Metals and Mercury

Not necessarily a health threat in itself; it is used to indicate whether other potentially harmful bacteria may be present

Coliforms are naturally present in the environment; fecal coliforms only come from human and animal fecal waste.

Biological pollution

Discovery of coliform bacteria had the greatest impacton municipal water systems and water treatment.

1/3 weight of average uninfected human waste

Forms of Water Treatment

Suspended SolidsFlocculation

Sand filtration

Flocculation – bringing together of high numbersof small particles to create larger particles whichsettle out of water quickly.

Advanced treatment uses chlorine disinfectionTo remove pathogenic organisms from water.

1880sScientists demonstrate that microorganisms can cause disease.

First application of chlorine disinfectants to U.S. municipal water facilities in Jersey City and Chicago.

1908

First U.S. drinking water bacterial standard.1915

Over 1,000 U.S. cities employ chlorine disinfection.

1918

More than 19,000 municipal water systems operate throughout the U.S.

1960

Biological Pollution and Chlorination

Chlorine is currently employed by over 98 percent of all U.S. water utilities that disinfect drinking water

Effectiveness of Chlorination: Typhoid Yardstick

De

ath

s p

er

100

,00

0

1860 1910 1935

Today: < 40 per 200 million people

bacterium Salmonella typhi

174 per 100,000 persons died of Typhoid in 1891

Metals: Mercury

ArsenicErosion of natural deposits; pesticide waste, runoff from glass & electronics production wastes, treated lumber, groundwater

MercuryErosion of natural deposits; discharge from refineries and factories; runoff from landfills, coal burning

LeadCorrosion of household plumbing systems; natural deposits, paint, fuels, electronics

Heavy Metals and Metalloids

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

Wells in Floodplain and Delta Sediments

Water Bearing Muds

Natural erosion ofarsenic to water-bearing units.

Well depths between 20m and 100 m

Arsenic

Majority of wells > 50 ppb arsenic Some wells contain 500 - 1000 ppb

WHO/U.S limit: 10 ppbBangladesh limit: 50 ppb

-lead pipes

-lead acetate sugar of lead

sweetener for wine

Lead (Plumbum)Father of all metals Possible cause of the

dementia which affected Roman Emperors and Citizens.

Contemporary Sources:

Paint, ceramics, glass, soils, pipes,Solder, brass faucets, gasoline

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 damagedigestive problems

kidney damagelack of coordination

cognitive 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 annually

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 is applied, the electrodes energize the mercury vapor, causing it to emit ultraviolet (UV) energy. The phosphor coating absorbs the UV energy, causing the phosphor 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+) metylmercury

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

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

Methylmercury is rapidly taken up but only slowly eliminated from the body by fish and other aquatic organisms, so each step up in the food chain (bio)magnifies the concentration from the step below.

Bioaccumulation factors (BAF's) of up to 10 million in largemouth bass have been reported for the Everglades.

Fish-eating birds, otters, alligators, raccoons and panthers can have even higher bioaccumulation factors.

Methylmercury in the organs and tissues causes birth defects & disorders of the brain, reproductive system, immune system, kidney, 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 tilefish) pose the greatest risk.

Five of the most commonly eaten fish that are low in mercury are shrimp, canned light tuna, salmon, pollock, and catfish.