PUBLIC HEALTH STATEMENT 

 BENZIDINE CAS#: 92-87-5 

Division of Toxicology September 2001 

__________________________________________________________________________________________

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 

Benzidine. 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 

benzidine 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. Benzidine has been found 

in at least 28 of the 1,585 current or former NPL 

sites. However, the total number of NPL sites 

evaluated for benzidine is not known. As more sites 

are evaluated, the sites at which benzidine is found 

may increase. This information is important because 

exposure to benzidine 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 benzidine, 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 BENZIDINE? 

 

Benzidine is a manufactured chemical that does not 

occur naturally. It is a crystalline (sandy or sugarlike) solid that may be grayish-yellow, white, or 

reddish-gray. It will evaporate slowly from water 

and soil. Its flammability, smell, and taste have not 

been described. Benzidine also has other names, 

such as 4,4'-diphenylenediamine or Fast Corinth 

Base B (a registered trade name). In the 

environment, benzidine is found in either its "free" 

state (as an organic base), or as a salt (for example, 

benzidine dihydrochloride or benzidine sulfate). In 

air, benzidine is found attached to suspended 

particles or as a vapor. 

In the past, industry used large amounts of 

benzidine to produce dyes for cloth, paper, and 

leather. However, it has not been made for sale in 

the United States since the mid-1970s. Major U.S. 

dye companies no longer make benzidine-based 

dyes. Benzidine is no longer used in medical 

laboratories or in the rubber and plastics industries. 

However, small amounts of benzidine may still be 

manufactured or imported for scientific research in 

laboratories or for other specialized uses. Some 

benzidine-based dyes (or products dyed with them) 

may also still be brought into the United States. 

1.2 WHAT HAPPENS TO BENZIDINE WHEN 

IT ENTERS THE ENVIRONMENT? 

In the past, benzidine entered the environment 

largely when it was being made or used to produce 
 PUBLIC HEALTH STATEMENT 

 BENZIDINE CAS#: 92-87-5 

Division of Toxicology September 2001 

__________________________________________________________________________________________

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 

dyes. Industry released it to waterways in the form 

of liquids and sludges, and transported benzidinecontaining solids to storage or waste sites. 

Benzidine was sometimes accidentally spilled, and 

it was released to the air as dust or fumes. For the 

most part, companies no longer make or use 

benzidine, and the government strictly regulates 

these activities. Today, most benzidine still entering 

the environment probably comes from waste sites 

where it had been disposed. Some may also come 

from the chemical or biological breakdown of 

benzidine-based dyes, or from other dyes where it 

may exist as an impurity. Only very small amounts 

of free benzidine will dissolve in water at moderate 

environmental temperatures. When released into 

waterways, it will sink and become part of the 

bottom sludge. Benzidine salts can dissolve more 

easily in water than free benzidine. Only a very 

small portion of dissolved benzidine will pass into 

the air. Benzidine exists in the air as very small 

particles or as a vapor, which may be brought back 

to the earth's surface by rain or gravity. In soil, most 

benzidine is likely to be strongly attached to soil 

particles, so it does not easily pass into underground 

water. 

Benzidine can slowly be destroyed by certain other 

chemicals, light, and some microorganisms (for 

example, bacteria). Certain fish, snails, algae, and 

other forms of water life may take up and store very 

small amounts of benzidine, but accumulation in the 

food chain is unlikely. 

 

1.3 HOW MIGHT I BE EXPOSED TO 

BENZIDINE? 

The general population is not likely to be exposed 

to benzidine through contaminated air, water, soil, 

or food. Benzidine is a manufactured chemical that 

does not occur naturally in the environment. Today, 

U.S. industry makes and uses very little (if any) 

benzidine, and no releases to air, water, or soil are 

reported on the Toxic Release Inventory (TRI). 

Only rarely has benzidine been detected in areas 

other than waste sites, and it has not been found in 

food. Some dyes used to color foods or drinks may 

contain impurities that can be broken down to 

benzidine once inside the body. 

If you live near a hazardous waste site, you could be 

exposed to benzidine by drinking contaminated 

water or by breathing or swallowing contaminated 

dust and soil. Benzidine can also enter the body by 

passing through the skin. Some quantities of dyes 

made from benzidine may still be brought into the 

United States. These may contain small amounts of 

benzidine as a contaminant, or chemicals that may 

be broken down in the body to benzidine. If you use 

such dyes to dye paper, cloth, leather, or other 

materials, you may be exposed by breathing or 

swallowing dust, or through skin contact with dust. 

You may be exposed in a similar way if you work at 

or near hazardous waste sites. 

1.4 HOW CAN BENZIDINE ENTER AND 

LEAVE MY BODY? 

Benzidine can enter your body if you breathe air 

that has small particles of benzidine or dust to 

which benzidine is attached. It can also enter your 

body if you drink water or eat food that has become 

contaminated with benzidine. If your skin comes in 

contact with benzidine, it could also enter your 

body. Generally, it will take only a few hours for 

most of the benzidine to get into your body through 

the lungs and intestines. It may take several days for 

most of the benzidine to pass through your skin. 

Breathing, eating, or drinking benzidine-based dyes 
 PUBLIC HEALTH STATEMENT 

 BENZIDINE CAS#: 92-87-5 

Division of Toxicology September 2001 

__________________________________________________________________________________________

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 

may also expose you to benzidine. Your intestines 

contain bacteria that can break down these dyes into 

benzidine. 

Once in your body, only a small portion of 

benzidine will leave as waste in your urine and 

feces. Your body will change most of the benzidine 

into many different chemical forms (called 

metabolites), which dissolve readily in your bodily 

fluids and are easy for your body to remove. Some 

of these changed forms of benzidine appear to cause 

many of the chemical's harmful effects. Studies 

show that after benzidine has entered your body, 

most of it (and its changed forms) will be removed 

within a week. 

1.5 HOW CAN BENZIDINE AFFECT MY 

HEALTH? 

Very little information is available on the noncancer 

health effects that may be caused by exposure to 

benzidine. Benzidine contact with your skin could 

possibly cause a skin allergy. Except for the cancer 

discussed next, benzidine has not been definitely 

shown to cause major adverse health effects in 

humans. 

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. 

Benzidine can cause cancer. This has been shown in 

studies of workers who were exposed for many 

years to levels much higher than the general 

population would experience. It is important to note 

that most of the workers did not develop cancer, 

even after such high exposures. When cancer does 

occur, most often it is cancer of the urinary bladder. 

Some evidence suggests that other organs, such as 

the stomach, kidney, brain, mouth, esophagus, liver, 

gallbladder, bile duct, and pancreas, may also be 

affected. Experiments with animals have also 

shown benzidine to be a carcinogen (a cancer 

causing substance). The Department of Health and 

Human Services (DHHS), the International Agency 

for Research on Cancer (IARC), and the EPA have 

determined that benzidine is a human carcinogen. In 

addition, dyes made from benzidine, such as Direct 

Blue 6, Direct Black 38, and Direct Brown 95, have 

been shown to cause cancer in animals, and there is 

some evidence that they may cause bladder cancer 

in humans. DHHS has determined that Direct Black 

38 and Direct Blue 6 cause cancer in animals, and 

IARC has also determined that Direct Black 38, 

Direct Blue 6, and Direct Brown 95 cause cancer in 

animals. 

1.6 HOW CAN BENZIDINE 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 
 PUBLIC HEALTH STATEMENT 

 BENZIDINE CAS#: 92-87-5 

Division of Toxicology September 2001 

__________________________________________________________________________________________

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 

exposed to benzidine if they eat small amounts of 

soil contaminated with benzidine. However, studies 

suggest that it is difficult to release benzidine once 

it becomes attached to most types of soils. Exposure 

by contaminated soil may occur if the children live 

in an area near a source of the chemical (such as a 

hazardous waste site that contains benzidine). There 

are no studies on health effects in children exposed 

to benzidine. There is no information on whether 

benzidine causes birth defects in children. It is 

unknown whether birth defects would occur in the 

newborn babies of animals that breathed or ate 

benzidine, or had it on their skin while they were 

pregnant. There is no information to determine 

whether children differ from adults in their 

sensitivity to the health effects of benzidine. There 

is indirect evidence that benzidine or its breakdown 

products can cross the placenta, but it is not known 

whether it can be transferred to the young through 

the mother’s milk. 

 

1.7 HOW CAN FAMILIES REDUCE THE 

RISK OF EXPOSURE TO BENZIDINE? 

If your doctor finds that you have been exposed to 

significant amounts of benzidine, ask whether your 

children might also be exposed. Your doctor might 

need to ask your state health department to 

investigate. Benzidine has no agricultural or food 

chemical uses, so exposure to it by eating 

contaminated food is not likely. Impurities in 

certain food dyes can be transformed inside the 

body to benzidine. Children may be exposed to 

benzidine if they eat small amounts of soil 

contaminated with benzidine. Children should be 

prevented from eating soil; make sure they wash 

their hands frequently, and before eating. 

Discourage your children from putting their hands 

in their mouths or from doing other hand-to-mouth 

activities. 

1.8 IS THERE A MEDICAL TEST TO 

DETERMINE WHETHER I HAVE BEEN 

EXPOSED TO BENZIDINE? 

Several tests have been developed to help determine 

whether you have been exposed to benzidine. 

Although these tests must be performed by experts 

in special laboratories, your doctor can collect the 

blood or urine samples and send them to an 

appropriate testing facility. Benzidine and its 

breakdown products can be detected in your urine, 

but only within about 2 weeks after your last 

exposure. Benzidine and some of its changed forms 

will bind to proteins within your red blood cells, 

and this can be detected for up to 4 months after 

your last exposure. Benzidine in some of its forms 

can bind to the DNA found in most of your cells. 

There are extremely sensitive tests that can detect 

such binding; scientists continue to investigate 

whether these tests can detect benzidine only or 

other similar chemicals too. None of these tests, 

however, can predict whether harmful effects will 

occur later. 

1.9 WHAT RECOMMENDATIONS HAS THE 

FEDERAL GOVERNMENT MADE TO 

PROTECT HUMAN HEALTH? 

The federal government develops regulations and 

recommendations to protect public health. 

Regulations can be enforced by law. Federal 

agencies that develop regulations for toxic 

substances include the Environmental Protection 

Agency (EPA), the Occupational Safety and Health 

Administration (OSHA), and the FDA. 

Recommendations provide valuable guidelines to 
 PUBLIC HEALTH STATEMENT 

 BENZIDINE CAS#: 92-87-5 

Division of Toxicology September 2001 

__________________________________________________________________________________________

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 

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 benzidine include the following: Because 

benzidine can cause cancer, the EPA has issued 

regulations that list it as a "priority" chemical, 

subject to rigid inspection and control. EPA allows 

0.10 parts of benzidine per million parts of waste 

(0.10 ppm) that is brought to waste disposal sites. 

EPA also requires that any release of one pound or 

more of benzidine or its salts to the environment 

must be reported to the federal government's 

National Response Center. EPA's Office of Water 

also has water quality guidelines to protect human 

health. These guidelines suggest that benzidine 

concentration limits should be maintained at less 

than 1 part benzidine in a trillion parts of water 

(ppt). Although zero benzidine is preferred, lifetime 

exposure to these concentrations is estimated to 

result in no more than one additional case of cancer 

in a million persons exposed. OSHA considers 

benzidine to be a carcinogen, and has issued 

regulations to reduce the risk of exposure in any 

workplace in which it might still be found. These 

regulations include entry controls, housekeeping 

and disposal rules, other rules on operating and 

handling procedures, and requirements that 

employers make showers and dressing rooms 

available. NIOSH recommends that worker 

exposure to benzidine-based dyes be kept to the 

lowest feasible concentration, and it considers 

benzidine to be an occupational carcinogen. EPA's 

Office of Water has set a discharge limit for 

benzidine-based dye applicators of 10 micrograms 

per liter (10 μg/L) (one μg is one millionth of a 

gram) over any calendar month or not more than 25 

μg/L in any working day. FDA allows a maximum 

of 1 part of benzidine per billion parts (ppb) of 

some color additives for foods. 

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. 
 PUBLIC HEALTH STATEMENT 

 BENZIDINE CAS#: 92-87-5 

Division of Toxicology September 2001 

__________________________________________________________________________________________

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 

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). 2001. Toxicological profile for 

Benzidine. Atlanta, GA: U.S. Department of Health 

and Human Services, Public Health Service.