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.
Pathways for 3,3'-dichlorobenzidine in 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 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.
Exposure 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.
Pathways for 3,3'-dichlorobenzidine in the 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.
Health effects of 3,3'-dichlorobenzidine
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 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.
You should know that one way to learn whether a chemical will harm people is to determine how the body absorbs, uses, and releases the chemical. For some chemicals, animal testing may be necessary. Animal testing may also help identify such health effects as cancer or birth defects. Without laboratory animals, scientists would lose a basic method for getting information needed to make wise decisions that protect public health. Scientists have the responsibility to treat research animals with care and compassion. Scientists must comply with strict animal care guidelines because laws today protect the welfare of research animals.
Additionally, there are vigorous national and international efforts to develop alternatives to animal testing. The efforts focus on both in vitro and in silico approaches and methods. For example, the National Toxicology Program (NTP) at the National Institute of Environmental Health Sciences (NIEHS) created the NTP Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) in 1998. The role of NICEATM is to serve the needs of high quality, credible science by facilitating development and validation—and regulatory and public acceptance—of innovative, revised test methods that reduce, refine, and replace the use of animals in testing while strengthening protection of human health, animal health and welfare, and the environment. In Europe, similar efforts at developing alternatives to animal based testing are taking place under the aegis of the European Centre for the Validation of Alternative Methods (ECVAM).
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.
Health effects in 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 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.
Reducing 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 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.
Medical tests for exposure to 3,3'-dichlorobenzidine
Exposure to 3,3'-dichlorobenzidine can be determined by finding the chemical or its metabolites in urine. This is known as biomonitoring. 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.
- The Agency for Toxic Substances and Disease Registry
- Interagency Coordinating Committee on the Validation of Alternative Methods
- European Centre for the Validation of Alternative Methods
- Institute for Laboratory Animal Research
Disclaimer: This article is taken wholly from, or contains information that was originally published by, the Agency for Toxic Substances and Disease Registry. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the Agency for Toxic Substances and Disease Registry should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.