Industrial Chemicals– Possible Carcinogen (IARC 2B)
CAS No. 91-20-3
Photo Credit: Wikimedia Commons
IARC Monograph Vol. 82, 2002 (Group 2B)
Naphthalene, a polycyclic aromatic hydrocarbon, may exist as white crystalline plates, balls or powder, and has a distinctive mothball odour. Naphthalene occurs naturally in fossil fuels and is a combustion product of organic material. It has several industrial uses, primarily as a chemical intermediate.
Naphthalene may also be referred to as “naphthalin” or “white tar”. There are numerous other synonyms and product names; see HSDB for more information.
Other substances related to naphthalene which are being considered by CAREX Canada are polycyclic aromatic hydrocarbons (PAHs), coal-tar and coal-tar pitches, and creosote; the Carcinogen Profiles for these substances should be consulted for further information.
In 2002, IARC classified naphthalene as Group 2B, possibly carcinogenic to humans. Epidemiological studies available were not adequate to provide evidence of carcinogenicity in humans, however animal studies showed increased rates of nasal/olfactory and respiratory tumours in rats and mice exposed to naphthalene.[2,4]
Other adverse health effects which may result from acute exposure to naphthalene include hemolytic anemia, liver and neurological damage, gastrointestinal upset, respiratory effects and dermatitis.[3,5] Chronic exposure may cause neuropathy, retinal damage, renal failure and liver necrosis.
stel = short term exposure limit (15 min. maximum)
TLV = threshold limit value
Health Canada Cosmetics Ingredient Hotlist
Ontario Ambient Air Quality Criteria
10-minute 50 µg/m3
24 hour 100 µg/m3
µg/m3 = micrograms per cubic meter
Naphthalene is not included in other Canadian environmental guidelines reviewed.[8,9,24]
DSL - high priority substance with the greatest potential for exposure
PMRA List of Formulants
List 2: potentially toxic formulant
Batch 1 [Health]
DSL = Domestic substance list
CEPA = Canadian Environmental Protection Act
CMP = Chemical Management Plan
Naphthalene is primarily used in the production of phthalic anhydride, which is an intermediate chemical in the manufacturing of polyvinyl chloride plasticizers, pharmaceuticals, insect repellents, and other materials.[2,4] Naphthalene also acts as a solvent and is used in the production of automobile paint, driveway sealants, various chemicals in the dye and synthetic leather tanning industries, surfactants, veterinary medicines, lubricants, motor fuels and in toilet deodorizers.[2,4] Historically, naphthalene was widely used as a moth and insect repellent. However, use of naphthalene as a moth-repellent and insecticide has been decreasing since the introduction of chlorinated compounds. Currently, out of five products containing naphthalene as the active ingredient registered with the PMRA for use in Canada, four of which are moth repellents. Naphthalene may also be found in commercially available consumer products such as paints, stains and coatings. In Canada, naphthalene is also used as an oilfield chemical, solvent, refinery cleaner, fuel additive and feedstock in the petroleum industry.
Canadian Production and Trade
Naphthalene is produced in Canada and is also imported into the country. Naphthalene is primarily produced from coal tar; it can also be produced from petroleum. Coal tar and petroleum contain up to 11% and 1.3% of naphthalene, respectively.
In 2000, there were 13 manufacturers and 18 importers of naphthalene listed in Canada. In that year, total of over 52,000 tonnes of naphthalene were produced, and over 150,000 tonnes were imported.
Production and Trade
Export: Mainly to the US
12,330 t of 'naphthalene'
Import: Mainly from Japan and the US
7,480 t of 'naphthalene'
t = tonne
Inhalation and dermal contact are the most important routes of occupational exposure.[2,18] CAREX Canada estimates that approximately 7,700 Canadians are exposed to naphthalene in their workplaces. The largest industrial groups exposed are in alumina/aluminum production and processing, petroleum and coal products manufacturing, and wood preservations respectively. Other industries that may be exposed to naphthalene include coal tar and coke industries, as well as construction industries (paving and roofing).
The largest occupational groups exposed to naphthalene are petroleum gas and chemical process operators, followed by machine operators in mineral and metal processing, and labourers in mineral and metal processing. Other workers may be exposed during the production of mothballs, grinding wheels, and when exposed to petroleum products, especially jet fuels.[18, 19]
The general population’s major source of exposure to naphthalene is indoor air. Exposure in indoor air occurs mainly through inhalation of naphthalene-containing moth repellents and tobacco smoke. Other sources of inhalation exposure include: driveway sealants, fuel additives, paints, epoxies, some hydrocarbon solvents, and pesticides.[13,20] Additional ambient air sources include combustion of organic material, coal and oil, forest fires, and power plants. In 2005, 34 of 73 facilities using naphthalene reported releases into the environment. The top 4 emitters were located in Ontario.
Dermal exposures from products treated with mothballs (blankets, clothing etc.) can be significant. The concentration of naphthalene in consumer goods can range up to 13% (excluding moth balls). Ingestion exposure to naphthalene is also possible through contaminated drinking water and food. Although naphthalene is not permitted as a food additive in Canada, it is used as a solvent in coatings for food packaging. Small amounts of naphthalene used in food packaging may migrate into food.
Naphthalene levels in water, soil and sediment tend to be low except in close proximity to point sources, where there is potential for contamination. Naphthalene evaporates and degrades quickly, and is not expected to bioaccumulate.
Searches of environmental and consumer product databases yielded the following results on current potential for exposure to naphthalene in Canada:
NPRI and US Household Products Database
Search Term: 'naphthalene'
Released into Environment
Oil and gas extraction, petroleum and coal product manufacturing, Pulp and paper mills, chemical manufacturing, iron and steel mills and manufacturing (99 facilities)
Sent to off-site recycling
t = tonne
US Household Products 2013
Search Term: naphthalene
Gasoline additives and fuel injector cleaners, ceramic paints, pesticides/repellants, and oil products
Our team has performed a detailed scan of exposure control resources and assembled a compilation of key publications and resources. These are organized by type of exposure (environmental or occupational) and by specificity (general or carcinogen-specific). Please visit our Exposures Reduction Resources page to view.
We also recommend exploring the Prevention Policies Directory, a freely-accessible online tool offering information on policies related to cancer and chronic disease prevention. Providing summaries of the policies and direct access to the policy documents, the Directory allows users to search by carcinogen, risk factor, jurisdiction, geographical location, and document type. Click here to learn more about policies specific to naphthalene in the Directory. For questions about this resource, please contact a member of the Prevention Team at the Canadian Partnership Against Cancer at email@example.com.