What are the different target organs of lead and its mechanism of action of these different organs?
Lead affects many organs and functions of the body to varying degrees. The major health effects of lead are manifest essentially in three organ systems: the hematological system, the central nervous system and the renal system. The frequency and severity of symptoms among exposed individuals depends upon the amount of exposure. I suggest you to consult this document: ATSDR toxicological profile for lead.
Lead affects every one of the body's organ systems, especially the nervous system, but also the bones and teeth, the kidneys, and the cardiovascular, immune, and reproductive systems. Hearing loss and tooth decay have been linked to lead exposure,] as have cataracts.Intrauterine and neonatal lead exposure promote tooth decay.] Aside from the developmental effects unique to young children, the health effects experienced by adults are similar to those in children, although the thresholds are generally higher.
Renal system
Kidney damage occurs with exposure to high levels of lead, and evidence suggests that lower levels can damage kidneys as well.The toxic effect of lead causes nephropathy and may cause Fanconi syndrome, in which the proximal tubular function of the kidney is impaired.[93] Long-term exposure at levels lower than those that cause lead nephropathy have also been reported as nephrotoxic in patients from developed countries that had chronic kidney disease or were at risk because of hypertension or diabetes mellitus. Lead poisoning inhibits excretion of the waste product urate and causes a predisposition for gout, in which urate builds upThis condition is known as saturnine gout.
Cardiovascular system
Evidence suggests lead exposure is associated with high blood pressure, and studies have also found connections between lead exposure and coronary heart disease, heart rate variability, and death from stroke, but this evidence is more limited.People who have been exposed to higher concentrations of lead may be at a higher risk for cardiac autonomic dysfunction on days when ozone and fine particles are higher.
Reproductive system
Lead affects both the male and female reproductive systems. In men, when blood lead levels exceed 40 μg/dL, sperm count is reduced and changes occur in volume of sperm, their motility, and their morphology. A pregnant woman's elevated blood lead level can lead to miscarriage, prematurity, low birth weight, and problems with development during childhood.Lead is able to pass through the placenta and into breast milk, and blood lead levels in mothers and infants are usually similar.] A fetus may be poisoned in utero if lead from the mother's bones is subsequently mobilized by the changes in metabolism due to pregnancy; increased calcium intake in pregnancy may help mitigate this phenomenon
Nervous system
Eight MRI views of a brain in black and white, with yellow, orange, and red areas overlaid in spots mainly toward the front.
The brains of adults who were exposed to lead as children show decreased volume, especially in the prefrontal cortex, on MRI. Areas of volume loss are shown in color over a template of a normal brain.
Lead affects the peripheral nervous system (especially motor nerves) and the central nervous system.peripheral nervous system effects are more prominent in adults and central nervous system effects are more prominent in children. Lead causes the axons of nerve cells to degenerate and lose their myelin coats.
The brain is the organ most sensitive to lead exposure. Lead is able to pass through the endothelial cells at the blood brain barrier because it can substitute for calcium ions and be uptaken by Calcium-ATPase pumps. Lead poisoning interferes with the normal development of a child's brain and nervous system; therefore children are at greater risk of lead neurotoxicity than adults are. In a child's developing brain, lead interferes with synapse formation in the cerebral cortex, neurochemical development (including that of neurotransmitters), and organization of ion channels It causes loss of neurons' myelin sheaths, reduces numbers of neurons, interferes with neurotransmission, and decreases neuronal growth.
Lead exposure in young children has been linked to learning disabilities,[106] and children with blood lead concentrations greater than 10 μg/dL are in danger of developmental disabilities. Increased blood lead level in children has been correlated with decreases in intelligence, nonverbal reasoning, short-term memory, attention, reading and arithmetic ability, fine motor skills, emotional regulation, and social engagement. The effect of lead on children's cognitive abilities takes place at very low levels. There is apparently no lower threshold to the dose-response relationship (unlike other heavy metals such as mercury).[108] Reduced academic performance has been associated with lead exposure even at blood lead levels lower than 5 μg/dL. Blood lead levels below 10 μg/dL have been reported to be associated with lower IQ and behavior problems such as aggression, in proportion with blood lead levels.[6] Between the blood lead levels of 5 and 35 μg/dL, an IQ decrease of 2–4 points for each μg/dL increase is reported in children.
High blood lead levels in adults are also associated with decreases in cognitive performance and with psychiatric symptoms such as depression and anxiety.It was found in a large group of current and former inorganic lead workers in Korea that blood lead levels in the range of 20–50 μg/dL were correlated with neuro-cognitive defects.Increases in blood lead levels from about 50 to about 100 μg/dL in adults have been found to be associated with persistent, and possibly permanent, impairment of central nervous system function.
Lead exposure in children is also correlated with neuropsychiatric disorders such as attention deficit hyperactivity disorder and antisocial behavior.Elevated lead levels in children are correlated with higher scores on aggression and delinquency measures. A correlation has also been found between prenatal and early childhood lead exposure and violent crime in adulthood. Countries with the highest air lead levels have also been found to have the highest murder rates, after adjusting for confounding factors.A May 2000 study by economic consultant Rick Nevin theorizes that lead exposure explains 65% to 90% of the variation in violent crime rates in the US.] A 2007 paper by the same author claims to show a strong association between preschool blood lead and subsequent crime rate trends over several decades across nine countries. It is believed that the U.S. ban on lead paint in buildings in the late 1970s, as well as the phaseout of leaded gasoline in the 1970s and 1980s, partially helped contribute to the decline of violent crime in the United States since the early 1990s
Calcium is one of the most important nutrients to combat lead levels in bone, brain and the nervous system. Effects of high calcium levels decrease the absorption of lead and his retention.
How dietary calcium decreased lead absorption?
Hi Yanick. Lead also has a charge density, that is to say an ionic radius and a valence charge, identical to that of calcium. This structural similarity is causing interactions with this element. The affinity of lead dicarboxylic derivatives can understand its transport osteocalcin (a non-collagenous bone matrix protein) and allows the use of complexing agents such as EDTA (ethylene amine tetraacetic acid) in the treatment poisoning. In the case of EDTA, Pb is exchanged for calcium.
Hi Islande, further to the previous answers, particularly the Yanick answers, I am pleased to send you one of my papers on lead risk assessment in drinking water.
Article Human health risk assessment of lead in drinking water: A ca...
You may also read the following paper.
Data Groundwater contamination by microbiological and chemical su...
Lead and calcium have the same transport sites for the transport and absorption into the body. Lead also has a direct effect (affects bone cells so demolish and build bone) and indirect (renal function) influence on bone remodeling. Note that the lead acts as the competitor calcium and blocks cellular exchanges and intracellular calcium-dependent reactions. By cons, added a healthy diet of iron and calcium is always useful, probably by a competitive mechanism in the gut. There are not as calcium but gastrointestinal absorption of lead can be significantly reduced with a diet rich in phosphorus and iron (Bruening et al, 1999. Hammad et al, 1996. Blake Mann, 1983; Heard and Chamberlain, 1982). Lead reacts with zinc also, for the latter, it reduces the toxicity of lead in thwarting the enzyme inhibition effect of the latter (Agency for Toxic Substances and Disease Registry, 1999).
Lead strongly affects hematological system. Hypochromic anemia is a common finding in significant exposure of lead when the blood lead level is above 15 microgram/dl. Children are the most vulnerable. Lead exposure in various occupations are reported in our several papers/reports published earlier. Please refer to these papers in my profile. Have a look at the paper attached.
Its already said, Pb has a strong affinity for the nervous system that is why some scientists even recommend that there is no safe level for lead intake. Well done colleagues!
Lead induces too many adverse health effects interfering with haem synthesis, central nervous system's higher functions (especially during its development), many enzymes and essential trace elements, it is nephrotoxic etc, etc - too many to answer the original question of Islande in the boundaries of the RG discussion. Is it really necessary? There are not only thousands scientific papers about lead as a toxic but also several comprehensive monographs you can find through the Internet (e.g. "Inorganic Lead" - in the Environmental Health Criteria series of the International Program on Chemical Safety, WHO)
You are welcome! Are you interested in some epi and animal-experimental studies of ours pertaining to adverse health effects of lead? For instance, one of them dealing with combined Pb-F toxicity was published in La Medicina del Lavoro, 2012, vol. 22, No1 (I believe its full text is available on my RG profile).
Many thanks dear Katsnelson. I work on cumulative risks related to these three heavy metals: lead, chromium and nickel in drinking water in my country. I collect data on each of these substances, and then settling on the mix. Their mode of action, if one inhibits the action of the other, etc.. I also try to see what is the best method I could take to do my work.
Cumulative risk assessment of lead, chromium and nickel in driking water.
Yes, I think it is a very interesting topic and (meaning not just this triade but the problem of combined toxicity of metals in general) one of my hobbies. For instance we made some research (both exptl and epi) on cadmium-lead combined effects,and published their results not onle in Russian but in English as well. May I ask you how comes that drinking water in your country is contaminated with Pb, Ni and Cr - not a quite common situauation indeed!
Drinking water in urban areas of Haiti in contaminated by Pb, Ni and Cr. I am pleased to share with the link of a paper on metal contamination of drinking water (Emmanuel et al, 2009).
Data Groundwater contamination by microbiological and chemical su...
Dear Islanda, if you give me your e-mail address (posting it here or sending it to mine: [email protected] and [email protected]) I'll send to it a short list of my papers in the field of our mutual interest and perhaps some of those papers as published - of course, only if you would be interessed..
Dear Boris, I'm very interested and very honored. Thank you very much. My main email address is [email protected] (posting it here and sending it to your email address). Thank you again!
I've got your e-mail message and will send you 1pdf and 2 links tomorrow.
Good luck!
Thank you so much dear Boris. I'm waiting for the papers. Good job!
So I sent them twice to 2 e-mail addresses of yours, but have not got any confirmation of the receipt as yet . Is everything ok?
Getting no answer at all seems rather strange and is so unlike your usual politeness that I really worry if something isn't a matter with you.
Dear Boris, Please excuse me, I had some difficulties. I sent you an email.
I made a reply to the email that contained the pdf. I just send the email on both your email addresses.
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