Dinitrophenols are a class of manufactured chemicals that do not occur naturally in the environment. There are six different dinitrophenols. The most commercially important dinitrophenol, 2,4-dinitrophenol (DNP), is a yellow solid with no smell. It is used in making dyes, wood preservatives, explosives, insect control substances, and other chemicals, and as a photographic developer.

It was used in diet pills in the 1930s but was banned for this use in 1938. It may be sold under several trade names, including Caswell No. 392, Sulfo Black B, and Nitro Kleenup.





Structural diagrams: National Institutes of Health

Fate & Transport

DNP enters the air, water, and soil during its manufacture and use.

It may be formed from reaction of other chemicals in the air.

DNP may also enter the environment through landfill and storage tank leaks, or accidental spills during manufacture or transport.

It dissolves slightly in water, and does not easily evaporate to air.

It can be broken down slowly in water and soil by small organisms or by reacting with other chemicals.

DNP sticks to particles in water, which will cause it to eventually settle to the bottom sediment.

DNP also sticks to some types of soil particles, which may prevent it from moving very deep into the soil with rainwater.

DNP probably does not build up significantly in fish.

Exposure Pathways

Breathing contaminated workplace air where it is manufactured or used.

Breathing contaminated air from DNP-containing waste sites, waste incineration, or automobile exhaust.

Touching contaminated soil or water near DNP-containing waste sites.

Ingesting contaminated soil or water near DNP-containing waste sites.

Health Effects

Most of the information on the health effects of dinitrophenols comes from old studies of patients who were prescribed diet pills containing dinitrophenol before it was banned. Deaths have occurred in people who ingested 3-46 milligrams of dinitrophenols per kilogram of body weight per day (3-46 mg/kg/day) for short periods, or 1-4 mg/kg/day for long periods. Also, people who breathed air containing 40 mg dinitrophenols per cubic meter of air (40 mg/m3) for long periods have died.

The amount of dinitrophenols ingested that causes harmful effects varies among people. Increased basal metabolic rate (the rate that you use energy at complete rest), increased sweating, a feeling of warmth, weight loss, and increased heart rate, breathing rate, and body temperature have been observed in people who swallowed as little as 1 mg/kg/day or as much as 46 mg/kg/day for short or long periods of time.

Ingesting 2-4 mg/kg/day DNP for short or long periods has caused cataracts in some people, while ingesting 1-4 mg/kg/day for short or long periods has caused skin rashes and decreases in white blood cells.

The Department of Health and Human Services (DHHS), the International Agency for Research on Cancer (IARC), and the EPA have not classified dinitrophenols for carcinogenicity. There are no studies available in people or animals on the carcinogenic effects of dinitrophenols.

Tests are available that measure the amount of DNPs or their breakdown products in blood, urine, and samples of tissue from the body. However, these tests may require special equipment and may not be available in your doctor's office.

Information excerpted from:

Toxicological Profile for Dinitrophenol 1995

Agency for Toxic Substances and Disease Registry
U.S. Dept. of Health and Human Services