Chronic effects of UV radiation include:
Cataract: an eye disease where the lens becomes increasingly opaque, resulting in impaired vision and eventual blindness;
Pterygium: a white or creamy fleshy growth on the surface of the eye;
Squamous cell carcinoma of the cornea or conjunctiva: a rare tumour of the surface of the eye.
UV radiation levels are influenced by a number of factors.
Sun elevation: the higher the sun in the sky, the higher the UV radiation level.
Latitude: the closer to the equator, the higher the UV radiation levels.
Cloud cover: UV radiation levels are highest under cloudless skies but even with cloud cover, they can be high.
Altitude: UV levels increase by about 5% with every 1000 metres altitude.
Ozone: ozone absorbs some of the UV radiation from the sun. As the ozone layer is depleted, more UV radiation reaches the Earth's surface.
Ground reflection: many surfaces reflect the suns rays and add to the overall UV exposure (e.g. grass, soil and water reflect less than 10% of UV radiation; fresh snow reflects up to 80%; dry beach sand reflects 15%, and sea foam reflects 25%).
UV ทำให้เป็นต้อกระจก ต้อเนื้อ และมะเร็งได้ มักพบความเข้มสูงในแถบบ้านเราและโดยเฉพาะที่ที่มีแสงสะท้อนครับ