Ozone Problem

Lecture-3

Introduction• That is, the layer of life-protecting ozone found at the top of the

stratosphere. A brief history of the discovery of the ozone 'hole' is included. The general concepts found in this section include the following:

– Concentrations of stratospheric ozone represent a balance, established over eons, between creative and destructive forces and this balance, or dynamic equilibrium, has been changed by human activity.

– Ozone is formed in the earth's stratosphere and is critical to life on earth as we know it.

– There is compelling scientific evidence that ozone is destroyed in the stratosphere and that some human-released chemicals are speeding up the breakdown of ozone in the atmosphere.

– CFCs, a human-developed compound, are particularly destructive to the breakdown of ozone in the atmosphere.

– Ultraviolet radiation is present in natural outdoor light and can be blocked or filtered by various substances.

Ozone Layer Depletion: Historical Perspective• The ozone 'hole', it is really not a hole but rather a thinning of

the ozone layer in the stratosphere. We will use the term 'hole' in reference to the seasonal thinning of the ozone layer.

– The appearance of a hole in the earth's ozone layer over Antarctica, first detected in 1976.

– 1974: Rowland & Molina theorize CFCs destroy stratospheric ozone molecules

– 1975: U of M / Harvard papers predict that CFCs deplete Earth’s ozone layer

– 1985: Ozone holes found over Antarctic

– 1988: Ozone layer thinning over North Pole

– 1993: Thinning over mid-latitudes of the Northern Hemisphere

– 1997: Low values of total ozone occur in Arctic as well as Antarctic

Antarctic Ozone Hole Progression

1979 1986 1991

NOx

NMVOCs

NOx

NMVOCs

CONTINENT 2 OCEAN

O3

Boundary layer

(0-2.5 km)

Free Troposphere

CONTINENT 1

CH4 itself is an important greenhouse gas, and links climate with air pollution via its influence on tropospheric ozone

OH HO2

VOC, CH4, CO

NONO2

hO3

O3

Hemispheric Pollution

Direct Intercontinental Transport

greenhouse gas

air pollution (smog)

air pollution (smog)

Ozone Layer Depleting Chemicals

• chlorofluorocarbons (CFCs)

• carbon tetrachloride (CCl4)

• methyl chloroform (CH3CCl3)

• hydrochloric acid (HCl)

• methyl chloride (CH3Cl)

• methyl bromide(CH3Br)

International Response to Ozone Layer Depletion

• 1985: United Nations Environment Program (UNEP)

• 1987: The Montreal Protocol

• 1992: Copenhagen Amendments

• 1998: The Montreal Protocol is affecting stratospheric chemical composition.

International Response to Ozone Layer Depletion

• 1999-2000: Stratospheric ozone layer recovery will be a slow process and extend into the next century.

• Scientific Assessment of Ozone Depletion: 1994 and 1998 (World Meteorological Organization).

• Ozone Depletion Web Page: http://www.epa.gov/ozone

Ozone Layer Depleting Chemicals: Chlorine

CCl412%

CH3Cl & HCl

18%

CFC-1123%

CFC-1228%

CFC-1136%

HCFC-223%

CH3CCl310%

Ozone Layer Depleting Chemicals: CFCs

• CFCs are inert, nonreactive, nontoxic, nonflammable.

• Human-made CFCs used in:– refrigeration– air conditioning– foam blowing– cleaning electronic components– solvents

CFC Reactions Deplete Ozone Layer in Stratosphere

CFC Cl

UV

UV

O3O3

O3

CFCs

Ozone Depleting Process

Global Stratospheric Ozone Layer Depletion Trend

1980 1982 1984 1986 1988 1990 1992 1994

0

-2

-4

-6% D

evia

tion

from

mon

thly

ave

.

Biological Effects of Ultraviolet Radiation

• Sunburn,Premature Aging & PreCancer

• Cancer of Skin– Basal and Squamous Cell Carcinoma– Melanoma

• Cataracts

• Photosensitivity

• Immune system changes

Immunity

humoralsystem

cellularsystem

B Lymphocyte T Lymphocyte

Human Immune System can be suppressed by ultraviolet radiation

Human Immune System can be suppressed by ultraviolet radiation

B Lymphocyte T Lymphocyte

Immunoglobulins

Foreign Protein

Bacteria

Cancer

Parasites

Bacteria-Fungi

Viruses

Human Immune System can be suppressed by ultraviolet radiation

• suppression of immune system

• increased incidence of infection

• promotion of cancer growth

The Skin Cancer Epidemic

• skin cancer is the most common malignancy in the U.S.

• 1 in 5 Americans will become afflicted

• ~ 1.0 million new cases this year

• rates of skin cancer are rising 3 - 5% per year

The Skin Cancer Epidemic

• Basal cell carcinoma– most common, least aggressive, locally

destructive

• Squamous cell carcinoma– more aggressive, can metastasize

• Melanoma– most aggressive, ~75% of all skin cancer deaths

The Skin Cancer Epidemic

• melanoma is increasing in incidence faster than any other cancer

• lifetime probability of developing melanoma is 1 in 75

• 100 new cases of melanoma diagnosed per day, ~ one death per hour

The Skin Cancer Epidemic Problems

• knowledge: 1/3 of Americans know that melanoma is a kind of skin cancer

• attitudes: >60% of Americans think people look better with a tan

• behavior: only 1/4 of the population use sunscreens regularly

Cataracts of Eyes

• cataracts are when the lens of the eye becomes cloudy

• 20 million cases worldwide

• account for half of blindness in the world

Good & Bad Effects of SunlightGood & Bad Effects of Sunlight

Photosynthesis

Vitamin Dsynthesis

Vision

Kills pathogens

Phototherapy

Warmth

Pre-Cancer

Phototosensitivity

Cataracts

Cancer

Sunburn

Premature Aging

Immune systemchangesBADGOOD

References• “Environmental Effects of Ozone Depletion.” AMBIO 24 May(1995):137-

196.

• Cook, Elizabeth, ed. Ozone Protection in the United States: Elements of Success. Washington, D.C.: World Resources Institute,1996.

• UNEP Ozone Depletion Report 1994/98 http://www.gcrio.org/ozone/toc.html http://www.gcrio.org/UNEP1998/

• Southern Hemisphere Ozone Hole Size http://www.cpc.ncep.noaa.gov/products/stratosphere/sbuv2to/ozone_hole.html

• Health and Environmental Effects of Ultraviolet Radiation. INTERSUN: The Global UV Project. 9 Sep 1998. http://www.who.int/peh-uv/publications/index.html

• The health impact of solar radiation and prevention strategies. Report of the Environment Council, American Academy of Dermatology. J Am Acad Dermatol 1999; 41:81-99.

Think Globally and Act Locally