Sun radiates electromagnetic radiation, EMR

Part of spectrum corresponds to energy required to break chemical bonds in DNA

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  Damages genes and can lead to skin cancer

Brief exposure damages proteins, and can irritate blood vessels, giving sunburn

Most damaging part of spectrum is UV

Most UV absorbed in upper atmosphere

Sunscreens often contain benzene rings

Ozone absorbs UV-B and UV-C

Significant pollutant at ground level

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  Photochemical smog

Radiation not screened in ionosphere, so ionises molecules