Upload
vish-shar
View
221
Download
0
Embed Size (px)
Citation preview
8/3/2019 11839_CHE 883 Lecture 8
http://slidepdf.com/reader/full/11839che-883-lecture-8 1/12
Health Aspects of Ozone
Depletion
8/3/2019 11839_CHE 883 Lecture 8
http://slidepdf.com/reader/full/11839che-883-lecture-8 2/12
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.
8/3/2019 11839_CHE 883 Lecture 8
http://slidepdf.com/reader/full/11839che-883-lecture-8 3/12
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.
8/3/2019 11839_CHE 883 Lecture 8
http://slidepdf.com/reader/full/11839che-883-lecture-8 4/12
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
8/3/2019 11839_CHE 883 Lecture 8
http://slidepdf.com/reader/full/11839che-883-lecture-8 5/12
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
8/3/2019 11839_CHE 883 Lecture 8
http://slidepdf.com/reader/full/11839che-883-lecture-8 6/12
Biological Consequences of Ozone depletion
Skin Cancer due to the
exposure to UV r adiation
A 1% decrease in over head ozone is predicted to result in a 2% increase in
UV-B intensity at gr ound level.
Most biological effects of sunlight arise because UV-B can be absor bed by
DN A molecules
8/3/2019 11839_CHE 883 Lecture 8
http://slidepdf.com/reader/full/11839che-883-lecture-8 7/12
Absorption spectr um of DN A and the intensity of sunlight on gr ound level
8/3/2019 11839_CHE 883 Lecture 8
http://slidepdf.com/reader/full/11839che-883-lecture-8 8/12
Correlation between Ozonedepletion and skin diseases
8/3/2019 11839_CHE 883 Lecture 8
http://slidepdf.com/reader/full/11839che-883-lecture-8 9/12
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.
8/3/2019 11839_CHE 883 Lecture 8
http://slidepdf.com/reader/full/11839che-883-lecture-8 10/12
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.
8/3/2019 11839_CHE 883 Lecture 8
http://slidepdf.com/reader/full/11839che-883-lecture-8 11/12
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.
8/3/2019 11839_CHE 883 Lecture 8
http://slidepdf.com/reader/full/11839che-883-lecture-8 12/12
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.