Māris kļaviņŠ, azamat azizov, JĀnis zaļoksnis environment, pollution, development: the case of uzbekistan

Figure 7.21. 
Comparison 
of different technologies 
for dust and aerosol 
removal. 

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7. AIR POLLUTION
 145
medicine, and the production of substances that are used in 
everyday life. Already two examples of this group of substances – 
pesticide DDT and polymer polyvinyl chloride compound shows 
broad spectrum of features and usability characteristic to 
organohalogens. However, to talk about the effects of exposure to 
these substances, one must discuss the structure, areas of use and 
the main characteristics, as well as the main sources of environ-
mental pollution with halogenated organic compounds. First of all, 
halogenated organic compounds can be divided into organofluoride 
organic, chloro-organic and organobromide compounds.
Despite  the  extensive  production,  organofluorine  compound 
application range is narrower than that of the chloro-organic 
substances, which is mainly due to their high cost. The most popular 
of the organofluorines is dichlofluormethane (Freon). The methane 
derivatives are: Freon 11 (CFCl
3
, b.t. 23.8 °C); Freon 12 (CF
2
Cl
2
, b.t. 
–29.8 °C);  Freon  13  (CFCl
3
,  b.t.  –81.4 °C)  and  ethane  derivatives 
Forane 114 (CF
2
ClCF
2
Cl, b.t. 3.6 °C) and Forane 113 (CFCl
2
CF
2
Cl, b.t. 
47.6 °C). 
Such a wide scope of use of these substances is determined by 
many unique features of freons, among which the first to be noted 
is the high chemical stability of these substances (they do not break 
down in the aquatic environ ment, or when exposed to acids, bases 
and oxidizers). Freons are also characterized by low acute toxicity: 
inhalation of freons F11, 12, 22 and other freon vapour (0.5% vol.) 
for 90 days, 6 hours a day does not result in any symptoms of toxic 
effects. The maximum permissible concentration in the air for most 
of  the  freons  is  about  1000  mg/m
3
, but for liquid freons F11 and 
F113LD
50
 it is above 15 g/kg.
Furthermore, the other characteristics important from the prac-
tical point of view determine the extensive production of freon 
today. Taking into account the specificity of freon use, most of this 
volume is dispersed into the atmo sphere, where the freon decom-
position  is  slow.  At  the  same  time,  in  the  stratosphere  under  the 
influence  of  UV  radiation,  freon  molecules  decompose,  releasing 
the halogen radicals, which may subsequently act as catalysts 
for  ozone  decomposition  reaction.  Given  the  harmful  effects  of 
organo halogens, degrading the ozone layer (primarily freons), the 
production and consumption amount in the European Union Member 
States (Figure 7.22) as well as in other countries has significantly 
decreased in the last decades.
Chlorine derivatives C
1
 and C
2 
belong to low molecular weight 
organochlorine. Typically, this group of substances includes methane 
chlorine derivatives (carbon tetrachloride CCl
4
, chloroform CHCl
3
, 
methylene chloride CH
2
Cl
2
, methyl chloride CH
3
Cl), chlorine 
derivatives of ethane or ethylene. These substances form a separate 
These gaseous or easily 
liquefiable substances are 
mainly used, as follows:
1.  as propellants in 
aerosols (freons are 
chemically inert, 
non‑combustible, 
practically non‑toxic); 
2.  as heat carriers in 
cooling devices;
3.  as foaming agents in 
the manufacture of 
porous polymers; 
4.  in microelectronics;
5.  in chemical industry.

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146 
ENVIRONMENT, POLLUTION, DEVELOPMENT:  THE CASE OF UZBEKISTAN
group, taking into account the production of substantial size, and 
the similar toxicological spectrum. Halogenated hydrocarbons are 
obtained both by the direct chlorination of hydrocarbons, and by 
chlorination in the presence of atmo spheric oxygen as an oxidizing 
agent. Typical lower chlorinated hydrocarbons are liquid substances 
(with the exception of methyl and vinyl chloride, which are gases, 
and hexachloroethane, which is solid). Annual production of vinyl 
chloride (CH
2
=CHCl) amounts to 10 million tons. 1,2-dichloroethane 
is also produced in significant quantities (13 million tons per year) 
as  well  as  carbon  tetrachloride  (1  million  tons  per  year).  Large 
amounts of trichalomethanes (THMs) are formed as a result of 
water chlorination. These substances may be also formed as a result 
of various natural processes. It is assumed that burning fossil fuels 
and biomass release 5 × 10
6
 tons of methyl chloride per year into 
environ ment, but up to 40 000 tons of methyl chloride are formed in 
the ocean and sea algae life processes. 
0 
300 
400 
250 
200 
150 
100 
50 
350 
450 
Thousand Ozone Depleting Potential Tonnes (ODP Tonnes)* 
* Tonnes multiplied by the ozone depleting potential of the considered gas. 
CFCs 
United  
States 
China 
Russia 
European Community (25) 
1990 
1995 
2000 
2005  
2008
Lower halogenated hydrocarbons are widely used as solvents 
in the manufacture of polymers (vinyl chloride). The large amounts 
and  mode  of  use  result  in  release  of  significant  volumes  of  these 
substances  into  the  environ ment,  and  it  can  affect  human  health 
in the living and working environ ment. Lower molecular mass 
chlorinated hydrocarbons, when inhaled, act as anaesthetic 
substances, which can easily lead to poisoning, especially affecting 
the liver. In some chlorinated hydrocarbons the carcinogenic effects 
have been proven.