Lead is a heavy metal, naturally found in nature, often associated with Zn, Ag and S and other minerals.
For years it was used in paint industries, metal foundries, batteries for vehicles, bullets for guns.
People exposed the most to lead are metal workers, painters, families (in particular children) who live near factories that make lead dust. In these places, in fact, the soil and the groundwater are highly polluted.
People get lead poisoning from breathing its dust (from the soil, filings, paint and so on), swallowing polluted water (from leadpipes) or with the simple contact with skin and mucosa.
In the bloodstream lead spread to every organs, in particular in bones (with a half-life of about 30 years), hair follicles, hepatocytes, which contain several target enzymes. Lead in fact bonds with sulfuric group, mimicking the action of other metal cofactors, such as Fe, Ca, Zn
Lead interacts with ALAD the enzyme that takes part in the synthesis of Protoporphirine IX and acts by inhibiting Ferrochetalase that allows the bond between Fe and Protoporphirine IX. This cause a severe hypocromic anemia and the formation of ZPP.
On neurons lead interacts with NMDA receptor, blocking glutamate release.
In kidneys lead interacts with 25(OH)D-1α hydroxylase, essential for the vitamin D synthesis. A decrease of calcemia lead a loss of Calcium in skeletal muscle (that causes fatigue), cardiac failure, loss of those metabolic processes that require Calcium as second messenger.
In hepatocytes lead accumulates for the high affinity with CYP450, e.g. the 3A4, 2C9, 2C19. Because of its saturation, xenobiotic and the major medicines are less metabolized by the liver, this cause severe complications.
In CNS lead interacts with TPH, an enzyme that requires Fe as cofactor, involved in synthesis of the serotonin. Lead replace the iron, decreasing 5-HT levels. Severe depression can occur, more over many studies demonstrated the link between depression and immune system failure.
Often patients complain general weakness, anorexia, skeletal muscle fatigue, depression.
Haematic levels of lead are considered dangerous and harmful above 10 μg/dL in children and 25 μg/dL in adults. An easy blood test can be done to detect poisoning, as an alternative a hair follicle can be tested.
In case of acute or severe chronic poisoning a strong chelating agent is given (like an EDTA). A diet full of Fe, Ca, Zn and vitamin C is highly recommended.
To prevent lead poisoning is helpful replace old painting, leaded plumbing and clean down the house with HEPA vacuum.
Screening test for lead poisoning
Toxicokinetics of Bone Lead
Lead in the Home Garden and Urban Soil Environment