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Chemical Pollutants. Metals and Non-metals. Mercury, Arsenic, and Lead. Lead found in blood sample from 1 of 10 Washingtonians Arsenic found in urine samples from 4 of 10 Washingtonians Mercury found in hair samples from 10 of 10 Washingtonians. Mercury. Wonderland. Mercury Nitrate - PowerPoint PPT Presentation
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Chemical PollutantsMetals and Non-metals
Lead found in blood sample from 1 of 10 Washingtonians
Arsenic found in urine samples from 4 of 10 Washingtonians
Mercury found in hair samples from 10 of 10 Washingtonians
Mercury, Arsenic, and Lead
Common Health Effects
Lead
behavioral problemshigh blood pressure, anemiakidney damagememory and learning difficultiesmiscarriage, decreased sperm productionreduced IQ
Mercury
blindness and deafness brain damagedigestive problemskidney damagelack of coordinationcognitive degeneration
Arsenic
breathing problemsdeath if exposed to high levelsdecreased intelligenceknown human carcinogen: lung and skin cancernausea, diarrhea, vomitingperipheral nervous system problems
Mercury Nitrate
Symptoms included tremors, emotional instability, insomnia, dementia and hallucinations
Wonderland
Natural Groundwater Contaminants
Fluoride and Arsenic
water tables falling by 20 feet per year
21 million backyard tube wells
Failure of 246 surface irrigation projects
$600 electric pumps (1% of GDP)
India
95 %
What do you do when your water table falls?
Deeper Wells and Fluoride
Naturally occurring element in Granitewhich dissolves into the groundwater
Water near the surface is generally unaffected
Lowering water tables = deeper wells
Deep wells can contain granite and high fluoride levels
Fluoride in water can be a cumulative poison
What’s the obvious question?
Intentional Fluoridation of Water in the U.S.
Fluoridation became an official policy of the U.S. Public Health Service in 1951.
By 1960 water fluoridation had become widely used in the U.S. reaching about 50 million people.
By 2006, 69.2% of the U.S. population on public water systems were receiving fluoridated water.
How does it work?
Tooth enamel is made of a mineral called hydroxyapatite
Ca5(PO4)3OH
Hydroxyapatite is subject to dissolution by acids (H+)
Fluoridation changes the chemical composition ofhydroxyapatite to a crystal less subject to acid dissolution
Bacteria in the mouth create acids (H+)
Ca5(PO4)3
Sodium fluorosilicate (Na2SiF6) Sodium fluoride (NaF)
NaF Na+ + F-
OH
Ingestion of fluoridated water increases the F- concentration in saliva
F- replaces OH in hydroxyapatite making fluoroapatite
F-
Fluoroapatite is less soluble in acid than hydroxyapatite
Fluoride concentrationsIn U.S. tap water
0.5 – 1.0 mg/L
Lower values in warm climates
1.6 to 6.6 mg/day
Colorado Brown Stain
Dental Fluorosis
Intake:
Permissible fluoride limit in India is 1.2 mg/L
Fluoride levels between 5-25 mg/L have been found
Fluoride levels > 1.5 mg/L
9 mg/day to 12 mg/day
Fluorosis has risen from 1 million to 25 million and threatens 60 million people in India.
Skeletal Fluorosis
Intake
Fluoride levels > 10 mg/L
Extra Credit:
1. The chemical that made the Mad Hatter mad _____2. Country affected by fluoride poisoning __________3. Fluoride is naturally occurring. True or False4. Colorado Brown Stain is a name for ____________
Groundwater and Arsenic
Arsenic is Naturally Occurring
occurs primarily in association with sulfur-containing minerals
Mobilization of arsenic in the environment arises from anthropogenic activities related to mining and ore processing,
metallurgy, agriculture, wood preservation, and industry.
Natural waters, in general, contain low levels of total arsenic
Inorganic Forms of Arsenic
AsO4-3AsO3
-3
Arsenite Arsenate
Low Oxygen High Oxygen
Arsenite is more toxic than arsenate, interfering withenzyme activities which catalyze metabolic reactions
Arsenite compounds are also more mobile in the environmentdue to higher solubility compared to arsenate compounds
Both arsenate and arsenite are chronic accumulative toxins
“The World’s Largest Mass Poisoning”
Bangladesh and W. India
ranked among the world's 10 poorest countries
Accumulation ofthick mudsin the floodplainsand deltas
Floodplain and Delta of theGanges and Brahmaputra Rivers.
Floodplain: area paralleling a river that is periodically inundated
Deltas are formed from the deposition of sediment carried by the river as the flow leaves the mouth of the river
Himalayas
Ganges-Brahmaputra Delta
Bangladesh Prior to 1970s
One of the highest infant mortality rates in the worldPrincipally due to waterborne disease.
Ineffective water and sewage systemsPeriodic monsoons and floods
cholera, dysentery
water-borne pathogens
Deaths Due to Surface water contamination: 250,000/yr
Deaths Due to Surface water contamination: 250,000/yr
The Solution: Tap groundwater resources• easy• inexpensive• available
First 1 million wells were sunk with aid from
World GovernmentsUNICEF
World Bank
12 million hand-operated tube wellsdeliver water to over 80% of the rural village population
Infant mortality and diarrheal illness reduced by 50%
Wells in Floodplain and Delta Sediments
Water Bearing Muds
Natural erosion ofarsenic to water-bearing units.
Well depths between 20m and 100 m
Majority of wells > 50 ppb arsenic Some wells contain 500 - 1000 ppb
WHO/U.S limit: 10 ppbBangladesh limit: 50 ppb
Delta and Floodplain Regions
Exposure Estimates
Above 10 ppb: 57 million peopleAbove 50 ppb: 35 million people
Early Symptoms:Skin lesions and thickeningStrong skin pigmentation
Accumulative Toxin
Long-term Exposurebreathing problems
death if exposed to high levelslung and skin cancer
peripheral nervous system
2003 Studies
83 million people
Bihar: 40% wells contaminated
Red River Delta
11 million people
First wells sunk7 years ago
Mercury
Got Fish?
Mercury Advisories
70% of states
Where does it come from?
Mercury is naturally occurring
The number 1 anthropogenic sourceis the combustion of coal
Enters water bodies principally from the atmosphere
(coal, volcanism, rock weathering)
48 tons of elemental mercury to the atmosphere each year.
blindness, deafness brain damageblindness, deafness brain damagedigestive problemsdigestive problems
kidney damagekidney damagelack of coordinationlack of coordination
cognitive degenerationcognitive degeneration
Mercury
Electrical products such as dry-cell batteries, fluorescent light bulbs, switches, and other control equipment account for 50% of mercury used.
The drinking water standard for Mercury is 0.002 mg/L.
1 gram
Fluorescent LightsA typical fluorescent lamp is composed of a phosphor-coated glass tube with electrodes located at either end. The tube contains a small amount of mercury vapor. When a voltage isapplied, the electrodes energize the mercury vapor, causing it to emit ultraviolet (UV) energy. The phosphor coating absorbs the UV energy, causing the phosphorus to fluoresce and emit visible light.
Voltage
Hg gasUV
Phosphor Coating
Each year, an estimated 600 million fluorescent lamps are disposed of in US landfills amounting to 30,000 pounds of mercury waste.
Recycling and Handling
Forms of Mercury
The dominant inorganic forms are Hgo and Hg2+.Hg2+ often occurs as HgCl2 (mercuric chloride)
in many aqueous environments.
Hg2+ (inorganic) interacts with soil and sedimentparticles (- charge) becoming part of lake bottom sediments (limits availability)
Interaction with Sediment Particles
- charge
- charge- charge
Hg2+
Small organic andInorganic particles
Hg2+
Hg2+
- charge
sedimentsHg2+
Mercury Bound to Sediments
Hg2+
Negatively charged particles bind mercuryAnd retain it in bottom sediments.
Mercury, however, can undergo chemicalchanges in lakes which render mercury
more environmentally dangerous
Mercury can be converted to more toxic forms in bottom sediments
under anaerobic conditions
Mercury Methylation
Mercury Methylation
Methylation: conversion of inorganic forms of mercury, Hg2+, to an organic form: methyl mercury under anaerobic conditions
Hg2+ (CH3Hg+) methylmercury
Methylmercury is strongly accumulated in the bodyand is generally more toxic than inorganic Hg
Occurs primarily in bottom sediments as a byproduct of the life processes of anaerobic sulfate-reducing bacteria (SO4 to HS-) that live in high sulfur, low oxygen environments.
Mercury Methylation
When sulfur accepts electrons it is said to be “reduced”.
C6H12O6 + 3SO42- + 3H+ = 6HCO3
- + 3HS- Sulfate Respiration
Requires 4 elements:• anaerobic conditions• a carbon source (organic sediments)• a source of sulfur (SO4
-)• sulfur reducing bacteria
Desulfuromonas, Pseudomonas
However, bacterial sulfate respiration requires sulfate.
The addition of sulfate to water stimulates the metabolic activity of sulfate-reducing bacteria and the inadvertent methylation of inorganic mercury
Sulfate concentrations in EAA runoff and Lake Okeechobee average more than 50 times background concentrations than in the pristine Everglades
The exact role of sulfate-reducing bacteriaIn mercury methylation is poorly understood
Sulfate
Hg2+ from coal, volcanism, rock weathering, point sources
Water
Sediments(Bound)
Sulfur reducing bacteria, low O2
methylmercury Aquatic Organisms
Biomagnification: concentration of a chemical in organisms as it moves up the food chain.
Bioaccumulation: concentration of a chemical in organisms relative to the amount in water.
Enhanced Risk
Methylmercury has a half-life in human blood of about 70 days(almost twice as long as inorganic mercury (Hg2+).
Methylmercury attaches to proteins in animals (enters food chain)
Methylmercury is strongly accumulated in the bodyand is generally more toxic than inorganic Hg
Bio-magnification
MethylmercuryMethylmercury is rapidly taken up but only is rapidly taken up but only slowly eliminated fromslowly eliminated from the body by fish and the body by fish and other aquatic organisms, so each step up in other aquatic organisms, so each step up in the food chain (bio)magnifies the concentration the food chain (bio)magnifies the concentration from the step below.from the step below.
Bioaccumulation factorsBioaccumulation factors (BAF's) of up to (BAF's) of up to 10 10 million in largemouth bassmillion in largemouth bass have been have been reported for the Everglades.reported for the Everglades.
Fish-eating birds, otters, alligators, raccoons Fish-eating birds, otters, alligators, raccoons and panthers can have even higher and panthers can have even higher bioaccumulation factors. bioaccumulation factors.
Methylmercury in the organs and tissues Methylmercury in the organs and tissues causes birth defects & disorders of the brain, causes birth defects & disorders of the brain, reproductive system, immune system, kidney, reproductive system, immune system, kidney, and liver at extremely low levels in food. and liver at extremely low levels in food.
Bioconcentration and Biomagnification
Chemical Concentration in organismChemical Concentration in waterBAF =
Chisso Corporation, a company located in Kumamoto Japan, dumped an estimated 27 tons of mercury compounds into Minamata BayBetween 1932 and 1968.
As of March 2001, 2,265 victims had been officially recognized (1,784 died) and over 10,000 had received compensation from Chisso
Minamata Bay
1963
acetaldehyde
plastics, drugs, and perfumes
Assessing Your Risk
http://www.edf.org/page.cfm?tagID=17694
http://www.mercuryfacts.org/fSafeFish.cfm
Fish sticks and "fast-food" are commonly made from fish that are low in mercury.
Nearly all fish and shellfish contain traces of methylmercury.However, larger fish that have lived longer have the highest levels of methylmercury because they've had more time to accumulate it. These large fish (swordfish, shark, king mackereland Albacore tuna) pose the greatest risk.
Some of the most commonly eaten that are low in mercury are shrimp, canned light tuna, salmon, pollock, and scallops.
Next: Other Bioaccumulative Toxins