Toxic Bioaccumulative Chemicals

Most mercury enters aquatic environments from the atmosphere

The dominant inorganic forms are Hgo and Hg2+.

Positively charged Hg2+ can become attached to negativelycharged organic and inorganic particles in soils and sedimentswhich tends to immobilize them.

Under anaerobic conditions, Hg2+ can be converted to organic Methylmercury which is more toxic and persistent in organisms.

Mercury methylation is related to the metabolism of Sulfur-reducing bacterial under anaerobic conditions

The exact biochemical mechanism is poorly understood.

High sulfur concentrations increase mercury methylation

Mercury

The following are required for mercury methylation

Inorganic MercuryAnaerobic Conditions

Carbon Source (sediments)Sulfate/Sulfate-Reducing Bacteria

Methylmercury is more directly toxic and remains inThe tissues of organisms longer than inorganic Hg2+.

This allows methymercury to bioaccumulate in organisms

Bioaccumulation allows for biomagnification whichis the increase in concentration of a chemicalin organisms higher up in the food chain.

Bioaccumulation occurs when an organism absorbs a toxic substance at a rate greater than that at whichthe substance is lost from the body.

Biomagnification: concentration of a chemical in organisms as it moves up the food chain.

Organisms near the top of the food chain may have concentrationsof mercury millions of times greater than in the aquatic environment

Other Bioaccumulative Toxins

Synthetic Organic Chemicals

Synthetic Organic Chemicals

DioxinsPesticidesPCBsFlame Retardants

PBDE

Dioxin

PCBDDT

Organochlorines

Organic = carbon-rich compounds

Viktor Yushchenko Ukrainian President

Potential Toxicity

6,000 times the usual concentration in his body

July November

the second highest dioxin level ever measured in a human

2004

Chemicals like dioxin are acutely toxicIn high doses, but they also can bioaccumulate

creating chronic toxicity at lower doses

The cause of their ability to bioaccumulate is related to their water solubility.

Sodium Chloride 350 g/L

Potassium Chloride 280 g/L

Water Solubility

Why?

NaCl Na+ + Cl-

Water Molecules are Polar

++

-

Unequal distribution of electrons

Oxygen is electron-greedy

NaCl Na+ + Cl-Na+ Cl-

Sodium Chloride water solubility: 350 g/L

Contrast with Organic Chemicals

Organic Chemicals

Greases, Oils, Paints, Pesticides, Industrial Chemicals

Grease and Oil

Carbon 83 to 87%

Hydrogen 10 to 14%

C16H14OS

Oil Paint

Composed mostly of carbon and hydrogen,and possessing no electrical charge.

Carbon-rich compounds

Dioxin

PCB

DDT

Principally carbon, hydrogen

C11H18O2Cl4

C14H22Cl5

C12H21Cl2

Do not possess an electrical charge

Dioxin

Dioxin water solubility: 0.2 µg/L

Dioxin

PCB

DDT

10 µg/L

0.2 µg/L

Uncharged and principally carbon, hydrogen

< 0.1 µg/L

Toxaphene: 3 mg/L

Dieldrin: 186 ug/L

Chlordane: 9 ug/L

These types of chemicals are poorly soluble in water

In what substances do they dissolve?

Greases, Oils, Paints, Pesticides, Industrial Chemicals

Hexane

D-limonene oil

Common Organic Solvents

Carbon-based

petroleum

Organic Solvents

water

Hexane

Acetone

Lipids

Carbon-based compoundsdissolve more easily in carbon-based solvents.

carboncarbon

carbon

carbon

Dioxin

-SO4

SoapSoap

hydrophobichydrophilic

SO4-

SO4-

SO4-

SO4-

SO4-

SO4-

SO4-

SO4-

High Carbon Concentration

Bioaccumulation in Organisms

Fundamental similarity betweenthe chemical and the solvent.

Bioaccumulation in Organisms

Lipid Tissue in Organisms

The chemical essentially dissolves into the lipid tissues

carbon

Synthetic organic chemicals are poorly soluble in water

They are soluble in organic solvents and lipids

Lipids are found in all organisms

Despite low levels of organic chemicals in water dueto their low water solubility, high amounts canaccumulate in the tissues of living organisms

Magnification of 800 x

Water Concentration = 0.2μg/L

Zooplankton concentration = 160 μg/L

Bio-Magnification

Water and phytoplankton to zooplankton: 800 x

Zooplankton to fish: 31 x

Overall: 120,000 times original concentration in water

Fish to eagle: 4.8x

PCBs and Pesticides

PCBs

Electrical equipmentplasticizers in paints, plastics and rubber productspigments, dyes and carbonless copy paper

PCBs were “banned” in 1979

Used as insulating fluids and coolants in electrical equipment and machinery from 1929-1977.

EPA estimates that 150 million pounds of PCBs are dispersed throughout the environment,including air and water supplies; an additional 290 million pounds are located in landfills in this country

some PCBs act like hormones, and other PCBs are nerve poisons

PCBs in Marine Mammals

HazardousWaste level(Canada)

Killer Whales(1000 ppm)

High on food chainLipid tissues

Seawater

Arctic cod muscle

Narwhal blubber

14 - 46 ppb

0.0003 ppb

2440 - 9160 ppb

Toxaphene

50,000 X

~ 8 M X

carbon lipid400,000 tons: 1946 to 1974

(670 chemicals)

Toxaphene and Mirex: 1959 - 1976

highest levels ever recorded in a living organism.

1. Many synthetic organic chemicals are uncharged.

2. Because they are uncharged, they do not permit orientation of water molecules and are poorly soluble in water.

3. Ionic compounds (e.g. NaCl) are about 1 billion times more water-soluble than uncharged organics.

4. Uncharged organic chemicals, however, tend to be soluble in organic solvents and organic materials because of similar carbon-based chemistry.

5. These materials can include lipid tissues in organisms which can lead to biomagnification

Summary

Solubility

water

Hexane

Acetone

Lipids

Carbon-based compoundsdissolve more easily in carbon-based solvents.

carboncarbon

carbon

carbon

Dioxin

Where in these environmentsdo we find high levels of carbon?

Many synthetic organic chemicals, particularlythose like PCBs and DDT are very persistentin the environment. They last for decades.

They become stored in organic materialsthat naturally occur in aquatic and terrestrial systems

CarbonHydrogenOxygen

Organic MatterOrganic Matter

Coiled and convoluted chains of carbon, hydrogen, and oxygen

CarbonHydrogenOxygen

Organic MatterOrganic Matter

COOH

OH

carboxylic

enolic

CCCCCC

CC

CC

C

C

C

C

C

H

H

H

H

H

H

HH

HH

H

H

H

Partitioning/DistributionPartitioning/Distribution

Organic matter Soil Solution

Absorption

Partitioning of neutral organic chemicals into soil organic matter limits their mobility in the environment

Aquatic Systems

Water

Organic Sediments

Environmental Persistence

Solubility of < 0.1 μg/L

Organic chemicals become stored in organic sediments

This protects them from degradation and increases their lifetime in the environment

DDT

Lake Michigan

µg PCB/Kg sediment (parts per billion)

EPA 2004

mg Carbon /g sediment

N Concentration

Organic Carbon

PCBs

PCBs

“banned” in 1979

Open water PCB concentration = < 1 part per trillion

Lake Erie PCB levels

PCBs

After 30 years, PCBs continue to persist in the Environment

EPA, 2004

Persistence in the Environment

Old sediments

Florida and Organic Chemicals

DDT

dichloro-diphenyl-trichloroethane

First Modern Pesticide

Insecticide developed to combat insect-borne disease

Use was later expanded to include agriculture

DDT levels ranging from 2,200 to 110,000 µg/kg (ppb) in organic soils and sediments.

Rita Island, Okeechobee

Organic soils

Historically characterized by clear water and a highly prized sports fishery, it served as a popular destination for boaters, swimmers, and fishermen for decades.

Lake Apopka

30,800 acres

mean depth is 5.4 feet

15 miles northwest of Orlando

In the 1970s, scientists considered Lake Apopka a prime place to harvest eggs and hatchlings to studythem in captivity.

In 1980 and 1981, scientists counted populations of 1,200 to 2,000 alligators in a single night on the lake

By the late 1980s, they counted only 150 per night

AgricultureAgriculture

Pesticide Use in Agricultural Area

Pesticide use included high amounts of DDT

"Lake Apopka is a big chemical soup," Michael Fry, a researcher from the University of California

Tower Chemical Company

Produced dicofol, a mixture of the pesticide DDT and DDE, a by-product of DDT. Periodic spills occurred there, but a particularly large accident in 1980 caused dicofol to spread into the lake

TOC content ranges from 33 to 37%

Apopka's juvenile alligators have abnormal testes and ovaries and abnormal hormone balances

DDE, a breakdown product of DDT, is a major contaminant in Lake Apopka

DDE is known to block the action of testosterone

Alligator Population crash was linked to poor egg viability

Estradiol Testosterone

Apopka males had high levels of estradiol relative to testosterone

' Teeny Weenies '

Alligators in Florida's Lake Apopka have Smaller Penises 

Kyla Dunne for PBS June, 1998

http://www.mindfully.org/Pesticide/Alligators-Apopka-PBS2jun98.htm

Solubility

water

Hexane

Acetone

Lipids

Carbon-based compoundsdissolve more easily in carbon-based solvents.

carboncarbon

carbon

carbon

Dioxin

What is the most common way we dailydissolve organic substances/chemicals?

-SO4

SoapSoap

hydrophobichydrophilic

SO4-

SO4-

SO4-

SO4-

SO4-

SO4-

SO4-

SO4-

High Carbon Concentration

SoapSoap

SO4-

SO4-

SO4-

SO4-

SO4-

SO4-

SO4-

SO4-

Oil drop in water

Soap micelle

Assessing the Danger: Octanol

An Important Organic Solvent:Octanol

C8H18O

Neutral organic chemicals are soluble in organic solvents

cc c

c cc c

c

Octanol-Water Partitioning

Octanol and water are immiscible

Octanol Density: 0.824 g/cm3

octanol

water

C8H18O

C8H18O

Octanol (Carbon/Hydrogen)

water

Carbon/hydrogen

Partitioning Between Octanol and Water

C10H20

Octanol-Water Partitioning Coefficient

Kow = Concentration of chemical in octanolConcentration of chemical in water

At equilibrium

water

1 L Octanol1L Water

Add 10 mg chemical

separate

chemical

chemical

Analyze the water phase for the chemical.Difference between initial amount and amount in water = amount in octanolThe ratio between the two yields the Kow

octanol

Add 10 mg chemical

separate

chemical

chemical

0.01 mg L

9.99 mg L

Water phase octanol phase

Kow = 9.99 mg L

0.01 mg L

= 999

1 L Octanol1L Waterl

Kow of some Organochlorine Compounds

DDT 4,000,000

PCBs 2,000,000

Dioxin 6,000,000

A high Kow indicates strong interaction with organic solvents and lipid tissues

chemical in octanolchemical in water

PCBs

Electrical equipmentplasticizers in paints, plastics and rubber productspigments, dyes and carbonless copy paper

Kow = 2,000,000

PCBs were “banned” in 1979

Used as insulating fluids and coolants in electrical equipment and machinery from 1929-1977.

EPA estimates that 150 million pounds of PCBs are dispersed throughout the environment,including air and water supplies; an additional 290 million pounds are located in landfills in this country

some PCBs act like hormones, and other PCBs are nerve poisons

DDT

first modern pesticide (Nobel Prize, 1948)

Insoluble in water. Soluble in

most organic solvents, fat, and oils.

used with to combat mosquitoes spreading malaria (mosquitoes),

and typhus (lice)

Banned in 1972 (U.S.)

Kow = 4,000,000

Launch of the Environmental Movement

1962human volunteers ingested 35 mg of DDT

primates were fed 33,000 times more DDT than the estimated exposure

Thinning egg shells

Lower hatching rates

Declining Eagle population

Carcinogenic

decline in the eagle population occurred before the DDT years (bounties between 1917 and 1942)

http://faculty.unionky.edu/rbotkin/RECM_480_ISSUE_16A_YES_BLUE.PPT#291,22,Issue%2016:%20Yes

Simple Filtration

Carbon(most common component)

Ion Removal

Water Filters

Activated CarbonActivated Carbon

Activation by heating

Extremely porous with high surface area: 500 m2/g

Large surface area = high contact with contaminants

Activated CarbonActivated Carbon

Absorption: spontaneous movement of primarily organic contaminants from water to carbon matrix.

Pesticides and other organics essentially dissolve in the carbon

Chlorine sticks to the extensive surfaces

2,4-D2.4.5-TP (Silvex)AlachlorAtrazineCarbofuranChlordaneEndrinHeptachlor EpoxideLindaneMethoxychlorSimazineToxapheneBenzeneCarbon TetrachlorideChlorobenzene

EthylbenzeneMonochlorobenzeneMTBEO-DichlorobenzeneP-DichlorobenzeneStyreneTetrachloroetheneTolueneTrichloroetheneVOCsAntidepressantsSteroids/HormonesPrednisone, Prednisolone,Progesterone, Testosterone,Cortisol/HydrocortisoneAntibioticsCiprooxacin, Trimethroprin,SulfamethoxazoleAnxiolyticsMeprobamate

Carbon Filter Removal

Does not remove bacteria or most metals