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

Figure 8.14. 
Formula of 
methylmercury

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182 
ENVIRONMENT, POLLUTION, DEVELOPMENT:  THE CASE OF UZBEKISTAN
Furthermore, the illness was observed not only in the people, 
but also in those pets who consume fish – cats. These animals were 
recorded with behavioral problems – they had lost the aversion to 
water inherent to cats.
Minamata disease symptoms appeared at a mercury con centra-
tion of 10 mg/kg of edible fish. Numerous studies have found that 
dangerously high contamination with methylmercury has also been 
registered in other parts of the world, including the northern coast 
of the Mediterranean Sea, NE Atlantic and the Baltic Sea. Entry of 
mercury compounds in the Baltic Sea mainly takes place with river 
water  (8-44  t/year)  and  precipitation  (4-29  t/year)  they  reach  the 
sea in significantly smaller amounts by the waste water of the cities 
and factories located on the coast. Marine organisms accumulate 
methylmercury. The biggest concentrations of mercury are found at 
the highest stages of marine ecological food chain – the bodies of 
seals, and the concentration increases significantly with age.
The human health hazard lies in the increased consumption 
of the marine animal products containing growing quantities of 
mercury. The organisms of the predatory fish living and feeding in 
the Baltic Sea coastal area contain methylmercury concentrations 
exceeding  0.5  mg/kg.  In  the  Mediterranean  Sea  high  mercury 
content  was  found  in  swordfish.  Frequent  intake  of  mercury-
contaminated fish may cause health disorders. Particularly sensitive 
to contamination are the human foetus and growing child’s body.
One of the indicators that can be used to characterize the 
received doses of mercury in the body at different periods of human 
life is the content of this metal in hair. Studies in Japan have shown 
that the mercury concentration in the hair of the people who 
regularly, for several days a week had consumed seafood products, 
exceeded that of the people in the control group 5 to 10 times. 
However, in accordance with scientific findings, also the people of 
the studied control group, although to a much lesser extent, were 
exposed to mercury pollution, which was contained in the consumed 
agricultural production. Mercury compounds enter the agricultural 
products as a result of applying mercury-containing grain fungicide 
treatment substances. The chemical composition analysis of hair 
carried out on the citizens of European countries, showed that 
the mercury concentration there was similar to that found in the 
control group of Japan. It indicates that in this region there is 
also a heightened background of mercury pollution. Data from 
these studies at the end of 1960s prompted a number of European 
governments to adopt more stringent regulatory measures for 
mercury compound use in industry and agriculture. 
Ecologically no less dangerous are the cadmium compounds. 
Cadmium is one of the most mobile and biochemically active heavy 

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8. WATER POLLUTION
 183
metals. It accumulates in the kidney cortex, causing hemorrhages. 
When ingested, cadmium binds itself to proteins and accumulates in 
the kidneys and liver. In the Baltic Sea cadmium, similar to mercury, 
is brought mainly by river water and atmo spheric precipitation. 
The  concentrations  of  this  metal  in  fish  here  range  from  2  to 
200  µg/kg,  and  in  molluscs  –  1300  to  10 800  µg/kg  of  the  body 
weight. Cadmium, like many other polluting elements, tends to 
accumulate in the ecological food chain. Threat to human health is 
posed by increased accumulation of cadmium in those links of food 
chain  –  marine  organisms  widely  used  in  food.  One  of  these  fish 
species is herring, in whose body an increase in cadmium content 
has recently been observed.
One of the heavy metals of greatest ecological importance and 
toxic to living organisms is lead. In the last century large quantities 
of lead came into the sea and ocean ecosystem with industrial 
effluents  and  emissions  of  tetraethyllead  used  in  road  transport. 
Due to stricter environ mental legislation, waste water treatment 
technology improvements and the introduction of unleaded 
automotive fuel, since 1980s the lead concentrations in the have 
been decreasing, as shown by the analysis of fish and molluscs.
Biological pollution of waters is caused by inflow of untreated 
municipal or industrial wastewater from industrial plants and 
residential areas. Biological pollution consists of pathogens – viruses, 
bacteria and microscopic fungi, as well as a variety of organic 
substances subject to fermentation processes. Biological pollution 
also manifests itself as the appearance of species not characteristic 
of specific water bodies – the so-called invasive species. Pathogenic 
microorganisms cause public health and hygiene problems in 
bathing places. This contamination is evaluated according to the 
presence of intestinal bacillus Escherichia coli in the water sample. 
In itself, this bacillus is harmless to humans, they live as symbionts 
in the human intestinal tract and as a result of their life processes 
produce physiologically important substances, including vitamin 
B12. However, the presence of Escherichia coli serves as a faecal 
contamination indicator, but this contamination may conceal a 
number of pathogenic microorganisms, incl. infectious hepatitis, 
cholera, typhoid and dysentery agents, as well as staphylococci, 
streptococci, and pathogenic fungi. Humans become infested with 
these microorganisms while swimming in biologically contaminated 
water, so the most popular swimming sites on sea coast, including 
seaside, in summer season are regularly monitored regarding 
biological contamination and, if Escherichia coli in water sample 
exceeds a certain level, vacationers are warned not to go swimming. 
Water contamination with pathogenic microorganisms also 
makes  the  produce  of  mollusc  farms  –  oysters  and  other  edible