The pollutant cadmium in water may arise from
industrial discharges and mining wastes. Cadmium
is widely used in metal plating. Chemically, cadmium
is very similar to zinc, and these two metals frequently
undergo geochemical processes together. Both metals
are found in water in the +2 oxidation state. The effects
of acute cadmium poisoning in humans are very serious.
Among them are high blood pressure, kidney damage,
destruction of testicular tissue, and destruction of
red blood cells. Cadmium may replace zinc in some
enzymes, thereby altering the stereo-structure of the
enzyme and impairing its catalytic activity.
Cadmium and zinc are common water and sediment
pollutants in harbours surrounded by industrial
facilities. Concentrations of more than 100 ppm dry
weight sediment have been found in harbour
sediments.
Inorganic lead arising from a number of industrial
and mining sources occurs in water in the +2
oxidation state. Lead from leaded gasoline used to
be a major source of atmospheric and terrestrial lead,
much of which eventually enters natural water systems.
Despite greatly increased total use of lead by
industry, evidence from hair samples and other
sources indicates that body burdens of this toxic metal
have decreased during recent decades. This may be
the result of less lead used in plumbing and other
products that commonly come in contact with food
or drink. Acute lead poisoning in humans causes severe
dysfunction in the kidneys, reproductive system,
liver, and the brain and nervous system.