LEAD EXPOSURE IN HUMANS
LEAD EXPOSURE IN HUMANS 
Levels of lead exposure in the general population have fallen in the USA and Western Europe, with average national values for blood lead in the EU in the 1990s mostly well below 10μg/dl. Decreased exposure from several sources has brought this about, though it is believed that the reduction of leaded petrol is a major contributory factor. Other measures have included: improved water treatments reducing plumbosolvency; phasing out of leaded solders in food cans; and phasing out of the use of leaded paints. Improved industrial practices have resulted in lower emissions. A small proportion of individuals continue to receive doses of lead which are deemed unhealthy, particularly in the developing World and in Eastern Europe. The most highly exposed individuals tend to be the more deprived members of society. Occupational exposure has also decreased dramatically in the western world with improved technology, hygiene and management practices.
EFFECTS OF LEAD EXPOSURE ON HUMAN HEALTH
A small number of adults occupationally exposed to lead have in the past shown increased risk of kidney damage, nerve damage, infertility and, possibly, a small increase in blood pressure and the risk of contracting certain cancers at high levels of exposure. However, today such effects are rarely observed. The greatest concern for the general population is that lower levels of lead exposure, which some of the general population may receive, appear to cause a small decrease in the intellectual development of young children. Children are more vulnerable because their nervous system is developing; they absorb more lead than adults because of behavioural and physiological differences. There is no accepted threshold level, but the body of evidence to date does not find any effect below 10μg/dl blood lead. Individuals whose diet is lacking in iron or calcium absorb more lead than those who are well nourished.
ECOTOXICITY
Lead can have adverse effects on living organisms. High doses can interfere with some biochemical processes required for normal functioning. Most lead compounds have low solubilities in water and are not readily absorbed by most living organisms. Soluble compounds of lead can readily be taken in, and have been studied most widely (particularly for aquatic organisms). However, some organisms (such as molluscs) can absorb solid lead compounds from sediments, and there is little data available on the toxicity of this. Tetraethyl lead is much more toxic than inorganic lead compounds, but it breaks down quickly in the environment. Some aquatic species bioaccumulate lead, but there is no evidence for biomagnification at higher levels in food chains. Lead in soil generally does not have great effects on plants or earthworms except at highly elevated concentrations; its potency varies with soil type. In general, the bioavailability and toxicity of lead compounds are greater in acidic conditions, and less in alkaline or saline conditions. The major impact of lead on wildlife, particularly waterfowl, results from the ingestion of lead shot (from ammunition or fishing weights). This can cause acute lead poisoning, sometimes fatal. For this reason, the use of lead shot for small fishing weights, and in some cases, in ammunition, is restricted in an increasing number of countries.
Levels of lead exposure in the general population have fallen in the USA and Western Europe, with average national values for blood lead in the EU in the 1990s mostly well below 10μg/dl. Decreased exposure from several sources has brought this about, though it is believed that the reduction of leaded petrol is a major contributory factor. Other measures have included: improved water treatments reducing plumbosolvency; phasing out of leaded solders in food cans; and phasing out of the use of leaded paints. Improved industrial practices have resulted in lower emissions. A small proportion of individuals continue to receive doses of lead which are deemed unhealthy, particularly in the developing World and in Eastern Europe. The most highly exposed individuals tend to be the more deprived members of society. Occupational exposure has also decreased dramatically in the western world with improved technology, hygiene and management practices.
EFFECTS OF LEAD EXPOSURE ON HUMAN HEALTH
A small number of adults occupationally exposed to lead have in the past shown increased risk of kidney damage, nerve damage, infertility and, possibly, a small increase in blood pressure and the risk of contracting certain cancers at high levels of exposure. However, today such effects are rarely observed. The greatest concern for the general population is that lower levels of lead exposure, which some of the general population may receive, appear to cause a small decrease in the intellectual development of young children. Children are more vulnerable because their nervous system is developing; they absorb more lead than adults because of behavioural and physiological differences. There is no accepted threshold level, but the body of evidence to date does not find any effect below 10μg/dl blood lead. Individuals whose diet is lacking in iron or calcium absorb more lead than those who are well nourished.
ECOTOXICITY
Lead can have adverse effects on living organisms. High doses can interfere with some biochemical processes required for normal functioning. Most lead compounds have low solubilities in water and are not readily absorbed by most living organisms. Soluble compounds of lead can readily be taken in, and have been studied most widely (particularly for aquatic organisms). However, some organisms (such as molluscs) can absorb solid lead compounds from sediments, and there is little data available on the toxicity of this. Tetraethyl lead is much more toxic than inorganic lead compounds, but it breaks down quickly in the environment. Some aquatic species bioaccumulate lead, but there is no evidence for biomagnification at higher levels in food chains. Lead in soil generally does not have great effects on plants or earthworms except at highly elevated concentrations; its potency varies with soil type. In general, the bioavailability and toxicity of lead compounds are greater in acidic conditions, and less in alkaline or saline conditions. The major impact of lead on wildlife, particularly waterfowl, results from the ingestion of lead shot (from ammunition or fishing weights). This can cause acute lead poisoning, sometimes fatal. For this reason, the use of lead shot for small fishing weights, and in some cases, in ammunition, is restricted in an increasing number of countries.
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