Polycyclic Aromatic Hydrocarbons (Part1)

8/9/2019 Polycyclic Aromatic Hydrocarbons (Part1)

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large grp. of hydrocarbons containing

two or more benzene ring fused

together or to other hydrocarbon rings

mainly formed as pyrolysis by-

products

usually exist a mixtures

lipophilic, less volatile

PAHs can either be synthetic or non-

synthetic

possess many absorbance bands

fluorescent

An illustration of

typical polycyclic

aromatic

hydrocarbons.Clockwise from top

left:

benz[e]acephenanthryl

ene, pyrene and

dibenz[a,h]anthracene

Definition
http://en.wikipedia.org/wiki/Pyrenehttp://en.wikipedia.org/wiki/Pyrene


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Research purposes

Medicines

Used to make dyes, plastic, and

pesticides

Road construction

Uses


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Alternant

Non- alternant

-equal distribution of e density

-benzenoid PAHs

-uneven distribution of e density

Benzo[a]pyreneBenz[a]anthraceneChryseneDibenz[a,h]anthracene

FluorantheneBenzo[k]fluorantheneBenzo[i]fluoranthene

Indeno[1,2,3-c,d]pyrene


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Chemical compound Chemical compound

Anthracene Benzo[a]pyrene

Chrysene Coronene

Corannulene Naphthacene

Naphthalene Pentacene

Phenanthrene Pyrene

Triphenylene Ovalene


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Forest fires

Comets

And Volcanic activities

Meteorites

Bacterial decay of organic materials

Sources

Natural/

non-synthetic

Synthetic


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Aluminum production

Coke production

Iron & steel

Refinery & oil storage

wastes

Thermal power plant

occupational exposure

Sources

Natural/

non-synthetic

Synthetic

Automobile

Domestic

Human habitats

Others

Industrial


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motor vehicle emissions

burning & incomplete

combustion of diesel and

gasoline

air craft engine

Natural/

non-synthetic

Synthetic

Automobile

Domestic

Human habitats

Others

Industrial


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Domestic

-cooking (fuel burning)

-waste refuse incineration

Human habitats

-tobacco & cigarette smoke

-smoke, charcoal broiled, orpan fried foods

Natural/

non-synthetic

Synthetic

Automobile

Domestic

Human habitats

Others

Industrial


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rural and urban sewage sludge municipal wastewater discharges run off

surface soils

surface waters

river borne pollution

commercial and pleasure boating

activities

special purpose skin creams

Natural/

non-synthetic

Synthetic

Automobile

Domestic

Human habitats

Others

Industrial


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Coal combustion :phenenthrene, fluoranthene, pyrene

Coke production :anthracene,phenenthrene,benzo(a)pyrene

Incineration :pyrene, phenenthrene, fluorantheneWood combustion :benzo(a)pyrene, fluoranthene

Industrial oil burning :fluoranthene, pyrene, chrysene

Petrol powered vehicles :fluoranthene, pyrene w/higher ratios ofbenzo(b)fluoranthene &

benzo(k)fluoranthene, thiophene cmpds.

Diesel powered vehicles :fluoranthene, pyrene w/higher ratios ofbenzo(b)fluoranthene &

benzo(k)fluoranthene, thiophene cmpds.


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PAHs enter the air mostly as releases from burning coal, cokeoven plant, automobile exhaust and wood fire.

PAHs remains in air attached to dust particles.

Most PAHs do not dissolve easily in water. They stick to solid

particles and settle to the bottom of lakes or rivers.

Microorganisms break down PAHs in soil or water after a periodof weeks to months.

In soil, PAHs are most likely to stick tightly to particles. CertainPAHs move through soil to contaminate ground water.

PAHs in remote areas such as arctic & marine atmosphere areresult of long range transport.


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Cancer (lung, skin)

Reproductive effects

Organ-system damage

Capable of depositing in the airways

and alveoli

Effects


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Breathing air containing PAHs in theworkplace of coal, tar and asphalt production

plants, smoke houses and municipal incinerators

Breathing air containing PAHs from cigarettesmoke, wood smoke, vehicle exhaust andasphalt

Coming in contact with air, water or soil ,near hazardous waste site

Eating contaminated cereals, flour,. Bread,vegetables, fruits, meats

Drinking contaminated water or milk

Nursing infants of mothers living nearhazardous waste sites may be exposed to PAHsthrough their mother's milk


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Yes, you can get sick from PAHs. But gettingsick will depend on:

How much you were exposed to (dose)

How long you were exposed (duration)

How often you were exposed (frequency)

Route of exposure: Ingesting (eating) andinhaling (breathing) is more of a risk thandermal (skin) exposure

General Health, age, lifestyle: Youngchildren, the elderly and people withchronic (on going) health problems are moreat risk to chemical exposures


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PAHs are absorbedthrough:

Inhalation

Ingestion Dermal contact

PAHs can enter your body through your lungs

when you breathe air

Occupational studies provide evidence that

inhaled PAHs are absorbed by humans

inhaled PAHs are predominantly adsorbed on

soot particles

After deposition in the airways, the particles

can be eliminated by bronchial clearance

PAHs might be partly removed from the

particles during transport on the ciliated mucosa

and may penetrate into the bronchial epithelium

cells where metabolism takes place


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Inhalation


PAHs can enter your body through drinking

water and swallowing food, soil or dust particlesthat contain PAHs

But absorption is generally slow when PAHs

are swallowed because generally you will not be

ingesting large amounts of PAHs

BaP and other PAHs are readily absorbed from

the gastrointestinal tract when present as

solutes in various dietary lipids.

Oral absorption increases with more lipophilic

compounds


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Inhalation


PAHs could enter your body if your skin comes

into contact with soil that contains high levelsof PAHs

Studies have shown that low molecular

weight (lighter) PAHs can be absorbed through

the skin but the absorption of high molecularweight (heavy) PAHs is quite limited

Dermal absorption depends on:

Molecular weight

Rapid tissue deposition after absorption

Metabolic conjugation with rapid urine

Excretion


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Once absorbed, PAHs:

enter the body

circulate in the blood

metabolized primarily in the liver and kidney


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The pattern of distribution of PAHs was

found to be similar after oral, dermal and

respiratory administration.

Detectable levels of PAHs can be observed

in most internal organs from minutes to hours

after administration.

Highest levels are obtained in the liver.

Mammary and other fatty tissues are

significant storage depots for PAHs, but owing

to the rapid metabolism no significant

accumulation seems to take place.


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For pyrene, the distribution to the tissues

was highest in the liver, kidneys and lungs,

and lowest in the heart, testes, spleen and

brain

PAHs differ with respect to distribution

patterns and lipophilic properties [Busbee et

al. 1990].

Because of their lipophilic nature, PAHs

can accumulate in breast milk and adipose

tissue.

However, biliary and urinary excretion of

PAHs is relatively efficient because of the

wide distribution of enzymes that transform

PAHs into polar metabolites.


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The lipophilicity of PAHs enables them toreadily penetrate to the human body and

remain there indefinitely.


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The enzyme primarily responsible for PAH

metabolism is the microsomal mixed function

oxidase system.

Epoxides are the major intermediates in

oxidative metabolism of aromatic double

bonds.


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S O

NH

CH

2

C

O

O

NH

O

NH2

C O

O

OH

OH

OH

Glutathione-S-Transferase

Glutathione-S-

Urine

O

OH

OH


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Diol epoxides are highly reactive and

mutagenic.

Potent carcinogen bay region benzopyrene bay region is the space between the aromatic

rings of PAH molecules


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Metabolizing Capacity

Liver>lung>intestinal mucosa> skin> kidneys.

Metabolism may also take place in nasal

tissues, mammary glands, spleen, brain, hair

follicles, erythrocytes, platelets, leukocytes,

placenta and uterus.


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Animal and Human fetal tissues are able to

metabolize PAH but in a low rate compared

to adult tissues.


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Glucuronide and Glutathione sulfate

conjugates are excreted in the bile and in

urine.

Glutathione conjugates are further

metabolized in the kidneys to form

mercaptouric acids and excreted as urine


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The hydroxylated metabolites of PAHs are

excreted in the urine both as free

hydroxylated metabolite or hydroxylated

metabolite conjugated with glucuronic acids

or sulfate.


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The most common measured metabolite is 1-

hydroxypyrene.

Metabolism is a prerequisite for hepatobiliaryexcretion and elimination through the feces

regardless of the route of entry.


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Very structurally dependent, withisomers (PAHs with the same formula

and number of rings) varying from

being nontoxic to being extremely toxic

benzo[a]pyrene- first chemicalcarcinogen to be discovered

High prenatal exposure to PAH is

associated with lower IQ.


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PAHs can affect lungs (when swallowed and

which can lead to pneumonia), central nervous

system, the heart, bone marrow, and kidneys

Signs of hydrocarbon poisoning may include

severe coughing, stomach problems, nausea,

drowsiness and poor coordination. This may lead

to seizures.


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PAHs are changed into chemicals that can

attach to substances within the body.

The presence of PAHs attached to these

substances can then be measured in body tissues

or blood after exposure to PAHs.

PAHs or their metabolites can also bemeasured in urine, blood, or body tissues.

R ti t f


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Remove patient from exposure

The patient should remove all clothing and

personal effects

Double-bag soiled clothing and place in sealed

container clearly labeled biohazard

Brush away any adherent solid particles from

the patient

Wash hair and all contaminated skin with

copious amounts of water (preferably warm) and

soap for at least 10-15 minutes. Decontaminateopen wounds first and avoid contamination of

unexposed skin

Pay attention to skin folds, axillae, ears,

fingernails, genital areas and feet.

Decontaminationand First Aid

Dermal contact

Ocular exposure

Inhalation

Ingestion


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Remove contact lenses if necessary and

immediately irrigate the affected eye

thoroughly with water or 0.9% saline for at

least 10-15 minutes

Patients with corneal damage or those

whose symptoms do not resolve rapidly

should be referred for urgentophthalmological assessment


Dermal contact

Ocular exposure

Inhalation

Ingestion


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Ensure a clear airway and adequate

ventilation

Give oxygen to symptomatic patients

Apply other supportive measures as

indicated by the patients clinical

conditon


Dermal contact

Ocular exposure

Inhalation

Ingestion


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Give oxygen to symptomatic patients

Apply other supportive measures as

indicated by the patients clinical

conditon


Dermal contact

Ocular exposure

Inhalation

Ingestion


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Chimney sweeps


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Polynuclear aromatic hydrocarbons (PAH). In: Air


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oly uclea a o at c yd oca bo s ( ). :

quality guidelines for Europe.Copenhagen,World

Health Organization Regional Office for Europe,

1987, pp. 105117.

BAEK, S.O. ET AL. A review of atmospheric

polycyclic aromatic hydrocarbons: sources, fate and

behavior. Water, air, and soil pollution, 60: 279300

(1991).

Glenn Michael Roy (1995). Activated carbonapplications in the food and pharmaceutical

industries. CRC Press. p. 125. ISBN 1566761980.

http://books.google.com/books?

id=nmmpK0oDE20C&pg=PA125.

Agency for Toxic Substances and Disease Registry

(ATSDR). 1995. Toxicological profile for polycyclic

aromatic hydrocarbons (PAHs). Atlanta, GA: U.S.

Department of Health and Human Services, Public

Polycyclic Aromatic Hydrocarbons (Part1)

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