ETOX 80E - Lead

Lead

As illustrated in this figure, lead interferes with both the normal formation and dissolution of bone. It is also primarily stored in bone, because it is biochemically cycled as a calcium analogue. Note the role of estrogen in bone formation, which is interfered with by lead. This has resulted in the association of lead with xenoestrogens.

The relative blood lead (PbB) concentrations of humans is illustrated in this bar chart. It shows the current Centers for Disease Control (CDC) action level (10 ug/dL), average concentration in US adults ( 2.8 ug/dL), average concentration in Northern elephant seals in the northeast pacific (0.13 ug/dL), and average concentration of preindustrial humans (0.016 ug/dL). The latter value, which was derived from rations of blood lead to bone lead (Flegal and Smith, 1992), is consistent with the value derived from the US EPA Uptake/Biokinetic Model for Lead (Mushak, 1993).
Flegal, A.R. and D.R. Smith. 1992. Lead levels in preindustrial humans. New England Journal of Medicine 326: 1293-1294.
Mushak, P.1993. New directions in the toxicokinetics of human lean exposure. neurotoxicology 14: 29-43.

Collecting blood from an elephant seal, using trace metal clean techniques. The seals are identified by the markings on their sides, which are made with bleach.

The cycling of lead through food chains is normalized to calcium, because lead is biochemically cycled as a calcium analogue. The concentration factor (CF) is a measure of the increase (bioenrichment) or decrease (biopurification) of lead relative to calcium between trophic levels. Lead is bioenriched in plants (as well as zooplankton) because it is sorbed onto surfaces relatively more than calcium. It is then biopurfied at higher trophic levels because their surface area to volume ratios are much smaller and organisms tend to concentrate calcium relative to lead through biochemical pathways. There may also be active pathway for the removal of lead in some organisms.

This figure shows the difference in densities of normal and osteoporitic bone.

This figure shows a series of studies, each indicated by a different color, which indicate a systematic decrease in intelligence with an increase in lead body burden (measured by tooth lead concentrations). The reproducibility of the negative correlation among different populations (groups analyzed) substantiates the causal relationship.

A stylized diagram of the routes of lead exposure and assimilation, along with the distribution and residence times of lead in human tissues (blood, soft tissue, and bone).

A model of lead in 3 different food chains: green - contemporary marine organisms; orange - natural terrestrial organisms; red - contemporary terrestrial organisms. Differences between the latter two are attributed to anthropogenic inputs of industrial lead.

The sources of lead in the Great Lakes in 1987 was derived from stable lead isotopic composition analyses (Flegal et al., 1989). These indicated that Canadian leaded gasoline was the primary source of contamination in Lake Ontario and the northern part of Lake Erie, while US leaded gasoline was the primary source of contamination in the southern part of Lake Erie. Since then, both the US and Canada have eliminated the addition of lead to gasoline.

The "measles" figure by Clair Patterson illustrates the relative amount of contamination in natural (1 dot), contemporary (500 dots), and acute lead poisoned (2000 dots) inndividuals. The number of dots are based on the relative amounts (atomic ratios) of lead to calcium in bones. To put this figure in perspective, most of you have 500 times more lead than natural levels (which still may have been sub-lethally toxic) and only 4 times less lead than an individual who has to be hospitalized for acute lead toxicity. This figure was in his minority report in the 1980 National Research Council report, Lead in the Human Environment (NRC, 1980), because there were political concerns that Patterson's studies were too damning for the lead industry. However, it was the first figure in the subsequent (1993) National Research Council report, Measuring Lead Exposure in Infants, Children, and Other Sensitive Populations (NRC, 1993), which was unofficially called "Patterson's Revenge" by the NRC committee which concluded that essentially all of Patterson's research had been independently corroborated by preeminent scientists using state-of-the-art analyses.

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	As illustrated in this figure, lead interferes with both the normal formation and dissolution of bone. It is also primarily stored in bone, because it is biochemically cycled as a calcium analogue. Note the role of estrogen in bone formation, which is interfered with by lead. This has resulted in the association of lead with xenoestrogens.
	The relative blood lead (PbB) concentrations of humans is illustrated in this bar chart. It shows the current Centers for Disease Control (CDC) action level (10 ug/dL), average concentration in US adults ( 2.8 ug/dL), average concentration in Northern elephant seals in the northeast pacific (0.13 ug/dL), and average concentration of preindustrial humans (0.016 ug/dL). The latter value, which was derived from rations of blood lead to bone lead (Flegal and Smith, 1992), is consistent with the value derived from the US EPA Uptake/Biokinetic Model for Lead (Mushak, 1993). Flegal, A.R. and D.R. Smith. 1992. Lead levels in preindustrial humans. New England Journal of Medicine 326: 1293-1294. Mushak, P.1993. New directions in the toxicokinetics of human lean exposure. neurotoxicology 14: 29-43.
	Collecting blood from an elephant seal, using trace metal clean techniques. The seals are identified by the markings on their sides, which are made with bleach.
	The cycling of lead through food chains is normalized to calcium, because lead is biochemically cycled as a calcium analogue. The concentration factor (CF) is a measure of the increase (bioenrichment) or decrease (biopurification) of lead relative to calcium between trophic levels. Lead is bioenriched in plants (as well as zooplankton) because it is sorbed onto surfaces relatively more than calcium. It is then biopurfied at higher trophic levels because their surface area to volume ratios are much smaller and organisms tend to concentrate calcium relative to lead through biochemical pathways. There may also be active pathway for the removal of lead in some organisms.
	This figure shows the difference in densities of normal and osteoporitic bone.
	This figure shows a series of studies, each indicated by a different color, which indicate a systematic decrease in intelligence with an increase in lead body burden (measured by tooth lead concentrations). The reproducibility of the negative correlation among different populations (groups analyzed) substantiates the causal relationship.
	A stylized diagram of the routes of lead exposure and assimilation, along with the distribution and residence times of lead in human tissues (blood, soft tissue, and bone).
	A model of lead in 3 different food chains: green - contemporary marine organisms; orange - natural terrestrial organisms; red - contemporary terrestrial organisms. Differences between the latter two are attributed to anthropogenic inputs of industrial lead.
	The sources of lead in the Great Lakes in 1987 was derived from stable lead isotopic composition analyses (Flegal et al., 1989). These indicated that Canadian leaded gasoline was the primary source of contamination in Lake Ontario and the northern part of Lake Erie, while US leaded gasoline was the primary source of contamination in the southern part of Lake Erie. Since then, both the US and Canada have eliminated the addition of lead to gasoline.

	The "measles" figure by Clair Patterson illustrates the relative amount of contamination in natural (1 dot), contemporary (500 dots), and acute lead poisoned (2000 dots) inndividuals. The number of dots are based on the relative amounts (atomic ratios) of lead to calcium in bones. To put this figure in perspective, most of you have 500 times more lead than natural levels (which still may have been sub-lethally toxic) and only 4 times less lead than an individual who has to be hospitalized for acute lead toxicity. This figure was in his minority report in the 1980 National Research Council report, Lead in the Human Environment (NRC, 1980), because there were political concerns that Patterson's studies were too damning for the lead industry. However, it was the first figure in the subsequent (1993) National Research Council report, Measuring Lead Exposure in Infants, Children, and Other Sensitive Populations (NRC, 1993), which was unofficially called "Patterson's Revenge" by the NRC committee which concluded that essentially all of Patterson's research had been independently corroborated by preeminent scientists using state-of-the-art analyses.