Advances

in

analytical

techniques

for

polychlorinated

dibenzo-p-dioxins

polychlorinated

dibenzofurans

and

dioxin-like

PCBs

Analytical

techniques

for

the

determination

of

polychorinated

dibenzo-p-dioxins

-LRB-

PCDD

-RRB-

polychlorinated

dibenzofurans

-LRB-

PCDF

-RRB-

and

dioxin-like

PCBs

-LRB-

DLPCB

-RRB-

are

reviewed

The

focus

of

the

review

is

on

recent

advances

in

methodology

and

analytical

procedures

The

paper

also

reviews

toxicology

the

development

of

toxic

equivalent

factors

-LRB-

TEF

-RRB-

and

the

determination

of

toxic

equivalent

quantity

-LRB-

TEQ

-RRB-

values

Sources

occurrence

and

temporal

trends

of

PCDD/PCDF

are

summarized

to

provide

examples

of

levels

and

concentration

ranges

for

the

methods

and

techniques

reviewed

Introduction

In

this

review

we

describe

the

current

state-of-the-art

for

the

determination

of

the

chlorinated

dibenzo-p-dioxins

-LRB-

dioxins

-RRB-

chlorinated

dibenzofurans

-LRB-

furans

-RRB-

and

dioxin-like

polychlorinated

biphenyls

-LRB-

DLPCBs

or

coplanar

PCBs

-RRB-

Only

a

brief

summary

of

the

historical

development

of

methods

for

these

compounds

is

given

here

all

of

the

most

important

earlier

work

has

been

summarized

in

previous

reviews

-LSB-

-RSB-

The

characteristics

of

modern

methods

for

dioxin/furan/DLPCB

determination

are

derived

from

several

factors

related

to

their

chemical

physical

and

toxicological

properties

The

exceptionally

high

toxicity

of

-LRB-

-RRB-

meant

from

the

outset

that

very

low

detection

limits

-LRB-

DLs

-RRB-

were

required

consideration

of

their

hydrophobic

nature

and

concern

over

chronic

rather

than

acute

toxicity

effects

meant

that

bioaccumulation

was

of

increased

concern

which

pushed

the

need

for

even

lower

DLs

An

understanding

of

the

environmental

levels

transport

and

fate

of

these

compounds

is

important

if

we

wish

to

understand

the

significance

of

these

compounds

as

well

as

the

low

detection

limits

and

broad

range

of

detection

required

therefore

a

section

on

levels

transport

and

fate

of

these

compounds

is

included

in

this

review

A

variety

of

different

analytical

methods

and

techniques

have

been

developed

to

increase

sensitivity

and

selectivity

and

to

reduce

analysis

times

To

fully

understand

the

analytical

methods

developed

and

their

application

the

references

cited

in

Table

should

be

examined

Table

also

illustrates

the

wide

range

of

sample

types

and

concentration

ranges

of

dioxins

and

DLPCBs

detected

in

the

global

environment

which

explains

why

so

many

variations

on

the

basic

analytical

methodology

exist

Another

factor

in

method

development

and

application

was

the

large

amount

of

litigation

that

occurred

because

of

the

detection

of

these

compounds

in

humans

as

well

as

the

environment

Methods

of

analysis

were

required

to

generate

data

that

could

withstand

scrutiny

in

a

court

of

law

which

led

to

the

necessity

of

using

methods

based

on

isotope

dilution

HRMS

techniques

In

addition

the

rapid

growth

in

high-quality

standards

and

reference

materials

contributed

to

substantial

improvements

in

the

accuracy

and

precision

of

modern

methods

The

development

of

analytical

methods

was

also

influenced

by

the

need

for

regulators

to

be

able

to

evaluate

the

combined

toxicity

of

a

number

of

compounds

that

have

similar

toxic

properties

to

but

widely

varying

potencies

This

development

is

so

important

to

the

development

of

analytical

methods

that

we

have

included

a

section

below

on

toxicology

and

TEFs

The

bottom

line

for

dioxin

methods

was

that

definitive

separation

of

the

dioxins/furans

and

DLPCBs

from

a

large

number

of

other

congeners

with

almost

identical

physical

and

chemical

properties

as

well

as

numerous

other

potentially

interfering

compounds

was

essential

Brief

background

on

dioxin

determination

Chlorinated

dibenzo-p-dioxins

-LRB-

dioxins

-RRB-

have

been

of

concern

for

decades

because

of

their

toxic

properties

as

described

below

A

structurally

similar

series

of

compounds

the

chlorinated

dibenzofurans

-LRB-

furans

-RRB-

have

similar

chemical

properties

and

toxic

effects

and

are

generally

determined

as

a

group

with

the

dioxins

In

recent

years

there

has

been

a

growing

trend

to

include

a

specific

subgroup

of

the

polychlorinated

biphenyls

-LRB-

PCBs

-RRB-

the

so-called

dioxin-like

PCBs

-LRB-

DLPCBs

-RRB-

This

has

been

added

to

methods

along

with

the

dioxins

and

furans

Figure

shows

the

structures

of

and

The

carbon

numbering

system

is

marked

next

to

each

carbon

to

indicate

substitution

positions

Dioxin

and

furan

congeners

substituted

in

the

or

position

are

toxic

while

PCBs

substituted

in

the

or

position

and

no

or

only

one

or

substitution

are

considered

to

be

dioxin-like

and

to

exhibit

dioxin

toxicity

-LRB-

see

Table

-RRB-

Fig.

structures

of

the

chlorinated

dibenzo-p-dioxins

-LRB-

dioxins

-RRB-

chlorinated

dibenzofurans

-LRB-

furans

-RRB-

and

polychlorinated

biphenyls

-LRB-

PCBs

-RRB-

For

the

dioxins

and

furans

congeners

with

chlorine

substitution

at

the

and

positions

are

considered

toxic

Of

the

possible

dioxin

and

possible

furan

structures

only

have

Health

Organization

toxic

equivalent

factors

-LRB-

TEFs

-RRB-

for

humans/mammals

fish

and

birds

-LSB-

-RSB-

-LRB-

TCDD

-RRB-

1111,2,3,7,8-Pentachlorodibenzo-p-dioxin

-LRB-

PeCDD

-RRB-

1111,2,3,4,7,8-Hexachlorodibenzo-p-dioxin

-LRB-

HxCDD

-RRB-

0.10.50.051,2,3,6,7,8-Hexachlorodibenzo-p-dioxin

-LRB-

HxCDD

-RRB-

0.10.10.011,2,3,7,8,9-Hexachlorodibenzo-p-dioxin

-LRB-

HxCDD

-RRB-

0.10.10.11,2,3,4,6,7,8-Heptachlorodibenzo-p-dioxin

-LRB-

HpCDD

-RRB-

0.0011,2,3,4,5,6,7,8-Octachlorodibenzo-p-dioxin

-LRB-

OCDD

-RRB-

0.00010.0012,3,7,8-Tetrachlorodibenzofuran

-LRB-

TCDF

-RRB-

0.10.0511,2,3,7,8-Pentachlorodibenzofuran

-LRB-

PeCDF

-RRB-

0.050.050.12,3,4,7,8-Pentachlorodibenzofuran

-LRB-

PeCDF

-RRB-

0.50.511,2,3,4,7,8-Hexachlorodibenzofuran

-LRB-

HxCDF

-RRB-

0.10.10.11,2,3,6,7,8-Hexachlorodibenzofuran

-LRB-

HxCDF

-RRB-

0.10.10.11,2,3,7,8,9-Hexachlorodibenzofuran

-LRB-

HxCDF

-RRB-

0.10.10.12,3,4,6,7,8-Hexachlorodibenzofuran

-LRB-

HxCDF

-RRB-

0.10.10.11,2,3,4,6,7,8-Heptachlorodibenzofuran

-LRB-

HpCDF

-RRB-

0.010.010.011,2,3,4,7,8,9-Heptachlorodibenzofuran

-LRB-

HpCDF

-RRB-

0.010.010.011,2,3,4,5,6,7,8-Octachlorodibenzofuran

-LRB-

OCDF

-RRB-

-LRB-

PCB

-RRB-

Tetrachlorobiphenyl

-LRB-

PCB

-RRB-

-LRB-

PCB

-RRB-

-LRB-

PCB

-RRB-

-LRB-

PCB

-RRB-

Pentachlorobiphenyl

-LRB-

PCB

-RRB-

-LRB-

PCB

-RRB-

Hexachlorobiphenyl

-LRB-

PCB

-RRB-

-LRB-

PCB

-RRB-

Hexachlorobiphenyl

-LRB-

PCB

-RRB-

Hexachlorobiphenyl

-LRB-

PCB

-RRB-

Heptachlorobiphenyl

-LRB-

PCB

-RRB-

Originally

attention

was

focused

on

the

most

toxic

member

of

these

substances

Gas

chromatographic

columns

were

soon

developed

that

could

separate

from

the

other

TCDD

isomers

in

sample

extracts

-LSB-

-RSB-

and

other

columns

that

could

fortuitously

separate

the

groups

of

congeners

from

each

other

by

degree

of

chlorination

-LRB-

i.e.

all

tetrachlorinated

dioxins/furans

were

eluted

followed

by

all

of

the

pentachlorinated

dioxins/furans

followed

by

the

hexachlorinated

then

the

heptachlorinated

then

the

octachlorinated

-LSB-

-RSB-

Many

early

publications

reported

a

so-called

congener

group

determination

where

the

total

concentrations

of

all

of

the

isomers

from

each

group

containing

the

same

number

of

substituent

chlorines

were

quantified

and

summed

Under

this

approach

concentrations

would

be

reported

total

tetrachlorinated

dioxins

-LRB-

-RRB-

total

pentachlorinated

dioxins

-LRB-

-RRB-

total

hexachlorinated

dioxins

-LRB-

-RRB-

total

heptachlorinated

dioxins

-LRB-

-RRB-

the

octachlorinated

dioxin

-LRB-

OCDD

-RRB-

the

same

dibenzofuran

groups

-LRB-

OCDF

-RRB-

and

This

type

of

determination

is

often

incorrectly

termed

a

total

homolog

determination

Although

homolog

is

still

used

today

to

refer

to

dioxins

or

furans

that

have

different

numbers

of

chlorine

atom

substituents

the

chlorinated

dioxin

or

furan

series

are

not

homologous

because

the

different

members

of

the

series

are

not

formed

by

adding

the

same

structural

unit

-LRB-

Cl

atom

-RRB-

but

by

substituting

Cl

for

H

in

higher

members

of

these

series

The

various

chlorinated

dioxins

are

correctly

termed

congeners

-LRB-

members

of

a

like

series

-RRB-

as

are

the

chlorinated

dibenzofurans

It

was

clear

over

years

ago

that

gas

chromatography

mass

spectrometry

-LRB-

GC

MS

-RRB-

was

the

instrumental

method

of

choice

for

dioxin

and

furan

determinations

The

great

tunable

selectivity

of

mass

spectrometry

achieved

by

the

ability

to

monitor

specific

characteristic

ions

in

the

mass

spectrum

of

a

compound

combined

with

the

retention

time-matching

ability

of

a

gas

chromatogram

made

GC

MS

far

superior

to

other

detection

systems

Even

with

the

use

of

GC

MS

the

exceptionally

great

toxicity

of

meant

that

equally

exceptionally

low

detection

limits

were

required

for

this

compound

in

real

environmental

samples

At

such

DLs

as

parts-per-trillion

-LRB-

ppt

g

per

g

of

sample

-RRB-

or

parts-per-quadrillion

-LRB-

ppq

g

per

g

of

sample

-RRB-

the

principal

barrier

to

successful

analysis

of

samples

was

the

separation

of

TCDD

from

the

bulk

sample

matrix

and

from

all

other

organic

chemicals

in

the

matrix

The

keys

to

success

in

this

endeavor

were

the

number

of

separation

steps

in

the

entire

analytical

scheme

and

their

effectiveness

These

separation

steps

included

the

following

Representative

sampling

-LRB-

not

included

in

this

review

-RRB-

Separation

of

TCDD

from

the

sample

matrix

-LRB-

extraction

-RRB-

transfer

of

TCDD

to

an

appropriate

organic

solvent

Separation

of

TCDD

from

all

other

organic

coextractives

-LRB-

clean-up

can

involve

several

distinct

steps

-RRB-

Separation

of

TCDD

from

other

relatively

nontoxic

tetrachlorinated

dioxin

isomers

-LRB-

gas

chromatography

-RRB-

Separation

and

recording

of

characteristic

TCDD

molecular

fragments

using

a

mass

spectrometer

Although

an

impressive

degree

of

optimization

of

each

of

these

steps

has

occurred

over

the

past

decade

this

basic

approach

was

formulated

in

the

A

paper

published

in

showed

how

high-resolution

mass

spectrometry

-LRB-

HRMS

-RRB-

was

used

to

determine

in

various

sample

types

at

the

ppt

DL

-LSB-

-RSB-

Modern

dioxin/furan

determination

In

recent

years

methods

have

built

on

the

early

developments

referred

to

above

and

have

achieved

a

high

degree

of

sophistication

and

greatly

improved

accuracy

and

precision

The

various

stages

of

development

of

dioxin/furan

determination

can

be

generically

described

as

follows

to

The

principal

concern

was

to

ensure

correct

identification

of

TCDD

the

majority

of

analyses

reported

total

concentrations

of

dioxin

and

furan

-LRB-

tetrachlorinated

to

octachlorinated

-RRB-

congener

groups

and/or

very

few

reliable

analytical

standards

or

certified

reference

materials

were

available

few

laboratories

worldwide

could

perform

this

work

to

Fused

silica

open

tubular

GC

columns

predominantly

used

for

this

application

quality

control

for

GC

MS

methods

enhanced

greatly

by

the

use

of

the

isotope-dilution

technique

GC-HRMS

was

accepted

as

gold

standard

method

introduction

of

toxic

equivalent

factors

-LRB-

TEFs

-RRB-

made

it

imperative

to

improve

speciation

of

all

dioxins/furans

with

chlorine

substitution

at

the

and

ring

positions

or

so

laboratories

worldwide

were

proficient

in

this

work

to

labeled

standards

of

all

dioxins/furans

available

as

well

as

wide

array

of

certified

or

consensus

real-matrix

reference

materials

reliable

methods

available

for

precise

accurate

isomer-specific

determination

of

all

dioxins/furans

at

ppt

to

ppq

concentrations

in

virtually

any

sample

matrix

most

results

for

regulatory

work

reported

as

toxic

equivalent

quantity

-LRB-

TEQ

-RRB-

concentrations

coplanar

PCBs

began

to

be

included

in

TEQ

calculations

laboratories

worldwide

are

proficient

in

this

work

Future

focus

Detection

limits

are

low

enough

for

most

regulatory

purposes

but

may

need

to

be

pushed

lower

for

bioaccumulation

studies

and

determination

of

subtle

effects

from

these

compounds

like

changes

in

sex

ratios

future

improvements

will

be

difficult

due

to

ubiquitous

background

levels

of

these

compounds

and

potentially

interfering

compounds

at

such

low

DLs

biggest

challenges

could

be

to

lower

the

high

cost

and

to

improve

the

speed

of

analysis

bioanalytical

methods

may

help

but

are

still

of

limited

success

after

over

years

of

development

multidimensional

orthogonal

methods

such

as

two-dimensional

chromatography

-LRB-

GC

GC

LC

GC

-RRB-

or

tandem

mass

spectrometry

-LRB-

MS/MS

-RRB-

may

increase

selectivity

and

also

reduce

detection

limits

allowing

for

an

increased

number

of

analytes

in

a

single

analysis

Toxicology

and

TEFs

Dioxin-like

halogenated

aromatic

hydrocarbons

-LRB-

HAHs

-RRB-

provoke

an

extraordinarily

broad

spectrum

of

toxic

effects

in

vertebrate

laboratory

animals

Exposure

to

a

few

micrograms

per

kg

body

weight

of

the

most

potent

congener

leads

to

-LRB-

among

numerous

effects

-RRB-

loss

of

body

weight

liver

necrosis

immune

impairment

reproductive

toxicity

teratogenesis

and

cancer

in

many

laboratory

species

-LSB-

-RSB-

A

single

TCDD

dose

of

μg/kg

is

lethal

to

guinea

pigs

In

human

populations

exposed

to

HAHs

by

occupation

or

by

industrial

accident

the

reported

adverse

health

effects

include

reproductive

disorders

-LSB-

-RSB-

developmental

toxicity

-LSB-

-RSB-

insulin

insensitivity

-LSB-

-RSB-

and

cancer

-LSB-

-RSB-

However

there

is

considerable

controversy

and

uncertainty

about

the

degree

of

risk

to

human

health

from

dioxin-like

compounds

particularly

regarding

cancer

risk

-LSB-

-RSB-

There

is

no

question

however

that

TCDD

can

cause

the

severe

skin

disorder

known

as

chloracne

in

some

highly-exposed

individuals

-LSB-

-RSB-

chloracne

is

considered

to

be

the

hallmark

of

human

dioxin

toxicity

If

we

understand

the

mechanism

by

which

a

chemical

produces

its

toxic

effects

we

are

in

a

better

position

to

assess

the

risk

that

the

chemical

poses

to

humans

and

to

other

species

Extensive

research

over

the

past

quarter-century

has

demonstrated

that

all

major

toxic

effects

of

dioxin-like

chemicals

are

mediated

by

their

binding

to

a

soluble

intracellular

protein

the

aryl

hydrocarbon

receptor

-LRB-

AHR

-RRB-

-LSB-

-RSB-

The

AHR

's

normal

function

is

to

regulate

transcription

of

multiple

genes

that

are

important

in

development

physiologic

function

and

adaptive

responses

to

xenobiotic

chemicals

-LSB-

-RSB-

Dioxin-like

chemicals

appear

to

exert

their

toxicity

by

dysregulating

expression

of

key

genes

that

are

under

control

of

the

AH

receptor

-LSB-

-RSB-

Throughout

most

of

its

history

the

science

of

toxicology

has

needed

to

cope

with

the

effects

of

only

one

chemical

at

a

time

HAHs

present

an

unusual

challenge

to

the

toxicologist

because

real-world

HAH

exposure

is

not

to

single

compounds

rather

HAH

exposure

involves

complex

mixtures

of

dozens

to

hundreds

of

congeners

from

the

dioxins

-LRB-

possible

-RRB-

furans

-LRB-

possible

-RRB-

and

PCBs

-LRB-

possible

-RRB-

The

fact

that

dioxin-like

compounds

work

through

a

common

mechanism

the

AHR

-LSB-

-RSB-

fostered

development

of

the

toxic

equivalent

factors

-LRB-

TEF

-RRB-

approach

to

assessing

the

toxicological

potency

of

HAH

mixtures

-LSB-

-RSB-

The

TEF

approach

is

based

on

a

proposal

first

made

by

the

Ontario

Ministry

of

the

Environment

in

-LSB-

-RSB-

In

this

approach

the

most

potent

congener

is

assigned

a

TEF

of

and

all

other

congeners

are

assigned

TEFs

that

reflect

their

toxic

potency

relative

to

that

of

TCDD

For

example

and

-LRB-

-RRB-

each

are

assigned

a

TEF

of

whereas

octachlorodioxin

has

a

TEF

of

reflecting

its

very

low

toxicity

compared

with

that

of

The

toxicity

of

a

mixture

is

stated

as

TEQ

-LRB-

TCDD

equivalents

-RRB-

and

is

assumed

to

be

equal

to

the

sum

of

the

concentration

of

individual

congeners

multiplied

by

their

potencies

-LRB-

TEFi

-RRB-

-LSB-

-RSB-

Note

that

the

TEF

approach

applies

only

to

agents

that

are

dioxin-like

in

that

their

toxic

effects

are

mediated

by

the

AHR

Noncoplanar

PCBs

have

different

mechanisms

of

action

and

are

not

accommodated

in

the

TEF

approach

For

simplicity

it

is

assumed

that

all

dioxin-like

congeners

produce

toxic

responses

that

are

qualitatively

the

same

and

that

the

congeners

differ

only

in

their

potency

to

produce

these

adverse

effects

but

this

simplifying

assumption

should

not

be

viewed

as

being

true

in

a

literal

sense

It

is

true

however

that

the

toxic

potencies

of

congeners

within

the

dioxin-like

category

vary

over

several

orders

of

magnitude

By

definition

in

order

to

calculate

the

total

TEQ

of

a

mixture

we

need

to

know

the

concentration

of

each

dioxin-like

component

in

the

mixture

Hence

the

need

for

sensitive

and

reliable

congener-specific

chemical

analyses

Regulatory

decisions

and

risk

management

need

to

proceed

even

in

the

absence

of

perfect

information

The

TEQ

approach

is

a

useful

simplifying

strategy

to

allow

risk

assessment

to

move

forward

for

exposures

that

involve

complex

mixtures

but

it

includes

several

assumptions

-LSB-

-RSB-

There

are

two

key

issues

What

is

the

proper

TEF

for

each

congener?What

is

the

predominant

mode

of

interaction

between

congeners

when

present

in

a

mixture

The

first

question

what

is

the

proper

TEF

for

a

particular

congener

has

not

been

as

straightforward

as

was

initially

envisioned

The

main

difficulty

is

that

the

estimated

relative

potency

-LRB-

REP

-RRB-

of

congeners

differs

depending

on

what

endpoint

is

measured

in

what

tissue

and

in

what

animal

species

The

relative

potency

estimates

that

underlie

TEFs

are

derived

from

highly

heterogeneous

data

sets

-LSB-

-RSB-

that

require

judgment

and

interpretation

rather

than

providing

numbers

that

can

simply

be

plugged

into

an

equation

The

TEFs

currently

used

in

risk

assessment

are

not

based

on

a

single

biological

endpoint

Rather

current

TEFs

were

assigned

in

by

an

expert

panel

of

the

World

Health

Organization

-LRB-

WHO

-RRB-

who

took

into

account

multiple

biochemical

and

toxicologic

endpoints

The

highest

weight

was

given

to

studies

done

in

mammalian

systems

in

vivo

-LRB-

rather

than

in

vitro

-RRB-

to

chronic

studies

-LRB-

rather

than

acute

-RRB-

and

to

studies

that

measured

a

toxic

outcome

-LRB-

rather

than

a

biochemical

response

-RRB-

The

relative

potency

estimates

and

resulting

TEFs

derived

by

the

WHO

panel

are

now

undergoing

refinement

-LSB-

-RSB-

The

second

question

how

do

components

in

a

complex

HAH

mixture

interact

is

also

not

easily

answered

The

central

premise

in

the

equation

used

to

calculate

TEQ

is

that

the

toxic

effects

of

components

in

the

mixture

are

additive

i.e.

that

the

overall

toxicity

of

the

mixture

is

the

sum

of

the

concentration

of

each

congener

multiplied

by

its

TEF

There

is

experimental

evidence

to

support

the

assumption

of

additivity

-LSB-

-RSB-

However

principles

of

receptor

pharmacology

predict

that

compounds

which

compete

for

the

same

receptor

site

may

antagonize

each

other

so

that

the

overall

response

is

less

than

additive

From

the

viewpoint

of

risk

of

course

it

would

be

desirable

for

the

toxicity

of

mixtures

to

be

less

than

the

sum

of

toxicities

of

individual

components

Several

studies

have

found

antagonism

between

chemicals

that

act

at

the

AH

receptor

site

-LSB-

-RSB-

in

other

words

the

standard

TEQ

approach

in

these

circumstances

overestimates

the

toxic

potency

of

the

mixture

It

also

is

possible

that

components

in

a

mixture

might

synergize

to

produce

a

response

that

is

greater

than

that

predicted

by

the

additive

model

Fortunately

there

is

limited

evidence

of

such

an

unwanted

scenario

for

the

toxicity

of

dioxin-like

chemicals

-LSB-

-RSB-

It

is

important

to

recognize

that

TEF

values

for

some

congeners

can

differ

by

tenfold

or

more

among

different

animal

species

For

example

the

TEF

for

is

ten-fold

higher

in

fish

than

in

birds

-LRB-

Table

-RRB-

-LSB-

-RSB-

When

assessing

risks

to

wildlife

from

exposure

to

HAH

mixtures

we

need

to

be

aware

that

TEF

values

for

most

HAH

congeners

have

been

rigorously

determined

within

only

a

very

few

nonhuman

nonrodent

species

Risk

estimates

may

be

erroneous

or

misleading

if

TEF

values

from

one

animal

species

are

assumed

to

be

the

same

for

other

species

Congener-specific

chemical

assays

for

dioxin-like

compounds

have

dramatically

improved

in

sensitivity

and

reliability

over

the

past

two

decades

Nonetheless

such

assays

remain

expensive

Therefore

economical

alternatives

have

been

sought

which

would

permit

estimates

of

the

potential

toxicity

of

mixtures

to

be

made

Bioassays

such

as

the

chemically

activated

luciferase

gene

expression

assay

-LRB-

CALUX

-RRB-

assess

the

overall

biological

activity

of

a

mixture

and

do

not

require

knowledge

of

the

identity

or

concentration

of

individual

components

of

that

mixture

The

CALUX

cell

bioassay

is

predicated

on

the

AHR

being

the

mediator

of

toxicity

It

tests

sample

extracts

for

their

ability

to

increase

expression

of

a

luciferase

reporter

gene

that

is

under

the

control

of

the

AH

receptor

and

thereby

provides

an

index

to

the

total

equivalents

of

dioxin-like

chemicals

-LRB-

CALUX

TEQ

-RRB-

As

with

chemical

assays

sample

extraction

and

sample

clean-up

are

critical

stages

in

bioassays

such

as

CALUX

For

some

purposes

bioassays

such

as

CALUX

can

provide

a

useful

complement

or

alternative

to

congener-specific

chemical

assays

See

Windal

et

al.

-LSB-

-RSB-

for

an

excellent

review

of

the

properties

and

applications

of

CALUX

Modern

methods

of

analysis

The

gold

standard

for

the

analysis

of

dioxins

and

furans

uses

classical

extraction

techniques

such

as

Soxhlet

-LSB-

-RSB-

liquid/liquid

extraction

-LSB-

-RSB-

solid-phase

extraction

-LRB-

SPE

-RRB-

-LSB-

-RSB-

or

the

more

recent

pressurized

fluid

extraction

-LSB-

-RSB-

Once

the

extract

has

been

transferred

to

a

suitable

solvent

a

three-stage

-LRB-

silica

alumina

and

carbon

-RRB-

open-column

clean-up

is

followed

by

GC

HRMS

-LRB-

employing

isotope

dilution

-RRB-

as

the

analytical

finish

Minor

variations

on

this

method

have

been

used

since

the

late

and

it

continues

to

be

the

method

of

choice

for

regulatory

and

legal

purposes

A

number

of

these

methods

are

listed

in

Table

Table

methods

for

the

analysis

of

dioxins

furans

and

DLPCBsMethodAnalytes/CommentsReferenceUSEPA

dioxins

and

furans

and

congener

group

totals

in

water

and

wastewater

Uses

isotope

dilution

GC

HRMS

-LSB-

-RSB-

USEPA

PCB

congeners

WHO

dioxin-like

PCBs

by

GC

HRMS

the

remaining

by

GC

MS

-LSB-

-RSB-

USEPA

dioxins

and

furans

and

congener

group

totals

in

incinerator

stack

gasses

Uses

isotope

dilution

GC

HRMS

-LSB-

-RSB-

USEPA

-LRB-

-RRB-

Seventeen

dioxins

and

furans

and

congener

group

totals

in

materials

and

waste

Uses

isotope

dilution

GC

HRMS

-LSB-

-RSB-

ISO

to

USEPA

also

allows

GC

MS

as

an

alternate

detection

method

-LSB-

-RSB-

ISO

WHO

dioxin-like

PCBs

in

environmental

matrices

by

GC

HRMS

-LSB-

-RSB-

EN

dioxins

and

furans

and

congener

group

totals

in

stationary

sources

by

isotope

dilution

GC

HRMS

-LSB-

-RSB-

MOE

dioxins

and

furans

including

congener

group

totals

and

WHO

dioxin-like

PCBs

by

GC

HRMS

Uses

isotope

dilution

GC

HRMS

-LSB-

-RSB-

ENVCAN

dioxins

and

furans

and

congener

group

totals

in

pulp

and

paper

effluents

by

isotope

dilution

GC

HRMS

-LSB-

-RSB-

JIS

dioxins

and

furans

including

congener

group

totals

in

wastewater

by

isotope

dilution

GC

HRMS

-LSB-

-RSB-

JIS

dioxins

and

furans

including

congener

group

totals

in

incinerator

stack

gasses

by

isotope

dilution

GC

HRMS

-LSB-

-RSB-

Overview

of

analytical

process

The

generic

steps

of

the

analytical

process

were

listed

above

in

the

Introduction

except

for

the

objectives

and

data

evaluation

These

are

mentioned

here

because

of

their

great

importance

but

will

not

be

discussed

in

detail

It

is

important

to

be

clear

about

the

objectives

of

dioxin/furan/DLPCBs

determinations

because

there

are

several

choices

in

methodology

associated

with

substantially

different

costs

that

generate

data

of

differing

precision

and

accuracy

-LSB-

-RSB-

For

example

for

rapid

on-site

analysis

for

the

purpose

of

directing

a

site

remediation

project

a

substantially

different

methodology

can

be

used

compared

to

that

required

for

legal

action

Data

evaluation

will

also

not

be

discussed

but

the

authors

would

simply

like

to

make

the

point

that

in

spite

of

significant

advances

in

software

and

data

systems

the

low-level

determination

of

dioxins

furans

and

DLPCBs

still

requires

detailed

manual

examination

by

experienced

analysts

of

the

raw

data

generated

by

GC

HRMS

systems

A

discussion

of

sampling

is

beyond

the

intended

scope

of

this

review

but

it

may

often

be

the

case

that

the

imprecision

of

sampling

is

similar

to

or

significantly

greater

than

the

combined

imprecision

of

the

remaining

steps

of

the

analytical

process

Sample

extraction

methods

See

-LSB-

-RSB-

Classical

extraction

techniques

like

liquid/liquid

extraction

and

Soxhlet

extraction

are

described

in

detail

in

the

methods

listed

in

Table

and

will

not

be

addressed

in

this

review

A

number

of

alternative

extraction

techniques

are

summarized

in

Table

Supercritical

fluid

extraction

-LRB-

SFE

-RRB-

uses

a

gas

above

the

critical

point

-LRB-

the

combination

of

temperature

and

pressure

where

the

gas

has

liquid-like

properties

enabling

enhanced

extraction

capability

-RRB-

to

extract

analytes

from

the

matrix

The

main

advantage

with

SFE

is

that

the

extracting

gas

can

be

evaporated

and

so

solvent

disposal

is

not

required

SFE

behaves

significantly

differently

to

classical

solvent

extraction

and

recoveries

can

be

reduced

or

enhanced

Pressurized

liquid

extraction

-LRB-

PLE

-RRB-

also

known

as

accelerated

solvent

extraction

-LRB-

ASE

-RRB-

evolved

from

SFE

Solvents

were

added

to

SFE

extractions

as

modifiers

in

order

to

mimic

classical

liquid

extractions

SFE

without

extraction

gas

and

only

solvent

modifier

best

matched

classical

extraction

recoveries

This

led

to

the

development

of

PLE

Microwave-assisted

extraction

-LRB-

MAE

or

MASE

-RRB-

uses

closed

vessels

to

increase

pressure

and

extraction

efficiency

Polar

solvents

like

acetone

or

water

are

required

to

supply

heat

for

extraction

Sun

et

al.

-LSB-

-RSB-

reported

the

analysis

of

wet

samples

by

MAE

indicating

that

significant

time

was

saved

by

the

reduced

sample

drying

requirements

Table

extraction

techniquesMatrixTechnique

ReferenceSoil/sediment/solidPLE

-LSB-

-RSB-

SFE

-LSB-

-RSB-

MASE

-LSB-

-RSB-

AqueousSPMD

passive

sampling

-LSB-

-RSB-

SPE

-LSB-

-RSB-

AirSwipe/biofilms

-LSB-

-RSB-

Passive

sampling

-LSB-

-RSB-

Solid-phase

extraction

can

significantly

reduce

analysis

times

and

solvent

usage

for

the

extraction

of

water

and

waste

water

samples

even

with

significant

particulate

loadings

-LSB-

-RSB-

Particles

collected

on

extraction

disks

can

be

extracted

quantitatively

without

Soxhlet

or

PLE

extraction

Water

samples

have

also

been

analyzed

using

semi-permeable

membrane

devices

-LRB-

SPMD

-RRB-

SPMD

sampling

is

a

form

of

passive

sampling

that

can

be

used

for

water

air

or

sediments

Namiesnik

-LSB-

-RSB-

has

recently

reviewed

passive

sampling

techniques

in

environmental

samples

Passive

sampling

is

based

on

the

free

flow

of

analytes

from

the

sampling

medium

to

the

collecting

medium

This

technique

eliminates

the

requirement

for

power

and

is

a

composite

sampling

procedure

that

can

reduce

analysis

cost

because

of

reduced

sampling

events

and

analyte

loss

during

shipping

and

storage

as

the

analyte

is

on

a

trapping

medium

Swipe

tests

of

biofilms

on

surfaces

can

also

be

used

to

monitor

ambient

conditions

especially

after

fires

or

from

fugitive

emissions

Sample

extract

clean-up

methods

Sample

preparation

of

dioxin

extracts

is

one

of

the

most

challenging

in

analytical

chemistry

Many

coextractable

and

potentially

interfering

compounds

present

in

the

raw

extract

must

be

removed

in

order

provide

maximum

concentration

factors

-LRB-

to

-RRB-

to

meet

DLs

A

number

of

classical

adsorbents

can

be

used

including

silica

alumina

Florisil

and

carbon

Most

current

procedures

are

based

on

the

Dow

-LSB-

-RSB-

and

Smith-Stallings

-LSB-

-RSB-

procedures

These

procedures

are

described

in

detail

in

the

references

given

in

Table

above

Disposable

SPE

cartridges

-LSB-

-RSB-

have

been

used

for

rapid

clean-up

of

biological

materials.The

analysis

of

dioxins

is

very

costly

and

time-consuming

Over

the

past

years

a

number

of

modifications

have

been

made

to

automate

sample

extraction

and

sample

extract

preparation

to

reduce

analysis

times

and

to

attempt

to

reduce

costs

Focant

-LSB-

-RSB-

has

recently

reviewed

the

automated

sample

preparation

of

biological

samples

Multicolumn

automated

systems

like

the

FMS

-LRB-

fluid

management

system

-RRB-

automated

Power

Prep

system

were

developed

to

prepare

human

serum

extracts

and

have

subsequently

been

used

in

a

number

of

applications

including

biota

water

and

food

Interchangeable

cartridges

-LRB-

silica

alumina

carbon

-RRB-

can

be

used

in

different

configurations

-LSB-

-RSB-

The

addition

of

a

PLE

interface

preceding

the

Power

Prep

enables

the

sample

to

be

extracted

and

cleaned

in

the

same

automated

run

Food

samples

-LRB-

three

-RRB-

have

been

extracted

cleaned

and

analyzed

in

ten

hours

using

this

system

-LSB-

-RSB-

An

alternate

method

reported

by

Thal

-LSB-

-RSB-

used

an

automated

gel

permeation

chromatographic

-LRB-

GPC

-RRB-

carbon

system

The

GPC

removes

coextractables

like

lipids

from

the

extract

which

is

then

processed

on

activated

carbon

to

separate

the

planar

from

the

nonplanar

compounds

This

is

based

on

a

system

reported

by

Norstrom

et

al.

-LSB-

-RSB-

Van

Beuzekom

used

an

automated

microwave

solvent

extraction

system

-LRB-

MASE

-RRB-

coupled

to

a

liquid

chromatograph

for

the

analysis

of

fine

particles

from

fire

emissions

-LSB-

-RSB-

Nording

-LSB-

-RSB-

was

able

to

modify

a

PLE

extraction

cell

to

insert

the

sample

matrix

above

carbon

packing

in

order

to

perform

extraction

and

clean-up

in

the

cell

as

a

screening

method

Results

compared

well

with

GC/HRMS

confirmatory

analysis.Sample

preparation

schemes

are

developed

to

remove

most

interferences

from

the

sample

extract

Unfortunately

because

many

compounds

have

similar

physical

and

chemical

properties

a

considerable

number

of

interferences

often

still

remain

in

the

cleaned

sample

extracts

Some

examples

of

interferences

on

selected

DLPCBs

using

a

phenyl

column

are

listed

below

-LSB-

-RSB-

PCB

congenerPotential

interferencePCB

and

Gas

chromatography

columns

and

methods

PCB

interferences

can

be

eliminated

or

removed

physically

as

in

MOE

Method

or

by

analyzing

extracts

on

multiple

columns

-LRB-

US

EPA

Method

-RRB-

A

number

of

analyte-specific

columns

have

been

developed

to

reduce

both

dioxin

and

PCB

interferences

and

reduce

the

need

for

multicolumn

analysis

The

standard

phenyl

columns

exhibit

multiple

coelutions

for

PCBs

-LRB-

see

above

-RRB-

and

dioxins

The

-LSB-

-RSB-

column

has

very

few

interfering

compounds

BPX-DXN

exhibits

very

low

bleed

and

enhanced

separation

over

phenyl

columns

-LSB-

-RSB-

Liquid

crystal

columns

-LSB-

-RSB-

provide

outstanding

separation

for

dioxins

and

furans

but

suffer

from

high

bleed

and

low

column

temperature

maximum

limits.Fast

GC

is

accomplished

by

reducing

inner

column

diameters

and

phase

thickness

The

number

of

theoretical

plates

per

meter

is

increased

significantly

If

the

phase

ratio

-LRB-

inner

column

diameters/phase

thickness

-RRB-

remains

constant

the

chromatography

does

not

change

and

separations

in

micobore

columns

can

be

achieved

much

faster

because

of

the

shorter

column

lengths

-LSB-

-RSB-

MacPherson

-LSB-

-RSB-

reported

the

use

of

simultaneous

dual

parallel

column

analysis

of

dioxins/furans/coplanar

PCBs

-LRB-

Fraction

A

-RRB-

on

a

m

column

and

ortho-substituted

PCBs

-LRB-

Fraction

B

-RRB-

on

a

m

column

in

under

min

Extracts

were

separated

using

activated

carbon/silica

This

combination

can

meet

GC

HRMS

QC

specifications

-LRB-

e.g.

US

EPA

-RRB-

Two-dimensional

chromatography

-LSB-

-RSB-

has

been

investigated

by

a

number

of

researchers

in

order

to

solve

coelution

issues

from

single-column

analysis

A

number

of

column

combinations

have

been

used

to

solve

coelutions

for

dioxins

and

PCBs

-LSB-

-RSB-

GC

GC

produces

very

narrow

peaks

that

can

provide

significantly

enhanced

sensitivity

increased

column

capacity

and

reduced

analysis

times

It

requires

fast

detection

which

pushes

the

limits

of

HRMS

capability

A

number

of

applications

have

been

reported

using

TOFMS

-LSB-

-RSB-

ECD

-LSB-

-RSB-

ITMS

-LSB-

-RSB-

LRMS

-LSB-

-RSB-

and

HRMS

-LSB-

-RSB-

as

detectors

for

GC

GC

The

potential

for

enhanced

chromatographic

selectivity

and

reduced

analysis

times

has

created

a

lot

of

interest

in

this

area

Mass

spectrometry

detection

methods

See

-LSB-

-RSB-

HRMS

has

been

the

definitive

detection

method

since

the

beginning

of

dioxin

analysis

-LRB-

in

-RRB-

-LSB-

-RSB-

Many

detection

techniques

have

been

investigated

-LSB-

-RSB-

but

can

match

the

selectivity

and

sensitivity

of

HRMS

-LSB-

-RSB-

Tandem

mass

spectrometry

as

hybrid/MS

-LSB-

-RSB-

triple

quadrupole

MS/MS

-LSB-

-RSB-

or

ion

trap

MS/MS

-LSB-

-RSB-

have

been

used

to

analyze

dioxins

and

furans

MS/MS

is

more

selective

than

HRMS

for

dioxins

in

most

cases

because

the

parent

molecule

loses

COCl

weighing

amu

No

other

halogenated

organic

has

been

shown

to

fragment

in

this

way

The

sensitivities

of

MS/MS

instruments

are

typically

less

than

HRMS

but

with

slight

adjustments

to

sample

size

and

final

extract

volume

GC

HRMS

QC

specifications

can

typically

be

achieved

Eppe

-LSB-

-RSB-

achieved

signal

to

noise

with

the

injection

of

fg

of

Unfortunately

the

enhanced

selectivity

observed

with

MS/MS

analysis

of

dioxins

is

not

experienced

with

PCBs

The

loss

of

from

the

parent

molecule

is

not

unique

to

polychlorinated

compounds

and

typically

interfering

peaks

can

be

detected

in

the

MS/MS

chromatograms

of

PCBs.Electron

ionization

-LRB-

EI

-RRB-

with

reduced

electron

energy

-LRB-

eV

-RRB-

is

the

typical

method

of

ionization

used

in

dioxin/DLPCB

analysis

The

reduced

electron

energy

focuses

ion

current

towards

the

molecular

ion

reduces

the

number

of

fragment

ions

and

subsequently

enhances

sensitivity

Negative

ion

chemical

ionization

-LRB-

NICI

or

NCI

-RRB-

is

also

a

low-energy

ionization

technique

-LSB-

-RSB-

which

produces

mass

spectra

with

little

fragmentation

resulting

in

enhanced

parent

ion

signals

NCI

analysis

of

dioxins

furans

and

PCBs

has

recently

been

investigated

by

Chernestsova

using

a

variety

of

reagent

gases

-LSB-

-RSB-

Detection

limits

for

PCBs

are

equivalent

to

or

lower

than

for

EI

with

a

trend

of

increasing

signal

strength

with

increasing

degree

of

chlorination

Similar

results

were

observed

for

dioxins

except

for

which

is

up

to

two

orders

of

magnitude

less

sensitive

in

NCI

than

EI

-LSB-

-RSB-

The

molecular

anion

of

readily

fragments

to

the

chloride

anion

Unfortunately

many

other

coextractables

also

fragment

to

the

chloride

anion

significantly

reducing

selectivity

and

as

a

result

NCI

has

not

been

used

routinely

for

the

analysis

of

dioxins

and

furans

Alternate

methods

of

analysis

Due

to

the

challenging

sample

preparation

selectivity

and

ultra-low

detection

requirements

the

cost

of

dioxin

analysis

is

much

higher

than

any

other

analytical

method

Researchers

have

been

searching

for

alternate

low-cost

methods

for

years

Immunoassay

-LSB-

-RSB-

and

bioassay

-LSB-

-RSB-

methods

can

reduce

costs

by

or

more

and

have

been

used

to

analyze

food

samples

and

samples

collected

from

hazardous

sites

where

very

fast

analysis

is

needed

The

relative

potencies

for

bioassays

and

cross-reactivities

for

immunoassay

methods

roughly

mimic

toxic

equivalent

factors

used

in

mass

spectrometric

methods

enabling

results

to

be

obtained

in

TEQ

directly

The

main

disadvantages

of

these

types

of

methods

are

the

inability

to

use

labeled

internal

standards

to

correct

for

recovery

and

the

determination

of

congener

profiles

for

source

apportionment

Spiked

samples

similar

to

standard

addition

quantitative

analysis

permit

recoveries

to

be

estimated

overcoming

this

problem

Recent

publications

have

shown

that

bio/immuno

methods

compare

well

with

standard

GC/HRMS

methods

in

terms

of

sensitivity

selectivity

and

accuracy

-LSB-

-RSB-

Most

analytical

laboratories

are

now

being

challenged

to

analyze

for

multiple

analyte

groups

including

polybrominated

diphenyl

ethers

-LRB-

PBDEs

-RRB-

polychlorinated

naphthalenes

as

well

as

dioxins

furans

and

DLPCBs

Multicomponent

methods

have

been

developed

for

a

variety

of

matrices

-LSB-

-RSB-

in

order

to

reduce

costs

accrued

by

multiple

separate

extractions

clean-up

and

instrumental

analyses

Analysts

must

exercise

caution

when

adding

additional

analyte

groups

to

existing

methods

Modifying

methods

to

increase

the

number

of

analytes

can

result

in

compromised

-LRB-

less

than

ideal

-RRB-

conditions

for

a

number

of

analytes

giving

rise

to

potential

interferences

and/or

reduced

recoveries

for

these

analytes

Quality

control

and

data

reporting

Dioxin

methods

inherently

include

a

number

of

quality

control

standards

and

samples

Isotope

dilution

-LRB-

ID

-RRB-

methods

are

typically

used

with

internal

standards

ID

standards

are

added

prior

to

extraction

allowing

correction

for

recovery

over

the

multistage

clean-up

procedures

The

isotopically

labeled

standards

can

also

act

as

markers

for

the

identification

of

native

analytes

in

samples

As

the

ID

standards

are

often

added

at

concentrations

times

those

expected

for

the

analytes

the

standards

can

act

as

carriers

to

improve

recoveries

of

analytes

at

ultra-trace

concentrations

and

can

offset

losses

due

to

adsorption

The

isotopically

enriched

standards

aid

in

method

development/validation

as

they

can

be

added

at

various

stages

of

the

analytical

process

to

track

down

problems

associated

with

analyte

recovery

or

method

bias.Until

recently

very

few

reference

materials

were

available

for

method

validation

and

performance

evaluation

CRMs

for

sediments

-LSB-

-RSB-

and

biota

-LSB-

-RSB-

are

now

available.Uncertainty

in

analytical

data

is

an

important

method

attribute

The

calculation

of

uncertainty

is

carried

out

using

data

from

a

number

of

sources

including

instrument

precision

linearity

fortified

matrices

MDLs

spiked

samples

and

interlaboratory

data

-LSB-

-RSB-

Uncertainties

for

dioxins

furans

and

dioxin-like

PCBs

are

listed

in

Table

in

percent

-LRB-

-RRB-

-LSB-

-RSB-

Uncertainties

for

dioxins

and

furans

range

between

and

for

most

analytes

The

two

most

significant

errors

in

the

analysis

are

the

error

in

the

standards

-LRB-

-RRB-

quoted

by

the

manufacturer

and

the

error

of

calibration

-LRB-

typically

-RRB-

that

is

accepted

by

the

analyst

Other

errors

such

as

mass

and

volumetric

determinations

should

be

less

than

Uncertainties

are

elevated

for

water

samples

over

soil

and

biota

due

to

the

greater

amount

of

labware

that

contacts

the

sample

and

the

influence

of

particles

on

the

homogeneity

of

the

sample

Similar

levels

of

uncertainty

are

observed

for

dioxin-like

PCBs

except

for

PCB

and

These

congeners

are

typically

present

at

background

levels

of

and

pg

respectively

in

the

sample

Analyte

losses

from

the

extraction

and

sample

preparation

steps

are

corrected

by

the

isotope

dilution

analytical

technique

and

should

not

be

significantly

greater

than

the

error

in

the

addition

of

the

surrogate

internal

standard

Table

of

dioxin

furan

and

DLPCB

measurements

in

selected

matrices

reported

in

percent

-LRB-

-RRB-

-LSB-

-RSB-

ParameterCAS

No.Soil

N

N

N

N

assessing

the

overall

error

and/or

uncertainty

for

determinations

of

dioxins

and

DLPCBs

two

important

factors

are

often

overlooked

First

the

sampling

error

is

not

investigated

in

many

studies

This

is

very

difficult

to

assess

properly

because

it

requires

many

more

analyses

to

be

performed

and

the

cost

of

this

work

is

often

prohibitive

Second

a

growing

trend

is

to

report

results

as

total

TEQs

and

sometimes

the

concentration

data

for

individual

congeners

used

to

perform

the

TEQ

calculation

may

not

be

reported

at

all

Also

more

than

one

set

of

toxic

factors

exist

and

some

papers

do

not

report

which

set

of

factors

were

used

or

the

format

-LRB-

e.g.

ND

ND

-RRB-

in

the

TEQ

calculation

Baccarelli

-LSB-

-RSB-

has

recently

reviewed

the

reporting

of

TEQ

values

where

non-detect

values

are

used

in

the

TEQ

calculation

It

should

be

remembered

that

the

toxic

factors

used

are

themselves

approximations

and

may

contribute

significantly

to

the

degree

of

uncertainty

in

the

interpretation

of

results

Another

unfortunate

trend

is

that

reconstructed

chromatograms

and/or

congener

patterns

from

analyses

are

being

reported

less

and

less

These

patterns

can

be

useful

when

assessing

possible

sources

of

the

dioxins/DLPCBs

detected

Sources

occurrence

and

temporal

trends

in

PCDD/Fs

Alcock

and

Jones

-LSB-

-RSB-

have

previously

reviewed

the

occurrence

and

temporal

trends

in

PCDD/Fs

in

industrialized

countries

including

Germany

the

United

States

Sweden

the

Netherlands

and

the

United

Kingdom

This

review

covered

trends

in

sediments

air

vegetation

soils

sewage

sludge

livestock

tissue

and

milk

wildlife

and

human

tissues

The

authors

reported

a

general

global

temporal

trend

in

PCDD/F

inputs

to

the

environment

PCDD/F

contamination

increased

in

the

reaching

a

maximum

in

the

and

subsequently

declined

into

the

as

a

result

of

actions

to

reduce

emissions

There

is

general

agreement

in

the

temporal

trend

data

between

European

and

North

American

studies

however

some

European

studies

have

not

determined

the

declines

in

PCDD/F

contamination

evident

in

North

America

The

US

EPA

-LSB-

-RSB-

estimated

a

decrease

in

PCDD/F

emissions

over

the

period

Päpke

-LSB-

-RSB-

reported

declines

ranging

from

for

PCDD/F

levels

in

human

adipose

tissue

blood

and

breast

milk

in

Germany

over

the

period

There

is

also

now

a

considerable

body

of

literature

reporting

the

presence

of

preindustrial

baseline

trace

levels

of

PCDD/F

contamination

in

soils

and

sediments

prior

to

the

turn

of

the

nineteenth

century

-LSB-

-RSB-

Natural

sources

of

PCDDs/Fs

can

include

forest

fires

volcanic

activity

and

other

natural

combustion

processes

-LSB-

-RSB-

Although

natural

formation

of

PCDD/Fs

had

been

postulated

much

earlier

some

previous

studies

may

have

been

compromised

as

a

result

of

extraneous

contamination

of

field

samples

or

in

the

laboratory

-LSB-

-RSB-

These

measurements

are

significant

in

determining

the

relevance

of

natural

sources

vs.

anthropogenic

sources

in

order

to

assess

requirements

for

further

reductions

in

global

PCDD/F

emissions

However

it

is

also

evident

that

any

PCDD/F

loadings

from

natural

sources

are

dwarfed

by

contemporary

emissions

from

anthropogenic

sources

PCDD/F

contamination

in

the

North

American

Great

Lakes

has

been

recently

reviewed

by

Norstrom

-LSB-

-RSB-

including

occurrence

geographical

distribution

and

temporal

trends

in

air

water

sediments

fish

seabirds

snapping

turtles

and

humans

Patterns

and

concentrations

of

PCDD/Fs

in

sediment

indicate

that

atmospheric

inputs

dominate

in

Lake

Superior

lower

Lake

Michigan

and

Lake

Erie

Inputs

from

the

Saginaw

River

to

Lake

Huron

and

from

the

Fox

River

to

upper

Lake

Michigan

are

responsible

for

additional

PCDD/PCDF

loading

to

these

areas

beyond

atmospheric

deposition

Lake

Ontario

continues

to

be

heavily

impacted

by

input

of

PCDD/Fs

particularly

from

the

Niagara

River

-LSB-

-RSB-

According

to

Alcock

and

Jones

-LSB-

-RSB-

studies

of

sediment

cores

from

the

Great

Lakes

represent

the

bulk

of

sediment

temporal

trend

data

for

PCDD/Fs

-LRB-

e.g.

-LSB-

-RSB-

-RRB-

sediment

cores

are

particularly

useful

when

studying

the

chronology

of

PCDD/F

contamination

-LRB-

e.g.

-LSB-

-RSB-

-RRB-

North

American

Great

Lakes

sediment

core

and

biomonitoring

data

generally

show

that

PCDD/F

contamination

peaked

in

most

lakes

in

the

late

to

early

followed

by

rapid

order

of

magnitude

declines

in

the

mid

to

late

-LSB-

-RSB-

The

downward

trend

leveled

off

in

some

lakes

in

the

but

appears

to

have

continued

after

the

late

presumably

in

response

to

remedial

actions

and

reductions

in

PCDD/F

emissions

to

the

atmosphere

-LSB-

-RSB-

Pearson

et

al.

-LSB-

-RSB-

reported

that

PCDD/F

accumulation

rates

in

the

early

ranged

from

ng

cm

y

for

Lake

Superior

to

ng

cm

y

for

Lake

Ontario

these

rates

represent

of

maximum

accumulation

in

the

to

In

his

review

Norstrom

noted

the

lack

of

comprehensive

congener-specific

PCDD/F

data

for

Great

Lakes

sediment

cores

-LSB-

-RSB-

Cohen

et

al.

-LSB-

-RSB-

modeled

atmospheric

transport

and

deposition

of

PCDD/Fs

to

the

Great

Lakes

using

a

United

States

and

Canadian

air

emissions

inventory

based

on

data

from

point

sources

and

area

sources

-LRB-

Fig.

-RRB-

They

identified

municipal

waste

incineration

iron

sintering

medical

waste

incineration

and

burning

of

hazardous

waste

in

cement

kilns

as

the

most

significant

sources

based

on

emissions

data

Source

areas

up

to

km

removed

from

the

Great

Lakes

were

significant

contributors

Combustion

sources

continue

to

be

the

predominant

contributor

to

global

ambient

air

levels

of

PCDD/Fs

-LSB-

-RSB-

Subsequent

long-range

transport

of

combustion

emissions

are

thought

to

be

primarily

responsible

for

the

global

ubiquity

of

PCDD/Fs

-LSB-

-RSB-

Fiedler

recently

reviewed

global

inventories

of

PCDD/Fs

using

national

air

inventories

from

countries

to

formulate

a

global

air

flux

estimated

range

of

g

TEQs

per

annum

-LSB-

-RSB-

Brzuzy

and

Hites

estimated

total

global

deposition

from

the

atmosphere

to

land

at

kg

y

-LSB-

-RSB-

A

study

published

in

by

Wagrowski

and

Hites

using

tree

bark

and

soil

samples

estimated

global

deposition

from

the

atmosphere

to

land

at

t

y

-LSB-

-RSB-

Fig.

distribution

of

United

States

and

Canadian

dioxin

emissions

for

Reproduced

with

permission

from

Cohen

et

al.

-LSB-

-RSB-

The

recent

report

by

Fiedler

also

showed

sources

of

PCDDs/Fs

in

developed

countries

to

be

different

from

developing

countries

-LSB-

-RSB-

In

developed

countries

industrial

activities

are

the

primary

source

category

while

open-burning

activities

are

the

dominant

source

category

in

developing

countries

However

burn

barrels

and

other

household

garbage

burning

methods

are

estimated

to

emerge

as

the

greatest

source

of

PCDD/F

emissions

in

North

America

subsequent

to

implementation

of

new

industrial

air

emission

standards

-LSB-

-RSB-

Open-burning

processes

include

forest

fires

pre

and

post-harvest

burning

in

agriculture

burning

in

landfills

and

backyard

burning

High

releases

were

also

estimated

from

incineration

of

medical

waste

Emissions

from

municipal

solid

waste

incineration

-LRB-

MSWI

-RRB-

were

estimated

to

account

for

of

the

PCDD/F

burden

from

industrial

sources

in

the

United

Kingdom

in

-LSB-

-RSB-

other

significant

sources

included

emissions

from

metal

industries

and

coal

combustion

Industrial

emissions

account

for

roughly

of

the

total

inventory

in

the

United

Kingdom

-LSB-

-RSB-

Other

combustion

sources

contributing

to

PCDD/F

emissions

in

industrialized

countries

include

metal

reclamation

wood

burning

chemical

fires

automobile

exhaust

cement

kilns

and

cigarette

smoke

Non-combustion

sources

include

chemical

production

-LRB-

pesticides

perchloroethylene

pentachlorophenol

-RRB-

metal

production

and

pulp

and

paper

mills

Recent

data

on

PCDD/F

emissions

for

individual

industrialized

countries

has

been

reported

for

the

Netherlands

-LSB-

-RSB-

the

United

Kingdom

-LSB-

-RSB-

the

United

States

-LSB-

-RSB-

and

Canada

-LSB-

-RSB-

A

global

PCDD/F

emission

inventory

was

reported

by

the

United

Nations

Environmental

Program

-LSB-

-RSB-

The

multimedia

occurrence

of

PCDD/Fs

globally

in

industrialized

countries

is

fairly

well

documented

however

data

are

generally

far

less

common

than

for

other

chemicals

such

as

PCBs

and

organochlorine

pesticides

UNEP

-LSB-

-RSB-

has

produced

a

report

on

global

trends

in

persistent

toxics

including

PCDD/Fs

Table

shows

selected

global

data

for

levels

of

PCDD/Fs

in

a

variety

of

matrices

based

on

information

cited

in

the

UNEP

report

Table

global

environmental

concentrations

of

PCDD/FsMatrixRegionConcentration

RangeReferenceRemarksAirEurope

fg

fg

fg

fg

pg

pg

pg

sitesSeawaterJapanND

pg

sitesSoilSeveso

pg

pg

TEQ/g

-LSB-

-RSB-

pg

TEQ/g

-LSB-

-RSB-

pg

TEQ/g

-LSB-

-RSB-

UrbanSoilThe

pg

TEQ/g

-LSB-

-RSB-

RuralSoilThe

pg

TEQ/g

-LSB-

-RSB-

ContaminatedSoilUnited

Kingdom

pg

TEQ/g

-LSB-

-RSB-

RuralSoilUnited

pg

TEQ/g

-LSB-

-RSB-

ContaminatedSoilNew

pg

TEQ/g

-LSB-

-RSB-

RuralSoilNew

pg

TEQ/g

-LSB-

-RSB-

UrbanSedimentsLake

pg

TEQ/g

-LSB-

-RSB-

Lakewide

averageSedimentsPo

pg

TEQ/g

-LSB-

-RSB-

SedimentsLake

pg

pg

TEQ/gSedimentsNew

pg

TEQ/gMarine

sedimentsNorth

pg

TEQ/gMarine

sedimentsGulf

of

pg

TEQ/gHighly

contaminatedMarine

sedimentsCatalan

pg

TEQ/g

-LSB-

-RSB-

Marine

pg

pg

TEQ/gPine

pg

TEQ/gSpruce

needlesBirds

and

pg/g

fat

-LSB-

-RSB-

EagleBirds

and

pg/g

fat

-LSB-

-RSB-

OspreyBirds

and

pg/g

fat

-LSB-

-RSB-

Spotted

OwletBirds

and

pg

dioxins/g

fat

-LSB-

-RSB-

Spotted

Owlet

liverBirds

and

pg

furans/g

fat

-LSB-

-RSB-

Spotted

Owlet

liverFishGreat

Lakes

pg

TEQ/g

-LSB-

-RSB-

FishGreat

Lakes

pg

TEQ/g

-LSB-

-RSB-

Dioxin

TEQFishGreat

Lakes

pg

TEQ/g

-LSB-

-RSB-

PCB

TEQFishFinnish

pg

TEQ/g

lipid

-LSB-

-RSB-

Herring

muscleFishAdriatic

pg

TEQ/g

lipid

-LSB-

-RSB-

Mackerel

Red

mullet

AnchovyFishJapan

pg

TEQ/gCodMarine

mammalsBird

pg

TEQ/g

blubber

-LSB-

-RSB-

Fur

sealsMarine

mammalsCanadian

pg

TEQ/g

ww

-LSB-

-RSB-

Polar

bearsMarine

mammalsJapan

pg

TEQ/g

wwWhaleMarine

mammalsJapan

pg

TEQ/g

wwWhale

fatMarine

ng/g

wwBottlenose

pg

TEQ/g

fat

-LSB-

-RSB-

Milk

and

dairy

productsFoodNorth

pg

TEQ/g

fat

-LSB-

-RSB-

Milk

and

dairy

productsFoodSouth

pg

TEQ/g

fat

-LSB-

-RSB-

Milk

and

dairy

pg

TEQ/g

fat

-LSB-

-RSB-

Milk

and

dairy

productsHuman

milkThe

pg

TEQ/g

fatHuman

pg

TEQ/g

fatHuman

pg

TEQ/g

fatHuman

milkCzech

pg

TEQ/g

fatHuman

pg

TEQ/g

fatBlood/serum/plasmaGreat

ng

TEQ/L

-LSB-

-RSB-

Recreational

ng

TEQ/g

fat

-LSB-

-RSB-

Blood/serum/plasmaA

So

pg

TEQ/g

lipid

-LSB-

-RSB-

Blood/serum/plasmaNew

pg

TEQ/g

serum

fat

-LSB-

-RSB-

samplesAll

citations

are

UNEP

-LRB-

-RRB-

-LSB-

-RSB-

or

individual

UNEP

Regional

Assessments

unless

otherwise

noted

ND

denotes

not

detected

ww

denotes

wet

weight

Profiles

of

PCDD/Fs

in

abiotic

matrices

including

air

soils

and

sediments

in

some

areas

can

reflect

the

source

emission

profile

However

a

confounding

factor

in

attributing

PCDD/F

contamination

to

specific

sources

can

be

a

contrast

in

profiles

between

source

samples

and

corresponding

profiles

in

environmental

sinks

e.g.

soils

and

sediments

due

to

degradation

weathering

or

transformation

processes

-LSB-

-RSB-

Eitzer

and

Hites

observed

a

consistent

and

systematic

change

from

a

combustion

source

profile

to

a

sediment

profile

as

a

result

of

long-range

transport

and

depositional

processes

-LSB-

-RSB-

Tysklind

et

al.

attributed

differences

in

PCDD/F

source

profiles

and

air

profiles

to

transformation

processes

including

photolytic

degradation

or

hydroxyl

radical

reactions

-LSB-

-RSB-

Koester

and

Hites

reported

that

wet

and

dry

deposition

are

important

mechanisms

for

scrubbing

PCDD/Fs

from

the

atmosphere

and

that

these

mechanisms

contribute

to

the

predominance

of

OCDD

in

sediments

-LSB-

-RSB-

Ultimately

the

PCDD/F

profile

in

environmental

samples

can

be

influenced

by

both

source

type

and

environmental

processes

Studies

of

congener

and

homolog

profiles

for

source

apportionment

have

been

carried

out

in

abiotic

matrices

biota

have

a

tendency

to

accumulate

primarily

the

compounds

due

to

congeners

being

metabolized

-LSB-

-RSB-

There

are

numerous

examples

of

studies

of

the

variation

of

PCDD/F

congener

and

homolog

profiles

with

source

-LRB-

e.g.

-LSB-

-RSB-

-RRB-

these

studies

have

also

illustrated

how

different

sources

of

PCDD/Fs

have

influenced

temporal

trends

primarily

according

to

production

use

and

disposal

of

chlorinated

organics

Principal

component

analysis

-LRB-

PCA

-RRB-

of

profiles

of

source

and

sink

samples

have

also

proven

to

be

a

valuable

tool

for

source

apportionment

-LSB-

-RSB-

O O O O O O O O B I O O O O O O O O O O O O B O O B I O B O O O O O B O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O B O O O O O O B O O O O O O O O O B O O O O O B O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O B O O B O O O O O O O O O O O O O O O O O O B O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O 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O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O B O O O O B I O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O

review
pcdd
polychlorinated dibenzofurans
pcdf
dlpcb
extraction
sample preparation
analysis
mass spectrometry
toxicity
environmental levels

polychlorinated dibenzo-p-dioxins
dioxin-like pcbs