Book contents
- Frontmatter
- Contents
- Contributors
- Preface
- Acknowledgements
- Historical introduction
- PART I Epidemiological methods
- PART II Causative factors in human cancer
- 6 The concept of cause: epidemiological considerations
- 7 Chemical factors
- 8 Occupational factors
- 9 Cultural factors: tobacco
- 10 Cultural factors: alcohol
- 11 Sexual behavior and reproductive factors
- 12 Nutritional factors
- 13 Physical factors: fiber carcinogenesis (including crystalline silicates)
- 14 Physical factors: implants and thermal chronic injury
- 15 Physical factors: ultraviolet (UV) light
- 16 Ionizing radiation
- 17 Biological causes
- 18 Genetic and other host-risk factors
- 19 Socio-economic factors
- PART III Legal and ethical considerations
- PART IV Introduction: total and specific site epidemiology
- PART V Buccal cavity
- PART VI Digestive system
- PART VII Respiratory system
- PART VIII Bone and soft tissue
- PART IX Skin
- PART X Breast and genitourinary system
- PART XI Eye and nervous system
- PART XII Thyroid and other endocrine glands, lymphoid and hematopoietic system
- PART XIII Cancers in children and multiple primary cancers
- Conclusions
- Appendix 1 Cancer statistics
- Appendix 2 A glossary of epidemiological terms
- Appendix 3 Acronyms and abbreviations
- Supplement
- Index
15 - Physical factors: ultraviolet (UV) light
Published online by Cambridge University Press: 03 May 2010
- Frontmatter
- Contents
- Contributors
- Preface
- Acknowledgements
- Historical introduction
- PART I Epidemiological methods
- PART II Causative factors in human cancer
- 6 The concept of cause: epidemiological considerations
- 7 Chemical factors
- 8 Occupational factors
- 9 Cultural factors: tobacco
- 10 Cultural factors: alcohol
- 11 Sexual behavior and reproductive factors
- 12 Nutritional factors
- 13 Physical factors: fiber carcinogenesis (including crystalline silicates)
- 14 Physical factors: implants and thermal chronic injury
- 15 Physical factors: ultraviolet (UV) light
- 16 Ionizing radiation
- 17 Biological causes
- 18 Genetic and other host-risk factors
- 19 Socio-economic factors
- PART III Legal and ethical considerations
- PART IV Introduction: total and specific site epidemiology
- PART V Buccal cavity
- PART VI Digestive system
- PART VII Respiratory system
- PART VIII Bone and soft tissue
- PART IX Skin
- PART X Breast and genitourinary system
- PART XI Eye and nervous system
- PART XII Thyroid and other endocrine glands, lymphoid and hematopoietic system
- PART XIII Cancers in children and multiple primary cancers
- Conclusions
- Appendix 1 Cancer statistics
- Appendix 2 A glossary of epidemiological terms
- Appendix 3 Acronyms and abbreviations
- Supplement
- Index
Summary
Introduction
Certain types of ultraviolet (UV) light are strongly carcinogenic. Yet complete avoidance of exposure is almost impossible. Further, ultraviolet light is indispensable, permitting the skin to synthesize vitamin D, complementing that derived from dietary sources.
Spectrum of ultraviolet light
The UV portion of the electromagnetic spectrum occupies the wavelengths between 200 nm and 400 nm. It is customary to distinguish between UV-C (200–280 nm), UV-B (280–320 nm) and UV-A (320–400 nm), each having different effects on the skin and eye. The shorter the wavelength, the more destructive the radiation.
Ultraviolet light below 295 nm is totally absorbed by the oxygen and ozone of the atmosphere, that between 295 and 329 nm being partially absorbed. The more oblique the sun's rays, the greater thickness of atmosphere which has to be traversed and hence the shorter rays are diffused or absorbed. Considerable amounts of ultraviolet light may be reflected, thus the combination of snow and blue sky may expose the skin to as much UV-B (310 nm) as comes from the sky directly.
Effects
The amount of UV light reaching the melanocyte varies by wavelength. UV-A penetrates into the dermis, between 1 to 10% reaching the basal layer, a depth practically never reached by UV-C. Heavy skin pigmentation is, of course, protective. Sunburn is maximal about 24 hours after exposure to UV-B, occurring more rapidly than for UV-A.
- Type
- Chapter
- Information
- Human CancerEpidemiology and Environmental Causes, pp. 164 - 166Publisher: Cambridge University PressPrint publication year: 1992