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Much of what is known about human lead toxicity and its effects is derived from animal studies. [39] Animals are used to test the effects of treatments, such as chelating agents, [308] and to provide information on the pathophysiology of lead, such as how it is absorbed and distributed in the body. [309]
Therefore, a common characteristic of toxic metals is the chronic nature of their toxicity. This is particularly notable with radioactive heavy metals such as radium, which imitates calcium to the point of being incorporated into human bone, although similar health implications are found in lead or mercury poisoning.
Lead is widely understood to be toxic to multiple organs of the human body, particularly the human brain. Concerns about even low levels of exposure began in the 1970s; in the decades since, scientists have concluded that no safe threshold for lead exposure exists. [2] [3] The major source of lead exposure during the 20th century was leaded ...
Blood lead level (BLL), is a measure of the amount of lead in the blood. [1] [2] Lead is a toxic heavy metal and can cause neurological damage, especially among children, at any detectable level. High lead levels cause decreased vitamin D and haemoglobin synthesis as well as anemia, acute central nervous system disorders, and possibly death. [3]
Lead was used extensively in Roman aqueducts from about 500 BC to 300 AD. [54] Julius Caesar's engineer, Vitruvius, reported, "water is much more wholesome from earthenware pipes than from lead pipes. For it seems to be made injurious by lead, because white lead is produced by it, and this is said to be harmful to the human body."
Lead is a potent neurotoxin whose toxicity has been recognized for at least thousands of years. [97] Though neurotoxic effects for lead are found in both adults and young children , the developing brain is particularly susceptible to lead-induced harm, effects which can include apoptosis and excitotoxicity. [ 97 ]
In the human body, lead inhibits porphobilinogen synthase and ferrochelatase, preventing both porphobilinogen formation and the incorporation of iron into protoporphyrin IX, the final step in heme synthesis. This causes ineffective heme synthesis and microcytic anemia. [268] Symptoms of lead poisoning
An average 70 kg human body is about 0.01% heavy metals (~7 g, equivalent to the weight of two dried peas, with iron at 4 g, zinc at 2.5 g, and lead at 0.12 g comprising the three main constituents), 2% light metals (~1.4 kg, the weight of a bottle of wine) and nearly 98% nonmetals (mostly water). [51] [n 8]