8. WATER POLLUTION
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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
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