Industrial Chemicals– Possible Carcinogen (IARC 2B)
CAS No. 91-20-3
Photo: 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 Hazardous Substances Data Bank (HSDB) for more information.
In 2002, the International Agency for Research on Cancer (IARC) classified naphthalene as Group 2B, possibly carcinogenic to humans. The 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 high exposure may cause neuropathy, retinal damage, renal failure, and liver necrosis.
stel = short term exposure limit (15 min. maximum)
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value
Health Canada Cosmetics Ingredient Hotlist
Residential Indoor Air Quality Guidelines
24 hour limit: 10 μg/m3
Ontario Ambient Air Quality Criteria
10 minute: 50 µg/m3
24 hour: 100 µg/m3
Alberta Ambient Air Quality Objectives and Guidelines
Annual: 3 μg/m3
BC's Contaminated Sites Regulation, BC Reg 375/96
Sets soil standards for:
Agricultural soil: 0.1 μg/g
Urban park and residential soil: 5 μg/g
Commercial and industrial soil: 50 μg/g
µg/m3 = micrograms per cubic meter
µg/g = micrograms per gram
Naphthalene was not included in other Canadian environmental guidelines reviewed.[11,12,13,14]
DSL – high priority substance with the greatest potential for exposure
PMRA List of Formulants
List 2: potentially toxic formulant
Batch 1 [Health]
National Classification System for Contaminated Sites
Rank = "Medium hazard"
Agreement Respecting the Great Lakes Basin Ecosystem
Listed as a "Hazardous Polluting Substance"
DSL = domestic substance list
PMRA = Pest Management Regulatory Agency
CEPA = Canadian Environmental Protection Act
CMP = Chemical Management Plan
Naphthalene is primarily used to produce phthalic anhydride, which is an intermediate chemical in the manufacture of polyvinyl chloride plasticizers, pharmaceuticals, insect repellents, and other materials.[2,4] Naphthalene also acts as a solvent and is used to produce automobile paint, driveway sealants, various chemicals in the dye and synthetic leather tanning industries, surfactants, veterinary medicines, lubricants, motor fuels, and toilet deodorizers.[2,4]
Until recently, naphthalene was widely used as a moth and insect repellent. This use has been decreasing since chlorinated compounds were introduced. As of 2016, four products containing naphthalene as the active ingredient were registered with the Pest Management Regulatory Agency (PMRA) for use in Canada. Of these, three 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 primarily produced from coal tar, but can also be produced from petroleum. Coal tar and petroleum contain up to 11% and 1.3% of naphthalene, respectively.
No recent data on naphthalene manufacture in Canada was found.
Production and Trade
5,338 t of 'naphthalene'
1,710 t of 'naphthalene'
t = tonne
Inhalation and dermal contact are the most important routes of occupational exposure to naphthalene.[2,23]
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 preservation. 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 while producing mothballs, grinding wheels, and working with petroleum products, especially jet fuels.[23,24]
The general population's major source of exposure to naphthalene is indoor air. Exposure in indoor air occurs mainly by inhaling naphthalene-containing moth repellents and tobacco smoke.[2,26] Other sources of inhalation exposure include: driveway sealants, fuel additives, paints, epoxies, some hydrocarbon solvents, attached garages, and pesticides.[25,26,27,28] Systematic indoor air sampling of naphthalene has not been conducted in Canada, but numerous studies have evaluated levels of naphthalene in indoor air in specific Canadian cities.[29,30] Additional sources of naphthalene in ambient air include combusting organic material, coal and oil, forest fires, wood preserving operations, asphalt industries, and power plants.[5,31] Air emissions account for 92% of total naphthalene released to the environment. 
Dermal exposures from products treated with mothballs (blankets, clothing etc.) can be significant. Ingestion exposure to naphthalene is also possible through contaminated drinking water and food. Although naphthalene is not permitted as a food additive in Canada, as of 2008 it was 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 Environment Canada's National Pollutant Release Inventory (NPRI) and the US Household Products Database 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 (90 facilities)
Sent to off-site recycling
t = tonne
US Household Products 2016
Search Term: 'naphthalene'
Gasoline additives and fuel injector cleaners, ceramic paints, pesticides/repellents, 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 firstname.lastname@example.org.