naphthalene exposure toxicity

UNIVERSITY OF INDONESIA

NAPHTHALENE EXPOSURE TOXICITY AND

OCCUPATIONAL SCREENING TESTS

SCIENTIFIC WORK

David Rudy Wibowo, dr

1006826036

MEDICAL FACULTY

OCCUPATIONAL MEDICINE SPECIALIST EDUCATION PROGRAM

JAKARTA

MARCH 2012

ii

ACKNOWLEDGEMENTS

First of all, I as the author would like to express praise and thanksgiving to Almighty

God, for blessing and mercy because of work papers for Scientific Activities Courses

can be resolved properly.

Task of this paper is made in order to meet the criteria for graduation in the course of

Scientific Activities in the Occupational Medicine Specialist Education Program at

the Faculty of Medicine, University of Indonesia.

I would also like to thank the lecturer of Scientific Activities Subject, especially to

Dr. dr. Astrid W. Sulistomo, MPH, SpOk. which gives a lot of input and guidance in

order to accomplish this paper.

Finally, this paper may bring benefits to those who read and study it.

Jakarta, March 2012

David R. Wibowo

(author)

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TABLE OF CONTENTS

CHAPTER I: INTRODUCTION .................................................................................. 1

I.1 Background ................................................................................................................................................ 1

I.2 Problem Statement .................................................................................................................................. 1

I.3 Objective ...................................................................................................................................................... 1

I.4 Method ......................................................................................................................................................... 2

CHAPTER II: LITERATURE REVIEW .......................................................................... 3

II.1 Chemical and physical property of naphthalene .......................................................................... 3

II.2 Naphthalene productions ..................................................................................................................... 2

II.3 Naphthalene uses ..................................................................................................................................... 3

II.3.1 As a chemical intermediate ...................................................................................................... 3

II.3.2 Wetting agent/surfactant ......................................................................................................... 4

II.3.3 As a fumigant ................................................................................................................................. 4

II.3.4 Other applications ....................................................................................................................... 4

II.4 Naphthalene as an environmental pollutant ................................................................................. 4

II.5 Occupational exposure of naphthalene ........................................................................................... 5

II.6 Naphthalene toxicokinetics .................................................................................................................. 6

II.6.1 Absorption...................................................................................................................................... 7

II.6.2 Distribution ................................................................................................................................... 7

II.6.3 Metabolism..................................................................................................................................... 8

II.7 Health effects of naphthalene .............................................................................................................. 9

II.7.1 Acute poisoning effects .............................................................................................................. 9

II.7.2 Chronic effects ............................................................................................................................ 10

II.7.2.1 Dermal effects.............................................................................................................. 11

II.7.2.2 Hematologic effects ................................................................................................... 11

II.7.2.3 Ocular effects ............................................................................................................... 12

II.7.2.4 Carcinogenic effects .................................................................................................. 12

II.8 Diagnosis of naphthalene intoxication .......................................................................................... 13

II.8.1 Blood sample collection .......................................................................................................... 13

II.9 Recommended medical surveillance .............................................................................................. 14

II.10 Biomarkers for naphthalene exposure ....................................................................................... 15

II.11 Ambient monitoring of naphthalene ........................................................................................... 18

II.12 Journal Reviews ................................................................................................................................... 18

II.12.1 Research No.1 ....................................................................................................................... 19

II.12.2 Research No.2 ....................................................................................................................... 20

II.12.3 Research No.3 ....................................................................................................................... 21

II.12.4 Research No.4 ....................................................................................................................... 22

II.12.5 Research No.5 ....................................................................................................................... 23

CHAPTER III: DISCUSSION .................................................................................... 25

CHAPTER IV: CONCLUSIONS AND RECOMMENDATIONS ...................................... 29

IV.1 Conclusions ........................................................................................................................................... 29

IV.2 Recommendations .............................................................................................................................. 30

Naphthalene Exposure Toxicity And Biomonitoring Assays

David Rudy Wibowo, dr. (1006826036)

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CHAPTER I

INTRODUCTION

I.1 Background

Naphthalene is best known as the main ingredient of traditional mothballs. It is one of

the most abundant polycyclic aromatic hydrocarbons (PAHs) found in polluted urban

environments, which are ubiquitous environmental contaminants arising from various

sources, mainly attributable to processes of incomplete combustion or pyrolysis of

organic material (fire fumes, exhaust gases from engines, incinerator fumes, tobacco

smoke, charcoal grilled food, etc). The highest work-related exposure levels are found

at workplaces where PAH-rich materials such as coke, coal tar, pitch, creosote, or

heavy oils are handled. Naphthalene, phenanthrene, and pyrene are dominant

constituents in PAH mixtures.

I.2 Problem Statement

Previous studies have shown that naphthalene can be absorbed by pulmonary,

gastrointestinal, and cutaneous routes. In animals naphthalene has been shown to

affect hematologic parameters or cause histopathological lesions of the

liver,carcinogenicity in female mice, and cataractogenicity. (1)

Exposure to high

concentrations of naphthalene may have adverse health effects, possibly causing

cancer in humans. Nevertheless, until now there is no provision governing the

implementation of periodic medical examinations on workers exposed to naphthalene

in the workplace.

I.3 Objective

The objectives of this paper are:

• To explain about the health effect of naphthalene exposure

• To establish the potential and the most relevant biomarker for occupational

naphthalene exposure.

• To provide best practice recommendations on medical examinations for workers

exposed to naphthalene



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I.4 Method

For the literature sources, the scientific literature dealing with sources, exposure

measurements, and biomonitoring of occupational naphthalene exposure was

searched. Various online databases were used, and thorough search was conducted

using PubMed (http://www.ncbi.nlm.nih.gov/pubmed/), Google Scholar

(scholar.google.com) and ProQuest (search.proquest.com). Numerous free-for-

download articles were obtained and selected, including peer reviewed journal,

dissertations, and theses which are available online as cited on the bibliography at the

end of this paper, but only the full articles were used for the journal review. Online

articles and publications from NIOSH, OSHA, ACGIH, IARC, NTP, and ATSDR

regarding naphthalene exposure, toxicity, and biomonitoring properties were also

reviewed. E-books and other internet resources, as well as the references cited in the

bibliography also take part on the review of naphthalene exposure.



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II.1 Chemical and physical

Napththalene is an organic compound with formula

polycyclic aromatic hydrocarbon

crystalline solid with a characteristic odor that is detectable a

as 0.08 ppm by mass. As an aromatic hydrocarbon, naphthalene's structure consists of

a fused pair of benzene

polycyclic aromatic hydrocarbon (PAH).

Figure 1. Naphthalene balls

Table 1. Naphthalene essential

Nomenclature

Chem. Abstr. Serv. Reg. (CAS) No.

Chem. Abstr. Name

IUPAC Systematic Name

Synonyms

Structural and molecular formulae and relative molecular mass

Molecular formula

Relative molecular mass

Physical data

Description

Boiling-point

Melting-point

Flash point

Solubility


(1006826036)

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CHAPTER II

LITERATURE REVIEW

and physical property of naphthalene

is an organic compound with formula C10H8, and

polycyclic aromatic hydrocarbon (PAH). In purified form, naphthalene is

crystalline solid with a characteristic odor that is detectable at concentrations as low

ppm by mass. As an aromatic hydrocarbon, naphthalene's structure consists of

rings. As such, naphthalene is classified as a be

polycyclic aromatic hydrocarbon (PAH).

. Naphthalene balls

essential data (1,2)

erv. Reg. (CAS) No. 91-20-3

Naphthalene

IUPAC Systematic Name Naphthalene

Naphthalin; naphthene; tar camphor; white tar

Structural and molecular formulae and relative molecular mass

C10H8

ecular mass 128.17 g mol−1

White monoclinic prismatic plates

217.9 °C, sublimes

80.2 °C

88 °C (closed cup)

Slightly soluble in water (31–34 mg/L at 25 °C);

soluble in ethanol and methanol; very soluble in

acetone, benzene, carbon disulfide, carbon

Figure 2. Naphthalene chemical structure

Figure 3. Molecular comparison

between Benzene and Naphthalene

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, and the simplest

In purified form, naphthalene is a white

t concentrations as low

ppm by mass. As an aromatic hydrocarbon, naphthalene's structure consists of

hthalene is classified as a benzenoid

Naphthalin; naphthene; tar camphor; white tar

White monoclinic prismatic plates

34 mg/L at 25 °C);

ethanol and methanol; very soluble in

acetone, benzene, carbon disulfide, carbon

. Naphthalene chemical structure

omparison

between Benzene and Naphthalene



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tetrachloride, chloroform and diethyl ether

Volatility Vapour pressure, 0.011 kPa at 25 °C; relative

vapour density (air = 1), 4.42

Stability Volatilizes appreciably at room temperature;

sublimes appreciably at

temperatures above the melting-point

ACGIH’s Threshold Limit Value (TLV) – 2001

Conversion factor mg/m3 = 5.24 × ppm

Time Weighted Average (TWA) 10 ppm

Short Term Exposure Limit (STEL) 15 ppm

Carcinogenicity A4 (not classifiable as a Human Carcinogen)

NIOSH’s Recommended Exposure Limit (REL) – 2000

Time Weighted Average (TWA) 50 mg/m3

Short Term Exposure Limit (STEL) 75 mg/m3

OSHA’s Permissible Exposure Limit (PEL) – 2001

Time Weighted Average (TWA) 50 mg/m3

II.2 Naphthalene productions

Naphthalene is a natural constituent of coal tar and crude oil. Most naphthalene is

derived from coal tar, and in fact naphthalene is the most abundant single component

of it. From the 1960s until the 1990s, significant amounts of naphthalene were also

produced from heavy petroleum fractions during petroleum refining, but today

petroleum-derived naphthalene represents only a minor component of naphthalene

production.

Although the composition of coal tar varies with the coal from which it is produced,

typical coal tar is about 10% naphthalene by weight. In industrial practice, distillation

of coal tar yields an oil containing about 50% naphthalene, along with a variety of

other aromatic compounds. This oil, after being washed with aqueous sodium

hydroxide to remove acidic components (chiefly various phenols), and with sulfuric

acid to remove basic components, undergoes fractional distillation to isolate

naphthalene. The crude naphthalene resulting from this process is about 95%

naphthalene by weight. The chief impurities are the sulfur-containing aromatic

compound benzothiophene (<2%), indane (0.2%), indene (<2%), and

methylnaphthalene (<2%). Petroleum-derived naphthalene is usually purer than that

derived from coal tar. Where required, crude naphthalene can be further purified by

recrystallization from any of a variety of solvents, resulting in 99% naphthalene by

weight, referred to as 80 °C (melting point).



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World production of naphthalene in 1987 was around one million tonnes; about one-

fourth came from western Europe (210 thousand tonnes), one-fifth each from Japan

(175 thousand tonnes) and eastern Europe (180 thousand tonnes) and one-eighth from

the USA (107 thousand tonnes). (1)

II.3 Naphthalene uses

II.3.1 As a chemical intermediate

Naphthalene is used mainly as a precursor to other chemicals. The single largest use

of naphthalene is the industrial production of phthalic anhydride, although more

phthalic anhydride is made from o-xylene. Phthalic anhydride is used as an

intermediate for polyvinyl chloride plasticizers. Other naphthalene-derived chemicals

include alkyl naphthalene sulfonate surfactants, and the insecticide 1-naphthyl-N-

methylcarbamate (carbaryl). Naphthalenes substituted with combinations of strongly

electron-donating functional groups, such as alcohols and amines, and strongly

electron-withdrawing groups, especially sulfonic acids, are intermediates in the

preparation of many synthetic dyes. The hydrogenated naphthalenes

tetrahydronaphthalene (tetralin) and decahydronaphthalene (decalin) are used as low-

volatility solvents. Naphthalene is also used in the synthesis of 2-naphthol, a

precursor for various dyestuffs, pigments, rubber processing chemicals and other

miscellaneous chemicals and pharmaceuticals. Another new use for naphthalene is in

production of polyethylene naphthalene for making plastic beer bottles. (1)

Naphthalene sulfonic acids are used in the manufacture of naphthalene sulfonate

polymer plasticizers (dispersants), which are used to produce concrete and

plasterboard (wallboard or drywall). They are also used as dispersants in synthetic and

natural rubbers, and as tanning agents (syntans) in leather industries, agricultural

formulations (dispersants for pesticides), dyes and as a dispersant in lead–acid battery

plates.

Naphthalene sulfonate polymers are produced by reacting naphthalene with sulfuric

acid and then polymerizing with formaldehyde, followed by neutralization with



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sodium hydroxide or calcium hydroxide. These products are commercially sold in

solution (water) or dry powder form.

II.3.2 Wetting agent/surfactant

Alkyl naphthalene sulfonates (ANS) are used in many industrial applications as

nondetergent wetting agents that effectively disperse colloidal systems in aqueous

media. The major commercial applications are in the agricultural chemical industry,

which uses ANS for wettable powder and wettable granular (dry-flowable)

formulations, and the textile and fabric industry, which utilizes the wetting and

defoaming properties of ANS for bleaching and dyeing operations.

II.3.3 As a fumigant

The most familiar use of naphthalene is as a household fumigant, such as in mothballs

although 1,4-dichlorobenzene (or p-dichlorobenzene) is now more widely used. In a

sealed container containing naphthalene pellets, naphthalene vapors build up to levels

toxic to both the adult and larval forms of many moths that attack textiles. Other

fumigant uses of naphthalene include use in soil as a fumigant pesticide, in attic

spaces to repel animals and insects, and in museum storage-drawers and cupboards to

protect the contents from attack by insect pests.

II.3.4 Other applications

It is used in pyrotechnic special effects such as the generation of black smoke and

simulated explosions. In the past, naphthalene was administered orally to kill parasitic

worms in livestock. Naphthalene and its alkyl homologs are the major constituents of

creosote. Naphthalene is used in engineering to study heat transfer using mass

sublimation.

II.4 Naphthalene as an environmental pollutant

The extensive use of naphthalene as an intermediate in the production of plasticizers,

resins, insecticides and surface active agents, its presence as a major component of

coal tar and coal-tar products such as creosote and its inclusion in a wide variety of

consumer products (e.g., moth-repellents) has led to its frequent occurrence in



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industrial effluents and outdoor and indoor environments. Most of the naphthalene

entering the environment is discharged to the air (92.2%), the largest releases (more

than 50%) resulting from the combustion of wood and fossil fuels and the off-gassing

of naphthalene-containing moth-repellents and deodorants. Naphthalene and other

PAHs emitted into the air by coal-fired power plants and incinerators as the main

pollutant. (3)

Non-occupational exposure typically occurs through inhaling polluted ambient and

indoor air, and cigarette smoke. In fact, naphthalene is the most abundant PAH in

cigarette smoke (4)

, and it is present in fossil fuel smoke and exhaust fumes, especially

from diesel-fuelled vehicles and jet fuels. Another source is the use of kerosene

heaters. Forest fires also contribute to the presence of naphthalene in the environment,

as the chemical is a natural combustion product of wood. (1,3)

Naphthalene is also been

detected in ash from municipal refuse and hazardous waste incinerators. (1,3)

Vehicle

exhaust contains naphthalene both due to its presence in fuel oil and gasoline, and its

formation as a combustion by-product. In addition, there are discharges of

naphthalene on land and into water from spills during the storage, transport and

disposal of fuel oil, coal tar, etc. Another source for non occupational exposure of

naphthalene include eating contaminated food and drinking water, consuming smoked

and grilled food, ingestion of house dust, use of products containing coal-tar skin

preparations or hair shampoos, and dermal absorption from contaminated soil and

water. (3)

II.5 Occupational exposure of naphthalene

From the National Occupational Exposure Survey conducted between 1981–83, the

National Institute for Occupational Safety and Health (NIOSH) estimated that

approximately 113 000 workers, about 4.6% females, in 31 major industrial groups

were potentially exposed to naphthalene in the USA. The petroleum and coal products

and oil and gas extraction industries were among the top three industries and

comprised about 21.4% of the workers potentially exposed to naphthalene.

Naphthalene has been measured in a wide variety of workplaces for many years. At

repellents manufacturing and perfumed disinfectants, the naphthalene concentrations

can be above the limit of detection (1.0 mg/m3 for a 2-h sampling time).



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Naphthalene can be absorbed through the skin as a result of handling moth repellent

or wearing working clothes stored with moth repellent. Workers may be exposed via

inhalation or dermal absorption in settings such as naphthalene production, and other

occupational setting as described in Table 2. (3)

Table 2. Occupations in which there is exposure to naphthalene (and other PAHs)

High exposure

coke ovens

coal gasification plants

chimney sweeping

petroleum refineries (mainly exposed to naphthalene and its methyl derivatives)

impregnation of wood with creosotes (mainly exposed to naphthalene, phenanthrene, and fluorene)

handling of creosote-impregnated wood (e.g. railroad and utility workers, carpenters, mainly exposed

to naphthalene, phenanthrene, and fluorene)

Medium exposure

asphalt and pavement work

roofing

aluminium production

graphite electrode production (e.g. anode production for the aluminium industry)

foundries (processing of e.g. steel and other alloys, from coal additives in moulding sand)

smokehouses (processing of meat and fish)

Low exposure

mechanics, bus garage workers, and machinists (from diesel and spark-ignition engine exhaust gases)

mining (from diesel engine exhaust gases)

use of lubricating and cutting oils (e.g. in steel production)

cooking

II.6 Naphthalene toxicokinetics

Naphthalene and other PAHs are lipophilic compounds, therefore they can be

absorbed easily through the lungs, the gastrointestinal tract, and the skin. In the body,

naphthalene metabolism is complex, leading to biologically reactive metabolites and

other metabolites that are excreted in the urine. In studies of workers, naphthalene air

concentrations were correlated with 1-naphthol and 2-naphthol urine concentrations.

(5,6) Both naphthalene and the insecticide carbaryl are metabolized to 1-naphthol,

making it difficult to distinguish between these exposures in the general population. (7)

In contrast, only naphthalene metabolism – and not carbaryl – results in 2-naphthol in

urine.



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II.6.1 Absorption

In humans, the major routes of napthalene absorption are thought to be through: (1)

the lungs and the respiratory tract after inhalation of naphthalene-containing aerosols

or of particulates to which naphthalene, in the solid state, has become absorbed; (2)

the gastrointestinal tract after ingestion of contaminated food or water; and (3) the

skin as a result of contact with naphthalene-containing materials. Animal studies

suggest that naphthalene is readily absorbed following oral or inhalation exposure.

Nevertheless, no studies were found that quantitatively determine the extent of

absorption of naphthalene in humans following oral or inhalation exposure. (1)

ACGIH

were also designated naphthalene as “Skin” (2)

– a potential significant contribution to

the overall exposure by the cutaneous route, including mucous membranes and the

eyes (but not always iritating them), either by contact with naphthalene vapors,

liquids, and solids, even though the naphthalene airborne exposures are at or below

the TLV. ACGIH also notes the use of skin notation on naphthalene is intended to

alert the industrial hygienists that air sampling alone is insufficient to quantify

exposure accurately and that measures to prevent significant cutaneous absorption

may be required.

II.6.2 Distribution

In studies of the distribution of naphthalene and other PAHs in mice, both the parent

compounds and their metabolites were found in almost all tissues and particularly

those rich in lipids. Like many other xenobiotic substances, they would be expected to

dissolve readily in, and be transported through, the external and internal lipoprotein

membranes of mammalian cells. As a result of mucociliary clearance and

hepatobiliary excretion, naphthalene and other PAHs could present for example, in

the gastrointestinal tract even when they administered by non ingestion routes. (3)

In a

survey, naphthalene was detected in 40% of the human adipose tissue samples tested,

with concentrations up to 63 ng/g lipid. Naphthalene has also been identified in

samples of human breast milk. (1)



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Figure 4. Main metabolic pathways of naphthalene and resulting products in mammals (1)

II.6.3 Metabolism

The metabolism of naphthalene and other PAHs to more water-soluble derivatives,

which is a prerequisite for their excretion, is complex. The process follows the general

scheme of xenobiotic metabolism. The hydrocarbons are first oxidized to form phase-

I metabolites, including primary metabolites, such as epoxides, phenols, and

dihydrodiols, mainly catalysed by cytochrome P450-dependent mono-oxygenases;

and then secondary metabolites, such as diol epoxides, tetrahydrotetrols, and phenol

epoxides. The phase-I metabolites are then conjugated with either glutathione, sulfate,

or glucuronic acid to form phase-II metabolites, which are much more polar and



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water-soluble than the parent hydrocarbons. Most biotransformation leads to

detoxification products that are conjugated and excreted in the urine and faeces. (3)

The major metabolic pathways of naphthalene are illustrated in Figure 4. Naphthalene

is metabolized first to naphthalene 1,2-oxide (2, see Figure 4), which can yield 1-

naphthol (3, see Figure 4) or be converted by epoxide hydrolase to trans-1,2-dihydro-

1,2-dihydroxynaphthalene (trans-1,2-dihydrodiol) (5, see Figure 4). The hydroxyl

group of 1-naphthol may also be sulfated or glucuronidated. The 1,2-dihydrodiol can

also be converted to 2-naphthol (10, see Figure 4). The epoxide is also a substrate for

glutathione S-transferase, yielding glutathione conjugates which are eventually

eliminated as mercapturic acids.

II.7 Health effects of naphthalene

Regarding toxicological effect of naphthalene, no wonder several countries in the

world take extra caution from its usage. In China, the use of naphthalene in mothballs

is forbidden. It is due partly due to the health effects as well as the wide use of natural

camphor as a replacement.

II.7.1 Acute poisoning effects

The major toxicological responses reported in humans from acute exposure of

naphthalene is hemolytic anemia and cataracts. In 1902, a man reported to develop

cataract over 13 hours after ingestion of 5 g of naphthalene. Exposure to large

amounts of naphthalene may damage or destroy red blood cells, resulting hemolytic

anemia. The lethal oral dose is 5000-15.000 mg for adults and 2000 mg taken over

two days for a child. (3)

Poisoning from naphthalene may be accidental or suicidal and occurs as a result of

either inhalation of fumes containing naphthalene or by ingestion of mothballs. There

appears to be no cause for concern about any acute toxicity of occupational exposure

or exposure of the general population, with the exception of accidental ingestion.

Accidental ingestion of household products containing naphthalene, such as mothballs

or deodorant blocks, frequently occurs in children. (1,8)

Symptoms of naphthalene

poisoning through the gastrointestinal tract include abdominal cramps with nausea,



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vomiting and diarrhoea. Patients may have headache, profuse sweating, fatigue, and

confusion. In severe poisoning there is coma with or without convulsions.These

symptoms usually present by either inhalation or from skin exposure to clothing and

bedding treated with naphthalene moth repellents. Other mild symptoms include lack

of appetite, restlessness, and pale skin. Other symptoms of severe naphthalene

poisoning are blood in the urine, renal insufficiency, disturbances in liver function

and jaundice. Hemolysis caused by exposure to naphthalene has the potential to cause

blocking of renal tubules by hemoglobin precipitation. Hepatic necrosis may also

occur. In the absence of adequate supportive treatment, death may result from acute

renal failure in adults or kernicterus in young infants.

Excessive exposure to naphthalene vapors can irritate eyes and respiratory tract. In

some animal studies, high doses of acute exposure to the rabbit eye may cause

cataract formation. It is suggested due to one of the naphthalene metabolites,

naphthalene dihydrodiol which is produced in the liver, reaches the aqueous humour,

and penetrates the lens, where it is metabolized to naphthoquinone and causes lens

opacification. (3)

The International Agency for Research on Cancer (IARC) also stated

that acute exposure causes cataracts in humans, rats, rabbits, and mice; and that

hemolytic anemia, as described above, can also occur in children and infants after

maternal exposure during pregnancy. (1)

Treatment of acute naphthalene poisoning consists of blood transfusions and

additional alkalization of the urine. In many cases, rapid recovery, without persistent

damage, was observed. In five cases of acute haemolytic anaemia in children of about

two years of age who had eaten moth balls consisting of pure naphthalene, there was

complete recovery within one to four weeks after transfusion. (3)

II.7.2 Chronic effects

Both acute and chronic exposure of naphthalene gives similar results in terms of

cataract and hemolytic anemia. Chronic exposure of mothballs containing

naphthalene and was reported to cause peripheral neuropathy and chronic renal

failure. Chronic sniffing of naphthalene containing mothballs can cause liver necrosis.



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II.7.2.1 Dermal effects

Naphthalene can cause skin irritation and in the case of a sensitized person, severe

dermatitis can occur. Workers exposed to naphthalene may develop dermatitis on

their hands, arms, legs, and abdomen. Continuous handling of naphthalene may

produce a dermatitis characterized by itching, redness, scaling, weeping and crusting

of the skin. Lesions should clear spontaneously when the exposure is terminated.

Percutaneous absorption is apparently inadequate to produce acute systemic reactions

except in newborns.

II.7.2.2 Hematologic effects

Tests in vitro revealed that it was not naphthalene itself but its metabolites 1-

naphthoquinone and 1-naphthol that cause a decrease in reduced glutathione in

erythrocytes that can lead to hemolysis. Individuals with decreased glucose-6-

phosphate dehydrogenase activity in their erythrocytes are more sensitive to

hemolytic anemia following exposure to naphthalene. Over 400 million people in the

US have an inherited condition like that which called glucose-6-phosphate

dehydrogenase deficiency. Exposure to naphthalene is more harmful for these people

and may cause hemolytic anemia at lower doses, although toxic reactions have also

been observed in individuals without red cell defects. (1)

There are several case reports regarding naphthalene exposure on glucose-6-

phosphate dehydrogenase deficiency condition. One case report recorded by IARC

mentioned about naphthalene-induced hemolysis in a black female infant deficient in

glucose-6-phosphate dehydrogenase. Fourteen of 24 children identified as having

glucose-6-phosphatase deficiency were diagnosed with hemolysis associated with

exposure to naphthalene-containing moth-repellents. Another report mentioned acute

hemolysis with the presence of Heinz bodies and fragmented erythrocytes occurred

following inhalation of naphthalene in 21 newborn Greek infants, 12 of whom had

deficient glucose-6-phosphate dehydrogenase activity in the erythrocytes. Another

two case reports of hemolytic anaemia in newborn infants secondary to maternal

ingestion of mothballs or inhalation exposure to naphthalene have been reported. This

indicates that naphthalene and/or its metabolites can pass the placenta. (1)



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II.7.2.3 Ocular effects

Repeated exposure to naphthalene fumes or dust has led to corneal ulceration,

lenticular opacities, and cataracts; however these effects can also be seen in acute

poisoning of naphthalene. (8)

Occupational exposure to naphthalene for five years was

reported to have caused cataract, and studies in animals that are recognized by WHO

confirm the fact of the ocular toxicity of naphthalene. (3)

The effect of naphthalene in

inducing formation of cataracts in the rodent eye has been attributed to the

inducibility of the cytochrome P450 system in studies in which genetically different

mouse strains were used.

II.7.2.4 Carcinogenic effects

While other PAHs clearly reported to be carcinogenic substances by hundreds of

epidemiological studies (started about 200 years after Pott's initial finding of scrotal

cancer in chimney sweeps), no direct epidemiological evidence of an association

between occupational naphthalene exposure and cancer had been reported in human.

Early carcinogenicity studies (by various routes) of naphthalene had mostly equivocal

or non-positive results, although those studies were of low power. The data available

from epidemiological studies are inadequate to evaluate the relationship between

human cancer and exposure specifically to naphthalene.

Naphthalene was tested for carcinogenicity by oral administration in one study in rats,

by inhalation in one study in mice and one in rats and in one screening assay in mice,

by intraperitoneal administration in newborn mice and in rats, and by subcutaneous

administration in two studies in rats. Exposure of rats by inhalation was associated

with induction of neuroblastomas of the olfactory epithelium and adenomas of the

nasal respiratory epithelium in males and females. Both of these tumours were

considered to be rare in untreated rats. In the screening assay study by inhalation

using only female mice, there was an increase in lung adenomas per tumour-bearing

mouse. In the inhalation study in mice, there was an increase in the incidence of

bronchiolo-alveolar adenomas in female mice. An apparent increase in the incidence

of these tumours in male mice was not statistically significant. The studies by oral

administration in rats, intraperitoneal administration in mice and subcutaneous



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administration in rats were too limited for an evaluation of the carcinogenicity of

naphthalene.

Many international acclaimed institutions have different views about naphthalene.

The U.S. National Toxicology Program (NTP) in 1992 and 2000 conducted

researches with male and female rats and mice, exposed to naphthalene by inhalation.

After the male and female rats and mice exposed to naphthalene vapors on weekdays

for two years, they exhibited evidence of carcinogenic activity based on increased

incidences of adenoma and neuroblastoma of the nose; female mice exhibited some

evidence of carcinogenic activity based on increased incidences of alveolar and

bronchiolar adenomas of the lung, and male mice exhibited no evidence of

carcinogenic activity. (9)

These additional findings prompted IARC to re-evaluate

naphthalene, which was re-classified as Group 2B: possibly carcinogenic to humans.

(1) Under California's Proposition 65, naphthalene is listed as "known to the State to

cause cancer". In view of these new data and conclusions, it is appropriate to provide

a cancer risk estimate for naphthalene for use in the Toxic Air Contaminants program,

in addition to the Reference Exposure Level already available for the chronic non-

cancer effects. However, The American Conference of Governmental Industrial

Hygienists (ACGIH) as of 2009 has not adopted the results of NTP researches, and

still classified naphthalene as substance not classifiable as a Human Carcinogen (A4).

II.8 Diagnosis of naphthalene intoxication

Diagnosis of naphthalene acute or chronic intoxication is made from the history of

exposure and the presence of clinical manifestations and signs and symptoms of

hemolysis. Laboratory investigations may show anemia, methemoglobinemia and

elevated serum bilirubin levels.

II.8.1 Blood sample collection

Collecting blood samples should be conducted to to determine the haemoglobin

content reticulocyte count, methaemoglobin level, blood gases, blood, group and to

study the blood picture. Collect serum to determine the bilirubin level.



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14

Hematological findings may include a rapid fall in erythrocyte count, hemoglobin

concentration and hematocrit, followed by a temporary increase in reticulocytes and

normoblasts in the peripheral blood. During a haemolytic crisis, the fragility of the

remaining cells is increased. Haemoglobin is present in the plasma. Red cells may

contain Heinz bodies and the cells may be fragmented showing anisocytosis and

poikilocytosis. Serum bilirubin is also elevated.

The urine may be wine coloured brown or black. The colour may vary from patient to

patient or in the same patient during the course of illness. In most but not all persons

with naphthalene induced haemolysis, a deficiency of G6PD can be demonstrated.

II.9 Recommended medical surveillance

Workers who may be exposed to chemical hazards should be monitored in a

systematic program of medical surveillance that is intended to prevent occupational

injury and disease. The program should include education of employers and workers

about work-related hazards, early detection of adverse health effects, and referral of

workers for diagnosis and treatment. The occurrence of disease or other work-related

adverse health effects should prompt immediate evaluation of primary preventive

measures (e.g., industrial hygiene monitoring, engineering controls, and personal

protective equipment). A medical surveillance program is intended to supplement, not

replace, such measures. To detect and control work-related health effects, medical

evaluations should be performed (1) before job placement as initial medical

examination, (2) periodically during the term of employment, and (3) at the time of

job transfer or termination.

NIOSH (1978) has endorsed the Occupational Health Guideline for Naphthalene. The

guideline mentioned about medical surveillance of workers exposed with

naphthalene. The following medical procedures should be made available to each

employee who is exposed to naphthalene at potentially hazardous levels: (10)

1. Initial Medical Examination:

− A complete history and physical examination: The purpose is to detect pre-

existing conditions that might place the exposed employee at increased risk, and

to establish a baseline for future health monitoring. Persons with a deficiency of



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15

glucose-6-phosphate dehydrogenase in erythrocytes may be at increased risk

from exposure, therefore the glucose-6-phosphate dehydrogenase level should

be obtained. Examination of the eyes, blood, liver and kidney should be stressed

(baseline CBC, electrolytes, liver enzymes and renal function tests, urinalysis

and urine dipstick test for hemoglobinuria). The skin should be examined for

evidence of chronic disorders.

− A complete blood count: Naphthalene has been shown to cause red blood cell

hemolysis. A complete blood count should be performed, including a red cell

count, a white cell count, and a differential count of a stained smear, as well as

hemoglobin and hematocrit.

− Urinalysis: Since kidney damage may also occur from exposure to naphthalene,

a urinalysis should be performed, including at a minimum specific gravity,

albumin, glucose, and a microscopic on centrifuged sediment.

2. Periodic Medical Examination:

The aforementioned medical examinations should be repeated on annual basis.

II.10 Biomarkers for naphthalene exposure

Several methods have been developed to assess internal exposure to naphthalene. In

most studies, urinary biomarkers to detect naphthalene is considered the same as

biomarkers for PAH metabolites, such as urinary thioethers, 1-naphthol, b-

naphthylamine, hydroxyphenanthrenes, and 1-hydroxypyrene. The latter has been

used widely as a PAH biological index of exposure. (3)

Determination of thioethers in

urine as a biomarker for PAH is of little value, since smoking is a strong confounding

factor.

Urinary 1-hydroxypyrene has been investigated as markers for PAH in several

studies. Increased 1-hydroxpyrene excretion was found at various workplaces in coke

plants, aluminum manufacturing, wood impregnation plants, foundries, and asphalt

works. The highest exposures were those of coke-oven workers and workers

impregnating wood with creosote, who took up 95% of total of PAH through the skin,

in contrast to the general population in whom uptake via food and tobacco smoking

predominate. Although 1-hydroxypyrene is widely used to detect the presence of

PAH in the urine, but it cannot be used as a biomarker for naphthalene, for



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16

naphthalene metabolism in the human body does not produce 1-hydroxypyrene as one

of its metabolites.

The 1- and 2- naphthol as a urinary metabolites of naphthalene are useful biomarkers

of exposure. Seventy-five workers exposed to naphthalene while distilling

naphthalene oil excreted 7.48 mg/L (4.35 mg/g creatinine) 1-naphthol (geometric

mean values) at the end of the work shift. For 24 non-occupationally exposed

individuals, the mean urinary concentration of 1-naphthol was 0.13 mg/L. (5)

1-

Naphthol, 2-naphthol and 1,4-naphthoquinone (14, see Figure 4) were identified in

the urine of 69 coke-plant workers exposed to a geometric mean air concentration of

naphthalene of 0.77 mg/m3 during tar distillation. The end-of-work shift urinary

concentrations of 1-naphthol and 2-naphthol were 693 and 264 µmol/mol creatinine.

The correlation coefficients between the urinary excretion of naphthols and exposure

to naphthalene were 0.64 – 0.75 for 1-naphthol and 0.70 – 0.82 for 2-naphthol. There

was a linear relationship between the overall concentration of naphthols in urine and

the naphthalene concentration in air. (6)

In a further study of a coke plant, Bieniek

(1998) measured the concentrations of 1-naphthol and 2-naphthol in urine from eight

workers in coke batteries, 11 workers in the sorting department and 29 workers in the

distillation department. The mean urinary concentrations of 1-naphthol and 2-

naphthol were 294 and 89 µmol/mol creatinine for the coke-battery workers, 345 and

184 µmol/mol creatinine for the sorters and 1100 and 630 µmol/mol creatinine for the

distillation workers, respectively. (1)

Andreoli et al. (1999) examined 15 urine samples from workers in a naphthalene-

producing plant who were exposed to 0.1 – 0.7 mg/m3 naphthalene. At the end of the

work shift, the median urinary concentrations of 2-naphthyl sulfate, 2-naphthyl

glucuronide and 1-naphthyl glucuronide were 0.030 (range, 0.014 – 0.121), 0.086

(range, 0.013 – 0.147) and 0.084 (range, 0.021 – 0.448) mg/L, respectively. (1)

Since naphthalene is the most abundant component of creosote, urinary excretion of

1-naphthol was determined in three assembly workers handling creosote-impregnated

wood. (11)

The average airborne concentration of naphthalene in the breathing zone

was approximately 1 mg/m3. The average end-of-shift concentration of 1-naphthol in



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17

urine changed from 254 – 722 (mean, 556) µmol/mol creatinine on Monday to 1820 –

2190 (mean, 2060) µmol/mol creatinine on Wednesday and 870 – 2330 (mean, 1370)

µmol/mol creatinine on Friday. The same metabolite was measured in the urine of six

workers exposed to creosote in a plant impregnating railroad ties. (12)

As measured by

use of personal air samplers, the mean airborne concentration of naphthalene in the

workers’ breathing zone was 1.5 (range, 0.37 – 4.2) mg/m3. The mean end-of-shift

concentration of 1-naphthol was 20.5 (range, 3.5 – 62.1) µmol/L. There was a good

correlation (r = 0.745) between concentrations of airborne naphthalene and urinary 1-

naphthol. No 1-naphthol was detected (limit of detection < 0.07 µmol/L) in the urine

of five non-exposed controls. Hill et al. (1995) measured 1-naphthol and 2-naphthol

in the urine of 1000 adults without occupational exposure — a subset of the National

Health and Nutrition Examination Survey III — who may have been exposed to low

levels of naphthalene or pesticides that would yield these naphthols as metabolites. (13)

The frequency of detection was 86% for 1-naphthol and 81% for 2-naphthol. The

mean concentrations were 15 and 5.4 µg/g creatinine, respectively. Concentrations of

1-naphthol ranged up to 1400 µg/g creatinine.

Yang et al. (1999) examined the relationship between certain enzyme polymorphisms

and naphthalene metabolism in 119 men who were not occupationally exposed to

polycyclic aromatic hydrocarbons. A polymorphism in exon 7 of the CYP1A1 gene

was not related to urinary naphthol excretion. Smokers with the c1/c2 or c2/c2

genotype in CYP2E1 excreted higher concentrations of 2-naphthol in the urine than

smokers with the c1/c1 genotype. Smokers deficient in glutathione S-transferase M1

(GSTM1) showed higher urinary concentrations (without correction for creatinine) of

both 1-naphthol and 2-naphthol. (1)

Nan et al. (2001) examined the effects of occupation, lifestyle and genetic

polymorphisms of CYP1A1, CYP2E1 and the glutathione S-transferases GSTM1 and

GSTT1 on the concentrations of 2-naphthol in the urine of 90 coke-oven workers in

comparison with 128 university students. The urinary excretion of 2-naphthol was

higher in the coke-oven workers (7.69 µmol/mol creatinine) than in the students (2.09

µ mol/mol creatinine). In the control group, the excretion was higher in smokers (3.94

µ mol/mol creatinine) than in nonsmokers (1.55 µmol/mol creatinine). Urinary 2-



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18

naphthol concentrations were higher in coke-oven workers with the c1/c2 or c2/c2

genotypes than in those with the more common c1/c1 genotype of CYP2E1. Urinary

2-naphthol concentrations were also higher in the urine of GSTM1-null workers than

in GSTM1-positive workers. (14)

Urinary levels of 1-hydroxynaphthalene and 2-hydroxynaphthalene (1-naphthol and

2-naphthol, respectively) reflect recent exposure. Smokers typically have urinary 1-

and 2-naphthol levels that are about 2 to 3 times higher than nonsmokers in both

occupationally exposed and general populations. (15,16)

Depending on the intensity of

exposure, workers exposed to naphthalene have been found to have geometric mean

urinary 1- and 2-naphthol levels that range from around 2 to 100 times higher than

non-exposed persons. (6,17,18)

II.11 Ambient monitoring of naphthalene

Gas–liquid chromatography is used extensively to determine the naphthalene content

of mixtures. Naphthalene can be separated easily from other aromatics. Analysis of

other impurities may require the use of high-resolution capillary columns. Selected

methods for the analysis of naphthalene in various media are presented in Table 3.

Table 3. Selected methods for analysis of naphthalene in the air (1)

Sample preparation Assay procedure Limit of detection

Adsorb (charcoal); desorb

(carbon di-sulfide)

gas chromatography / flame ionization

detection

1–10 µ g/sample; 4 µ

g/sample

Adsorb (solid sorbent);

desorb (organic solvent)

high-performance liquid

chromatography / ultraviolet detection

0.6–13 µ g/sample

Adsorb (solid sorbent);

desorb (organic solvent)

gas chromatography / flame ionization

detection

0.3–0.5 µ g/sample

II.12 Journal Reviews

In order to study the most recent screening test on workers exposed to naphthalene, a

thorough search was conducted, either on PubMed, Google Scholar, or ProQuest.com.

Keyword "naphthalene exposure" AND "biomonitoring" is used. Fourteen articles of

full and free-for-download journals was found, and then selection was done on the



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journals which is published around 10 years ago (2002 and above), and found there

was 5 articles eligible enough to assess. Using the recommendation from Evidence-

Based Medicine Working Group method in appraising article on diagnosis, there are 4

questions to be answered according to the method for determining the validity of

these articles, they are: (19)

a. Was there are an independent, blind comparison with reference standard?

b. Did the patient sample include an appropriate spectrum of patients to whom the

diagnostic test will be applied in clinical practice?

c. Did the result of the test being evaluated influence the decision to perform the

reference standard?

d. Were the methods for performing the test described in sufficient detail to permit

replication?

Below is a partial summary of the journals that have been obtained using the methods

mentioned above.

II.12.1 Research No.1

Journal title: Simultaneous analysis of naphthols, phenanthrols, and 1-

hydroxypyrene in urine as biomarkers of polycyclic aromatic hydrocarbon exposure:

intraindividual variance in the urinary metabolite excretion profiles caused by

intervention with β-naphthoflavone induction in the rat. (20)

Researchers: Elovaara E, Väänänen V, Mikkola J.

Published online: February 2003

Abstract: Two fluorimetric HPLC methods are described for the quantification of

naphthols, phenanthrols and 1-hydroxypyrene (1-OHP) in urine specimens obtained

from male Wistar rats exposed to naphthalene, phenanthrene and pyrene. The

polycyclic aromatic hydrocarbons (PAHs) were given intraperitoneally, either alone

(1.0 mmol/kg body weight) or as an equimolar mixture (0.33 mmol/kg), using the

same dosages for repeated treatments on week 1 and week 2. Between these

treatments, PAH-metabolizing activities encoded by aryl hydrocarbon (Ah) receptor-

controlled genes were induced in the rats with β-naphthoflavone (βNF).

Chromatographic separation of five phenanthrols (1-, 2-, 3-, 4-, and 9-isomers) was



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20

accomplished using two different RP C-18 columns. Despite selective detection

(programmable wavelengths), the quantification limits in the urine ranged widely: 1-

OHP (0.18 lg/l) <phenanthrols (0.34–0.45 lg/l) <2-naphthol (1.5 lg/l) <1-naphthol (4

lg/l). The relative standard deviation of the methods was good, as also was the

reproducibility. The molar fraction of the dose excreted in 24-h urine as naphthols (≤

4.0%), phenanthrols (≤ 1.1%), and 1-OHP (≤ 2.4%) was low. Urinary disposition

increased differentially in βNF-induced rats: naphthols, 9-phenanthrol (1- to-2-fold);

2-, 3-, and 4-phenanthrols (4- to 5-fold); 1-phenanthrol and 1-OHP (over 11-fold).

The OH-metabolites were analyzed before and after enzymatic hydrolysis (β-

glucuronidase/arylsulfatase). The percentage excreted as a free phenol in urine varied

for 1-OHP (2–11%), 1-naphthol (36–51%), 2-naphthol (59–65%), and the

phenanthrols (29–94%). 1-Naphthyl- and 1-pyrenyl β-D-glucuronide served as

measures for the completeness of enzymatic hydrolysis. Characteristic differences

observed in the urinary disposition of naphthalene, phenanthrene, and pyrene are

described, as well as important factors (dose, metabolic capacity, relative urinary

output) associated with biomarker validation. This intervention study clarifies

intraindividual variation in PAH metabolism and provides useful information for the

development of new methods applicable in the biomonitoring of PAH exposure in

humans.


Journal title: Effects of genetic polymorphisms in metabolic enzymes on the

relationships between 8-hydroxydeoxyguanosine levels in human leukocytes and

urinary 1-hydroxypyrene and 2-naphthol concentrations. (21)

Researchers: Kim YD, Lee CH, Nan HM, et al.

Published: March 2003

Abstract: This study was designed to investigate the relationship between

environmental exposure to polycyclic aromatic hydrocarbons (PAHs) and oxidative

stress, and to evaluate the effects of cigarette smoking and the genetic polymorphisms

of CYP1A1, CYP2E1, GSTM1, NAT2 and UGT1A6 on the relationship. The subjects

of this study were 105 healthy Korean males without occupational exposure to PAHs.

The 8-hydroxydeoxyguanosine (8-OHdG) level in leukocytes, and urinary 1-

hydroxypyrene (1-OHP) and 2-naphthol concentrations, were measured by high-



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21

performance liquid chromatography. Genetic polymorphisms of CYP1A1, CYP2E1,

GSTM1, NAT2 and UGT1A6 were identified by PCR and PCR-RFLP methods. The

8-OHdG level showed a significant correlation with the 1-OHP concentration in all

subjects (p< .001) and in smokers (p< .01), and with the 2-naphthol level in non-

smokers (p< .01). The 8-OHdG level was significantly higher in smoking rapid

acetylators than in smoking slow or intermediate acetylators, and in individuals with

the UGT1A6 wild-type than in those with the UGT1A6 mutant genotype. Significant

positive correlations between 8-OHdG and 1-OHP concentrations were found in

subjects with every genotype of the CYP1A1 and CYP2E1 genes, with the GSTM1

null-type, with the NAT2 genotype of a rapid acetylator, and with the UGT1A6 wild-

type, respectively. The urinary 2-naphthol level significantly correlated with the 8-

OHdG level only in subjects with the GSTM1 null-type. In conclusion, there is a

significant correlation between the 8-OHdG level in leukocytes and the urinary 1-

OHP concentration in the population not occupationally exposed to PAHs. This

relationship is affected by genetic polymorphisms in PAH metabolic enzymes


Journal title: Occupational Exposure to Aromatic Hydrocarbons at a Coke Plant:

Part II. Exposure Assessment of Volatile Organic Compounds. (22)

Researchers: Bieniek G , Kurkiewicz S, Wilczok T, et al.

Published: January 2004

Abstract: The objective of the study is to assess the external and internal exposures

to aromatic hydrocarbons in the tar and oil naphthalene distillation processes at a coke

plant. 69 workers engaged as operators in tar and oil naphthalene distillation

processes and 25 non-exposed subjects were examined. Personal analyses of the

benzene, toluene, xylene isomers, ethylbenzene, naphthalene, indan, indene and

acenaphthene in the breathing zone air allowed us to determine the time weighted

average exposure levels to the aromatic hydrocarbons listed above. The internal

exposure was investigated by measurement of the urinary excretion of naphthols, 2-

methylphenol and dimethylphenol isomers by means of gas chromatography with a

flame ionization detection (GC/FID). Urine metabolites were extracted after

enzymatic hydrolysis by solid-phase extraction with styrene-divinylbenzene resin.

The time-weighted average concentrations of the hydrocarbons detected in the



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breathing zone air shows that the exposure levels of the workers are relatively low in

comparison to the exposure limits. Statistically significant differences between

average concentrations of aromatic hydrocarbons (benzene, toluene, xylene isomers)

determined at the workplaces in the tar distillation department have been found .

Concentrations of the naphthalene and acenaphthene detected in workers from the oil

distillation department are higher that those from the tar distillation department.

Concentrations of naphthols, 2-methoxyphenol and dimethylphenol isomers in the

urine of occupationally exposed workers were significantly higher than those of non-

exposed subjects. Concentrations of the 2-methoxyphenol and dimethylphenol

isomers in urine were significantly higher for the tar distillation workers, whereas

concentrations of naphthols were higher for the oil naphthalene distillation workers.

Operators at the tar and naphthalene oil distillation processes are simultaneously

exposed to a mixture of different hydrocarbons, mainly benzene and naphthalene

homologues.


Journal title: Urinary Biomarkers in Charcoal Workers Exposed to Wood Smoke in

Bahia State, Brazil. (23)

Researchers: Kato M, Loomis D,. Brooks LM, et al.

Published online: June 2004

Abstract: Charcoal is an important source of energy for domestic and industrial use

in many countries. Brazil is the largest producer of charcoal in the world, with

~350,000 workers linked to the production and transportation of charcoal. To evaluate

the occupational exposure to wood smoke and potential genotoxic effects on workers

in charcoal production, we studied urinary mutagenicity in Salmonella YG1041 +S9

and urinary levels of 2-naphthol and 1-pyrenol in 154 workers of northeastern Bahia.

Workers were classified into three categories according to their working location, and

information about sociodemographic data, diet, alcohol consumption, and smoking

was obtained using a standard questionnaire. Spot urine samples were collected to

evaluate urinary mutagenicity and urinary metabolites. Urinary mutagenicity

increased significantly with exposure to wood smoke and was modified by smoking.

The prevalence odds ratio was 5.31, and the 95% confidence interval was 1.85; 15.27

for urinary mutagenicity in the highly exposed group relative to the nonexposed



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23

group. The levels of urinary metabolites increased monotonically with wood smoke

exposure and were associated with the GSTM1 null genotype, which was determined

previously. The prevalence odds ratio (95% confidence interval) for higher levels of

2-naphtol among the highly exposed was 17.13 (6.91; 42.44) and for 1-hydroxyprene

11.55 (5.32; 25.08) when compared with nonexposed workers. Urinary 2-naphthol

was the most sensitive indicator of wood smoke exposure. This is the first reported

measurement of internal exposure to wood smoke among charcoal workers, and the

results showed that these workers receive a systemic exposure to genotoxic

compounds.


Journal title: Utility of urinary 1-naphthol and 2-naphthol levels to assess

environmental carbaryl and naphthalene exposure in an epidemiology study. (7)

Researchers: Meeker JD, Barr DB, Serdar B, et al.

Published online: May 2006

Abstract: We recently reported associations between urinary 1-naphthol (1N) levels

and several intermediate measures of male reproductive health, namely sperm

motility, serum testosterone levels, and sperm DNA damage. However, because 1N is

a major urinary metabolite of both naphthalene and the insecticide carbaryl, exposure

misclassification stemming from differences in exposure source was probable and

interpretation of the results was limited. As naphthalene, but not carbaryl, is also

metabolized to 2-naphthol (2N), the relationship of urinary 1N to 2N within an

individual may give information about source of 1N. Utilizing data from two previous

studies that measured both 1N and 2N in urine of men exposed to either carbaryl or

naphthalene, the present study employed several methods to differentiate urinary 1N

arising from exposures to carbaryl and naphthalene among men in the reproductive

health study. When re-evaluating the reproductive health data, techniques for

identifying 1N source involved exploring interaction terms, stratifying the data set

based on 1N/2N ratios, and performing an exposure calibration using a linear 1N to

2N relationship from a study of workers exposed to naphthalene in jet fuel. Despite

some inconsistencies between the methods used to distinguish 1N source, we found

that 1N from carbaryl exposure is likely responsible for the previously observed

association between 1N and sperm motility, whereas 1N from naphthalene exposure



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24

is likely accountable for the association between 1N and sperm DNA damage. We

demonstrate that studies of health effects associated with carbaryl should utilize a

1N/2N ratio to identify subgroups in which carbaryl is the primary source of 1N.

Conversely, studies of naphthalene-related outcomes may utilize 2N levels to estimate

exposure.



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25

CHAPTER III

DISCUSSION

Five journals were reviewed using the recommendation from Evidence-Based

Medicine Working Group method in appraising article on diagnosis as described in

the Table 4 below.

Table 4. Critical appraisal

Was there are an

independent,

blind comparison

with reference

standard?

Did the patient

sample include an

appropriate spectrum

of patients to whom

the diagnostic test

will be applied in

clinical practice?

Did the result of the

test being evaluated

influence the decision

to perform the

reference standard?

Were the methods

for performing

the test described

in sufficient detail

to permit

replication?

Are the

results of

the study

valid?

Elovaara E,

Väänänen V,

Mikkola J

(February 2003)

No control group

or comparison

between tests

The subjects consist

of animals and not

human

The test results were

evaluated using

reference standard

(HPLC system)

Yes, every steps

carefully recorded

so the methods

allowed to be

duplicated

restricted

Kim YD, Lee CH,

Nan HM, et al.

(March 2003)

Yes, there are

comparisons

between the

groups, but not

done before the

study begins, and

not a blind one.

Non specific human

subject

The test result were

evaluated by using

other researcher’s

method

Yes, because it

refers to the

method of

examination by

reliable

laboratories

doubtful

Bieniek G ,

Kurkiewicz S,

Wilczok T, et al.

(January 2004)

Yes, there are

comparisons

between the

groups, but the

blinding methods

did not

mentioned.

Yes, there are subject

classifications to this

type of exposure, the

workers exposed to

coal tar (naphthalene

and several other

PAH), workers

exposed to

naphthalene only, and

a control group not

exposed to both.

The test results were

evaluated using

reference standard

(HPLC system)

The procedure

involves the

examination only

in general terms

only, it seems a

lot of important

things is hidden

valid

Kato M, Loomis

D,. Brooks LM, et

al. (June 2004)

No control group

or comparison

between tests

Yes, but the selection

of subjects only done

among workers

exposed to coal tar

(naphthalene and

several other PAH),

so it represents less

relevance of the

research

The test result

evaluated by trusted

labs

The procedure is

not clear enough

to understand

doubtful

Meeker JD, Barr

DB, Serdar B, et

al. (May 2006)

No control group

or comparison

between tests

Non specific subjets;

selection of subjects

drawn from general

population, and not

from high-risk

workplaces

The test results

evaluated by reliable

test agencies (Harvard

School of Public

Health, US CDC and

trusted labs)

It is possible to

duplicate the

procedure,

because the

samples were sent

to various reliable

test agences

valid



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26

Based on appraised results above, only two articles are eligible to be discussed.

Bieniek et al. (2004) conducted a cross sectional research to to assess the mixed

exposure of naphthalene and other PAHs on coke-plant workers with air and

biological monitoring. Biological monitoring was conducted by the analysis of

urinary naphthols and phenols. The study group comprised of 69 workers, average

age 38 years (range 20-65) exposed to aromatic hydrocarbons in a coke plant. They

are divided into 2 groups. A group consists of workers who are involved as operators

in tar distillation department and group B consisted of operators in naphthalene oil

distillation department. The survey was performed on the 5th day of a working week,

by which time the metabolite excretion should have reached a plateau. The air and

urine samples were collected on the same day during the day shift (6:00 AM–2:00

PM). As a control, there were chosen 25 people who are not occupationally exposed

to aromatic hydrocarbons, but are actively smokers. Air samples were collected in the

breathing zone of the workers during the work shift with a charcoal tube collector.

The analysis of the charcoal extracts was performed with a gas chromatograph

equipped with a flame ionization detector. Aromatic hydrocarbons (naphthalene,

benzene, toluene, m+p-xylene and o-xylene) were analysed as previously described

by other researchers. Meanwhile, urine samples were collected rom the exposed

workers during the last 4 h of the work shift (10:00 AM to 2:00 PM). Samples were

kept at 20°C until analysis. After processed several steps, the samples were examined

by gas chromatography method. After all examination complete, the results are: for

A-group of workers, concentrations of benzene, toluene, m+p-xylene in air are higher

(p<0.05) than for B-group, whereas concentrations of naphthalene and acenaphthene

in air are higher for B-group than the A-group (p<0.05). As with urinary samples,

there are significant differences (p<0.05) between average concentrations of urinary

metabolites of non-exposed and exposed workers. The correlation between the time-

weighted average naphthalene exposure and the urinary naphthols level, during the

shift, were examined by regression analysis (as shown in figure below). The analysis

shows the correlation between the concentration of naphthalene in air and the sum of

1-naphthol and 2-naphthol concentrations in shift-end urine of operators of the

naphthalene oil distillation. The correlation between the summary concentration of

naphthols in urine and the naphthalene concentrations in the breathing zone air are

statistically significant at p<0.001. (22)



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27

Figure 5. Relation between naphthalene in breathing-zone air and the sum of 1-naphthol and 2-

naphthol in shift-end urine of operators of the naphthalene oil distillation

Another eligible considered research comes from Meeker et al. (2006). Previous study

by the same researcher in 2004 reported the associations between urinary 1-naphthol

levels and intermediate measures of male reproductive health, including reduced

sperm motility, increased sperm DNA damage, and reduced circulating testosterone.

Therefore, the research subjects were 370 men in subfertile couples seeking infertility

diagnosis who provided a urine sample analyzed for 1-naphthol and 2-naphthol. Of

these, 330 men without a history of medical factors for infertility were primarily

white (82%) nonsmokers (91%) with a mean (SD) age of 36 (5.5) years. A single spot

urine sample was collected from each subject. Urine samples were frozen at -20 oC

and sent to the US Centers for Disease Control and Prevention (CDC) where 1-

naphthol and 2-naphthol were measured. Urinary 1-naphthol and 2-naphthol were

isolated using liquid–liquid extraction, derivatized, and measured using gas

chromatography – chemical ionization – tandem mass spectrometry. Briefly, a semen

sample and a blood sample were collected from each subject on the same day that

urine was collected. Semen samples were analyzed for sperm count and motility, and

analyzed for DNA damage. Blood samples were centrifuged and serum stored at -80

oC until analysis. Testosterone was also measured directly with a certain test kit. As

for the statistical analysis, multiple linear regression was used to assess associations

between levels of 1-naphthol in urine and intermediate measures of male reproductive



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health. Outcome measures were chosen for this study based on researcher’s previous

work. For sperm motility and DNA damage, subjects with a history of medical risk

factors for infertility (e.g. varicocele, orchidopexy) were excluded from the analysis.

For testosterone, subjects taking hormone medication (e.g. GnRH, testosterone, or

prednisone taper) were excluded. Age, body mass index, abstinence time, smoking,

and season were considered as covariates, and were included or excluded from

models based on biologic and statistical considerations. In the case of testosterone,

sex hormone binding globulin and time of day that the blood was collected were also

included in the models. The association between urinary 1-naphthol and sperm

motility was also assessed by multiple logistic regression, where subjects were

dichotomized as either above or below 50% motile sperm based on WHO reference

levels (WHO, 1999). Some approaches were used in an attempt to separate carbaryl

and naphthalene exposure, such as 1-naphthol/2-naphthol ratio compared from

previous research. As the result, measurable levels of 1-naphthol and 2-naphthol were

found in 99.7% and 74.5% of samples, respectively. As expected, 1-naphthol and 2-

naphthol levels were higher among smokers. (median = 8.13 and 9.84 µg/l,

respectively) than among nonsmokers (median = 3.13 and 0.96 µg/l, respectively).

The correlation between 1-naphthol and 2-naphthol levels was also higher among

smokers (Spearman’s correlation coefficient - 0.89 among smokers vs. 0.42 among

nonsmokers), and the ratio of 1-naphthol over 2-naphthol was lower among smokers

as anticipated (median ratio = 3.44 among nonsmokers, 0.93 among smokers). Using

the ratio of 1-naphthol to 2-naphthol to differentiate between carbaryl and

naphthalene as sources of 1-naphthol in each subject, the researcher. Found strong

associations between 1-naphthol and sperm motility and serum testosterone when

carbaryl was the likely source of 1-naphthol. The opposite was found for DNA

damage, which was more strongly associated with 1-naphthol among men with low 1-

naphthol / 2-naphthol ratios, which is indicative of naphthalene exposure. These

results suggest that sperm DNA damage is associated with exposure to naphthalene

or, perhaps, to other PAH if naphthalene is serving as a surrogate for PAH more

generally. Results from this study indicate that sperm motility and circulating

testosterone are associated with carbaryl exposure, rather than naphthalene itself. (24)



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CHAPTER IV

CONCLUSIONS AND RECOMMENDATIONS

IV.1 Conclusions

Naphthalene is a commercially important aromatic hydrocarbon which is produced

from coal tar and petroleum. It is used mainly as an intermediate in the production of

phthalic anhydride, naphthalene sulfonates and dyes and to a lesser extent as a moth-

repellent. Human exposure to naphthalene can occur during its production, in creosote

treatment of wood, in coal coking operations, during its use as an industrial

intermediate, as a result of its use as a moth-repellent, and as a result of cigarette

smoking.

Naphthalene causes cataracts in humans, rats, rabbits and mice. Humans accidentally

exposed to naphthalene by ingestion develop haemolytic anaemia. Cases of aemolytic

anaemia have been reported in children and infants after oral or inhalation exposure to

naphthalene or after maternal exposure during pregnancy.

Regarding the possible carcinogenicity of naphthalene, there is no sufficient data to

prove that naphthalene causes cancer in humans. The IARC concluded there is

inadequate evidence in humans for the carcinogenicity of naphthalene, but there is

sufficient evidence in experimental animals for the carcinogenicity of naphthalene.

Hence, naphthalene regarded as possibly carcinogenic to humans (Group 2B).

In order to detect and control work-related health effects on naphthalene exposed

workers, medical evaluations should be performed (1) before job placement, (2)

periodically during the term of employment, and (3) at the time of job transfer or

termination. An initial or periodical medical evaluations should consist:

1. A complete history and physical examination:

a. Glucose-6-phosphate dehydrogenase level.

b. Examination of the eyes, blood, liver and kidney.

c. The skin should be examined for evidence of chronic disorders.



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2. Complete Blood Count, including a red cell count, a white cell count, and a

differential count of a stained smear, as well as hemoglobin and hematocrit,

electrolytes, liver enzymes and renal function tests

3. Urinalysis: minimum specific gravity, albumin, glucose, and a microscopic

hemoglobinuria on centrifuged sediment.

Although no data are available from human studies on absorption of naphthalene, the

determination of metabolites in the urine of workers indicates that absorption does

occur, and there is a good correlation between exposure to naphthalene and the

amount of 1-hydroxynaphthalene and 2-hydroxynaphthalene (1-naphthol and 2-

naphthol, respectively) excreted in the urine. Therefore, the most suitable

biomonitoring for naphthalene exposure is 1-naphthol and 2-naphthol. Finding a

measurable amount of 1- or 2-naphthol in the urine does not mean that the level

causes an adverse health effect, but reflect recent exposure. Smokers typically have

urinary 1- and 2-naphthol levels that are about 2 to 3 times higher than nonsmokers in

both occupationally exposed and general populations. Depending on the intensity of

exposure, workers exposed to naphthalene have been found to have geometric mean

urinary 1- and 2-naphthol levels that range from around 2 to 100 times higher than

normal.

IV.2 Recommendations

For researchers in the field of occupational medicine, further studies on biomonitoring

of urinary levels of 1 - and 2-naphthol should be done in the future. Such studies may

provide occupational physicians, industrial hygienists, and government officials with

reference values, so that they can create specific guidelines for naphthalene exposure

and biomonitoring in various industries, which are not yet available in Indonesia.

As for industries which are associated with exposure to naphthalene, an improved

industrial hygiene program should be implemented in order to protect the workers

from the danger of naphthalene exposure, such as:

• Conducting proper engineering control of industrial exhaust fumes, so they cannot

endanger the workers and people outside the industry, by providing good

ventilation.



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• Encourage the exposed workers to wear specific personal protective equipment

(PPE), such as respirators and impermeable gloves when handling naphthalene-

contained chemicals or when naphthalene exposure is present in the workplace.

• Periodic measurement of the airborne exposure levels of naphthalene in the

workplace should be performed anually, to minimize the negative health effects on

the exposed workers.

• Pre employment medical examinations and annual medical surveillance should be

performed. The annual result should be compared to the baseline level to control

the hazards from naphthalene to workers’ health.

• Workers with G6PD deficiency should not work on the working environment with

high levels of exposure to naphthalene.



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naphthalene exposure toxicity

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