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HEAVY METALS
Substances
*Hg

13.5

*Pb

11.3

Cu

9.0

*Cd

8.7

*Cr

7.2

Sn

5.8-7.3

*As

5.8

Al

2.7

Mg

1.7

H2O

D...
Figure 1. Relationship between metal generation, exposure pathway and environmental impact.
BIOACCUMULATION OF HEAVY METALS
Pollutants like heavy metals are
CONSERVATIVE pollutants – i.e. they aren’t
broken down by...
BIOMAGNIFICATION


those animals feeding on bioaccumulators
gain even higher inputs of contaminants and
bioaccumulate eve...
SPECIATION AND TOXICITY OF HEAVY METALS
Poisonous in their cations form
 Highly toxic when bonded to short chains of
carb...
CADMIUM (Cd)
Discovered in 1817 by the German chemist
Friedrich Stromeyer
 Cadmium melts at 321°C (610°F), boils at
767°C...
ENVIRONMENTAL SOURCES OF CADMIUM
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Cd compounds form ionic salts with simple anions
Found in water in ...
HUMAN INTAKE OF CADMIUM









High intake for humans living near mines and
smelters
Smokers are also exposed
From ...
PROTECTION AGAINST LOW LEVELS OF
CADMIUM
Cadmium is acutely toxic; lethal dose is 1g
 Humans are protected by methallothi...
EFFECTS IT CAUSE IN THE BODY
Affects important enzymes
 Cause osteomalacia and kidney damage
 Cadmium pneumonitis charac...
CHROMIUM (Cr)

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


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It has atomic number 24, atomic mass 51.996g/mol
Its melting point and boiling point of 190...
CHROMIUM
Normally occurs in the form of inorganic ions
 Common oxidation states: Cr(VI) and Cr(III)
 In aerobic conditio...
ENVIRONMENTAL SOURCES OF CHROMIUM
Predominantly mined as chromate ore
(FeCr2O4)
 Used to manufacture stainless and in
sup...
CHROMIUM CONTAMINATION OF WATER
Contaminates groundwater beneath areas
with metal-plating
 second most abundant inorganic...
HEALTH EFFECTS OF CHROMIUM
People are exposed to chromium in these four basic ways:
 Breathing (inhalation)
 Eating of c...
Health effects: Trivalent chromium (Cr3+)
Hexavalent chromium (Cr6+) is a danger to human health, it is
carcinogenic. The ...
THE WOOD PRESERVATIVE CCA
Chromated Copper Arsenate
 A waterborne mixture of metal oxides with
which wood is treated usin...
ARSENIC
A metalloid
 It is metallic in appearance and has a specific
gravity of 5.7g·cm-3.
 The atomic weight of arsenic...
COMMON MINERALS OF ARSENIC
arsenopyrite (FeAsS)
 realgar (As2S2)
 orpiment (As2S3)
 arsenic trioxide (As2O3)


When th...
ARSENIC
White arsenic As2O3 is a common poison
 Believed to cure certain ailments, impotence,
prophylactic against plague...
ANTROPOGENIC SOURCES OF ARSENIC
use of its compounds in pesticides
 during mining, smelting of gold, lead. copper,
and ni...
ARSENIC(III) VS. ARSENIC(V) TOXICITY
As(III) commonly exists in aqueous solution
and in solids as arsenite ion AsO33 has ...
acute poisoning
Inorganic As(III) is more toxic than As(V)
methylated arsenic in the liver does not bind tightly so it
...
ARSENIC IN DRINKING WATER
one of the most serious environmental health
hazards
 can cause cancer
 Linked to diabetes and...
DRINKING WATER STANDARD FOR ARSENIC
global average inorganic arsenic content of
drinking water is about 2.5ppb
 WHO and E...
Manifestations of acute arsenic
Bodily system
Symptoms or signs
Time of onset
poisoning
affected

Systemic

Thirst
Hypovol...
REMOVAL OF ARSENIC FROM WATER
to flow the water over activate
alumina(aluminum oxide)
 reverse osmosis can also be used
...
LEAD (Pb)
Its atomic number is 82, atomic weight is 207.2g/mol
 Bluish-white in color.
 It is very soft, highly malleabl...
OCCURRENCE OF LEAD
Lead occurs naturally in the earth crust, usually in
ores such as:
 Galena (PbS) (major ore)
 Cerrusi...
ENVIRONMENTAL SOURCES/USES OF LEAD
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Soundproofing in buildings
Solder- alloy of lead and tin
lining p...
ENVIRONMENTAL SOURCES/USES OF LEAD
(cont.)
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




Lead in automobile batteries
As additives in gasolines
tetraethyl lea...
EFFECTS OF LEAD IN HUMAN REPRODUCTION
AND INTELLIGENCE
Pb2+ replaces Ca2+ in bones
 Pb2+ remains in bones for decade
 Hi...
HEALTH EFFETC IN ADULTS AND CHILDREN
Blood lead
levels

Adults

Children

10 g/dL

Hypertension may occur

•Crosses placen...
MERCURY
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symbol Hg
From the Latin word, hydrargyrum, “liquid silver,”
Shining, mobile liquid, silvery-w...
ENVIRONMENTAL SOURCES/USES OF MERCURY
Electrical switches in automobiles built
before 2000
 In fluorescent light bulbs an...
ENVIRONMENTAL SOURCES/USES OF MERCURY
(cont.)
Fossil fuel coal lignite (100ppb)
 Discarded laboratory chemicals
 Pharmac...
MERCURY AND THE INDUSTRIAL CHLOR-ALKALI
PROCESS
amalgam of sodium and mercury is used in
some industrial chlor-alkali plan...
MERCURY VAPOR
It is composed of free, neutral atoms.
 If inhaled the atoms diffuse from the lungs to
the bloodstream


...
METHYLMERCURY TOXICITY




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methyl anion combines with Hg2+ to yield volatile
molecular liquid dimethylmercury
t...
(cont.)
between methylmercury in fish muscle and
that dissolved in the water: 1 million to 1, and
can exceed 10 million to...
METHYLMERCURY ACCUMULATION IN THE
ENVIRONMENT AND IN THE HUMAN BODY
Half-life of methylmercury in human body is
70days
 C...
MINAMATA DISEASE
Occurred in a village in Minamata, Japan
 CH3Hg-SCH3
 100ppm of mercury in fish tissues
 Onset symptom...
SOURCES OF METHYLMERCURY
Fungicide in agriculture and industry
 Leaching from rocks and soil into water
systems by natura...
SAFE LEVEL OF MERCURY IN THE BODY


10-20ppm of CH3Hg+ in hair can be
dangerous

INTERNATIONAL CONTROL ON MERCURY



Uni...
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heavy metals

  1. 1. HEAVY METALS Substances *Hg 13.5 *Pb 11.3 Cu 9.0 *Cd 8.7 *Cr 7.2 Sn 5.8-7.3 *As 5.8 Al 2.7 Mg 1.7 H2O Densities of Some Important Heavy Metals and Other Substances Density (gcm-3 ) 1.0 their standard state have specific gravity (density) of more than 5g/cm3  occur near the middle and bottom of the periodic table type of chemical element which are poisonous to humans
  2. 2. Figure 1. Relationship between metal generation, exposure pathway and environmental impact.
  3. 3. BIOACCUMULATION OF HEAVY METALS Pollutants like heavy metals are CONSERVATIVE pollutants – i.e. they aren’t broken down by bacteria etc and are effectively permanent  Most plants and animals can regulate their metal content to a certain point-but metals that can’t be excreted buildup in an organism over its lifetime  BIOACCUMULATION
  4. 4. BIOMAGNIFICATION  those animals feeding on bioaccumulators gain even higher inputs of contaminants and bioaccumulate even greater concentrations and so on.. with animals at the highest trophic level obtaining highest concentrations
  5. 5. SPECIATION AND TOXICITY OF HEAVY METALS Poisonous in their cations form  Highly toxic when bonded to short chains of carbon atoms ex. Alkyl groups with mercury and lead attached 
  6. 6. CADMIUM (Cd) Discovered in 1817 by the German chemist Friedrich Stromeyer  Cadmium melts at 321°C (610°F), boils at 767°C (1413°F)  Has a specific gravity of 8.64g·cm-3  Its atomic number is 48 and atomic weight is 112.41g·mol-1 .  When heated, cadmium burns in air with a bright light, forming the oxide CdO.  Cadmium occurs as the principal constituent of a mineral only in the rare greenockite 
  7. 7. ENVIRONMENTAL SOURCES OF CADMIUM           Cd compounds form ionic salts with simple anions Found in water in the +2 oxidation state By-product of zinc smelting Burning coals Incinerating waste materials containing cadmium As an electrode in rechargeable NiCad batteries Incinerating plastics and other materials that contain as pigment or as a stabilizer As pigment Use in paints to produce brilliant yellow color recycling cadmium-plated steel
  8. 8. HUMAN INTAKE OF CADMIUM      High intake for humans living near mines and smelters Smokers are also exposed From food supply-wheat rice, grains, seafood, organ meats Maximum containment level is 5ppb in US and Canada Acute environmental problem occurred in Jintsu River Valley region of Japan- ouch-ouch or itai-itai
  9. 9. PROTECTION AGAINST LOW LEVELS OF CADMIUM Cadmium is acutely toxic; lethal dose is 1g  Humans are protected by methallothionein  It is a cumulative poison  Greatest risk of Cd exposure is Japan and Central Europe 
  10. 10. EFFECTS IT CAUSE IN THE BODY Affects important enzymes  Cause osteomalacia and kidney damage  Cadmium pneumonitis characterizes by edema and pulmonary epithelium necrosis 
  11. 11. CHROMIUM (Cr)        It has atomic number 24, atomic mass 51.996g/mol Its melting point and boiling point of 1907oC and 2672oC respectively. From Greek word chroma refers to its many colorful compounds It is a silvery, lustrous , brittle hard metal It does not tarnish in air. Chromium is unstable to oxygen i.e. it react with oxygen to produce a thin oxide layer that is impermeable to oxygen and thus protects the metal below. Is considered also as crucial metal
  12. 12. CHROMIUM Normally occurs in the form of inorganic ions  Common oxidation states: Cr(VI) and Cr(III)  In aerobic condition it occurs as +6 as chromate ion Suspected to be carcinogenic  In anaerobic condition it occurs as +3 less toxic and acts as a trace nutrient 
  13. 13. ENVIRONMENTAL SOURCES OF CHROMIUM Predominantly mined as chromate ore (FeCr2O4)  Used to manufacture stainless and in superalloys  Tanned leather  Metal plating industries  CCA treated wood  Smelters 
  14. 14. CHROMIUM CONTAMINATION OF WATER Contaminates groundwater beneath areas with metal-plating  second most abundant inorganic contaminant under hazardous waste sites  MCL for drinking water in US is 100ppb  Cr(VI) is extracted by reducing it to Cr(III) 
  15. 15. HEALTH EFFECTS OF CHROMIUM People are exposed to chromium in these four basic ways:  Breathing (inhalation)  Eating of contaminated food)  Drinking of contaminated water  Skin contact (with chromium compounds/salts). Health effects: Trivalent chromium (Cr3+) Chromium (III) is an essential nutrient to humans and its deficiency may cause diseases such as heart problems, diabetes and metabolic disorders. Yet when consumed in excess can be harmful. It can cause adverse health effect such as skin rashes. Chromium (III) is not yet classified as carcinogenic according to International Agency for Research on Cancer (IARC).
  16. 16. Health effects: Trivalent chromium (Cr3+) Hexavalent chromium (Cr6+) is a danger to human health, it is carcinogenic. The most dangerous compounds of Cr6+ are:  Calcium chromate  Chromium trioxide  Lead chromate  Strontium chromate  Zinc chromate Health problem caused by chromium (VI) compounds are:  Skin rashes  Upset stomach and ulcers  Respiratory problems  Weakened immune systems  Kidney and liver damage  Alteration of genetic materials  Lung cancer  Death.
  17. 17. THE WOOD PRESERVATIVE CCA Chromated Copper Arsenate  A waterborne mixture of metal oxides with which wood is treated using vacuumpressure impregnation process  10% of the mass of the lumber  Cr(IV) is used here  Protects wooden structures  Replaced creosote and pentachlorophenol 
  18. 18. ARSENIC A metalloid  It is metallic in appearance and has a specific gravity of 5.7g·cm-3.  The atomic weight of arsenic is 74.9216.  Gray arsenic is the most common. When gray arsenic is heated under standard pressure it sublimes, passing directly from solid to gaseous form at 613°C (1135°F).  A yellow, nonmetallic form also exists and has a specific gravity of 2.0. 
  19. 19. COMMON MINERALS OF ARSENIC arsenopyrite (FeAsS)  realgar (As2S2)  orpiment (As2S3)  arsenic trioxide (As2O3)  When these ores are roasted, the arsenic sublimes and can be collected from the dust in the flues as a by-product.
  20. 20. ARSENIC White arsenic As2O3 is a common poison  Believed to cure certain ailments, impotence, prophylactic against plague  50 Chinese drugs contain the element  Trace amount is good for human health  Used to treat syphilis 
  21. 21. ANTROPOGENIC SOURCES OF ARSENIC use of its compounds in pesticides  during mining, smelting of gold, lead. copper, and nickel  production of iron and steel  combustion of coal  added to chicken feed to simulate growth and prevent diseases  Manufacturing of glass to eliminate a green color caused by impurities of iron compounds  CCA preservative 
  22. 22. ARSENIC(III) VS. ARSENIC(V) TOXICITY As(III) commonly exists in aqueous solution and in solids as arsenite ion AsO33 has more tendency to form ionic rather than covalent bonds since it is more metal-like  often contaminates phosphate deposits and commercial phosphates 
  23. 23. acute poisoning Inorganic As(III) is more toxic than As(V) methylated arsenic in the liver does not bind tightly so it is largely detoxified  Arsenic’s lethal effect when consumed is due to gastrointestinal damage
  24. 24. ARSENIC IN DRINKING WATER one of the most serious environmental health hazards  can cause cancer  Linked to diabetes and cardiovascular diseases  affects intellectual levels 
  25. 25. DRINKING WATER STANDARD FOR ARSENIC global average inorganic arsenic content of drinking water is about 2.5ppb  WHO and European Union-10ppb  in developing countries is 50ppb 
  26. 26. Manifestations of acute arsenic Bodily system Symptoms or signs Time of onset poisoning affected Systemic Thirst Hypovolemia, Hypotension Minutes Minutes to hours Gastrointestinal Garlic or metallic taste Burning mucosa Nausea and vomiting Diarrhea Abdominal pain Hematemesis Hematochezia, melena Rice-water stools Immediate Immediate Minutes Minutes to hours Minutes to hours Minutes to hours Hours Hours Hematopoietic system Hemolysis Hematuria Lymphopenia Pancytopenia Minutes to hours Minutes to hours Several weeks Several weeks Pulmonary (primarily in inhalational exposures) Cough Dyspnea Chest Pain Pulmonary edema Immediate Minutes to hours Minutes to hours Minutes to hours Liver Jaundice Fatty degeneration Central necrosis Days Days Days Kidneys Proteinuria Hematuria Acute renal failure Hours to days Hours to days Hours to days
  27. 27. REMOVAL OF ARSENIC FROM WATER to flow the water over activate alumina(aluminum oxide)  reverse osmosis can also be used  water pass through a bed of ferric oxide  capturing arsenic when iron hydroxide is precipitated(similar to removal of colloids) 
  28. 28. LEAD (Pb) Its atomic number is 82, atomic weight is 207.2g/mol  Bluish-white in color.  It is very soft, highly malleable, ductile and a relatively poor conductor of electricity.  It melts at 327oC and its boiling point is 1750oC.  Lead has low water solubility, is very resistant to corrosion but tarnishes upon exposure to air.  Lead is a highly toxic trace element with no recognized biological requirement in organisms. 
  29. 29. OCCURRENCE OF LEAD Lead occurs naturally in the earth crust, usually in ores such as:  Galena (PbS) (major ore)  Cerrusite (PbCO3)  Anglesite (PbSO3)  Lanarkite (PbO·PbSO3)
  30. 30. ENVIRONMENTAL SOURCES/USES OF LEAD           Soundproofing in buildings Solder- alloy of lead and tin lining pipes, tanks, X-ray apparatus Weather-proofing buildings Protective shielding for radioactive material Smelters Sheathing electric cables Additives for gasoline Ammunitions Lead in solder to seal tin cans
  31. 31. ENVIRONMENTAL SOURCES/USES OF LEAD (cont.)     Lead in automobile batteries As additives in gasolines tetraethyl lead Pb(C2H5)4 and tetramethyl lead Pb(CH3)4 Lead salts as glazes in pots (PbO) Lead salts as pigments PbCrO4 -paints applied to school buses and yellow stripes on road Pb3O4 -as corrosion-resistant paints and has a bright red color Pb(CH2COOH)2 -used in preparations to cover gray hair
  32. 32. EFFECTS OF LEAD IN HUMAN REPRODUCTION AND INTELLIGENCE Pb2+ replaces Ca2+ in bones  Pb2+ remains in bones for decade  High levels of inorganic Pb2+ is general poison  deleterious effects on children's behavior and attentiveness and IQs  Dysfunctional sperm in males  Miscarriages and stillbirth in pregnant women 
  33. 33. HEALTH EFFETC IN ADULTS AND CHILDREN Blood lead levels Adults Children 10 g/dL Hypertension may occur •Crosses placenta •Impairment IQ, growth •Partial inhibition of heme synthesis 20 g/dL Inhibition of heme synthesis Increased erythrocyte protoporphyrin 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
  34. 34. MERCURY          symbol Hg From the Latin word, hydrargyrum, “liquid silver,” Shining, mobile liquid, silvery-white in color It is liquid at -38.9oC Becomes solid when subjected to a pressure of 7,640 atmospheres Freezing point of about -39°C (about -38°F), a boiling point of about 357°C Density of 13.55 grams per cu cm. The atomic weight of mercury is 200.59gmol-1 Conducts electricity well Its principal ore is cinnabar
  35. 35. ENVIRONMENTAL SOURCES/USES OF MERCURY Electrical switches in automobiles built before 2000  In fluorescent light bulbs and in street lamps before  dental amalgam  Gold and silver mining  Pesticides  Used to make felt for hats 
  36. 36. ENVIRONMENTAL SOURCES/USES OF MERCURY (cont.) Fossil fuel coal lignite (100ppb)  Discarded laboratory chemicals  Pharmaceutical products  Crematoria  Wastewater from dentists’ offices  Preserve paint  Used as slimicides in pulp-and-paper industry  As topical antiseptic and in cosmetics 
  37. 37. MERCURY AND THE INDUSTRIAL CHLOR-ALKALI PROCESS amalgam of sodium and mercury is used in some industrial chlor-alkali plants in process that converts aqueos sodium chloride into the commercial products chlorine and sodium hydroxide and gaseous hydrogen by electrolysis.  Flowing mercury is used as the cathode  Some of the mercury find its way to the air and water 
  38. 38. MERCURY VAPOR It is composed of free, neutral atoms.  If inhaled the atoms diffuse from the lungs to the bloodstream   liquid mercury is not highly toxic, when ingested most are excreted
  39. 39. METHYLMERCURY TOXICITY       methyl anion combines with Hg2+ to yield volatile molecular liquid dimethylmercury the formation occurs in muddy sediments of rivers and lakes, under anaerobic condition methylmercury(or monomethylmercury) its production predominates over dimethylmercury in acidic or neutral aqueous systems sulfate ions stimulates sulfate-reducing bacteria that methylate mercury sulfide ions results in formation of mercury sulfide complexes that do not undergo methylation
  40. 40. (cont.) between methylmercury in fish muscle and that dissolved in the water: 1 million to 1, and can exceed 10 million to 1  High methylmercury concentration in large, long-lived predatory marine species 
  41. 41. METHYLMERCURY ACCUMULATION IN THE ENVIRONMENT AND IN THE HUMAN BODY Half-life of methylmercury in human body is 70days  Cumulative poison  dialkylmercury including dimethylmercury is supertoxic 
  42. 42. MINAMATA DISEASE Occurred in a village in Minamata, Japan  CH3Hg-SCH3  100ppm of mercury in fish tissues  Onset symptoms were first seen in cats  Symptoms in humans arise from dysfunctions of the central nervous system  Methylmercury can be passed to fetus  U.S. has EPA maximum conc of 0.3ppm in fish tissue 
  43. 43. SOURCES OF METHYLMERCURY Fungicide in agriculture and industry  Leaching from rocks and soil into water systems by natural processes  Preservative Thimerosal 
  44. 44. SAFE LEVEL OF MERCURY IN THE BODY  10-20ppm of CH3Hg+ in hair can be dangerous INTERNATIONAL CONTROL ON MERCURY  United Nations Environment Programme in 2005 devised a global treaty to curb the production if mercury and to ban completely the export of mercury between countries

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