Aniline

What is Aniline?

Aniline, also known as phenylamine or aminobenzene, is an organic compound with the formula C₆H₅NH₂. It has a phenyl group attached to an amino group, making it an aromatic amine. Aniline has a distinct unpleasant odour like rotten fish. It burns with a smoky flame and changes from colourless to reddish-brown as it oxidises with air exposure. Aniline does not evaporate easily, is slightly soluble in water, and mixes well with most organic solvents.

What is Aniline used for?

Aniline is a key chemical in many industries, used for:

  • Making rubber accelerators and antioxidants
  • Producing dyes, pigments, and intermediates
  • Photographic chemicals
  • Isocyanates for urethane foams
  • Pharmaceuticals and explosives
  • Petroleum refining
  • Manufacturing diphenylamine, phenolics, herbicides, and fungicides
  • Producing polyurethanes, fibers, and rubber processing chemicals
Aniline is used for photographic chemicals.

Sources & Routes of Exposure

Sources of Exposure

Aniline exposure can occur from various sources:

  • Environmental Sources:
    • Breakdown of certain pollutants in outdoor air
    • Burning of plastics and tobacco
    • Volatile emissions from industrial operations
  • Occupational Sources:
    • Industries using aniline in the production of chemicals
  • Food & Water:
    • Trace amounts in corn, grains, rhubarb, apples, beans, and rapeseed cake (animal feed)
    • Detected as a volatile component in black tea
    • Present in some surface and drinking water

Routes of Exposure

The primary ways aniline can enter the body include:

  • Inhalation: Breathing in vapours from contaminated air
  • Dermal Contact: Absorption through the skin
  • Ingestion: Consuming contaminated food or water

Health Effect

Acute Effects

  • Inhalation exposure to high levels of aniline can cause:
    • Lung effects, such as upper respiratory tract irritation and congestion
  • Classified as highly toxic in humans, with a probable lethal dose of 50 to 500 mg/kg body weight
  • Short-term animal tests show high acute toxicity

Chronic Effects

  • Methemoglobinemia: A condition affecting the blood's oxygen-carrying capacity, leading to cyanosis (bluish skin)
  • Irritation: Severe effects on mucous membranes, eyes, skin, and upper respiratory tract
  • Absorption: Significant absorption through the skin
  • Animal Studies: Dose-related decreases in red blood cell count, haemoglobin, and hematocrit
  • Reference Concentration (RfC) for aniline: 0.001 mg/m³ based on spleen toxicity in rats

Reproductive/Developmental Effects

No conclusive data for humans

Animal studies show:

  • Birth defects in mice exposed to aniline
  • Decreased total number of offspring
  • Increased mortality among pregnant mice and offspring

Carcinogenicity

Human Studies:

  • Insufficient evidence linking aniline directly to bladder tumours

Animal Studies:

  • Increased spleen tumours in rats exposed to aniline hydrochloride

EPA Classification: Probable human carcinogen (Group B2)

Aniline Safety

First Aid Measures

  • Eye Contact:
    • Remove any contact lenses immediately.
    • Flush eyes with running water for at least 15 minutes, keeping eyelids open. Cold water may be used.
    • Seek medical attention.
  • Skin Contact:
    • Flush skin immediately with plenty of water.
    • Cover irritated skin with an emollient.
    • Remove contaminated clothing and shoes. Wash clothing before reuse.
    • Seek medical attention.
  • Serious Skin Contact:
    • Wash with disinfectant soap.
    • Apply an antibacterial cream.
    • Seek immediate medical attention.
  • Inhalation:
    • Move the victim to fresh air.
    • If breathing is difficult, administer oxygen.
    • If not breathing, perform artificial respiration.
    • Seek immediate medical attention.
  • Serious Inhalation:
    • Evacuate the victim to a safe area.
    • Loosen tight clothing (collar, tie, or belt).
    • Administer oxygen if breathing is difficult.
    • WARNING: Avoid mouth-to-mouth resuscitation when the material inhaled is toxic or corrosive.
    • Seek immediate medical attention.
  • Ingestion:
    • Do NOT induce vomiting unless instructed by medical personnel.
    • Never give anything orally to an unconscious person.
    • Seek immediate medical attention.

Handling & Storage

Precautions

  • Keep locked up and away from heat or ignition sources.
  • Ground all equipment handling the material.
  • Avoid ingestion, inhalation, and skin/eye contact.
  • Wear appropriate protective clothing and respiratory equipment if ventilation is insufficient.
  • Seek medical advice if ingestion occurs, showing the container/label.
  • Avoid incompatible substances like oxidisers, metals, acids, and alkalis.

Storage

  • Store in a light-resistant container.
  • Keep in a cool, well-ventilated space.
  • Ensure the container is tightly sealed until use.
  • Avoid ignition sources (spark or flame).

Exposure Controls/Personal Protection

Engineering Controls

  • Use exhaust ventilation to maintain vapour levels below permissible limits.
  • Ensure eyewash stations and safety showers are available.

Personal Protection

  • For General Handling:
    • Splash goggles
    • Lab coat
    • Vapour respirator (certified or approved type)
    • Gloves
  • For Large Spills:
    • Full suit
    • Splash goggles
    • Vapour respirator
    • Boots and gloves
    • Use self-contained breathing apparatus (SCBA) to prevent inhalation

Note: Always consult a safety specialist for proper protective measures before handling large quantities.

Regulation

United States

OSHA: The Occupational Safety & Health Administration has set the following Permissible Exposure Limits (PEL) for aniline:

  • General Industry: 29 CFR 1910.1000 Z-1 Table -- 5 ppm, 19 mg/m³ TWA; Skin
  • Construction Industry: 29 CFR 1926.55 Appendix A -- 5 ppm, 19 mg/m³ TWA; Skin
  • Maritime: 29 CFR 1915.1000 Table Z-Shipyards -- 5 ppm, 19 mg/m³ TWA; Skin

ACGIH: The American Conference of Governmental Industrial Hygienists has set a Threshold Limit Value (TLV) for aniline of 2 ppm, 7.6 mg/m³ TWA; Skin; Appendix A3, Confirmed Animal Carcinogen with Unknown Relevance to Humans; BEI

NIOSH: The National Institute for Occupational Safety and Health has listed aniline as a Potential Occupational Carcinogen.

Australia

Safe Australia: Safe work Australia has set the following exposure limits for aniline:

  • TWA: 2 ppm and 7.6 mg/m³