Naphthalene

Naphthalene is a polycyclic aromatic hydrocarbon (PAH) naturally found in coal tar and crude oil [1]. It was first isolated from coal tar distillation in the early 19th century and became commercially important as a wood preservative, moth repellent, and chemical intermediate. Mothballs were one of the first widely used consumer pest-control products, and naphthalene remained the dominant active ingredient until paradichlorobenzene (1,4-dichlorobenzene) largely displaced it from the US market [2]. However, naphthalene mothballs are still sold and still widely used, particularly in immigrant communities from countries where they remain the standard product. Cigarette smoke is a significant source of naphthalene — tobacco combustion produces naphthalene as a PAH. Vehicle exhaust and the combustion of other petroleum products also release naphthalene. Industrial sources include naphthalene production facilities (for phthalic anhydride manufacture) and petroleum refineries [3].

Consumer use of naphthalene mothballs in poorly ventilated indoor spaces is the most common high-level exposure scenario [1]. Naphthalene sublimes — it transitions directly from solid to vapor — and in a closed closet, chest, or room, concentrations can reach levels that cause symptoms. Indoor air in homes where naphthalene mothballs have been used can have elevated naphthalene for months after use. Opening stored containers or chests in spring can release accumulated vapor [2]. Dietary exposure occurs through contaminated water and food (naphthalene is present in some foods as a natural trace component). Occupational exposure occurs in naphthalene production facilities, wood preservation, and among workers who handle moth-repellent products. Tobacco smoke is a dietary-equivalent exposure for smokers [3].

Naphthalene is classified as a possible human carcinogen (IARC Group 2B) based on strong animal evidence for nasal tumors and supporting human data [1]. The EPA classifies it as a probable human carcinogen for upper respiratory cancer. But the acute effects in children and people with G6PD deficiency (a common inherited enzyme deficiency, particularly in people of African, Mediterranean, and Asian descent) are more dramatic: naphthalene causes hemolytic anemia by damaging red blood cells — infants and children exposed to naphthalene mothballs through skin contact, inhalation, or accidental ingestion have developed life-threatening hemolytic crises [2]. Symptoms include pallor, jaundice, dark urine, fatigue, and shortness of breath. Chronic lower-level exposure causes neurological effects (headache, dizziness), liver damage, and cataracts [3].

Infants and young children in homes where naphthalene mothballs are used — particularly if balls are placed in easily accessed areas or in rooms where children spend time — face the highest risk of acute hemolytic anemia [1]. Individuals with G6PD deficiency are disproportionately sensitive and can develop severe hemolysis from relatively low exposures. Occupational workers in naphthalene production, wood preservation, and pest control have elevated chronic exposures [2]. Communities near petroleum refineries and coal tar processing facilities have elevated ambient air naphthalene levels.

Replace naphthalene mothballs with safer alternatives for moth protection: cedar blocks or chips, lavender sachets, or sealed storage containers that physically prevent moth access [1]. If naphthalene mothballs are used, use them only in tightly sealed, well-ventilated areas — never in living spaces, bedrooms, or areas where children or infants are present. Store with items in sealed chests or trunks, not in open closets [2]. When opening stored clothes that have been with naphthalene, air them outside thoroughly before bringing indoors. If you have G6PD deficiency, avoid all naphthalene contact. For occupational exposure: use local exhaust ventilation and NIOSH-approved organic vapor respirators [3]. If a child or infant is accidentally exposed and develops symptoms of pallor, jaundice, or unusual fatigue, seek emergency medical care and inform healthcare providers of potential naphthalene exposure.