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GEOG 221 (32)
Nancy Ross (14)
Lecture 6

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GEOG 221
Nancy Ross

GEOG 221 Lecture 6 Ultraviolet Radiation and Health: Friend or Foe?  Health effects of UV  Example where the physical environment is there, a policy has been installed, but behavior is still the most important factor to reduce health effects  Depleting ozone levels matters for exposure  Zero exposure is the best (eg. no smoking) but with sunlight it gets tricky: we need some but not too much o Too much: cancer, cataracts, etc  Public health standpoint: smoking is easy to tackle, uv exposure is hard o Start getting mixed messages o Telling people to get the right amount of something, but this is tailored to region where you live, skin tone, etc.  Take home message o Various models can predict increases in disease based on ozone depletion but HUMAN CHOICE IN DETERMINING WHERE, WHEN, HOW AND FOR HOW LONG AN INDIVIDUAL IS EXPOOSDE TO SOLAR RADIATION IS THE PRINCIPAL FACTOR DRIVING HEALTH OUTCOMES  What are the behavioral changes? o Increased exposures from: desirability of tanned skin, rise in popularity of sunshine holidays (‘cheap’ air travel) o Decreased exposures from: fewer outdoor occupations, urban lifestyles  Where do we see health effects? o Eyes o Skin o To a lesser extent immune system o Mood, depression  Exposure/absence of exposure  Relationship between UVR (personal exposure to UVR relative to skin type – this depends on the person) and Disease Burden o Not enough sunlight/UV  Skeletal disease, vitamin D insufficiency (rickets) o Optimal amount:  Minimum risk  Not zero exposure, just the right amount o High exposure:  Skin cancers, eye disease o U shaped graph  Human evolution: a key part of the story o Skin cancer: uncommon in deeply pigmented populations o Human migration to higher latitudes likely favored fairer skin that allows more efficient UV induced vitamin D production – key for avoiding deficiency diseases (rickets) o Now see high rates of skin cancer in fair-skinned populations displaced to areas of high ambient UV (and vitamin D deficiency diseases in deeply pigmented people who migrated to high latitudes)  Risk factors for low vitamin D o Inadequate exposure to the sun  Skin type – dark skin requires up to 5 times the length of exposure because of melanin content  Sliiiide o Inadequate dietary intake  Sliiiide o Obesity  Sliiide  How times change o Circa 1900  Stratospheric ozone levels higher than 2000 levels  Ultraviolet B radiation at ground level possibly 15-20% lower than in 2000  Hats fashionable, with clothing covering most of body in fair-skinned body populations  Sun avoidance popular o Consequences  Low incidence of cataract, skin cancers  High incidence of rickets (related to insufficient vitamin D) o Public health advice  Sun is good for health (eg solar radiation therapy used to treat tuberculosis)  Possible scenarios, circa 2100 (behavioral changes’ effects on overall health) o 1 (adherence to Copenhagen Amendments and to Montreal protocol)  return to 1900 levels of ozone by 2050  outdoor activity common  maximum increase in skin cancer incidence by 2060, due to exposure to UVR around 2000 o 2 (adherence to unamended montreal protocol only)  continuing loss of stratospheric ozone  outdoor activity common  doubling of skin cancer incidence (assuming no behavior change)
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