Lead and water quality
Lead: The primary natural source of lead is in the mineral galena (lead sulfide). It also occurs
as carbonate, as sulfate and in several other forms. The solubility of these minerals and also of
lead oxides and other inorganic salts is low. Major modern day uses of lead are for batteries,
pigments, and other metal products. In the past lead was used as an additive in gasoline and
became dispersed throughout the environment in the air, soils, and waters as a result of
automobile exhaust emissions. For years this was the primary source of lead in the environment.
However, since the replacement of leaded gasoline with unleaded gasoline in the mid-1980's,
lead from that source has virtually disappeared. Mining, smelting and other industrial emissions
and combustion sources and solid waste incinerators are now the primary sources of lead. Another
source of lead is paint chips and dust from buildings built before 1978 and from bridges and other
metal structures.
Lead is not an essential element. In humans it can affect the kidneys, the blood and most
importantly the nervous system and brain. Even low levels in the blood have been associated
with high blood pressure and reproductive effects. It is stored in the bones.
Lead reaches water bodies either through urban runoff or discharges such as sewage treatment
plants and industrial plants. It also my be transferred from the air to surface water through
precipitation (rain or snow). Toxic to both plant and animal life, lead's toxicity depends on its
solubility and this, in turn, depends on pH and is affected by hardness.
Criteria: The level considered protective for aquatic life at a hardness of 100 is less than 0.003
mg/L. Use as a domestic water source requires less than 0.05 mg/L. Drinking water must contain
less than 0.015 mg/L.
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