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ozone depletion and human health.docx

8 Pages
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Department
Life Sciences
Course Code
LIFESCI 2H03
Professor
Luc Bernier

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March 18 , 2013 Life Sci 2H03: Environmental Life Sciences Ozone Depletion and Human Health Ozone Depletion and Human Health - increase risk of skin cancer - southern most regions, the risk has increased drastically - higher exposure to UVB radiation Exposure to UV Radiation - most personal exposures to UVR occur from: outdoor activities in the sun - work or recreational activity, greater exposure to radiation - risk of reaching higher doses of UVB throughout their lifetime Possible Interactions between Climate Change and Ozone Depletion - predicted higher ambient temperatures in summer due to global warming - e.g. study on risk in children in the UK and the possibility of developing skin cancer - with warmer temperature exposed to more UVB - children in the UK are at higher risk for skin cancer - regions where it is drier or warmer - regions of higher precipitation, less exposure to UV radiation as they are not outside - e.g.: study on incidence of skin cancer in fair-skinned males and females in 10 different regions of continental USA compared with UV-B measurements - cases of skin cancer and the predicted rate by the end of 2100 - extent of ozone depletion - more pronounced if change in climate continues UVB and Insolation - at any given latitude and altitude: solar zenith angle has the most profound effect on the terrestrial UV-B readings - as we move further away from the equator the angle is increasing and the same dose of UVB is distributed over a greater area - greater chance of developing cancer with high sun as there is greater exposure to a smaller area Earth-Sun Distance - Earth’s distance from the sun, especially during the summer, also affects the: intensity of UV-B reaching the surface - Periphilion: less radiation reaching the Earth in the Northern hemisphere Decline in Depth of Ozone Layer and Increased UV Index - since 1978 - with the decrease of the overall depth in New Zeland, the overall exposure of UVB increases - increase in the risk of doveloping skin cancer - at midlatitudes (28-46 ) around the world the increase in erythemally effective UV for every degree of latitude toward the equator: between 3% and 3.6% - increase at the poles have been greater: 4.2% - UVB exposure is greater at the equator but the poles have experienced a greater increase Percent Lifetime UV Dose - with less protection, the window is reduced - usually in the 80s, yet the window is getting smaller UV Exposure Trends - e.g. on average, people living in the contiguous United States get about:  erythemally-weighted UV per year, not including vacation: 25,000J/m 2  including a continental U.S. vacation: 33,000J/m per year - effect in 40 year old male, greater exposure UV Doses of Males and Females - southern hemisphere values - as we move further from the equator, the dose diminishes as there is not as much of a concentrated beam of sunlight - lifetime exposure is also increasing in infants UV and Cancer - causes DNA damage  gives rise to gene mutation  contributes to skin cancer formation - genetic variations in repair enzymes can modify the efficacy of DNA repair – mechanism because faulty therefore more genetic variation is being introduced increasing skin can
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