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Lead - instituto de estudios ecologistas

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Lead - instituto de estudios ecologistas
CONTAMINACIÓN POR
METALES PESADOS
PLOMO
Prof. Jesús Olivero Verbel. Ph.D.
Grupo de Química Ambiental y Computacional
Universidad de Cartagena
LA CONTAMINACIÓN POR METALES
Jesús Olivero Verbel. Ph.D
Grupo de Química Ambiental y Computacional
Universidad de Cartagena
Metals
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‘Metals’ originally included only gold, silver, copper, iron,
lead, and tin.
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Dense, malleable, lustrous
Conduct heat and electricity, cations
Many other elements since added to the list with some of
these characteristics
Metalloids are elements with features intermediate
between metals and non-metals. Example: Arsenic
Heavy Metal
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A metal having an atomic weight greater
than sodium, a density greater than 5
g/cm3.
Some notion of toxicity.
Usually includes lead, cadmium and
mercury.
Many others may variably be added to list.
Lead
Lead
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Plomo
La mayoría de las aguas municipales contienen menos de 0.05 µg/L
La ingestión diaria a partir del consumo de agua  10 µg.
Adultos absorben 5-15% del total ingerido.
 90% del plomo sanguíneo es encontrado en los glóbulos rojos.
Interferencia con mecanismos de transmisión nerviosa.
Encefalopatías aparecen en niños con plomo sanguíneo de 80 µg/dL
En niños: Déficit auditivo (20 µg/dL).
En niños: Disminución en el coeficiente intelectual (10-15 µg/dL)
Anemia (80-100 µg/dL). Hipertensión (30 µg/dL).
Nefropatías. Cambios funcionales y morfológicos en el Túbulo Proximal.
Lead Sources
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The use of lead in residential paint was banned in 1977.
Lead-containing pigments still are used for outdoor paint
products because of their bright colors and weather
resistant properties.
Tetraethyl and tetramethyl lead are still used as
additives in gasoline in several countries.
Petrol (tetraethyl lead)
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Soil and dust
Paint chips
Contaminated water
Parents lead-related
occupation.
Folk remedies
Congenital exposure.
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Azarcon is a folk remedy
that contains 85-96% lead
tetroxide.
Other lead containing
remedies include Greta.
Lead
More Uses and Sources of Lead
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TV's, Computer monitors
Batteries, Bullets Sinkers
X-ray shields
Crystal-ware
Explosives
Plastic colouring (wire, blinds)
Lead
Toxicocokinetics and Toxicodynamics
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Absorption:
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Lungs: depends on size particle
GI:
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Adults: 20-30%
Children: as much as 50% of dietary lead.
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Skin:
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Inadequate intake of iron, calcium, and total
calories are associated with higher lead levels.
Inorganic lead is not absorbed.
Organic lead is well absorbed.
Lead is carried bound to the RBC.
Absorption of Lead
16
Lead
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Absorption of Lead
Lead goes down iron or calcium absorption pathway in
GIT.
Children absorb lead well orally (~50%). Adults
poorly (~10%). Children also have more hand to mouth
activity.
Lead absorption is enhanced if diet is poor in iron or
calcium.
Pica is one of the worst risk factors.
Lead can be inhaled.
Tetraethyl lead can be absorbed via skin.
Lead
Toxicocinética del Plomo
Distribution of
Lead
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95% long bones.
Released during
osteolysis.
4% brain, liver, kidneys.
1% blood.
Crosses placenta.
Lead
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Distributed extensively throughout tissues: bone,
teeth, liver, lung, kidney, brain, and spleen.
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Body lead storage: bones- can constitute a source of
remobilization and continued toxicity after the
exposure has ceased.
Lead crosses the BBB and concentrates in the
brain.
Lead crosses the placenta
Excretion:
 Kidneys. Feces
Lead
Lead in bone has a
biological half- life of about
ten years.
The half-life of lead
in adult human blood
has been estimated
to be from 28 days to
36 days
Data from the US NHANES 3 study showing the second
peak of lead levels in adulthood. Higher adult male
levels reflect occupation and hobby. High risk
occupations would be even higher. Women get a postmenopausal peak.
22
Lead
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Acute toxicity
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Clinical Manifestation
Acute encephalopathy, renal failure and
severe GI symptoms
Lead has affinity for SH groups and is toxic to zincdependent enzyme systems.
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Heme synthesis: hemoglobin, cytochromes.
Steroid metabolism and membrane integrity.
Interference in vitamin D synthesis in renal tubular cells
(conversion of 1-hydroxyvitamin D to 1,25hydroxyvitamin D)
Lead
Mecanismo de Toxicidad del
Plomo en el Sistema Sanguíneo
LTP: Long term potentiation
NMDAR:
N-methyl-d-aspartate receptor.
ERK1/2:
Extracellular signal regulated kinase.
BDNF: Brain-derived neurotrophic
factor.
Lead
Toxicology of Lead
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Lead disrupts the main structural components
of the blood-brain barrier by primary injury to
astrocytes with a secondary damage to the
endothelial microvasculature. Within the
brain,
lead-induced
damage
occurs
preferentially in the prefrontal cerebral
cortex, hippocampus and cerebellum. Some
characteristic clinical features of lead
poisoning may be attributed to this specific
anatomical pattern.
Lead
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Toxicology of Lead
Although the molecular targets for lead are unknown,
a vast amount of evidence accumulated over many
years has shown that lead disrupts processes that
are regulated by calcium.
Picomolar concentrations of lead can replace
micromolar concentrations of calcium in a
protein kinase C enzyme assay. Furthermore, lead
activates protein kinase C in intact cells and induces
the expression of new genes by a mechanism
dependent on protein kinase C. We propose that
the learning deficits caused by lead are due to
events regulated by protein kinase C that most
likely occur at the synapse.
Lead
Toxicology
At a neuronal level, exposure to lead alters the release of
neurotransmitter
from
presynaptic
nerve
endings.
Spontaneous release is enhanced and evoked release is
inhibited. The former may be due to activation of protein
kinases in the nerve endings and the latter to blockade of
voltage-dependent calcium channels. This disruption of
neuronal activity may, in turn, alter the developmental
processes of synapse formation and result in a less efficient
brain with cognitive deficits.
The cellular, intracellular and molecular mechanisms of lead
neurotoxicity are numerous, as lead impacts many biological
activities at different levels of control: at the voltage-gated
channels and on the first, second and third messenger
systems. These effects could be related to lead's ability to
interfere with the regulatory action of calcium in cell
functions.
Lead
Lead Poisoning
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Lead has no known biological function.
There is no proven safe lower limit for lead.
Lead Pb++, competes with Ca++, Fe++
It is cheap, useful,easy to mine, therefore
Lead is ubiquitous- in air, food, water, soil, ceilings
etc.
Leaded petrol means that all environmental dusts are
high in lead- contaminating ceiling dust, topsoil,
window wells etc.
Lead
Lead
General Signs and Symptoms of Lead Toxicity
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Fatigue
Irritability
Lethargy
Paresthesis
Myalgias
Abdominal pain
Tremor
Headache
Vomiting
Weight loss
Constipation
Loss of libido
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Motor neuropathy
Encephalopathy
Cerebral edema
Seizures
Coma
Severe abdominal
cramping
Epiphyseal lead lines in
children (growth arrest)
Renal failure.
Metaphyseal bands.
This patient was encephalopathic
and anemic and had a lead level of
60 μg/dL at admission.
Lead
Lead
Range of Lead-induced Health Effects in Adults and Children
Blood lead
levels
Adults
10 g/dL
Hypertension may occur
20 g/dL
Inhibition of heme
synthesis
Increased erythrocyte
protoporphyrin
Children
• Crosses placenta
• Impairment IQ, growth
• Partial inhibition of
heme synthesis.
Beginning impairment of
nerve conduction velocity.
30 g/dL
• Systolic hypertension
• Impaired hearing()
Impaired vitamin D
metabolism
40 g/dL
• Infertility in males
• Renal effects
• Neuropathy
• Fatigue, headache,
• Abd. pain.
Hemoglobin synthesis
inhibition
50 g/dL
Anemia, GI sx, headache,
tremor
Colicky abd pain,
neuropathy.
100 g/dL
Lethargy, seizures,
encephalopathy
Encephalopathy, anemia,
nephropathy, seizures
Recommended Lead level
<0.48 (10 µg/dL)
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< 0.48µmol/L (10µg/dL)
= Goal.
>0.48µmol/L (10µg/dL)
= elevated.
>0.72µmol/L (15µg/dL)
=substantially elevated. Notifiable level.
1.20µmol/L (25µg/dL)
= dangerously elevated.
>2.20µmol/L (45µg/dL)= Symptomatic.
Lead
A través de los años, los límites máximos establecidos
para plomo en sangre han disminuído. En la actualidad no hay límites seguros.
Lead
Childhood Lead Poisoning
Childhood lead poisoning is now defined as a
blood lead level of 10 g/dL.
Lead
Neurotoxicity of Lead in Childhood
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Mental retardation in severe lead intoxication
 5 points in IQ for every 10 g/dl  in blood lead levelpopulation based studies
Other adverse developmental outcomes:
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Aggression
Hyperactivity
Antisocial behaviors
Learning disability- impairment in memory, auditory
processing, and visual-motor integration. The IQ is
normal. These effects has been demonstrated with blood
lead levels as low as 6 g/dL.
Lead
Nutritional Supplementation
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Iron supplementation
Calcium supplementation – calcium rich foods
Phosphorus supplementation
Frequent food consumption- regular meals +
snacks.
Chelation Therapy
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BLL > 70 g/dL or encephalopathy
 Hospital admission
 Administration of a parenteral chelator
BLL > 45 g/dL- oral chelator
BLL 25-45 g/dL- if these levels persist despite
environmental intervention.
Lead
Efectos del Plomo en Humanos
Lead
Lead and Neurodevelopment
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Each 0.48 µmol/l(10µg/dl) in children.
= 4 to 7 IQ points (US Acad. Pediatrics).
Industry/ Australian government consensus
of 3-5 IQ points.
Effects on behaviour are FAR WORSE.
Delinquency rates are 8 times higher in the top
30% of bone lead. Needleman 1996.
Needleman, Herbert L. et al, "Bone Lead Levels and Delinquent Behavior," JOURNAL OF THE AMERICAN
MEDICAL ASSOCIATION Vol. 275, No. 5 (February 7, 1996), pgs.363-369.

Measurable adverse behaviour changes in 2 year
olds Mendelsohn 1999. Alan L. Mendelsohn, Benard P. Dreyer, Arthur H.
Fierman, Carolyn M. Rosen, Lori A. Legano, Hillary A. Kruger, Sylvia W. Lim, and Cheryl D. Courtlandt
"Low-Level Lead Exposure and Behavior in Early Childhood“ Pediatrics 1998; 101: e10
Lead
El plomo disminuye el coeficiente intelectual,
particularmente en niños!
Lead
Lead and IQ
Lead
El plomo reduce el coeficiente intelectual de los niños. La gráfica señala la relación
entre el valor del coeficiente intelectual y los niveles de plomo en sangre en una muestra
De niños de los Departamentos de Bolívar y Cesar. CopyRight. GQAC-UniCartagena. 2011.
Lead
Dementia and lead
The relationship between performance on cognitive tasks
and circulating levels of lead in blood and accumulated
levels of lead in bone was examined in 141 middle-aged
and elderly men Men with higher levels of blood and bone
(tibia) lead copied spatial figures less accurately; men with
higher levels of bone (tibia) lead had slower responses for
pattern memory. These findings suggest that low levels of
lead contribute to impairments in cognitive function
among elderly men.
Blood lead levels as low as 8 micrograms/dL were
significantly associated with poorer cognitive function
as measured by certain neuropsychological tests.
Even a slight decrement in cognition would have a
large public health impact due to the large number of
elderly at risk.
Lead
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U.S. Lead Situation
1. 1978 Lead banned from paint
2. 1980's- Levels higher than Australia
3. Late 1980's Removal of lead from gasoline
4. 1980's Universal questionnaire screening
5. 1991 Universal blood testing
6. 1990's Public housing program
7. 1990's Private housing program
8. 1990's Massive EPA environmental program
9. 1998 Builders, tradesmen required to issue
documents warning clients of risk when they
renovate properties built before 1978.
10. 1998 Successful reduction in community
levels leads to reintroduction of questionnaire
screening in some areas.
CopyRight. GQAC-UniCartagena. 2011
Lead
CopyRight. GQAC-UniCartagena. 2011
En las fundidoras de metales los niños están expuestos al
plomo depositado en el suelo. La educación ambiental y el
seguimiento de normas básicas de higiene son
fundamentales para disminuir la exposición al metal tóxico.
Lead
En Cartagena la exposición al Plomo es generalizada en algunos sectores,
en particular en aquellos en donde existen fundidiras de metales.
La foto corresponde a un Jardín Infantil en el cual existe una fundidora de
metales. Como es posible?
25
20
BPb concentrations in children
from Cartagena
BPb (µg/dL)
15
10
5
0
Lead
H
A.B
O
A
B.Ch Bos S.F
Sampling Sites
T
Fly UP