Lead

Inorganic lead is the most extensively studied environmental toxin. Today's humans have in the order of 100 times higher lead exposure, compared to prehistoric humans, mainly from food. The exposure was even higher during the 20th century, mainly due to lead addition to gasoline. Today, high exposures occur in many occupations, but also through, for example, contaminated drinking water, traditional drugs, lead paint, and soil and dust in "hotspots" around mines and smelters. Absorbed lead is widely distributed in the body. It accumulates in the skeleton, which, in turn, causes endogenous exposure, especially during pregnancy/lactation and in osteoporosis. Lead passes over the placenta into the fetus, and via breast milk into the infant. The mode(s) of action is not known; different mechanisms might be operating at different concentrations. Toxic effects occur first in the nervous system of fetuses/infants/children, with small cognitive effects already at a mean blood lead concentration (B-Pb) of ≤0.05. μmol/L (≤10. μg/L; which is well below the worldwide mean), without any threshold. Lead effects have also been reported for the cardiovascular system [increase of blood pressure at B-Pb well below 0.5. μmol/L (100. μg/L)], the kidney, post- and prenatal growth, cognition in also adults and elderly, the blood, the immune system, the gastrointestinal tract, and the female and male reproduction. There is important genetic modification of the toxicity. Lead is carcinogenic in animal experiments, but there is only limited evidence in humans.The organolead compounds tetraethyl- and tetramethyllead, earlier used in enormous quantities in leaded gasoline, are easily absorbed at inhalation and through the skin and may cause acute encephalopathia.