2.95 - Atmospheric pollution

What are CFCs and why have they been banned

• Chlorofluorocarbons

• Banned because they were harmful to the ozone layer when emitted into the air

What is the ozone layer

A layer of ozone which is 5km thick surround the earth in the stratosphere

Why is the ozone layer important

Because it acts as a protective screen against the excessive UV radiation reaching the earths surface.

(Protects life from suns UV rays)

What are examples of CFCs

CFCL3, CF2CL2

What where CFCs used for from the 1930s until the late 1980s

• Refrigerants

• Spray propellants

• Air conditioning systems

• Production of plastic

Why did CFCs seem ideal for these purposes

Their

• Lack of reactivity

• Low flammability

• Low toxicity

What happens when CFCs are released into the air

They slowly (20-30yrs) rise into the stratosphere and here their CFC molecules are broken apart by U.V radiation and release reactive chlorine atoms. These atoms in turn destroy ozone molecules in a repeating cycle.

What do ozone “holes” refer to

Areas where the concentration of ozone is very low

Why are CFCs also considered to be greenhouse gases

Because they contribute to global warming

Why is the recovery of the ozone layer expected to take several lifetimes

Because CFCs have extremely long atmospheric lifetimes (50-100yrs)

What happens when the amount of ozone gets depleted

More UV light reaches the earths surface

What can long exposure to ultraviolet light cause

• skin cancer

• additional cases of eye cataracts

• weakens the immune system

• damage crops

• excess UV kills phytoplankton (primary food in the ocean)