Nitrobenzene Profile

INDUSTRIAL CHEMICALS – POSSIBLE CARCINOGEN (IARC 2B)

CAS No. 98-95-3
IARC Monograph Vol. 65, 1996 (Group 2B)

Nitrobenzene Profile

General Information

Nitrobenzene is an oily yellow liquid with an almond-like odour that has been used commercially for many years as a chemical intermediate.[1] Nitrobenzene does not occur naturally – it is formed through the nitration of benzene.[2]

Nitrobenzene may also be referred to as mononitrobenzene or nitrobenzol; other synonyms and product names are listed in the Hazardous Substances Data Bank (HSDB).[3]

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.[1] 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.[5] Acute ingestion or chronic inhalation of nitrobenzene can cause anemia.[6] Effects on the liver (toxic hepatitis) and spleen have also been reported.[7] Nitrobenzene can irritate skin and eyes.[6]

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
1 [sk]
NT, NU, SK, YT 1 [sk]
2 [stel]
Other Jurisdiction OEL (ppm)
ACGIH 2018 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

Jurisdiction Limit Year
Cosmetic Ingredients Hotlist Not Permitted 2014[23]
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:
Agricultural, urban park, residential use standard: 1 μg/m3
Commercial use standard: 1 μg/m3
Industrial use standard: 2.5 μg/m3
Parkade use standard: 2 μg/m3

2017[24]
µg/g = micrograms per gram
µg/L = micrograms per litre
*Vapours derived from soil, sediment, or water

Nitrobenzene was not included in other Canadian government environmental guidelines reviewed.[25,26,27,28,29,30,31,32]

Canadian Agencies/Organizations

Agency Designation/Position Year
Health Canada DSL – high priority substance with the lowest potential for exposure 2006[7]
Agreement Respecting the Great Lakes Basin Ecosystem Listed as a “Hazardous Polluting Substance” 1987[32]
Environment Canada’s National Pollutant Release Inventory Reportable to NPRI if manufactured, processed, or otherwise used at quantities greater than: 10 tonnes 2016[33]
DSL = domestic substance list

Nitrobenzene was not included in other Canadian government chemical listings reviewed.[34,35]

Main Uses

Nitrobenzene is used primarily to manufacture aniline (97%), which is used to produce diphenylmethane diisocyanate (MDI) for polyurethane foams.[2]

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.[2,36] Historically, nitrobenzene was used as a food additive and ingredient in shoe polish, inks, and various disinfectants.[36]

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 2016.[37] There is, however, some minor Canadian trade in aniline (the production of which is the main use for nitrobenzene), with approximately 1 tonne exported and 18 tonnes imported in 2015.[37]

Environmental Exposures Overview

Due to its chemical properties, nitrobenzene tends to volatilize from bodies of water into the air.[38] Thus, the greatest likelihood of environmental exposure to nitrobenzene is from ambient air.[2] Higher ambient levels may be found in close proximity to production plants, particularly coal and petroleum refining and some chemical manufacturing plants.[5] Nitrobenzene does not bioaccumulate.[38]

Nitrobenzene has also been detected from sewage sludge incineration units and near hazardous waste landfills.[36] 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.[38] 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.[39]

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.[6]

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.[40] No household products containing nitrobenzene are listed in the U.S. Household Products Database.[41]

Occupational Exposures Overview

The most important routes of occupational exposure to nitrobenzene include inhaling vapours and dermal contact with vapours or liquid.[2]

CAREX Canada estimates that approximately 500 Canadians are exposed to nitrobenzene in their workplaces. The largest industrial groups exposed to nitrobenzene are basic chemical manufacturing, petroleum and coal products manufacturing, and paint, coating and adhesive manufacturing.

The largest occupational groups exposed to nitrobenzene are chemists, chemical plant operators, and gas and chemical process operators. Other potentially exposed occupations include equipment maintenance or janitorial staff working in chemical manufacturing or laboratories that use nitrobenzene.[6]

Engineering controls (activated charcoal filters) and closed systems minimize releases of nitrobenzene during production.[2]

For more information, see the occupational exposure estimate for nitrobenzene.

Sources

Photo: Flickr, dunktanktechnician

1. International Agency for Research on Cancer (IARC). Monograph summary, Volume 65 (1996) (PDF)
2. National Toxicology Program (NTP). 14th Report on Carcinogens for Nitrobenzene (2016) (PDF)
3. US National Library of Medicine. Hazardous Substances Data Bank (Search term: ‘Nitrobenzene’)
6. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for Nitrobenzene (1990) (PDF)
7. Health Canada. Prioritization of the DSL (2006)
9. Government of Newfoundland and Labrador. Regulation 5,12 Occupational Health and Safety Regulations (2012)
10. Government of the Northwest Territories. Occupational Health and Safety Regulations, R-039-2015 (2016) (PDF)
12. The Canadian Legal Information Institute (CanLII). Government of Nunavut’s Occupational Health and Safety Regulations, Nu Reg 003-2016 (2010)
15. Government of Prince Edward Island. Occupational Health and Safety Act Regulations Chapter 0-1 (2013) (PDF)
17. Government of Saskatchewan. The Occupational Health and Safety Regulations, 1996 (2016) (PDF)
18. The Canadian Legal Information Institute (CanLII). Yukon’s Occupational Health Regulations, O.I.C. 1986/164 (2012) (PDF)
19. Occupational Safety and Health Administration (OSHA). Annotated PELs (2018)
23. Health Canada. Cosmetic Ingredient Hotlist (2014)
24. Government of British Columbia. Contaminated Sites Regulation B.C. Reg. 375/96 (2017)
28. The Canadian Legal Information Institute (CanLII). Ontario Drinking Water Quality Standards, O Reg 169/03 (2017)
30. Ontario Ministry of the Environment and Climate Change. Ontario’s Ambient Air Quality Criteria (2016)
31. Alberta Environment and Parks. Ambient Air Quality Objectives (2017)
32. International Joint Commission (IJC). Revised Great Lakes Water Quality Agreement of 1978 (1978) (PDF)
34. Environment and Climate Change Canada. CEPA List of Toxic Substances (1999)
36. International Programme on Chemical Safety (IPCS) INCHEM. Environmental Health Criteria Sheet for Nitrobenzene (2003) (PDF)
37. International Trade Centre. TradeMap (Free subscription required)
39. Otson R, Williams DT, Bothwell PD. “Volatile organic compounds in water at thirty Canadian potable water treatment facilities”. J Assoc Off Anal Chem1982;65(6):1370-1374
40. Environment and Climate Change Canada. National Pollutant Release Inventory (NPRI) Facility Search (Substance name: ‘Nitrobenzene’)
41. US Household Products Database (HPD). Household Products (Search term: ‘Nitrobenzene’)

Other Resources

  1. Agency for Toxic Substances and Disease Registry (ATSDR). ToxFAQ Sheet for Nitrobenzene (1999) (PDF)
  2. Health Canada. Aniline Priority Substances List Assessment Report (1994) (PDF)
  3. US Environmental Protection Agency (EPA). Toxicology Review of Nitrobenzene, Draft (2007) (PDF)
  4. US Environmental Protection Agency (EPA). Technology Transfer Network: Air Toxics Web Site: Nitrobenzene (2000)

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