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PUBLIC HEALTH STATEMENT 

DINITROPHENOLS 

CAS#: 51-28-5 (2,4-DNP) 

Division of Toxicology August 1995 

This Public Health Statement is the summary 

chapter from the Toxicological Profile for 

Dinitrophenols. It is one in a series of Public Health 

Statements about hazardous substances and their 

health effects. A shorter version, the ToxFAQsTM is 

also available. This information is important 

because this substance may harm you. The effects 

of exposure to any hazardous substance depend on 

the dose, the duration, how you are exposed, 

personal traits and habits, and whether other 

chemicals are present. For more information, call 

the ATSDR Information Center at 1-888-422-8737. 

This statement was prepared to give you 

information about dinitrophenols and to emphasize 

the human health effects that may result from 

exposure to them. The Environmental Protection 

Agency (EPA) has identified 1,408 hazardous waste 

sites as the most serious in the nation. These sites 

make up the National Priorities List (NPL) and are 

the sites targeted for long-term federal clean-up 

activities. Dinitrophenols have been found in at 

least 61 of the sites on the NPL. However, the 

number of NPL sites evaluated for dinitrophenols is 

not known. As EPA evaluates more sites, the 

number of sites at which dinitrophenols are found 

may increase. This information is important because 

exposure to dinitrophenols may cause harmful 

health effects and because these sites are potential 

or actual sources of human exposure to 

dinitrophenols. 

When a substance is released from a large area, 

such as an industrial plant, or from a container, such 

as a drum or bottle, it enters the environment. This 

release does not always lead to exposure. You can 

be exposed to a substance only when you come in 

contact with it. You may be exposed by breathing, 

eating, or drinking substances containing the 

substance or by skin contact with it. 

If you are exposed to substances such as 

dinitrophenols, many factors will determine whether 

harmful health effects will occur and what the type 

and severity of those health effects will be. These 

factors include the dose (how much), the duration 

(how long), the route or pathway by which you are 

exposed (breathing, eating, drinking, or skin 

contact), the other chemicals to which you are 

exposed, and your individual characteristics such as 

age, sex, nutritional status, family traits, lifestyle, 

and state of health. 

1.1 WHAT ARE DINITROPHENOLS? 

Dinitrophenols are a class of synthetic organic 

chemicals that can exist in six individual forms. 

Dinitrophenols do not occur naturally in the 

environment. This profile mainly contains 

information on the most commercially important 

dinitrophenol, 2,4-dinitrophenol, which is called 

DNP in this document. Industries manufacture 

dinitrophenols. DNP is sold under many trade 

names, some are Caswell No. 392®, Sulfo Black 

B®, and Nitro Kleenup®. It is a yellow solid with 

no known smell. It dissolves slightly in water. DNP 

present in water and soil as a pollutant does not 

easily evaporate to air. The taste of DNP is not 

known. Commercial DNP is primarily used for 

making dyes, other organic chemicals, and wood 

preservatives. It is also used to make photographic 

developer, explosives, and insect control 

substances. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

DINITROPHENOLS 

CAS#: 51-28-5 (2,4-DNP) 

Division of Toxicology August 1995 

1.2 WHAT HAPPENS TO DINITROPHENOLS 

WHEN THEY ENTER THE 

ENVIRONMENT? 

DNP enters the air, water, and soil during its 

manufacture and use. It forms in the air when other 

pollutants react with oxides of nitrogen present in 

polluted air. Automobile exhaust releases DNP into 

the air. Burning certain wastes also produces DNP. 

Wastes containing DNP that are generated during 

its manufacture and use are sometimes disposed in 

landfills. DNP enters the environment from these 

landfills. It also enters the environment from 

accidental spills during transport and leaks from 

storage containers. 

The loss of DNP into air due to chemical reactions 

with other pollutants or interaction with sunlight 

may not be significant. It eventually returns from air 

to land and water by settling and washout by snow 

and rainwater. We do not know how long it stays in 

the air before it is removed. Chemical reactions do 

not remove significant amounts of DNP from 

natural bodies of water. The action of 

microorganisms in water may be the most important 

process to remove DNP from water. The loss of 

DNP from water due to evaporation into air is 

insignificant. The percentage of DNP in water that 

sticks to particles present in water becomes 

substantial in acidic water containing particles high 

in organic matter and clay. This process partially 

transfers DNP from water to the bottom sediment. 

DNP is not likely to build up in fish from water. We 

do not know how long DNP remains in water. 

Chemical reactions do not remove DNP from soil 

under natural conditions. The loss of DNP from soil 

to the air due to evaporation is not important. The 

extent that DNP seeps into soil from rainwater 

depends on the properties of the soil. DNP may 

travel deeper into certain soils than others, 

especially soils that are not acidic. Groundwater 

from a few disposal sites contains DNP. DNP in soil 

is destroyed primarily by microorganisms. It may 

take between 4 and 80 days for the level of DNP in 

soil to decrease by half. 

1.3 HOW MIGHT I BE EXPOSED TO 

DINITROPHENOLS? 

During the 1930s, DNP was used extensively as a 

diet pill, so those most exposed were dieters who 

used these pills. Because of the harmful effects 

observed (cataracts in young people) the use of 

DNP was stopped by the United States government 

in 1938. Since that time, there has been at least one 

case where a doctor gave DNP to patients for 

weight reduction even though DNP is known to be 

harmful. Today, 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 waste water from 

certain industries. For example, waste water from a 

dye manufacturing plant contained 3.2 milligrams 

DNP per liter of water (mg/L) (1 mg = one 

thousandth of a gram and 1 liter = about one quart). 

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. People who live near waste sites with DNP 

may be exposed by breathing contaminated air. 

Children playing at or near these sites may be 

exposed by touching and eating soil that contains 

DNP. You may be exposed to DNP if your work 

involves manufacturing or using DNP. You also 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

DINITROPHENOLS 

CAS#: 51-28-5 (2,4-DNP) 

Division of Toxicology August 1995 

may be exposed to DNP if your work involves 

incinerating certain wastes or cleaning up waste 

sites containing DNP. 

1.4 HOW CAN DINITROPHENOLS ENTER 

AND LEAVE MY BODY? 

DNP can readily enter your body through the lungs 

by breathing, through the stomach if swallowed. It 

can probably be absorbed through the skin also. 

Animal studies show that after DNP enters the 

body, the blood can carry it to organs and tissues 

such as the liver, the kidneys, and the eyes. DNP 

does not build up in organs and tissues, but it is 

metabolized or broken down to other chemicals. We 

do not know if these breakdown products are 

harmful. DNP and these breakdown products leave 

your body in the urine. 

1.5 HOW CAN DINITROPHENOLS AFFECT 

MY HEALTH? 

Most of what we know about how DNP can affect 

your health comes from old reports by doctors who 

prescribed DNP to patients who wanted to lose 

weight. A person could even buy DNP at a drug 

store without a prescription. DNP has been banned 

by the U.S. Food and Drug Administration as a diet 

pill since 1938 because of the harmful effects that 

occurred in their patients, especially cataracts. Most 

of the ways that DNP can affect your health do not 

depend on how you are exposed or for how long. 

Some people who took DNP were harmed, while 

others were not, even though they took the same or 

higher doses. Although some people became ill 

after taking DNP for short periods, other people 

could take DNP for longer periods before becoming 

ill. This means that some people are more sensitive 

to the harmful effects of DNP than others. Brief or 

long-term exposure to DNP can cause increased 

basal metabolic rates (the rate that you use energy at 

complete rest); a feeling of warmth; sweating; 

weight loss; and increased heart rate, breathing rate, 

and body temperature. Some or all of these effects 

have occurred in some people after they swallowed 

doses as high as 46 milligrams of DNP per kilogram 

of their body weight per day (mg/kg/day) or doses 

as low as 1 mg/kg/day DNP. Some people who took 

doses of 2 mg/kg/day DNP or more for short or long 

periods experienced numbness in their hands and 

feet. Some people who swallowed doses of 6 mg 

DNP/kg/day for short periods or doses of 1 to 4 

mg/kg/day DNP for long periods had a serious 

decrease of certain types of white blood cells that 

fight disease. Some people who swallowed doses of 

1 to 4 mg/kg/day DNP for short or for long periods 

developed serious skin reactions that sometimes 

disappeared even while they were still being 

exposed. DNP caused cataracts in both eyes of 

some people who swallowed about 2 to 4 

mg/kg/day DNP for short or long periods. This 

condition could lead to blindness in both eyes. If 

you breathe in, swallow, or have skin contact with 

large amounts of DNP, you may die. A few people 

have died after swallowing 3 to 46 mg/kg/day of 

DNP for short periods or doses as low as 1 to 4 

mg/kg/day for long periods. Some workers who 

breathed in air containing 40 mg DNP per cubic 

meter of air (mg/m3) or more for long periods have 

also died. 

The effects of DNP found in animals are similar to 

those in humans, except that the effects on feeling 

in the hands and feet, and on white blood cells were 

not found in animals. Cataracts also occurred in 

some types of animals that swallowed DNP. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

DINITROPHENOLS 

CAS#: 51-28-5 (2,4-DNP) 

Division of Toxicology August 1995 

We do not know whether DNP causes reproductive 

or birth defects or cancer in humans. One study in 

rats suggested that if DNP is swallowed during 

pregnancy or nursing, it may cause death in 

newborn babies. Two other studies in mice 

suggested that DNP did not have effects on the 

unborn infant. We do not know whether DNP 

causes cancer in animals. 

1.6 IS THERE A MEDICAL TEST TO 

DETERMINE WHETHER I HAVE BEEN 

EXPOSED TO DINITROPHENOLS? 

DNP can be measured in blood, urine, and several 

body tissues. The main breakdown product of DNP 

in people, 2-amino-4-nitrophenol, can also be 

measured in the blood, urine, and tissues. The 

Derrien test is routinely used to measure this 

breakdown product in urine. This test produces a 

purple color if 2-amino-4-nitrophenol is present, but 

similar chemicals can also produce a purple color 

with this test. The total amount or concentration of 

DNP and its main breakdown products in urine or 

blood is a better indicator of DNP exposure. More 

modern tests can now identify and measure total 

DNP and breakdown products in blood or urine. 

However, these tests are not routinely available at 

your doctor's office, but can be performed at special 

laboratories or hospitals. These tests have not been 

used to tell exactly how much DNP people were 

exposed to or for how long. They also have not 

been used to predict harmful effects. 

1.7 WHAT RECOMMENDATIONS HAS THE 

FEDERAL GOVERNMENT MADE TO 

PROTECT HUMAN HEALTH? 

EPA 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. 

1.8 WHERE CAN I GET MORE 

INFORMATION? 

If you have any more questions or concerns, 

please contact your community or state health or 

environmental quality department or: 

Agency for Toxic Substances and Disease Registry 

Division of Toxicology 

1600 Clifton Road NE, Mailstop F-32 

Atlanta, GA 30333 

Information line and technical assistance: 

Phone: 888-422-8737 

FAX: (770)-488-4178 

ATSDR can also tell you the location of 

occupational and environmental health clinics. 

These clinics specialize in recognizing, evaluating, 

and treating illnesses resulting from exposure to 

hazardous substances. 

To order toxicological profiles, contact: 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

DINITROPHENOLS 

CAS#: 51-28-5 (2,4-DNP) 

Division of Toxicology August 1995 

National Technical Information Service 

5285 Port Royal Road 

Springfield, VA 22161 

Phone: 800-553-6847 or 703-605-6000 

Reference 

Agency for Toxic Substances and Disease Registry 

(ATSDR). 1995. Toxicological profile for 

dinitrophenols. Atlanta, GA: U.S. Department of 

Health and Human Services, Public Health Service. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov