CHAPTER.5

Ozone depletion and the ozone hole have generated worldwide concern over increased cancer risks and other negative effects. • The ozone layer prevents most harmful UVB wavelengths of ultraviolet light (UV light) from passing through the Earth's atmosphere. • These wavelengths cause skin cancer, sunburn, and cataracts, which were projected to increase dramatically as a result of thinning ozone, as well as harming plants and animals.

Effects of ozone ? ozone hole?

Depletion of the ozone layer has consequences on humans, animals and plants. • This typically results from higher UV levels reaching us on earth.

what are the consequences of depletion ?

then react with ozone, initiating a process whereby a single chlorine atom can cause the conversion of thousands of ozone molecules to oxygen.

what happens with the chlorine atoms ?

cause non-melanoma skin cancer. Additionally, it plays a major role in malignant melanoma development.

what is caused by UV

• a layer in the earth's stratosphere at an altitude of about 6.2 miles (10 km) containing a high concentration of ozone, which absorbs most of the ultraviolet radiation reaching the earth from the sun.

what is ozone layer

ozone? • a colorless unstable toxic gas with a pungent odor and powerful oxidizing properties, formed from oxygen by electrical discharges or ultraviolet light. It differs from normal oxygen (O2) in having three atoms in its molecule (O3).

what is ozone?

a global agreement to protect the stratospheric ozone layer by phasing out the production and consumption of ozone-depleting substances (ODS).

what is the Montreal protocol?

• EPA: The UV Index scale used in the United States conforms with international guidelines for UVI reporting established by the World Health OrganizationExitLearn how to read the UV index Scale to help you avoid harmful exposure to UV radiation.

what is the UV scale ?

• The Ozone Hole-Chlorofluorocarbons or CFCs. • Chlorofluorocarbon (CFC) is an organic compound that contains carbon, chlorine, and fluorine, produced as a volatile derivative of methane and ethane. • A common subclass is the hydrochlorofluorocarbons (HCFCs), which contain hydrogen, as well.

CFC's

Ozone depletion describes two related events observed since the late 1970s: • a steady lowering of about four percent in the total amount of ozone in Earth's atmosphere(the ozone layer), and • a much larger springtime decrease in stratospheric ozone around Earth's polar regions. • The latter phenomenon is referred to as the ozone hole. • There are also springtime polar tropospheric ozone depletion events in addition to these stratospheric events.

how is Ozone described?

is man-made chemicals, especially man-made - halocarbon refrigerants - Solvents - Propellants, and - foam-blowing agents chlorofluorocarbon(CFCs), HCFCs, halons, referred to as ozone-depleting substances (ODS). • These compounds are transported into the stratosphere by the winds after being emitted at the surface.

what is the main cause of ozone depletion?

Once in the stratosphere, they release halogen atoms through photodissociation, which catalyze (speed up) the breakdown of ozone (O3 ) into oxygen (O2 ). • Both types of ozone depletion were observed to increase as emissions of halocarbons increased.

what occurs in stratosphere?

• An easy way to tell how much UV exposure you are getting is to look for your shadow: • If your shadow is taller than you are (in the early morning and late afternoon), your UV exposure is likely to be lower. • If your shadow is shorter than you are (around midday), you are being exposed to higher levels of UV radiation. Seek shade and protect your skin and eyes.

what's the shadow rule?