Transcript Lead: the Versatile Metal - University of California, Irvine

LEAD
Bio 2b seminar
By David Vo
What is Lead??
• Lead is a naturally occurring bluish-gray metal found
in small amounts in the earth's crust.
– It has no characteristic taste or smell.
– Metallic lead does not dissolve in water and does not burn.
– Lead can combine with other chemicals to form what are
usually known as lead compounds or lead salts.
– Some lead salts dissolve in water better than others.
– Some natural and manufactured substances contain lead
but do not look like lead in its metallic form.
– Some of these substances can burn—for example, organic
lead compounds in some gasoline.
•
Lead: the Versatile Metal
•Its softness and low
melting point make lead
very easy to handle
•Its high resistance to
corrosion makes it ideal for
weatherproofing buildings
and for equipment used in
the manufacture of acids
Protection
• Lead’s high density makes it
particularly appropriate as a
a shield against radiation in
the nuclear industry and in
hospitals and its also good at
stopping sound waves
which is good in the
blocking the noise from the
machinery in factories and
from engine rooms on ships.
The Chemical:
Lead
• Lead in soil is in the +2 oxidation state. In its natural state PbS
(galena) will become insoluble in reduced soils due to
precipitation with sulphide.
• Lead +2 ions become less soluble as soil pH rises.
– At high pH it will precipitate as a carbonate, hydroxide or phosphate,
also in alkaline soils solubility may increase by the formation of soluble
Pb-organic and Pb-hydroxy complexes.
•
Pb2+ has a strong complexation with organic matter leading
to bioaccumulation in the humus rich topsoil.
• Therefore soils polluted with atmospheric lead have little
leaching over many years. Note, however that lead acetate
forms a strong soluble complex in water.
Lead’s early history
• Early uses of lead included
building materials, pigments
for glazing ceramics, and
pipes for transporting
water.
• The castles and cathedrals
of Europe contain
considerable quantities of
lead in decorative fixtures,
roofs, pipes, and windows.
Continue…
• Prior to the early 1900's, uses of
lead in the United States were
primarily for ammunition, brass,
burial vault liners, ceramic glazes,
leaded glass and crystal, paints or
other protective coatings, pewter,
and water lines and pipes.
• With the growth in production of
public and private motorized
vehicles and the associated use of
starting-lighting-ignition (SLI)
lead-acid storage batteries and
terne metal for gas tanks after
World War I
Sources and Production
• About 3 million tons of lead is mined in the
world each year.
• Australia, China and the United States
account for more than 50%
• The most common lead ore is galena or lead
sulphide, but the common ones are zinc and
silver.
• Lead is obtain from ores by a process called
smelting.
– This involves roasting the ore to remove
the sulphur and to obtain lead oxide
which is then reacted with coke in a
furnace. But then it has to be refined to
remove the impurities
Where is Lead Found?
• Paint.
– Many homes built before 1978
have lead-based paint.
• In soil around a home, where it
can pick up lead from exterior
paint or from soil tracked into a
home.
• Household dust
– Dust can pick up lead from
deteriorating lead-based paint or
from soil tracked into a home.
Continue…
• Drinking water.
– Your home might have
plumbing with lead or lead
solder. If you can’s see, smell,
or taste lead, it doesn’t mean
that its not there
• The job.
– If you work with lead, you can
bring it home on your hands
and clothes
• Old painted toys and
furniture
• Food and liquids stored in
lead crystal or lead-glazed
pottery or porcelain
Uncommon sources of lead exposure in
children
• High Amount Sources
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Water boiled in leaded pots and pans
Foreign cosmetics: Kohl, Surina
Foreign cold medicines: Azarcon 93.5%, (also Rueda, Coral, Alarcon, Liga, Maria Luisa);
Pay-loo-ah 90% lead with arsenic; Yogran Guggulu
• Medium Amount Sources
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Soil from smelter area
Ceramics
• Low Amount Sources
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Old newsprint
Leaded crystal
• Other sources of lead exposure
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Leaded gasoline fumes
Leaded soldering fumes
Leaded foil wine bottle caps
Natural distribution
• The average level of lead in
the lithosphere is 16 ppm
• Lead tends to be enriched in
soils with concentrations in
the range of 2 to 200 ppm
• Studies of ice cores in the
northern hemisphere
indicate lead levels have
increased from zero level in
2800 years ago to above 0.2
ppb in 1950.
Impacts on vegetation
• Lead appears to be
unavailable to plant
parts.
– If lead is absorbed it
concentrates in the roots
of plants. Foliage
contamination is due to
soil particles from splash
and/or the atmosphere.
Lead Being Banned
• Lead and Copper Rule 1991
– The rule aimed to minimize lead and copper in drinking water, primarily by
reducing water corrosivity
•
Lead Contamination Control Act of 1988
– The U.S. Department of Health and Human Services has set as an objective the
elimination of elevated blood lead levels (BLLs) in children in the United
States by the year 2010
– an interim goal, specified as a national health objective for the year 2000, is to
reduce BLLs greater than 15 ug/dL and greater than 25 ug/dL among children
aged 6 months-5 years to no more than 500,000 and zero, respectively
(objective 11.4)
– screen infants and children for elevated BLLs,
– ensure referral for medical and environmental intervention for lead-poisoned
infants and children
– ensure referral for medical and environmental intervention for lead-poisoned
infants and children
•
Lead in Gasoline
• Before the use of leaded gasoline was
banned, most of the lead released into
the U.S. environment came from car
exhaust.
– In 1979, cars released 94.6 million
kilograms (kg; 1 kg equals 2.2 pounds) of
lead into the air in the United States.
– In 1989, when the use of lead was limited
but not banned, cars released only 2.2
million kg to the air.
– Since EPA banned the use of leaded gasoline
for highway transportation in 1996, the
amount of lead released into the air has
decreased further.
Lead poison symptoms
•
Symptoms:
– irritation of the alimentary canal;
spasm; nervous symptoms; paralysis,
either partial or complete.
•
When taken for some time, in small
quantity,
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•
violent and obstinate colic; rigidity
of abdominal muscles, cramps;
remission of pain; obstinate
constipation, urine diminished, saliva
increased; countenance anxious and
gloomy.
If relief be not promptly obtained,
– giddiness, debility, torpor, coma,
convulsions and death. The paralysis
affects generally the upper
extremities.
•
…
• Lead poisoning, or plumbism, a disease of
occupations, which is itself the cause of
organic disease, particularly of the nervous
and urinary systems.
• The workpeople affected are principally
those engaged in potteries where lead-glaze
is used; but other industries in which health is
similarly affected are filemaking, housepainting and glazing, glass-making,
copperworking, coach-making, plumbing and
gasfitting, printing, cutlery, and generally
those occupations in which lead is concerned.
More symptoms…
• The symptoms of
chronic lead poisoning
vary within very wide
limits, from colic and
constipation up to total
blindness, paralysis,
convulsions and death.
Protecting Your home
• If you suspect that your house has lead hazards, you can take
some immediate steps to reduce your family's risk:
• If you rent, notify your landlord of peeling or chipping paint.
• Clean up paint chips immediately.
• Clean floors, window frames, window sills, and other surfaces
weekly. Use a mop, sponge, or paper towel with warm water
and a general all-purpose cleaner or a cleaner made
specifically for lead. Thoroughly rinse sponges and mop heads
after cleaning dirty or dusty areas.
• Wash children's hands often, especially before they eat and
before nap time and bed time.
• Keep children from chewing window sills or other painted
surfaces.
• Make sure children eat nutritious, low-fat meals high in iron
and calcium, such as spinach and dairy products. Children
with good diets absorb less lead.
Latest controversy
• powdered candy called Lucas Limon has been
found on sale in Adams Morgan for 39 cents a
pack. The candy mixes salt and limejuice for a
salty and sweet taste.
• The product is also used as a food seasoning.
• It was removed from the market last year.
However, congressional staffers spotted it, and
alerted city officials
Work Cited
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http://www.wjla.com/news/stories/0405/224240.html
http://www.antiquusmorbus.com/English/Poison.htm
http://wpspaint.com/Library/Lead_Paint/lead_Prevention.htm
http://www.atsdr.cdc.gov/toxprofiles/phs13.html
http://www.nsc.org/library/facts/lead.htm
http://www.hud.gov/offices/lead/leadsaferule/index.cfm
http://minerals.usgs.gov/minerals/pubs/commodity/lead/
http://www.epa.gov/lead/leadinfo.htm#where
http://www.chemicalelements.com/elements/pb.html