Nitrobenzene

by Posted on

2023-02-17

Nitrobenzene is an organic compound with the chemical formula C6H5NO2. It is a pale yellow oil with an almond-like odour. It freezes to give greenish-yellow crystals. [1] The solid crystals melt at 6 degrees celsius and the liquid boils at 211 degrees celsius. Nitrobenzene is flammable. It dissolves only slightly in water, but mixes well with most organic (carbon-containing) solvents. Nitrobenzene is one of a group of substances known as the volatile organic compounds (VOCs). [2]

Uses [1,2]

The main use of Nitrobenzene is to make the important industrial chemical Aniline, which is used in the manufacture of plastics and rubbers, dyes, agrochemicals and petrol additives. Furthermore, nitrobenzene is used in shoe and floor polishes, leather dressings, paint solvents, and other materials to mask unpleasant odours. Redistilled, as oil of mirbane, nitrobenzene has been used as an inexpensive perfume for soaps. A significant merchant market for nitrobenzene is its use in the production of the analgesic paracetamol (also known as acetaminophen).

Sources & Routes of Exposure [3]

Sources of Exposure

Exposure can occur in the workplace during its manufacture, processing, and use, or in the environment following releases to air, water, land, and groundwater. Exposure can also occur when people use nitrobenzene-containing paints and polishes.

Routes of Exposure

Nitrobenzene enters the body when people breathe air or consume food or water contaminated with nitrobenzene. It can also be absorbed through skin contact. It does not remain in the body due to its breakdown and removal.

Health Effects [4]

Acute Effects

Acute inhalation, oral, and dermal exposure to nitrobenzene in humans produces methemoglobinemia, in which haemoglobin (which carries oxygen in the blood) is converted to methemoglobin, resulting in lowering the amount of oxygen released to the tissues of the body. This lowered oxygen capacity is associated with fatigue, weakness, dyspnea, headache, and dizziness. At higher concentrations, depressed respiration, bluish-grey skin, disturbed vision, and coma may occur. Animal studies have reported methemoglobinemia and effects on the liver, kidney, spleen, and central nervous system (CNS) from acute inhalation exposure to nitrobenzene. Tests involving acute exposure of rats have shown nitrobenzene to have moderate acute toxicity from oral exposure.

Chronic Effects

Chronic exposure to nitrobenzene in humans also results in methemoglobinemia. There is also some evidence that the human liver is damaged after chronic inhalation of nitrobenzene. Chronic, inhalation exposure to nitrobenzene in animals results in methemoglobinemia, and effects on the liver and kidney. EPA has calculated (by an alternate method) a provisional Reference Concentration (RfC) of 0.002 milligrams per cubic metre (mg/m3) for nitrobenzene based on haematological, adrenal, renal, and hepatic effects in mice. The Reference Dose (RfD) for nitrobenzene is 0.0005 milligrams per kilogram body weight per day (mg/kg/d) based on haematologic, adrenal, renal, and hepatic lesions in rats and mice.

Reproductive/Developmental Effects

No information is available on the reproductive or developmental effects of nitrobenzene in humans. Developmental effects, such as birth defects or embryotoxic effects, have not been reported in animal studies with inhalation exposure to nitrobenzene. However, reproductive effects, including a decrease in fertility, reduced testicular weights, and decreased sperm production have been noted in inhalation and oral animal studies.

Cancer Risk

EPA has classified nitrobenzene as a Group D, not classifiable as to human carcinogenicity.

Environment Effects [2]

High-level exposure to Nitrobenzene is classed as toxic to wildlife, particularly aquatic life. However, it breaks down quickly in the environment and so only very large releases (resulting from an accidental spill for example) are likely to cause harm. Nitrobenzene is broken down quickly in the atmosphere. In soil and water, it is readily broken down by micro-organisms. Nitrobenzene is not accumulated by fish or animals, but some plants can take it up and store it. As a VOC, Nitrobenzene may be involved in the formation of ground level ozone, which can damage crops and materials. It is not considered likely that Nitrobenzene pollution has any effects on the global environment.

Safety [5]

First Aid Measures

  • Eye Contact: Check for and remove any contact lenses. Immediately flush eyes with running water for at least 15 minutes, keeping eyelids open. Cold water may be used. Do not use an eye ointment. Seek medical attention.
  • Skin Contact: After contact with skin, wash immediately with plenty of water. Gently and thoroughly wash the contaminated skin with running water and non-abrasive soap. Be particularly careful to clean folds, crevices, creases and groin. Cover the irritated skin with an emollient. If irritation persists, seek medical attention. Wash contaminated clothing before reusing.
  • Serious Skin Contact: Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream. Seek immediate medical attention.
  • Inhalation: Allow the victim to rest in a well ventilated area. Seek immediate medical attention.
  • Serious Inhalation: Evacuate the victim to a safe area as soon as possible. Loosen tight clothing such as a collar, tie, belt or waistband. If breathing is difficult, administer oxygen. If the victim is not breathing, perform mouth-to-mouth resuscitation. Seek medical attention.
  • Ingestion: Do not induce vomiting. Examine the lips and mouth to ascertain whether the tissues are damaged, a possible indication that the toxic material was ingested; the absence of such signs, however, is not conclusive. Loosen tight clothing such as a collar, tie, belt or waistband. If the victim is not breathing, perform mouth-to-mouth resuscitation. Seek immediate medical attention.

Exposure Control & Personal Protection

Engineering Controls

Provide exhaust ventilation or other engineering controls to keep the airborne concentrations of vapours below their respective threshold limit value. Ensure that eyewash stations and safety showers are proximal to the work station location.

Personal Protective Equipment

It is recommended that the following personal protective equipment be used when handling nitrobenzene:

  • Splash goggles;
  • Lab coat;
  • Vapour respirator (be sure to use an approved/certified respirator or equivalent);
  • Gloves

Personal Protection in Case of a Large Spill:

  • Splash goggles;
  • Full suit;
  • Vapour respirator;
  • Boots;
  • Gloves;
  • A self contained breathing apparatus should be used to avoid inhalation of the product.
  • Note: Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling this product.

Regulation [6,7]

United States

EPA: The Environmental Protection Agency recommends that levels in lakes and streams should be limited to 17 parts of nitrobenzene per million parts of water (17 ppm) to prevent possible health effects from drinking water or eating fish contaminated with nitrobenzene. The EPA requires that discharges, spills, or accidental releases of 1,000 pounds or more of nitrobenzene must be reported to the EPA.

OSHA: The Occupational Safety and Health Administration has set a permissible exposure limit of 5 milligrams nitrobenzene per cubic metre of air (5 mg/m³) for an 8-hour workday in a 40-hour workweek.

ACGIH & NIOSH: The American Conference of Governmental and Industrial Hygienists and the National Institute for Occupational Safety and Health also recommend an occupational exposure limit of 5 mg/m³ for nitrobenzene.

Australia

Safe Work Australia has established a TWA of 5mg/m³ for nitrobenzene for an 8-hour workday.

References

http://en.wikipedia.org/wiki/Nitrobenzene

http://apps.sepa.org.uk/spripa/Pages/SubstanceInformation.aspx?pid=76

http://www.epa.gov/chemfact/nitro-fs.pdf

http://www.epa.gov/ttn/atw/hlthef/nitroben.html

https://www.sciencelab.com/msds.php?msdsId=9926260

http://www.atsdr.cdc.gov/toxfaqs/tf.asp?id=531&tid=95

http://www.google.com.au/url?sa=t&rct=j&q=safe%20work%20australia%20exposure%20limits%20for%20nitrobenzene&source=web&cd=2&ved=0CC4QFjAB&url=http%3A%2F%2Fwww.safeworkaustralia.gov.au%2Fsites%2FSWA%2FAboutSafeWorkAustralia%2FWhatWeDo%2FPublications%2FDocuments%2F639%2FWorkplace_Exposure_Standards_for_Airborne_Contaminants.docx&ei=t7OFUMT-K_GhiAfqy4GwBA&usg=AFQjCNFxbRVXcwvV7klOuJXqga2X0vwBJQ