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11839_CHE 883 Lecture 8

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    Health Aspects of Ozone

    Depletion

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    Why care about diminished ozone?

    A diminished ozone layer allows more

    radiation to reach the Earth's surface.

    For people, overexposure to UV rays can leadto skin cancer, cataracts, and weakened

    immune systems.

    Increased UV can also lead to reduced crop

    yield and disruptions in the marine food chain.

    UV also has other harmful effects.

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    Effects of UV rays on AquaticEcosystems

    Ozone depletion causes increases inUV rayss effects on aquaticecosystems by:

    1. decreasing the abundance of

    phytoplankton affects the food stock for

    fishes and the absorption of CO2

    2. decreasing the diversity of aquatic

    organisms reduces food stock and also

    destroys several fish and amphibians.

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    Effects of UV rays on

    Terrestrial Ecosystems

    Damage to plant cell DNA molecules - makes

    plants more susceptible to pathogens and pests

    Reductions in photosynthetic capacity in the

    plant - results in slower growth and smaller leaves

    Causes mutations in mammalian cells and destroysmembranes

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    Harmful effects of UV rays on

    people Skin cancer

    Premature aging (photoaging) of the skin

    (different from normal chronological aging)

    Cataracts and eye disorders (corneal sunburnand blindness)

    Immune system damage

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    Biological Consequences of Ozone depletion

    Skin Cancerdue to the

    exposure to UV radiation

    A 1% decrease in overhead ozone is predicted to result in a 2% increase in

    UV-B intensity at ground level.

    Most biological effects of sunlight arise because UV-B can be absorbed by

    DNA molecules

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    Absorption spectrum ofDNA and theintensity ofsunlight on ground level

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    Correlation between Ozonedepletion and skin diseases

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    What is being done about the

    depletion of the ozone layer? The United States, along with over 180 other

    countries, recognized the threats posed by

    ozone depletion and in 1987 adopted a treaty

    called the Montreal Protocol to phase out the

    production and use of ozone-depleting

    substances.

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    Global Ozone Depletion (and

    Effects) Roughly 3% global stratospheric ozone has been depleted (averaged

    globally excepting the ozone hole and annually)

    The Montreal Protocol was signed in 1987 by 46 countries, including

    the US. It entered into force in 1989.

    By 1996, developed countries phased out use of CFCs, halons and

    CCl4; developing countries have until 2010.

    Developed countries are scheduled to phase out production of HCFCs

    by 2030; developing countries have until 2040.

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    Factors affecting UV exposure..2

    The time of year - more UV is received in thelate spring and early summer and much less isreceived in the late fall and early winter.

    Life style determines a persons risk to UVexposure. Skiing, sunbathing, or swimmingcan lead to extremely high exposures. Use of

    tanning parlors also increase risk.

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    Policy responses to Ozone depletion

    MarioMolina and Sherwood Rowland showed in 1974that CFC gases destroy ozone

    Coordinating committee on Ozone Layer (CCOL)

    established by UNEP in the 1970s

    Vienna Convention for the protection of the ozone layer

    held in 1985

    Montreal Protocol to ban substances that deplete the

    ozone layer held in 1987 Amendments to the Montreal Protocol: London - 1990,

    Copenhagen - 1992 and Montreal - 1997.

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Health Aspects of Ozone Depletion
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