Nitrobenzene

Full Profile

General Information

Nitrobenzene, an oily yellow liquid with an almond-like odour, has been used commercially for many years as a chemical intermediate.^[2] Nitrobenzene does not occur naturally but is formed by the nitration of benzene.^[3]

Nitrobenzene may also be referred to as mononitrobenzene or nitrobenzol; other synonyms and product names are listed in the HSDB.^[4]

Nitrobenzene has been classified by IARC as Group 2B, possibly carcinogenic to humans, based on studies in experimental animals.^[2] Increased incidence of tumours in multiple sites including the lungs, liver, and thyroid, were evident in mice and rats exposed to nitrobenzene.^[2,3] Human carcinogenicity data is limited.^[2]

Although no epidemiological studies are available, data from poisonings have established adverse health effects in humans from oral, inhalation and dermal exposures.^[5] Acute ingestion or chronic inhalation of nitrobenzene can cause anaemia.^[6] Effects on the liver (toxic hepatitis) and spleen have also been reported.^[9] Nitrobenzene can cause skin and eye irritation.^[6]

Nitrobenzene has been ranked by CAREX Canada as Group A (immediate high priority) for occupational settings and as Group B (possible high priority) for environmental settings. Prioritization was based on the carcinogenicity and other toxic properties of the substance, the prevalence of exposure in Canada, and the feasibility of assessing exposure.

Regulations and Guidelines

Occupational Exposure Limits (OEL)

Canadian Jurisdictions	OEL (ppm)
Canada Labour Code	1 [sk]
BC, AB, MB, NT, NU, YT	1 [sk] 2 [stel]
AB, BC, MB, ON, QC, NL, PE, NS, NB	1
SK	0.15 [sk] 0.30 [stel, sk]
Other Jurisdiction	OEL (ppm)
ACGIH 2011 TLV	1 [sk]

Canadian Environmental Guidelines

Jurisdiction	Limit	Year
Cosmetic Ingredients Hotlist	Not Permitted	2011[13]

Canadian Agencies/Organizations

Agency	Designation/Position	Year
Health Canada	DSL – high priority substance with the lowest potential for exposure	2006[9]

Main Uses

Nitrobenzene is used primarily for the manufacture of aniline (97%), used in the production of diphenylmethane diisocyanate (MDI) for polyurethane foams.^[3,11]

Miscellaneous other uses include the manufacture of rubber chemicals, herbicides, dyes, pigments, fibres and other chemicals, as a solvent in petroleum refining, and in the synthesis of organic compounds, including acetaminophen.^[3,12] Historically, nitrobenzene was used as a food additive, in shoe polish, inks, and various disinfectants.^[12]

Canadian Production and Trade

Nitrobenzene is not likely to be produced in significant quantities in Canada. There is no domestic production of aniline (which is the main use of nitrobenzene),^[11] and it is not produced from benzene.^[16]

Japan, China, India and some Western European countries have the capacity to produce nitrobenzene.^[12] However, nitrobenzene was not included in the TradeMap Database in 2010.^[17]

Occupational Exposures

Inhalation of vapours and dermal contact with vapours or liquid are the most important routes of occupational exposure to nitrobenzene.^[3]

Individuals occupationally exposed include those who work in the production of nitrobenzene itself, or who use nitrobenzene to make other products.^[6] Others potentially exposed include chemists and equipment maintenance or janitorial staff working with nitrobenzene in a laboratory setting.^[6]

Engineering controls (activated charcoal filters) and closed systems minimize releases of nitrobenzene during production.^[3]

Environmental Exposures

The greatest likelihood of environmental exposure to nitrobenzene is from ambient air.^[3] Higher ambient levels may be found in close proximity to production plants, particularly petroleum refining, leather finishing and some chemical manufacturing plants.^[6]

Nitrobenzene has also been detected from sewage sludge incineration units and near hazardous waste landfills.^[12] Although nitrobenzene may be in wastewater from manufacturing (particularly the organics and plastics industries), most is degraded by sewage organisms or lost to air, minimizing levels in water.^[6]

The photochemical reaction of nitrous oxides and benzene (from automobile exhaust) contributed to ambient levels of nitrobenzene in the past. However, with restrictions on levels of benzene in gasoline, atmospheric nitrobenzene will also decline.^[6]

Nitrobenzene does not bioaccumulate.^[12]

Nitrobenzene is reportable to the NPRI in Canada but no companies on record have reported any releases since its inception in 1994.^[18] No household products containing nitrobenzene are listed in the U.S. Household Products Database.^[19]

Sources

1. Wikimedia Commons Photo: Nitrobenzene
2. IARC monograph summary, Volume 65 (1996) (PDF)
3. NTP 12th Report on Carcinogens for Nitrobenzene (2011) (PDF)
4. Hazardous Substances Database entry for nitrobenzene (Search term: ‘nitrobenzene’)
5. Report on Carcinogens Background Document for Nitrobenzene, prepared for US Dept. of Health and Human Service (2002) (PDF)
6. ATSDR Toxicological Profile for Nitrobenzene (1990) (PDF)
7. Health Canada (2010) Guidelines for Canadian Drinking Water
8. Exposure Guidelines for Residential Indoor Air Quality (1987) (PDF)
9. Health Canada’s Prioritization of the DSL (2006)
10. CEPA List of Toxic Substances (1999)
11. CPI Product Profiles, Camford Information Services: Aniline (aminobenzene) (2001)
12. IPCS: International Programme on Chemical Safety (INCHEM): Environmental Health Criteria Sheet for Nitrobenzene (PDF)
13. Health Canada (2011) Cosmetic Ingredient Hotlist
14. Health Canada (2006) Food Additives Permitted for Use in Canada
15. NORAM Website, Nitration Group, Technologies
16. Camford Information Services Inc. CPI Product Profile: Benzene, October 2003.
17. TradeMap
18. The National Pollutant Release Inventory
19. Household Products Database (US)
20. Government of Canada (2010) Chemicals Management Plan – List of all Challenge Substances

Other Resources

1. ATSDR ToxFAQ Sheet for Nitrobenzene (PDF)
2. Health Canada, Aniline Priority Substances List Assessment Report (1994) (PDF)
3. EPA, Toxicology Review of Nitrobenzene, Draft (2007) (PDF)
4. EPA Technology Transfer Network: Air Toxics Web Site: Nitrobenzene