ESTONIAN ENVIRONMENTAL REVIEW 2009

4.2.3. Use and emissions of ozone
depleting substances
The ozone layer is a part of the atmosphere where the
concentration of ozone is greater than it is elsewhere.
In general, the ozone layer is about 10–50 km in altitude
and surrounds the entire earth. The ozone layer protects
humans and the environment from excessive ultraviolet
radiation. Ozone holes were discovered at the poles in the
1970s. To a lesser extent, the ozone layer varies seasonally
in thickness in all geographic regions. The ozone layer is
depleted by hydrocarbons that contain fluorine, chlorine
or bromine. These compounds are very stable (they are
inert, they do not readily react with other compounds)
and if they are released they may end up high in the ozone
later where they break down in sunlight and react with
ozone molecules, thus depleting the ozone.
CFCs are considered among the greatest threats to the
ozone layer. Freons are organic compounds that contain
carbon and fluorine, and in many cases, other halogens
(generally chlorine) and hydrogen. Depending on the
elements contained in the compound, they are termed
CFCs (fully halogenated chlorofluorocarbons) or HCFCs
(partially halogenated CFCs or hydrochlorofluorocarbons).
The latter were developed as a replacement for CFCs as
they break down more easily and are less harmful to the
ozone layer.
One-half of the CFCs originate from chlorine which
is generated by humans and reaches the stratosphere.
In the everyday world, CFCs have been widely used in
refrigeration and climate equipment control, as a solvent
in electronics industry, production of Styrofoam, paint
and lacquer, fire extinguishers and the perfume and pharmaceutical
industry. Once they enter the atmosphere,
CFCs can stay there for up to 200 years, depending on
the compound; some even longer.
Another class of substances that deplete the ozone
layer are the halons. Halons are bromine compounds
that contain fluorine as well, but instead of chlorine, the
ozone-depleting element in them is bromine. Halons
destroy ozone 3–10 times more than CFCs; at the same
time they are used much less.
The Estonian Environmental Strategy 2030 sets the
goal of gradually phasing out synthetic substances that
deplete the ozone layer from both industry and households.
No statistical overview of CFCs in household use
has been conducted, but compliance with the goal has
gone fairly well to this point with regard to industry/
companies – use of halons and CFCs is down significantly.
Instead, HFCs – which are harmless to the ozone layer
– have entered use.
Strategic accomplishments:
• use of substances that thin the ozone layer has
ceased to a 90% extent in Estonia (figure 4.8);
• agencies and procedures for use, collection and
organization of substances that deplete the
ozone layer have been formed;
• competency requirements have been established
for mechanics working with equipment containing
substances that deplete the ozone layer as well as
for technicians engaged in installing, dismantling/
demolishing and carrying leak inspections of such
equipment and who use collection recovery
equipment for such substances;
• use of CFCs and HCFCs has decreased
significantly (figure 4.9).
Ozone depletion potential ODP
Various substances deplete the ozone layer at different rates. The harmfulness of substances to the ozone layer
is expressed by the ODP, or ozone depleting potential. The ODP of CFC-11 is fixed at 1 and the ODP of all other
compounds is expressed with respect to it.
Table 4.2. Comparison of the ODP of various substances. Source: EERC
Substance
Chlorofluorocarbons (CFC) 0.6–1.0
Halons 3–10.0
Carbon tetrachloride CCl 4
1.1
1,1,1-trichloroethane (methyl chloroform) CH 3
CCl 3
0.1
Methyl bromide CH 3
Br 0.7
Hydrobromofluorocarbons (HBFCs) 0.02–7.5
Hydrocholorofluorocarbons (HCFCs) 0.02–0.11
Chlorobromomethane 0.12
ODP
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