviolet radiation.