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

particularly hazardous impact on the aquatic environ ment are lead, 
mercury, copper, zinc, cadmium, chromium and nickel. In the last 
century, when tetraethyllead lead was added as antiknock agent to 
automotive fuel, 25 000 tons of lead compounds annually entered sea 
and ocean waters. All heavy metals are highly toxic to aquatic life. 
Particularly high toxicity is characteristic of mercury (Hg). The 
exposure to this pollutant was first noted in 1956, in Minamata Bay, 
Japan, where more than 100 people died of a massive poisoning and 
10 000 more developed serious health disorders. Intoxication was 
caused by methylmercury contamination of marine products – fish, 
crabs and shellfish – consumed by coastal fishermen. The pollutant 
had run into the sea with the sewage of a chemical plant. The 
mercury salts were used as a catalyst in the production process of 
acetaldehyde. Due to the accumulation of mercury compounds in 
the ecological food chain, the content in marine organisms used for 
human consumption was 500 000 times higher than in the sea water. 
The mercury poisoning consequences for people who regularly ate 
seafood included severe central nervous system disorders in the 
form of a narrowing of the visual field, hearing impairment, speech 
impairment, loss of reason, unsafe walk and seizures. As the disease 
causes were not yet cleared, the symptoms were named Minamata 
disease. For many people who had apparently ingested smaller 
amounts of methylmercury, the symptoms began to appear only after 
several years, but the children born in the region were observed to 
have different congenital deformities.
The sources of substan‑
ces conferring unpleasant 
taste and odour are 
different: 
1.  living organic 
matter decomposition 
products;
2.  phenols and lignins, 
which, at water disin‑
fection with chlorine, 
form chlorophenols 
with a strong unple‑
asant smell;
3.  algae and bacteria give 
off many metabolites, 
whose presence in 
water may give it the 
odour of rot, soil, hay, 
potatoes etc., as well 
as, for example, a bitter 
taste.