What is 4-Nitrophenol?

4-Nitrophenol (also called p-nitrophenol or 4-hydroxynitrobenzene) is a phenolic compound with the molecular formula C₆H₅NO₃. It is a colourless to light yellow solid with very little odour and is not found naturally in the environment.

What is 4-Nitrophenol used for?

4-Nitrophenol is used to manufacture

• Drugs (e.g., acetaminophen)
• Fungicides
• Methyl and ethyl parathion insecticides
• Dyes
• To darken leather

In the Environment

Most 4-nitrophenol enters the environment during manufacturing and processing.

It can also be formed in the air as a result of the breakdown of other manufactured chemicals.

• Most goes to water and soil, with very little entering the air
• It readily breaks down in surface water
• It takes a long time to break down in deep soil and groundwater
• 4-Nitrophenol has not been found in foods
• It is a breakdown product of pesticides such as parathion and fluoridifen
• It is also formed in auto exhaust

Sources and Routes of Exposure

Sources of Exposure

Exposure to 4-nitrophenol can occur via:

• Air, water, and soil contaminated with the chemical
• Breathing contaminated workplace air (especially during spills)
• Breathing contaminated air or drinking contaminated water near farming areas where certain fungicides are used
• Breathing contaminated air or drinking contaminated water near waste sites and landfills

Routes of Exposure

4-nitrophenol can enter the body through:

• Lungs (breathing contaminated air)
• Stomach (swallowing the chemical)
• Skin (some may pass through the skin, but how much is unknown)

Once inside the body, 4-nitrophenol metabolises into other chemicals that are quickly (in hours) excreted in urine.

Health Effects

Acute Effects

In humans, acute inhalation or ingestion of 4-nitrophenol causes:

• Headaches
• Drowsiness
• Nausea
• Cyanosis

Eye contact causes irritation.

Animal studies reported:

• Increased methemoglobin
• Corneal opacity (eye damage)
• High toxicity from oral and dermal exposure in rats and mice

Chronic Effects

• No information is available on the chronic effects in humans or animals from inhalation or oral exposure
• One animal study found no major system effects from chronic dermal exposure
• The only observed effects were dermal irritation, including
  • Erythema
  • Scaling
  • Scabbing
  • Cracking of the skin
• The EPA has not established a Reference Concentration (RfC) or a Reference Dose (RfD) for 4-nitrophenol

Reproductive/Developmental Effects

No information available for humans

Animal studies reported:

• No histological alterations in the testes and epididymides in mice exposed by inhalation
• No changes in reproductive index in pregnant mice given the chemical by gavage (feeding tube)

Cancer Risk

• No information available on carcinogenic effects in humans
• No evidence of carcinogenic activity in mice exposed dermally for 18 months (NTP study)
• EPA has not classified 4-nitrophenol for carcinogenicity

Safety

First Aid Measures

Eye Contact

• Remove contact lenses (if any)
• Flush eyes with running water for at least 15 minutes (cold water may be used)
• Do not use eye ointment
• Seek medical attention

Skin Contact

• Wash skin immediately with plenty of water
• Use non-abrasive soap; cold water may be used
• Cover irritated skin with emollient
• If irritation persists, seek medical attention
• Wash contaminated clothing before reuse

Serious Skin Contact

• Wash with disinfectant soap
• Cover contaminated skin with anti-bacterial cream
• Seek immediate medical attention

Inhalation

• Let the victim rest in a well-ventilated area
• Seek immediate medical attention

Serious Inhalation

• Evacuate the victim to a safe area
• Loosen tight clothing (e.g., collar, tie, belt)
• Administer oxygen if breathing is difficult
• If not breathing, perform mouth-to-mouth resuscitation
• Seek medical attention

Ingestion

• Do not induce vomiting
• Check mouth and lips for signs of damage
• Loosen tight clothing
• If not breathing, perform mouth-to-mouth resuscitation
• Seek immediate medical attention

Exposure Control & Personal Protection

Engineering Controls

• Use process enclosures, local exhaust ventilation, or other controls to keep airborne levels below recommended exposure limits
• If operations generate dust, fumes, or mist, use ventilation to reduce exposure

Personal Protective Equipment (PPE)

When handling 4-nitrophenol, wear:

• Splash goggles
• Lab coat
• Dust respirator (approved/certified)
• Gloves

In case of large spills, wear:

• Splash goggles
• Full suit
• Dust respirator
• Boots
• Gloves
• Use a self-contained breathing apparatus to avoid inhalation
• Suggested protective clothing may not be sufficient—consult a specialist before handling.

Regulation

United States

• No occupational exposure limits have been established for 4-Nitrophenol. This does not mean that this substance is not harmful. Safe work practices should always be followed. 
•  It should be recognised that 4-Nitrophenol can be absorbed through your skin, thereby increasing your exposure.
• Environmental Protection Agency (EPA) says that industry must tell the National Response Centre when 100 pounds or more of 4-nitrophenol have been disposed of.