2,4-Dinitrophenol (DNP)


2,4-Dinitrophenol (2,4-DNP, or DNP), molecular formula C6H4N2O5, is an inhibitor of efficient energy (ATP) production in cells with mitochondria. It uncouples oxidative phosphorylation by carrying protons across the mitochondrial membrane, leading to a rapid consumption of energy without generation of ATP. [1]

2,4-Dinitrophenol is a yellow solid with no known smell. It dissolves slightly in water. When present in water and soil as a pollutant, DNP does not easily evaporate to air. [2]

Uses [2,3]

2,4-Dinitrophenol is used in the manufacture of dyes and wood preservatives, as a pesticide, and as an indicator for the detection of potassium and ammonium ions. It is also used to make photographic developer and explosives. During the 1930s, 2,4-dinitrophenol was used as a diet pill, but this use was stopped in 1938.

Sources and Routes of Exposure [2]

Sources of Exposure

People can be exposed to DNP by breathing contaminated air, drinking contaminated water, eating contaminated food, or by contact with contaminated soil. Other than the air in certain workplaces, the levels of DNP in air we breathe are not known. DNP is present in wastewater from certain industries. Groundwater from a waste site that was once occupied by a factory that used DNP contained 30.6 mg DNP/L of water. The levels of DNP in drinking water and food are not known. Certain people may be exposed to low levels of DNP where they live or work. Breathing contaminated air may expose people who live near waste sites with DNP. Touching and eating soil that contains DNP may expose children playing at or near these sites. Exposure may occur in the workplace in those industries manufacturing or using DNP. Furthermore, workers involved in incinerating certain wastes or cleaning up waste sites containing DNP may be exposed.

Routes of Exposure

The major routes of exposure are:

  • Inhalation
  • Ingestion
  • Dermal/eye contact

Health Effects [3]

Acute Effects

  • Acute oral exposure to high levels of 2,4-dinitrophenol in humans has resulted in increased basal metabolic rate, nausea, vomiting, sweating, dizziness, headache, loss of weight, and other symptoms.
  • 2,4-Dinitrophenol is considered to have high acute toxicity, based on short-term animal tests in rats and mice.

Chronic Effects

  • Chronic oral exposure to 2,4-dinitrophenol in humans and animals has resulted in the formation of cataracts and skin lesions and has caused effects on the bone marrow, CNS, and cardiovascular system.
  • The Reference Dose (RfD) for 2,4-dinitrophenol is 0.002 milligrams per kilogram body weight per day (mg/kg/d) based on cataract formation in humans. The RfD is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily oral exposure to the human population (including sensitive subgroups) that is likely to be without appreciable risk of deleterious noncancer effects during a lifetime.
  • EPA has not established a Reference Concentration (RfC) for 2,4-dinitrophenol.
  • Case reports of women taking 2,4-dinitrophenol orally for weight loss suggest that it may affect the female reproductive system, but the limited information is inconclusive.
  • One study reported an increased incidence of stillborn animals and increased pup mortality in the offspring of animals exposed to 2,4-dintrophenol by gavage.
  • No information is available on the carcinogenic effects of 2,4-dinitrophenol in humans.
  • One study reported that 2,4-dinitrophenol did not promote tumour development in mice.
  • EPA has not classified 2,4-dinitrophenol for potential carcinogenicity.


First Aid Measures

  • Eye Contact: Check for and remove any contact lenses. In case of contact, immediately flush eyes with plenty of water for at least 15 minutes. Cold water may be used. Get medical attention.
  • Skin Contact: In case of contact, immediately flush skin with plenty of water for at least 15 minutes while removing contaminated clothing and shoes. Cover the irritated skin with an emollient. Cold water may be used. Wash clothing before reuse. Thoroughly clean shoes before reuse. Get medical attention immediately.
  • Serious Skin Contact: Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial cream. Seek immediate medical attention.
  • Inhalation: If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get medical attention immediately.
  • 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.
  • WARNING: It may be hazardous to the person providing aid to give mouth-to-mouth resuscitation when the inhaled material is toxic, infectious or corrosive. Seek immediate medical attention.
  • Ingestion: If swallowed, do not induce vomiting unless directed to do so by medical personnel. Never give anything by mouth to an unconscious person. Loosen tight clothing such as a collar, tie, belt or waistband. Get medical attention immediately.

Fire Information

  • DNP is highly flammable in presence of open flames and sparks, of heat, reducing materials and combustible materials.
  • Explosion is caused by heat, friction or shock.
  • Dinitrophenol forms explosive salts with alkali or ammonia and should not be heated with them in closed vessels.
  • Dry chemical powder should be used to fight small fires and water spray or fog should be used on large fires.
  • Cool containing vessels with water jet should be used to prevent pressure build-up, auto-ignition or explosion.

Exposure Controls and Personal Protection

Engineering Controls

The following engineering controls should be used when handling DNP:

  • Explosion-proof electrical (ventilating, lighting and material handling) equipment;
  • Process enclosures, local exhaust ventilation, or other engineering controls to keep airborne levels below recommended exposure limits. If user operations generate dust, fume or mist, use ventilation to keep exposure to airborne contaminants below the exposure limit.

Personal Protection

The following personal protective equipment is recommended when handling DNP:

  • Splash goggles;
  • Lab coat;
  • Dust respirator (be sure to use an approved/certified respirator or equivalent);
  • Gloves;
  • Suggested protective clothing might not be sufficient; consult a specialist BEFORE handling this product.

Personal Protection in Case of a Large Spill:

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

Regulation [2,5]

United States

No workplace exposure limited have been set for DNP

EPA: The United States Environmental Protection Agency lists DNP as a hazardous air pollutant under the Clean Air Act. EPA recommends that the amount present in bodies of water, such as lakes and rivers, should not be more than 0.07 mg/L in water used for swimming or where water might possibly be swallowed. No more than 0.765 mg/L should be present in water where people catch fish to eat, but there is no swimming. EPA requires industry to report releases or spills of 10 pounds or more of DNP. EPA has designated DNP as a hazardous substance, and intends to cancel, restrict, or require reregistration of pesticide products containing dinitrophenols. DNP is also listed as a waste constituent and specific regulations regarding its disposal are in effect.


A Temporary Emergency Exposure Limit (TEEL) for DNP has been set at the following:

  • TEEL-1: 0.61mg/m3
  • TEEL-2: 6.8mg/m3
  • TEEL-3: 16mg/m3