Vital Ozone Graphics 3

05 consequences We need the sun: psychologically, because sunlight warms our hearts; physically, because our body needs it to produce vitamin D, essential to the healthy development of our bones. Yet increased doses of ultraviolet rays penetrating the ozone layer and reaching the surface of the Earth can do a lot of harm to plants, animals and humans. and effects 2 uv radiation and human health 18

who is most at risk? In the last few hundred years however, there has been rap- id human migration out of the areas in which we evolved. Our skin colour is no longer necessarily suited to the en- vironment in which we live. Fair skinned populations who have migrated to the tropics have suffered a rapid rise in the incidence of skin cancers.

Over thousands of years humans have adapted to varying intensities of sunlight by developing different skin colours. The twin role played by the skin – protection from exces- sive UV radiation and absorption of enough sunlight to trig- ger the production of vitamin D – means that people living in the lower latitudes, close to the Equator, with intense UV radiation, have developed darker skin to protect them from the damaging effects of UV radiation. In contrast, those living in the higher latitudes, closer to the poles, have de- veloped fair skin to maximize vitamin D production.

Behavioural and cultural changes in the 20th century have meant that many of us are now exposed to more UV ra-

Skin colour map (indigenous people) Predicted from multiple environmental factors

From lightest ...

... to darkest skin

no data

Source: Chaplin G. © , Geographic Distribution of Environmental Factors Influencing Human Skin Coloration , American Journal of Physical Anthropology 125:292–302, 2004; map updated in 2007.