Chemistry and Source 

Naphthalene belongs to the polycyclic aromatic hydrocarbons—PAHs for short—and is a bicyclic aromatic hydrocarbon with the chemical formula C10H8. The substance is the smallest member of the PAH group. Until the late 1950s coal tar was the principal source of naphthalene. This chemical is a component of crude oil and is found in petroleum-derived fuels and consumer products. 

History

The name “naphthalene” comes from the Persian word naphtha, meaning “oil” or “pitch.” This chemical was first extracted from coal tar in 1819 by the English chemist and physician John Kidd (1775–1851) and his extraction of naphthalene was of considerable historic significance because it demonstrated that coal had other important applications than its use as a fuel. Naphthalene has since been utilized as the source of chemical compounds with a host of important commercial and industrial uses. Later, naphthalene’s chemical structure was determined by the German chemist Richard August Carl Emil Erlenmeyer (1825–1909) and in 1841 Naphthalene was introduced by Rossbach as an antiseptic for combating typhoid fever. Although naphthalene was widely used, only nine cases of poisoning were reported between 1947 and 1956, suggesting that the condition was underdiagnosed. Consequently, there are few reports on this condition in medical journals.¹ 

Uses 

In 2000, about 100,000 metric tons (110,000 short tons) of naphthalene were produced in the United States. About 60% of that amount was used for the synthesis of phthalic anhydride [C₆H₄(CO)₂O], a compound used as the starting point in the manufacture of a host of products, including a variety of dyes, resins, lubricants, and a number of other products. One use of naphthalene is as an insecticide that is used as a moth repellent in mothballs and moth flakes and in the manufacture of fungicides. Naphthalene functions by sublimating into a gas that repels insects. Naphthalene is also used as a deodorant for toilets and urinals. However, demand for these applications has decreased with the introduction of a class of compounds known as chlorinated hydrocarbons. 

Other Uses of Naphthalene 

• Ingredient in the manufacture of the explosive known as smokeless gunpowder
• Manufacture of scintillation counters, devices used to detect and measure radioactivity

• Production of lubricants
• Manufacture of various types of dyes and coloring agents
• Antiseptic and antihelminthic (a substance used to kill disease-causing worms)
• Deodorant in toilets, diaper pails, and other settings

A large proportion of naphthalene is used as a raw material for the production of plastics. Consequently, it may be present in a wide range of consumer products.

One of the most terrible weapons used during the Vietnam War of the 1960s and 1970s was a mixture of naphthalene and palmitate, called napalm, that ignited and burned at a very high temperature causing widespread destruction of plant life, structures, and human life. 

Health Hazards

Naphthalene can be toxic by ingestion, inhalation, or absorption through the skin when humans are exposed to it in more than a passing way. In small amounts it may produce symptoms such as nausea, vomiting, headache, and fever. In larger amounts, it may induce more serious problems, including liver damage, blindness, coma, convulsions, and death. One medical problem that has been associated with exposure to large amounts of naphthalene is hemolytic anemia, a condition in which red blood cells are destroyed, resulting in fatigue, restlessness, jaundice, loss of appetite, and, in more serious cases, kidney failure. Allergic reactions and, very rarely, cataracts—have been reported (Mackell et al. 1951; Melzer-Lange and Walsh-Kelly 1989; Shannon and Buchanan 1982; Todisco et al. 1991; Valaes et al. 1963; Van Heyningen and Pirie 1967; Zuelzer and Apt 1949). Hemolytic anemia induced by naphthalene metabolites occurs particularly in newborns, fetuses, and individuals from ethnic groups with hereditary glucose-6-phosphate dehydrogenase deficiency (Lau et al. 2006).

Common Source

According to the German Environment Agency (UBA) and the Federal Office of Consumer Protection and Food Safety (BVL), smoking is cited as the primary source of exposure. 

Naphthalene is found in many consumer products, including everyday items. As part of monitoring conducted by the Federal Office of Consumer Protection and Food Safety (BVL), products intended for bodily contact—such as sports equipment handles, bicycle helmets, and watch straps—as well as toys were tested for PAHs in 2017 and 2021. Naphthalene was detected in 14 out of 22 toys. In 2024, naphthalene was found in strollers, bicycle trailers, and massage guns. In 2025, naphthalene was detected in children’s raincoats purchased in China or online. Additionally, naphthalene is present in fuels and has been detected in temporary tattoos for children.

Analytic

The National Center for Health Statistics (NCHS), part of the CDC, recommends to measure urinary levels of 1-hydroxynaphthalene (NAP1) and 2-hydroxynaphthalene (NAP2) as biomarkers for environmental and occupational exposure. Apparently, higher levels of NAP1 are positively associated with increased hemoglobin and hematocrit levels, an unexpected finding given naphthalene’s potential to cause hemolysis. Recent analyses also link higher levels of naphthalene metabolites with an increased risk of hypertension, particularly in obese individuals.² 

Sudakin DL et al. examined blood along with urine and noticed differences in results among race ethnicity. They concluded that further research is needed to better understand this association.³ The present reference or guidance value for naphthalene in blood as recommended by environmental agencies is 5 µg/L.⁴ 

Treatment

Treatment is symptomatic and resembles the therapy for hemolytic anemia, including blood transfusions to restore hemoglobin levels. Intravenous methylene blue (to convert methemoglobin) and ascorbic acid are used as specific countermeasures.

References:

1. E. Gidron, J. Leurer: Naphthalene Poisoning. In: The Lancet. Band 267, Nr. 6910, 1956, ISSN 0140-6736, S. 228–230,

2. Wang, F., Wang, Y., Wang, Y. et al. Urinary polycyclic aromatic hydrocarbon metabolites were associated with hypertension in US adults: data from NHANES 2009–2016. Environ Sci Pollut Res 29, 80491–80501 (2022).

3. Sudakin DL, Smit E, Cardenas A, Harding A. Naphthalene biomarkers and relationship with hemoglobin and hematocrit in White, Black, and Hispanic adults: results from the 2003-2004 National Health and Nutrition Examination Survey. J Med Toxicol. 2013 Jun;9(2):133-8.

4. Naphthalin/ Naphthole und Human- Biomonitoring. Stellungnahme der Kommission Human-

Biomonitoring des Umweltbundesamtes. Bundesgesundheitsbl – Gesundheitsforsch –

Gesundheitsschutz 2007;50:1357–1364