INDUSTRIAL CHEMICALS – POSSIBLE CARCINOGEN (IARC 2B)
Nitrobenzene is an oily yellow liquid with an almond-like odour that has been used commercially for many years as a chemical intermediate. Nitrobenzene does not occur naturally – it is formed through the nitration of benzene.
Nitrobenzene may also be referred to as mononitrobenzene or nitrobenzol; other synonyms and product names are listed in the Hazardous Substances Data Bank (HSDB).
Nitrobenzene has been classified by the International Agency for Research on Cancer (IARC) as Group 2B, possibly carcinogenic to humans, based on studies in experimental animals. Mice and rats exposed to nitrobenzene had an increased incidence of tumours in multiple sites including the lungs, liver, and thyroid.[1,2] Human carcinogenicity data was limited at the time of evaluation, though few studies on nitrobenzene have been published since then.[1,4]
Data from poisonings have established adverse health effects in humans from oral, inhalation, and dermal exposure to
nitrobenzene. Acute ingestion or chronic inhalation of nitrobenzene can cause anemia. Effects on the liver (toxic hepatitis) and spleen have also been reported. Nitrobenzene can irritate skin and eyes.
Regulations and Guidelines
Occupational exposure limits (OEL) [8,9,10,11,12,13,14,15,16,17,18,19,20,21,22]
|Canadian Jurisdictions||OEL (ppm)|
|Canada Labour Code||1 [sk]|
|AB, BC, MB, NB, NL, NS
ON, QC, PE
|NT, NU, SK, YT||1 [sk]
|Other Jurisdiction||OEL (ppm)|
|ACGIH 2020 TLV||1 [sk]|
ppm = parts per million
sk = easily absorbed through the skin
stel = short term exposure limit (15 min. maximum)
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value
Canadian environmental guidelines
|Cosmetic Ingredients Hotlist||Not Permitted||2004|
|BC’s Contaminated Sites Regulation, BC Reg 375/96||Sets soil standards for the protection of human health:
Agricultural and low density residential sites: 30 μg/g
Urban park and high density residential sites: 60 μg/g
Commercial and industrial sites: 450 μg/g
Drinking water: 8 µg/L
Sets vapour standards* for the protection of human health:
µg/g = micrograms per gram
µg/L = micrograms per litre
*Vapours derived from soil, sediment, or water
|Health Canada||DSL – high priority substance with the lowest potential for exposure||2006|
|Environment Canada’s National Pollutant Release Inventory||Reportable to NPRI if manufactured, processed, or otherwise used at quantities greater than: 10 tonnes||2016|
DSL = domestic substance list
Nitrobenzene was not included in other Canadian government guidelines, standards, or chemical listings reviewed.
Nitrobenzene is used primarily to manufacture aniline (97%), which is used to produce diphenylmethane diisocyanate (MDI) for polyurethane foams.
Other uses for nitrobenzene include: manufacturing rubber chemicals, herbicides, dyes, pigments, fibres, and other chemicals; acting as a solvent in petroleum refining; and synthesizing organic compounds, including acetaminophen.[2,26] Historically, nitrobenzene was used as a food additive and ingredient in shoe polish, inks, and various disinfectants.
Canadian Production and Trade
We did not find evidence that nitrobenzene is produced in significant quantities in Canada. It was not included in the TradeMap Database in 2020. There is, however, some minor Canadian trade in aniline (the production of which is the main use for nitrobenzene), with approximately 27 tonnes exported and 1 tonne imported in 2020.
Environmental Exposures Overview
Due to its chemical properties, nitrobenzene tends to volatilize from bodies of water into the air. Thus, the greatest likelihood of environmental exposure to nitrobenzene is from ambient air. Higher ambient levels may be found in close proximity to production plants, particularly coal and petroleum refining and some chemical manufacturing plants. Nitrobenzene does not bioaccumulate.
Nitrobenzene has also been detected from sewage sludge incineration units and near hazardous waste landfills. Although it may be found in wastewater from manufacturing (particularly the organics and plastics industries), most nitrobenzene is either degraded by sewage organisms and by photolysis or lost to air, which minimizes levels in water. Potential for contamination is greater for groundwater than for surface water. In a survey of water treatment facilities in Canada in 1982, nitrobenzene was not detected in any of the 30 samples.
The photochemical reaction of nitrous oxides and benzene (from automobile exhaust) has contributed to ambient levels of nitrobenzene in the past. However, restrictions on levels of benzene in gasoline has reduced atmospheric nitrobenzene.
Nitrobenzene is reportable to the Environment Canada’s National Pollutant Release Inventory (NPRI) but no companies on record have reported any releases since its inception in 1994. No household products containing nitrobenzene are listed in the U.S. Consumer Product Information Database.
Occupational Exposures Overview
The most important routes of occupational exposure to nitrobenzene include inhaling vapours and dermal contact with vapours or liquid.
CAREX Canada estimates that approximately 530 Canadians are exposed to nitrobenzene in their workplaces. The largest industrial groups exposed to nitrobenzene are remediation and other waste management services, waste treatment and disposal, and basic chemical manufacturing.
The largest occupational groups exposed to nitrobenzene are water and waste treatment plant operators, chemists, central control and process operators in petroleum, gas and chemical processing, and chemical plant machine operators. Other potentially exposed occupations include equipment maintenance or janitorial staff working in chemical manufacturing or laboratories that use nitrobenzene.
Engineering controls (activated charcoal filters) and closed systems minimize releases of nitrobenzene during production.
For more information, see the occupational exposure estimate for nitrobenzene.
Photo: Flickr, dunktanktechnician
- Agency for Toxic Substances and Disease Registry (ATSDR). ToxFAQ Sheet for Nitrobenzene (1999) (PDF)
- Health Canada. Aniline Priority Substances List Assessment Report (1994) (PDF)
- US Environmental Protection Agency (EPA). Toxicology Review of Nitrobenzene, Draft (2007) (PDF)
- US Environmental Protection Agency (EPA). Technology Transfer Network: Air Toxics Web Site: Nitrobenzene (2000)
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