PUBLIC HEALTH STATEMENT 

 3,3'-DICHLOROBENZIDINE CAS#: 91-94-1 

Division of Toxicology September 1998 

__________________________________________________________________________________________

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 

This Public Health Statement is the summary 

chapter from the Toxicological Profile for 3,3'-

Dichlorobenzidine. 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 public health statement tells you about 3,3'-

dichlorobenzidine and the effects of exposure. 

The Environmental Protection Agency (EPA) 

identifies the most serious hazardous waste sites in 

the nation. These sites make up the National 

Priorities List (NPL) and are the sites targeted for 

long-term federal cleanup activities. 3,3'-

Dichlorobenzidine has been found in at least 32 of 

the 1,467 current or former NPL sites. However, 

the total number of NPL sites evaluated for this 

substance is not known. As more sites are 

evaluated, the sites at which 3,3'-dichlorobenzidine 

is found may increase. This information is 

important because exposure to this substance may 

harm you and because these sites may be sources of 

exposure. 

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 are 

exposed to a substance only when you come in 

contact with it. You may be exposed by breathing, 

eating, or drinking the substance or by skin contact. 

If you are exposed to 3,3'-dichlorobenzidine, many 

factors determine whether you'll be harmed. These 

factors include the dose (how much), the duration 

(how long), and how you come in contact with it. 

You must also consider the other chemicals you're 

exposed to and your age, sex, diet, family traits, 

lifestyle, and state of health. 

 

1.1 WHAT IS 3,3'-DICHLOROBENZIDINE? 

3,3'-Dichlorobenzidine is a gray-to-purple colored 

crystalline solid. It changes from a solid to a gas 

very slowly. 3,3'-Dichlorobenzidine salt, the major 

form in actual use, is a stable, off-white colored 

crystalline solid that does not evaporate. Neither 

3,3'-dichlorobenzidine nor its salt occur naturally in 

the environment. They are manufactured for use in 

the production of pigments for printing inks, 

textiles, plastics and enamels, paint, leather, and 

rubber. Whether 3,3'-dichlorobenzidine or the salt 

is present as such depends on the acidity of the soil 

or water as well as other factors. In most 

environmental samples, such as water and soils, 

3,3'-dichlorobenzidine would be expected to exist in 

the free amino form, not as the salt. 

 

1.2 WHAT HAPPENS TO 3,3'-

DICHLOROBENZIDINE WHEN IT 

ENTERS THE ENVIRONMENT? 

3,3'-Dichlorobenzidine breaks down rapidly when 

exposed to natural sunlight. In air and sunshine, it 

is estimated that half of the chemical breaks down 

within 9.7 hours. In water exposed to natural 

sunlight, 3,3'-dichlorobenzidine is expected to break 

down rapidly, with half being removed in 
 PUBLIC HEALTH STATEMENT 

 3,3'-DICHLOROBENZIDINE CAS#: 91-94-1 

Division of Toxicology September 1998 

__________________________________________________________________________________________

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 

approximately 90 seconds. In soil, where no 

sunlight is present, the compound may last for 

several months. Under certain conditions, 3,3'-

dichlorobenzidine can break down in soil to form 

another compound, benzidine, which is toxic. 

 

1.3 HOW MIGHT I BE EXPOSED TO 3,3'-

DICHLOROBENZIDINE? 

3,3'-Dichlorobenzidine is used to make pigments 

(substances used to give color to something, for 

example, paint). You are most likely to be exposed 

to 3,3'-dichlorobenzidine if you work inside plants 

where the chemical is manufactured or used. 

However, employers have limited workers' 

exposure to the chemical by using closed systems 

for processing as well as other methods for reducing 

its concentration in the air to very low levels and by 

requiring workers to wear protective clothing and 

use special equipment. If you were exposed in such 

a workplace, it would probably be by breathing in 

the dust or by getting the chemical on your skin. 

Careless handling or accidental spillage of the 

chemical could result in exposure to potentially 

hazardous levels of 3,3'-dichlorobenzidine. People 

may be exposed to the chemical if they live or work 

near land where plant wastes have been stored or 

buried, or close to lakes, streams, or rivers near 

where plants discharge process water or store 

wastes. Most people do not live near a source of the 

chemical. The Canadian government has published 

calculations that show that exposure of the 

Canadian general population to 3,3'-

dichlorobenzidine in air, soil, or water is extremely 

low. If you do live in areas near a source of the 

chemical (such as a hazardous waste site that 

contains dye or pigment manufacturing wastes), 

some exposure could occur if you or a child 

accidentally or purposely ingested small amounts of 

contaminated soil, drank contaminated water, or ate 

fish caught in waters near the source. However, 

studies of water and fish taken from locations near 

dye-manufacturing plants did not find the chemical. 

3,3'-Dichlorobenzidine has no agricultural or food 

chemical uses, so exposure to it by eating 

contaminated food is not likely. 

 

1.4 HOW CAN 3,3'-DICHLOROBENZIDINE 

ENTER AND LEAVE MY BODY? 

In the workplace, 3,3'-dichlorobenzidine may enter 

the body when workers breathe dust contaminated 

by 3,3'-dichlorobenzidine and through skin contact. 

You are not likely to be exposed to 3,3'-

dichlorobenzidine unless you drink water or eat dirt 

contaminated with 3,3'-dichlorobenzidine in the 

vicinity of a hazardous waste site where 3,3'-

dichlorobenzidine has been stored and leakage has 

occurred. When 3,3'-dichlorobenzidine does enter 

the body, very little of it leaves the body 

unchanged. Most of it (over 90%) is changed to 

related chemical substances called metabolites, 

which leave the body, mainly in urine and to a 

lesser extent in feces, within 72 hours after 

exposure. 

1.5 HOW CAN 3,3'-DICHLOROBENZIDINE 

AFFECT MY HEALTH? 

Some workers exposed to the salt form of 3,3'-

dichlorobenzidine complained of sore throat, 

respiratory infections, stomach upset, headache, 

dizziness, caustic burns, and dermatitis (an 

inflammation of the skin). However, with the 

exception of dermatitis, it is not certain that 3,3'-

dichlorobenzidine causes these health effects 

because the workers were also exposed to other 
 PUBLIC HEALTH STATEMENT 

 3,3'-DICHLOROBENZIDINE CAS#: 91-94-1 

Division of Toxicology September 1998 

__________________________________________________________________________________________

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 

chemicals at the same time. There is no evidence 

that 3,3'-dichlorobenzidine affects the nervous 

system, the ability to fight disease, or the ability of 

people to have children. 

To protect the public from the harmful effects of 

toxic chemicals and to find ways to treat people 

who have been harmed, scientists use many tests. 

One way to see if a chemical will hurt people is to 

learn how the chemical is absorbed, used, and 

released by the body; for some chemicals, animal 

testing may be necessary. Animal testing may also 

be used to identify health effects such as cancer or 

birth defects. Without laboratory animals, scientists 

would lose a basic method to get information 

needed to make wise decisions to protect public 

health. Scientists have the responsibility to treat 

research animals with care and compassion. Laws 

today protect the welfare of research animals, and 

scientists must comply with strict animal care 

guidelines. 

Death has occurred in laboratory animals that ate 

very high levels of 3,3'-dichlorobenzidine mixed in 

their food for short periods of time. Laboratory 

animals exposed to moderate levels of 3,3'-

dichlorobenzidine mixed with food for a long time 

suffered mild injury to the liver. 

Studies show that 3,3'-dichlorobenzidine caused 

cancer of the liver, skin, breast, bladder, and tissues 

that form blood (leukemia), and other sites in 

laboratory animals that ate 3,3'-dichlorobenzidine in 

their food. There is no evidence that 3,3'-

dichlorobenzidine has caused cancer in people who 

worked with it or who were exposed to it 

unknowingly or by accident for a short or long time. 

However, because of the many types of cancer that 

3,3'-dichlorobenzidine has caused in different 

tissues of many types of laboratory animals, 3,3'-

dichlorobenzidine should be thought of as probably 

capable of causing human cancer if exposure to the 

chemical is sufficiently high. 

The Environmental Protection Agency (EPA) has 

determined that 3,3'-dichlorobenzidine is a 

"probable human carcinogen." The U.S. Department 

of Health and Human Services (DHHS) has 

determined that 3,3'-dichlorobenzidine and its salt 

may reasonably be expected to be cancer-causing 

substances (carcinogens). The International Agency 

for Research on Cancer (IARC) has determined that 

3,3'-dichlorobenzidine is possibly carcinogenic to 

humans. 

 

1.6 HOW CAN 3,3'-DICHLOROBENZIDINE 

AFFECT CHILDREN? 

This section discusses potential health effects from 

exposures during the period from conception to 

maturity at 18 years of age in humans. Potential 

effects on children resulting from exposures of the 

parents are also considered. 

Children might be exposed to 3,3'-

dichlorobenzidine if they eat small amounts of soil 

contaminated with 3,3'-dichlorobenzidine. 

However, studies suggest that it is very difficult to 

release 3,3'-dichlorobenzidine once it becomes 

attached to soil. Exposure via contaminated soil 

may occur if they live in an area near a source of the 

chemical (such as a hazardous waste site that 

contains 3,3'-dichlorobenzidine). Children can also 

be exposed if the parents work at chemical facilities 

where 3,3'-dichlorobenzidine is handled and bring 

home contaminated clothing or tools or if they do 
 PUBLIC HEALTH STATEMENT 

 3,3'-DICHLOROBENZIDINE CAS#: 91-94-1 

Division of Toxicology September 1998 

__________________________________________________________________________________________

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 

not shower before coming home. There are no 

known unique exposure pathways for children. 

There have been no studies of health effects in 

children exposed to 3,3'-dichlorobenzidine. We 

have no information on whether 3,3'-

dichlorobenzidine causes birth defects in children. 

It is unknown whether birth defects would occur in 

the offspring of pregnant animals that breathed or 

eaten 3,3'-dichlorobenzidine, or had it on their skin. 

In studies in which pregnant mice were injected 

with high amounts of 3,3'-dichlorobenzidine under 

the skin, the kidneys of their babies did not develop 

properly and some babies developed renal tumors. 

However, it is highly unlikely that humans will 

encounter such exposure conditions. 

There is no information to determine whether 

children are different in their sensitivity to the 

health effects of 3,3'-dichlorobenzidine from adults. 

There is indirect evidence that 3,3'-

dichlorobenzidine or its breakdown products can 

cross the placenta, but we do not know for certain 

whether it can be transferred to the young via the 

mother's breast milk. Sometimes when children 

have been exposed to chemicals before they are 

born, the chemical or its breakdown products can be 

found in amniotic fluid, meconium, cord blood, or 

neonatal blood; however, no information about such 

measurements was found for 3,3'-

dichlorobenzidine. 

 

1.7 HOW CAN FAMILIES REDUCE THE 

RISK OF EXPOSURE TO 3,3'-

DICHLOROBENZIDINE? 

If your doctor finds that you have been exposed to 

significant amounts of 3,3'-dichlorobenzidine, ask 

your doctor if children may also be exposed. When 

necessary your doctor may need to ask your state 

Department of Public Health to investigate. 

3,3'-Dichlorobenzidine has no agricultural or food 

chemical uses, so exposure to it by eating 

contaminated food is not likely. It is sometimes 

possible to carry 3,3'-dichlorobenzidine from work 

on your clothing, skin, hair, tools, or other objects 

removed from the workplace. This has happened in 

factories that produce 3,3'-dichlorobenzidine. In 

this way, you may contaminate your car, home, or 

other locations outside work where children might 

be exposed to 3,3'-dichlorobenzidine. You should 

know about this possibility if you work with 3,3'-

dichlorobenzidine. 

Your occupational health and safety officer at work 

can and should tell you whether chemicals you 

work with are dangerous and likely to be carried 

home on your clothes, body, or tools. Ask if you 

should shower and change clothes before you leave 

work, store your street clothes in a separate area of 

the workplace, or launder your work clothes at 

home separately from other clothes. The 

Occupational Safety and Health Administration 

(OSHA) requires Material Safety Data Sheets 

(MSDSs) for many chemicals used at your place of 

work. MSDS information should include chemical 

names and hazardous ingredients, and important 

information such as fire and explosion data, 

potential health effects, how you get the chemical(s) 

in your body, how to properly handle the materials, 

and what to do in the case of emergencies. Your 

employer is legally responsible for providing a safe 

workplace and should freely answer your questions 

about hazardous chemicals. U.S. OSHA or your 

state OSHA-approved occupational safety and 

health program can answer any further questions 

and help your employer identify and correct 
 PUBLIC HEALTH STATEMENT 

 3,3'-DICHLOROBENZIDINE CAS#: 91-94-1 

Division of Toxicology September 1998 

__________________________________________________________________________________________

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 

problems with hazardous substances. OSHA or 

your state OSHA-approved occupational safety and 

health program will listen to your formal complaints 

about workplace health hazards and inspect your 

workplace when necessary. Employees have a right 

to seek safety and health on the job without fear of 

punishment. 

 

1.8 IS THERE A MEDICAL TEST TO 

DETERMINE WHETHER I HAVE BEEN 

EXPOSED TO 3,3'-

DICHLOROBENZIDINE? 

 

Exposure to 3,3'-dichlorobenzidine can be 

determined by finding the chemical or its 

metabolites in urine. The test is not commonly 

available to the general population, but it is 

available to workers who may be exposed to 

potentially hazardous levels of the chemical in the 

workplace (for example, by careless handling or 

accidental spills). The test is accurate and provides 

evidence that exposure has occurred. However, 

since 3,3'-dichlorobenzidine does not remain long in 

the body, the test must be performed very soon after 

the possible exposure. Also, measured urine levels 

of 3,3'-dichlorobenzidine or its metabolites do not 

tell you whether it will affect your health. 

 

1.9 WHAT RECOMMENDATIONS HAS THE 

FEDERAL GOVERNMENT MADE TO 

PROTECT HUMAN HEALTH? 

Federal agencies that develop regulations for toxic 

substances include the Environmental Protection 

Agency (EPA), the Occupational Safety and Health 

Administration (OSHA), and the Food and Drug 

Administration (FDA). Recommendations provide 

valuable guidelines to protect public health but 

cannot be enforced by law. Federal organizations 

that develop recommendations for toxic substances 

include the Agency for Toxic Substances and 

Disease Registry (ATSDR) and the National 

Institute for Occupational Safety and Health 

(NIOSH). 

Regulations and recommendations can be expressed 

in not-to-exceed levels in air, water, soil, or food 

that are usually based on levels that affect animals; 

then they are adjusted to help protect people. 

Sometimes these not-to-exceed levels differ among 

federal organizations because of different exposure 

times (an 8-hour workday or a 24-hour day), the use 

of different animal studies, or other factors. 

Recommendations and regulations are also 

periodically updated as more information becomes 

available. For the most current information, check 

with the federal agency or organization that 

provides it. Some regulations and 

recommendations for 3,3'-dichlorobenzidine include 

the following: 

EPA has determined that 3,3'-dichlorobenzidine is a 

"probable human carcinogen" and has placed 

several limits on the chemical in the environment to 

protect human health. Under the Clean Water Act 

of 1977, EPA controls discharges of 3,3'-

dichlorobenzidine to industrial waste waters. The 

agency has listed 3,3'-dichlorobenzidine as a 

hazardous waste and requires that any spill of one 

pound or more be reported to the National Response 

Center. 

Although the FDA has classified 3,3'-

dichlorobenzidine as a carcinogen, no regulatory 

guidelines have been enacted. The FDA has 

concluded that the food supply is not in danger from 

3,3'-dichlorobenzidine. 
 PUBLIC HEALTH STATEMENT 

 3,3'-DICHLOROBENZIDINE CAS#: 91-94-1 

Division of Toxicology September 1998 

__________________________________________________________________________________________

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 

3,3'-Dichlorobenzidine is one of a number of 

compounds regulated by OSHA. To control 

exposures to 3,3'-dichlorobenzidine in workplace 

air and to protect the health of workers, OSHA's 

regulatory standards provide strict guidelines for 

handling, using, and storing the compound. They 

also include the requirements for personal 

protective equipment, training, labeling, and posting 

and engineering controls. OSHA also requires that 

initial medical screening and regular medical 

examinations be made available to any employee 

who is exposed to 3,3'-dichlorobenzidine at 

potentially hazardous levels. 

NIOSH considers 3,3'-dichlorobenzidine a 

"potential occupational carcinogen" and 

recommends workplace practices and controls to 

reduce exposures to the lowest possible level. 

NIOSH defines potential occupational carcinogens 

as substances which may cause an increased 

incidence of benign and/or malignant neoplasm, or 

a substantial decrease in the latency period between 

exposure and onset of neoplasms in humans. 

 

1.10 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: 

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). 1998. Toxicological profile for 3,3-

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

Health and Human Services, Public Health Service.