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