'
 

TOXICOLOGICAL PROFILE FOR
 

METHYLENEDIANILINE
 

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES
 

Public Health Service
 

Agency for Toxic Substances and Disease Registry
 

August 1998 
METHYLENEDIANILINE ii 

DISCLAIMER 

The use of company or product name(s) is for identification only and does not imply endorsement by the 

Agency for Toxic Substances and Disease Registry. 
METHYLENEDIANILINE iii 

UPDATE STATEMENT
 

A Toxicological Profile for methylenedianiline was released in October 1995. This edition supersedes 

any previously released draft or final profile. 

Toxicological profiles are revised and republished as necessary, but no less than once every three years. 

For information regarding the update status of previously released profiles, contact ATSDR at: 

Agency for Toxic Substances and Disease Registry
 

Division of Toxicology/Toxicology Information Branch
 

1600 Clifton Road NC, E-29
 

Atlanta, Georgia 30333
 


*Legislative Background vi 

The toxicological profiles are developed in response to the Super-fund Amendments and 

Reauthorization Act (SARA) of 1986 (Public Law 99-499) which amended the Comprehensive 

Environmental Response, Compensation, and Liability Act of 1980 (CERCLA or Super-fund). Section 

211 of SARA also amended Title 10 of the U. S. Code, creating the Defense Environmental 

Restoration Program. Section 2704(a) of Title 10 of the U. S. Code directs the Secretary of Defense 

to notify the Secretary of Health and Human Services of not less than 25 of the most commonly found 

unregulated hazardous substances at defense facilities. Section 2704(b) of Title 10 of the U. S. Code 

directs the Administrator of the Agency for Toxic Substances and Disease Registry (ATSDR) to 

prepare a toxicological profile for each substance on the list provided by the Secretary of Defense 

under subsection (b). 
METHYLENEDIANILINE vii 

CONTRIBUTORS 

CHEMICAL MANAGER(S)/AUTHORS(S): 

Zemoria A. Rosemond, B.A.
 

ATSDR, Division of Toxicology, Atlanta, GA
 

Fernando Llados, Ph.D.
 

Research Triangle Institute, Research Triangle Park, NC
 

THE PROFILE HAS UNDERGONE THE FOLLOWING ATSDR INTERNAL REVIEWS:
 

1. Green Border Review. Green Border review assures consistency with ATSDR policy. 

2. Health Effects Review. The Health Effects Review Committee examines the health effects 

chapter of each profile for consistency and accuracy in interpreting health effects and classifying 

end points. 

3. Minimal Risk Level Review. The Minimal Risk Level Workgroup considers issues relevant to 

substance-specific minimal risk levels (MRLs), reviews the health effects database of each 

profile, and makes recommendations for derivation of MRLs. 

4. Data Needs Review. The Research Implementation Branch reviews data needs sections to assure 

consistency across profiles and adherence to instructions in the Guidance. 

METHYLENEDIANILINE ix 

PEER REVIEW
 

A peer review panel was assembled for 4,4 ́-methylenedianiline. The panel consisted of the following 

members : 

1 . Dr. G.A.S. Ansari, Professor, Department of Human Biological Chemistry and Genetics and 

Pathology, University of Texas Medical Branch, Galveston, TX 77555; 

2 . Dr. W. Decker, Private Consultant, El Paso, TX 79904; and 

3 . Dr. E. Sowinski, Vice President, Environmental Health Management and Science, 

Hudson, OH 44236. 

These experts collectively have knowledge of 4,4 ́-methylenedianiline’s physical and chemical properties, 

toxicokinetics, key health end points, mechanisms of action, human and animal exposure, and 

quantification of risk to humans. All reviewers were selected in conformity with the conditions for peer 

review specified in Section 104(i)( 13) of the Comprehensive Environmental Response, Compensation, 

and Liability Act, as amended. 

Scientists from the Agency for Toxic Substances and Disease Registry (ATSDR) have reviewed the peer 

reviewers’ comments and determined which comments will be included in the profile. A listing of the 

peer reviewers’ comments not incorporated in the profile, with a brief explanation of the rationale for their 

exclusion, exists as part of the administrative record for this compound. A list of databases reviewed and 

a list of unpublished documents cited are also included in the administrative record. 

The citation of the peer review panel should not be understood to imply its approval of the profile’s final 

content. The responsibility for the content of this profile lies with the ATSDR. 









METHYLENEDIANILINE 1 

1. PUBLIC HEALTH STATEMENT 

This public health statement tells you about 4,4'-methylenedianiline 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 clean-up activities. 4,4'-methylenedianiline has not been found 

in any of the 1,445 current or former NPL sites. However, the total number of NPL sites 

evaluated is not known. As more sites are evaluated, the number of sites at which 

4,4'-methylenedianiline is found may increase. This 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 can be exposed to a substance only when you come in contact with it 

by breathing, eating, touching, or drinking. 

If you are exposed to 4,4'-methylenedianiline 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 METHYLENEDIANILINE? 

Methylenedianiline exists in several very similar forms. Of these various forms,-

4,4'-methylenedianiline is the form used by industries. This profile discusses this important 

form of methylenedianiline. Other forms of methylenedianiline are only used as laboratory 

chemicals and have no commercial uses at this time. 4,4'-Methylenedianiline is also 

commonly known as diaminodiphenylmethane or MDA. It is a colorless (like an ice cube) to 

pale yellow solid with a faint amine odor (sharp odor). The taste of the compound is not 
METHYLENEDIANILINE 

4,4'-methylene2 

1. PUBLIC HEALTH STATEMENT 

known. It is very slightly soluble in water (does not mix well with water) and does not 

readily evaporate at room temperature. If left in an open container, it slowly turns brown 

because of chemical reactions with components present in air. 

4,4'-methylenedianiline is an industrially produced compound that is not known to occur 

naturally. It is produced by industries mainly for making polyurethane foams (such as 

insulating materials in mailing containers). Smaller amounts are used for making coating 

materials, epoxy resins (glues), Spandexfiber, and dyes and for other purposes. You can 

find more information on the properties, sources, and uses of 4,4'-methylenedianiline in 

Chapters 3 and 4. 

1.2 WHAT HAPPENS TO WHEN IT ENTERS THE 

ENVIRONMENT? 

Most 4,4'-methylendianiline enters the environment when it’s produced or when it’s used to 

make other compounds. Of the total environmental release of at least 20,000 pounds per 

year, 52.6% is released to the air and 45% is released to deep soil during underground 

injection. Only 2.4% of the total is released to land and water. In addition, about 

2,000 pounds per year are transferred to public sewer systems for treatment. No estimate is 

available for the amounts of 4,4'-methylenedianiline that enter the environment from 

accidental spills or from identified hazardous waste sites that may contain 

dianiline. 

The lack of experimental data makes it difficult to be certain about what happens to 

4,4'-methylenedianiline when it enters the environment. In air, 4,4'-methylenedianiline will 

mostly be present as tiny particles and will eventually return to land and water by settling and 

by being brought down in rain and snow. In water, most of the 4,4'-methylenedianiline will 

tend to attach itself to particles and sediments, and will eventually settle to the bottom. 

4,4'-methylenedianiline present in water and sediment will eventually be broken down by 

bacteria and other microorganisms. This process may take as long as 10-40 days. 

4,4'-methylenedianiline does not tend to build up in the food chain, and it is uncertain 
4,4'-methylene-

 

making 

kidney 

METHYLENEDIANILINE 3 

1. PUBLIC HEALTH STATEMENT 

whether it accumulates in fish. When deposited on soil, 4,4'-methylenedianiline will become 

strongly attached to it and, as a result, will not move quickly with rainwater into deeper 

groundwater. Bacteria and microorganisms present in soil will break down 

dianiline, but the process may take as long as 10 days. See Chapter 5 for more information 

about what happens to 4,4'-methylenedianiline in the environment. 

1.3 HOW MIGHT I BE EXPOSED TO METHYLENEDIANILINE? 

You are most likely to be exposed to 4,4'-methylenedianiline if you work with it. The 

general population may be exposed to extremely low levels of 4,4'-methylenedianiline 

through consumer goods such as polyurethane cushioning or products that contain epoxy. 

The Food and Drug Administration (FDA) reports that the level of exposure to 

4,4'-methylenedianiline through food is virtually zero. People who live near hazardous waste 

sites that contain 4,4'-methylenedianiline are susceptible to exposure if dust particles 

containing the substance are released from the waste site, enter the air, and are breathed into 

the body. Children playing near these sites may be exposed by touching and eating soil that 

contains 4,4'-methylenedianiline However, there is no experimental or estimated value for 

the intake of 4,4'-methylenedianiline by the general population. 

People who work in the following industries can be exposed to 4,4'-methylenedianiline by 

breathing in the dust or aerosol, or by getting it on their skin:manufacture, formulation, and 

packaging of 4,4'-methylenedianiline certain paint making industries that use epoxy 

materials; pattern and tool with polyurethane; potting and encapsulation with 

polyurethane; and casting and molding with resins made with 4,4'-methylenedianiline 

4,4'-methylenedianiline has been detected in workplace air, in skin patches worn by workers, 

and in the urine of workers in these industries. However, the level in work atmaspheres 

rarely exceeds the level of 0.8 milligram (mg) of 4,4'-methylenedianiline in a cubic meter of 

air (1 mg is equivalent to a thousandth of a gram), which is suggested as a safe level by the 

American Conference of Governmental Industrial Hygienists (ACGIH). The maximum 

exposure was found to occur in workers in the manufacturing and formulating industries. 

People with diseases or who need frequent blood transfusions may be exposed to tiny 
METHYLENEDIANILINE 4 

1. PUBLIC HEALTH STATEMENT 

amounts of 4,4 ́-methylenedianiline during their treatment by machines like dialyzers. The 

compound is released from polyurethane parts of equipment when they are sterilized with 

radiation or heat. See Chapter 5 for more information about 4,4 ́-methylenedianiline 

exposure. 

1.4 HOW CAN METHYLENEDIANILINE ENTER AND LEAVE MY BODY? 

If you breathe air containing dust contaminated with 4,4 ́-methylenedianiline, it can enter your 

body through your lungs and pass into the bloodstream. We do not know how much of the 

4,4 ́-methylenedianiline will pass into your bloodstream or how fast this will happen. If you 

swallow food, water, or soil contaminated with 4,4 ́-methylenedianiline, some of it will 

probably enter your body and pass from the stomach into the bloodstream, but we do not 

know how much or how fast this will occur. If you touch soil containing 4,4 ́-'methylenedianiline 

(for example, at a hazardous waste site), some 4,4 ́-methylenedianiline will pass 

through the skin into the bloodstream, but we do not know how much or how fast. For 

people living around waste sites, or processin, or storage facilities, the most likely way it will 

enter their bodies is from skin contact with contaminated soil. For people who work with or 

around 4,4 ́-methylenedianiline, skin contact with contaminated dirt particles is the most likely 

way it will enter the body. Once 4,4 ́-methylenedianiline is in your body, it may change into 

other related chemicals called metabolites. We think that some metabolites of 

4,4 ́-methylenedianiline may be more harmful than unchanged 4,4 ́-methylenedianiline, but 

there is no conclusive experimental evidence to support this assumption. Some of the 

metabolites may leave your body in the urine within hours. We do not know if 

4,4 ́-methylenedianiline is stored in the body. For more information on how 4,4 ́-methylenedianiline 

can enter and leave your body, see Chapter 2. 

1.5 HOW CAN METHYLENEDIANILINE AFFECT MY HEALTH? 

Studies in the workplace suggest that exposure to 4,4 ́-methylenedianiline may cause skin 

irritation and can damage your liver. People who ate bread that was accidentally 

contaminated with 4,4 ́-methylenedianiline also experienced liver damage. We do not know, 
METHYLENEDIANILINE 5 

1. PUBLIC HEALTH STATEMENT 

however, how much 4,4 ́-methylenedianiline was in the bread. We do not know if breathing 

air contaminated with 4,4 ́-methylenedianiline, or eating contaminated food, or skin contact 

affects human reproduction or development. We also do not know if 4,4 ́-methylenedianiline 

affects the nervous system or the ability to fight disease 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 must treat research animals with care and 

compassion. Laws today protect the welfare of research animals, and scientists must comply 

with strict animal care guidelines. 

Some mice that drank water containing large amounts of 4,4 ́-methylenedianiline for a short 

period died as a result. Rats that ate food or drank water containing smaller amounts of 

4,4 ́-methylenedianiline for months or years had liver damage and thyroid gland injuries. 

Only a small amount of information exists on the health effects in animals exposed to 

4,4 ́-methylenedianiline by breathing or skin contact. This information indicates that guinea 

pigs that breathed air contaminated with a very high amount of 4,4 ́-methylenedianiline for 

2 weeks suffered damage to their eyes. Rabbits that received repeated skin exposure to 

relatively high amounts of 4,4 ́-methylenedianiline also had liver damage. There is not 

enough information to determine if exposure to 4,4 ́-methylenedianiline affects reproduction, 

development, the nervous system, or the ability to fight disease in animals. 

There is not enough information on workers to determine if 4,4 ́-methylenedianiline is 

carcinogenic (causes cancer) in people. Rats and mice that drank water containing 

4,4 ́-methylenedianiline throughout their lives developed cancer in their liver and thyroid 

glands. The International Agency for Research on Cancer (IARC) has determined that 
METHYLENEDIANILINE 6 

1. PUBLIC HEALTH STATEMENT 

4,4 ́-methylenedianiline is possibly carcinogenic to humans. For more information on how 

4,4 ́-methylenedianiline can affect your health, see Chapter 2. 

1.6	 IS THERE A MEDICAL TEST TO DETERMINE WHETHER I HAVE BEEN EXPOSED 

TO METHYLENEDIANILINE? 

Samples of your urine can be tested to find out if you have recently been exposed to 

4,4 ́-methylenedianiline. These tests will only confirm if you have been exposed. They 

cannot estimate how much of it has entered your body and will not tell you whether your 

health will be affected by exposure to 4,4 ́-methylenedianiline. The exposure tests are not 

routinely available in hospitals and clinics because they require special analytical equipment 

and must be specially requested by your physician. See Chapters 2 and 6 for more 

information about tests for exposure to 4,4 ́-methylenedianiline. 

1.7 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 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. 
METHYLENEDIANILINE 7 

1. PUBLIC HEALTH STATEMENT 

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 4,4 ́-methylenedianiline include 

the following: 

NIOSH recommends that workers should not breathe air that contains more than 

0.03 milligram of 4,4 ́-methylenedianiline per cubic meter of air (0.03 mg/m3

) during a 

10-hour workday, 40-hour workweek. 

OSHA recommends that workers should not be exposed to more than 0.081 mg/m3 

4,4 ́-methylenedianiline during an 8-hour workday. 

ACGIH recommends that workers should not be exposed to more than 0.81 mg/m3 

4,4 ́-methylenedianiline for an 8-hour workday, 40-hour workweek. 

See Chapter 7 for more information on regulations and guidelines concerning 4,4 ́-methylenedianiline. 

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 E-29
 

Atlanta, GA 30333
 

Information line and technical assistance 

Phone: (404) 639-6000 

Fax: (404) 639-6315 or 6324 

ATSDR can also tell you the location of occupational and environmental health clinics. 

These clinics specialize in recognizing, evaluation and treating illnesses resulting from 

exposure to hazardous substances. 
METHYLENEDIANILINE 8 

1. PUBLIC HEALTH STATEMENT 

To order toxicological profiles, contact 

National Technical Information Service 

5285 Port Royal Road 

Springfield, VA 22161 

Phone: (800) 553-6847 or (703) 487-4650 
 

 

METHYLENEDIANILINE 9 

2. HEALTH EFFECTS 

2.1 INTRODUCTION 

The primary purpose of this chapter is to provide public health officials, physicians, toxicologists, and 

other interested individuals and groups with an overall perspective of the toxicology of 4,4 ́­

methylenedianiline. It contains descriptions and evaluations of toxicological studies and epidemiological 

investigations and provides conclusions, where possible, on the relevance of toxicity and toxicokinetic 

data to public health. 

Methylenedianilines can exist in five isomeric forms: 2,2’-methylenedianiline; 2,4’-methylenedianiline; 

3,3’-methylenedianiline; 3,4’-methylenedianiline; and 4,4 ́-methylenedianiline. Of the various isomers, 

2,2’-methylenedianiline, 3,4’-methylenedianiline, 3,3’-methylenedianiline, and 2,4’-methylenedianiline 

are produced on a very small scale as a research chemical (HSDB 1996). The isomer 4,4 ́­

methylenedianiline is produced in the United States for industrial use. Therefore, this profile will limit its 

discussion to 4,4 ́-methylenedianiline. 

A glossary and list of acronyms, abbreviations, and symbols can be found at the end of this profile. 

2.2 DISCUSSION OF HEALTH EFFECTS BY ROUTE OF EXPOSURE 

To help public health professionals and others address the needs of persons living or working near 

hazardous waste sites, the information in this section is organized first by route of exposure-inhalation, 

oral, and dermal; and then by health effect-death, systemic, immunological, neurological, reproductive, 

developmental, genotoxic, and carcinogenic effects. These data are discussed in terms of three exposure 

periods-acute (14 days or less), intermediate (15-364 days), am chronic (365 days or more). 

Levels of significant exposure for each route and duration are presented in tables and illustrated in 

figures. The points in the figures showing no-observed-adverse-effect levels (NOAELs) or lowestobserved-adverse-effect levels (LOAELs) reflect the actual doses (levels of exposure) used in the 

studies. LOAELS have been classified into “less serious” or “serious” effects. “Serious” effects are 

those that evoke failure in a biological system and can lead to morbidity or mortality (e.g., acute 
METHYLENEDIANILINE 10 

2. HEALTH EFFECTS 

respiratory distress or death). “Less serious” effects are those that are not expected to cause significant 

dysfunction or death, or those whose significance to the organism is not entirely clear. ATSDR 

acknowledges that a considerable amount of judgment may be required in establishing whether an end 

point should be classified as a NOAEL, “less serious” LOAEL, or “serious” LOAEL, and that in some 

cases, there will be insufficient data to decide whether the effect is indicative of significant 

dysfunction. However, the Agency has established guidelines and policies that are used to classify 

these end points. ATSDR believes that there is sufficient merit in this approach to warrant an attempt 

at distinguishing between “less serious” and “serious” effects. The distinction between “less serious” 

effects and “serious” effects is considered to be important because it helps the users of the profiles to 

identify levels of exposure at which major health effects start to appear. LOAELs or NOAELs should 

also help in determining whether or not the effects vary with dose and/or duration, and place into 

perspective the possible significance of these effects to human health. 

The significance of the exposure levels shown in the Levels of Significant Exposure (LSE) tables and 

figures may differ depending on the user’s perspective. Public health officials and others concerned 

with appropriate actions to take at hazardous waste sites may want information on levels of exposure 

associated with more subtle effects in humans or animals (LOAEL) or exposure levels below which no 

adverse effects (NOAELs) have been observed. Estimates of levels posing minimal risk to humans 

(Minimal Risk Levels or MRLs) may be of interest to health professionals and citizens alike. 

Levels of exposure associated with carcinogenic effects (Cancer Effect Levels, CELs) of 

4,4 ́-methylenedianiline are indicated in Tables 2-2 and 2-3 and Figure 2-2. 

Estimates of exposure levels posing minimal risk to humans (Minimal Risk Levels or MRLs) have 

been made for 4,4 ́-methylenedianiline. An MRL is defined as an estimate of daily human exposure to 

a substance that is likely to be without an appreciable risk of adverse effects (noncarcinogenic) over a 

specified duration of exposure. MRLs are derived when reliable and sufficient data exist to identify 

the target organ(s) of effect or the most sensitive health effect(s) for a specific duration within a given 

route of exposure. MRLs are based on noncancerous health effects only and do not consider 

carcinogenic effects. MRLs can be derived for acute, intermediate, and chronic duration exposures for 

inhalation and oral routes. Appropriate methodology does not exist to develop MRLs for dermal 

exposure. 
METHYLENEDIANILINE 11 

2. HEALTH EFFECTS 

Although methods have been established to derive these levels (Barnes and Dourson 1988; EPA 1990), 

uncertainties are associated with these techniques. Furthermore, ATSDR acknowledges additional 

uncertainties inherent in the application of the procedures to derive less than lifetime MRLs. As an 

example, acute inhalation MRLs may not be protective for health effects that are delayed in 

development or are acquired following repeated acute insults, such as hypersensitivity reactions, 

asthma, or chronic bronchitis. As these kinds of health effects data become available and methods to 

assess levels of significant human exposure improve, these MRLs will be revised. 

A User’s Guide has been provided at the end of this profile (see Appendix B). This guide should aid 

in the interpretation of the tables and figures for Levels of Significant Exposure and the MRLs. 

2.2.1 Inhalation Exposure 

Occupational exposure to 4,4 ́-methylenedianiline probably involves both inhalation of dust particles 

containing the chemical, and dermal contact with these particles. In addition, direct ingestion of 

contaminated dust or ingestion of particles that are expelled from the respiratory tree cannot be ruled 

out. It is generally agreed, however, that dermal contact is the main contributing route of exposure in 

occupational settings. For this reason, health effects in humans attributed to occupational exposure to 

4,4 ́-methylenedianiline are discussed in Section 2.2.3, Dermal Exposure. 

2.2.1.1 Death 

No studies were located regarding death in humans or animals after inhalation exposure to 

4,4 ́-methylenedianiline. 

2.2.1.2 Systemic Effects 

No studies were located regarding systemic effects in humans after inhalation exposure to 

4,4 ́-methylenedianiline. In addition, no studies were located regarding cardiovascular, gastrointestinal, 

hematological, or musculoskeletal effects in animals after inhalation exposure to 4,4 ́-methylenedianiline. 

Only one study was located that provided some information on systemic effects of inhaled 

4,4 ́-methylenedianiline in animals; this limited information is summarized below. 
 

METHYLENEDIANILINE 12 

2. HEALTH EFFECTS 

The highest NOAEL values and all LOAEL values for each species and duration category are recorded 

in Table 2-l and plotted in Figure 2-l. 

Respiratory Effects. Guinea pigs exposed nose-only to 440 mg/m3

 of an aerosol of 

4,4 ́-methylenedianiline in propylene glycol 4 hours per day, 5 days per week for 2 weeks experienced 

no respiratory distress during exposures (Leong et al. 1987). The mean particle diameter was 2.4 μm. 

Two weeks after exposures terminated and prior to sacrifice, tests were conducted to detect possible 

changes in the distensibility of the lungs from an intratracheal challenge dose of 4,4 ́-methylenedianiline; 

the results were unremarkable. Histopathologic examination of the lungs revealed mild to 

slight pneumonia and pulmonary granulomas. 

Hepatic Effects. No histopathological alterations were observed in the liver of guinea pigs 

exposed nose-only to 440 mg/m3 of an aerosol of 4,4 ́-methylenedianiline 4 hours per day, 5 days per 

week for 2 weeks (Leong et al. 1987). The animals were sacrificed 2 weeks after the exposure period 

terminated. No further information regarding hepatic effects after inhalation exposure to 

4,4 ́-methylenedianiline was located. 

Renal Effects. No histopathological alterations were observed in the kidneys of guinea pigs 

exposed nose-only to 440 mg/m3

 of an aerosol of 4,4 ́-methylenedianiline 4 hours per day, 5 days per 

week for 2 weeks (Leong et al. 1987). Sacrifices were conducted 2 weeks after the exposure period 

terminated. No further information regarding renal effects following inhalation exposure to 

4,4 ́-methylenedianiline was located. 

Dermal Effects. The possibility that inhalation exposure to 4,4 ́-methylenedianiline could induce 

dermal sensitization was explored in guinea pigs (Leong et al. 1987) (see Section 2.2.3.2). The 

animals were exposed nose-only to 440 mg/m3

 of an aerosol of 4,4 ́-methylenedianiline 4 hours per 

day, 5 days per week for 2 weeks. Two weeks after exposure ceased, 4,4 ́-methylenedianiline 

(0.2-22 mg/kg) was applied to shaved sites of skin and observations were made for up CO 24 hours. 

Neither erythema nor edema were observed suggesting that under the conditions of the experiment, 

4,4 ́-methylenedianiline was not a dermal sensitizer. No further information was located regarding 

dermal effects after inhalation exposure to 4,4 ́-methylenedianiline. 


 

METHYLENEDIANILINE 15 

2. HEALTH EFFECTS 

Ocular Effects. The role of melanin in ocular toxicity of 4,4 ́-methylenedianiline was examined in 

guinea pigs (Leong et al. 1987). Two strains were used, albino (lacking melanin) and pigmented. The 

animals were exposed nose-only to 440 mg/m3

 of an aerosol of 4,4 ́-methylenedianiline 4 hours per 

day, 5 days per week for 2 weeks. Two weeks after exposure terminated, the animals were sacrificed 

and the retinas examined. The retinas of both strains showed marked alterations ranging from 

retraction and thickening of the outer segments of the photoreceptor cells to swelling and retraction 

extended through the inner segments of the photoreceptors to the outer nuclear layer. There were also 

degenerative changes in the pigmented epithelial cells. Since the retinal lesions were similar in both 

strains, the authors concluded that these changes were not related to the affinity of 4,4 ́-methylenedianiline 

for melanin. No further information was located regarding ocular effects after inhalation 

exposure to 4,4 ́-methylenedianiline. 

Body Weight Effects. Guinea pigs exposed nose-only to 440 mg/m3

 of an aerosol of 

4,4 ́-methylenedianiline 4 hours per day, 5 days per week for 2 weeks experienced a slight weight loss 

during exposure days, but recovery was apparent during the 2 resting weekend days (Leong et al. 

1987). The authors attributed this temporary loss in weight to the stress of being restrained during 

exposure since the trend over the entire experimental period was similar between exposed and control 

animals. No further information was located regarding body weight effects after inhalation exposure 

to 4,4 ́-methylenedianiline. 

No studies were located regarding the following health effects in humans or animals after inhalation 

exposure to 4,4 ́-methylenedianiline: 

2.2.1.3 Immunological and Lymphoreticular Effects 

2.2.1.4 Neurological Effects 

2.2.1.5 Reproductive Effects 

2.2.1.6 Developmental Effects 

2.2.1.7 Genotoxic Effects 

Genotoxicity studies are discussed in Section 2.5. 
METHYLENEDIANILINE 16 

2. HEALTH EFFECTS 

2.2.1.8 Cancer 

No studies were located regarding carcinogenic effects in humans or animals after inhalation exposure 

to 4,4 ́-methylenedianiline. 

2.2.2 Oral Exposure 

2.2.2.1 Death 

No cases of human deaths attributed to oral exposure to 4,4 ́-methylenedianiline were located in the 

literature reviewed. The only relevant information was found in a study that examined the potential 

long-term health effects in a population that had consumed bread contaminated with 4,4 ́­

methylenedianiline in 1965 in the Epping district of Essex, England (Hall et al. 1992). Liver toxicity was 

the main adverse effect reported at the time of the accident (Kopelman et al. 1966). Of the original 

84 cases, 55 people were alive, 18 had died, and 16 could not be traced (Hall et al. 1992). The causes 

of death (neoplastic and non-neoplastic diseases) were, by and large, unremarkable, and the 

observed/expected ratios for death from all causes were well below 1.0. Thus, there was no obvious 

relationship between ingestion of 4,4 ́-methylenedianiline in that particular episode and death in 

humans. 

Several studies have reported death in animals after oral administration of 4,4 ́-methylenedianiline. In 

Wistar rats, oral LD50 values of 335 mg/kg (Schmidt et al. 1980) and 830 mg/kg (Pludro et al. 1969) 

were reported. In the former study, the test material was administered in propylene glycol, whereas 

peanut oil was used as vehicle in the latter. Two of 5 male mice died in a 14-day study after 

receiving daily doses of 207 mg 4,4 ́-methylenedianiline/kg/day in the drinking water, 1 of 5 females 

died at a 220 mg/kg/day dose level; all males and females (5/5) died at 829 mg/kg/day and 

882 mg/kg/day, respectively (NTP 1983). The cause of death was not reported. The LD50 values in 

male guinea pigs and male rabbits administered 4,4 ́-methylenedianiline in peanut oil were 260 mg/kg 

and 620 mg/kg, respectively (Schmidt et al. 1974). In an intermediate-duration study, female SpragueDawley rats were treated by gavage intermittently for 30 days with 36 mg 4,4 ́-methylenedianiline/ 

kg/day in sesame oil (Griswold et al. 1968). Forty-five days after treatment started, survival 

in treated rats was reduced 16% relative to untreated controls; the cause of death was not reported. In 

a chronic-duration study, survival rate was reduced by approximately 20% in male B6C3F1 mice 
METHYLENEDIANILINE 17 

2. HEALTH EFFECTS 

administered doses of 57 mg 4,4 ́-methylenedianiline/kg/day in the drinking water for 103 weeks 

(Lamb et al. 1986; NTP 1983). 

LOAEL and LD50 values for death for each species and duration category are recorded in Table 2-2 

and plotted in Figure 2-2. 

2.2.2.2 Systemic Effects 

Little information is available regarding systemic effects in humans after oral exposure to 

4,4 ́-methylenedianiline. In contrast, numerous studies have examined the effects of oral 

administration of 4,4 ́-methylenedianiline in animals, particularly in rats. The overall evidence 

suggests that the liver and perhaps the thyroid are target organs for 4,4 ́-methylenedianiline toxicity. 

The highest NOAEL values and all reliable LOAEL values for systemic effects for each species and 

duration category are recorded in Table 2-2 and plotted in Figure 2-2. 

Respiratory Effects. Abnormal respiratory rhythm was reported in a man on arrival to the 

hospital after drinking an unspecified amount of a liquid containing 4,4 ́-methylenedianiline, potassium 

carbonate, and gamma-butyrolactone (Roy et al. 1985). Because of the simultaneous ingestion of other 

chemicals, the role of 4,4 ́-methylenedianiline, if any, in causing this respiratory effect cannot be 

ascertained. 

No gross or histopathogical alterations were observed in the lungs, trachea, bronchi, or nasal cavity of 

rats administered up to 141 mg 4,4 ́-methylenedianiline/kg/day in drinking water for 13 weeks or up to 

19 mg/kg/day for 103 weeks (Lamb et al. 1986; NTP 1983). Similar findings were reported in mice 

administered up to 116 mg 4,4 ́-methylenedianiline/kg/day in the drinking water for 13 weeks or up to 

57 mg/kg/day for 103 weeks (Lamb et al. 1986; NTP 1983). An earlier study reported lung 

congestion and hyperemia, pneumonia, and pulmonary edema in female beagle dogs treated with doses 

of approximately 2.7 mg 4,4 ́-methylenedianiline/kg/day for 54-84 months (Deichmann et al. 1978). 

The test material was dissolved in corn oil and administered in a gelatin capsule 3 times per week. 

Because this study used only a total of 9 animals and no concurrent controls were-used, the validity of 

the findings is unclear. 













METHYLENEDIANILINE 31 

2. HEALTH EFFECTS 

Cardiovascular Effects. Very limited and inconclusive information exists regarding cardiovascular 

effects in humans after ingestion of 4,4 ́-methylenedianiline. Bradycardia, hypotension, and 

abnormal electrocardiogram were reported in a male subject who accidentally drank an undetermined 

amount of a solution containing 4,4 ́-methylenedianiline, potassium carbonate, and gamma-butyrolactone 

(Roy et al. 1985). These signs were observed on arrival to the hospital shortly after the 

accident occurred. Because of the simultaneous ingestion of other chemicals, the role of 

4,4 ́-methylenedianiline, if any, cannot be determined. 

Information on effects in animals is also limited. No gross or histopathogical alterations were 

observed in the heart of rats administered up to 141 mg 4,4 ́-methylenedianiline/kg/day in drinking 

water for 13 weeks or up to 19 mg/kg/day for 103 weeks (Lamb et al. 1986; NTP 1983). Similar 

findings were reported in mice administered up to 116 mg 4,4 ́-methylenedianiline/kg/day in the 

drinking water for 13 weeks or up to 57 mg/kg/day for 103 weeks (Lamb et al. 1986; NTP 1983). 

Gastrointestinal Effects. Nausea, abdominal pain, and vomiting were reported in one female and 

five males (ages 17-25) who drank an alcoholic beverage spiked with 4,4 ́-methylenedianiline 

(Tillmann et al. 1997); the amount of 4,4 ́-methylenedianiline ingested was not known. No further 

information was located regarding gastrointestinal effects in humans following oral exposure to 

4,4 ́-methylenedianiline. 

Doses of ≥261 mg 4,4 ́-methylenedianiline/kg/day administered in the drinking water for 14 days 

induced crater-like foci in the cardiac portion of the stomach in female rats (NTP 1983). The NOAEL 

for this effect in females was 130 mg/kg/day. No such lesions were seen in males treated with up to 

235 mg/kg/day for the same period of time (NTP 1983), but lesions were evident at 469 mg/kg/day. 

Longer-duration studies reported no gross or histopathogical alterations in the salivary glands, 

esophagus, stomach, pancreas, duodenum, jejunum, ileum, and colon from rats administered up to 

141 mg 4,4 ́-methylenedianiline/kg/day in drinking water for 13 weeks or up to 19 mg/kg/day for 

103 weeks (Lamb et al. 1986; NTP 1983). Similar findings were reported in mice administered up to 

116 mg 4,4 ́-methylenedianiline/kg/day in the drinking water for 13 weeks or up to 57 mg/kg/day for 

103 weeks (Lamb et al. 1986; NTP 1983). Intestinal occlusion was reported in an earlier study in rats 

treated by gavage with 83 mg 4,4 ́-methylenedianiline/kg/day for 12 weeks; the NOAEL was 

8.3 mg/kg/day (Pludro et al. 1969). No further information was provided in this study. 
METHYLENEDIANILINE 32 

2. HEALTH EFFECTS 

Hematological Effects. Limited information was located regarding hematological effects in 

humans after oral exposure to 4,4 ́-methylenedianiline. A male subject developed eosinophilia with 

left shift in neutrophils 7-35 days after accidentally ingesting a solution containing a 4,4 ́­

methylenedianiline, potassium carbonate, and gamma-butyrolactone (Roy et al. 1985). This is consistent 

with the appearance of erythema multiform which is characterized by eosinophilia. A recent study reports 

that an 18-year-old male had mild leucocyte elevation 1 day after drinking an alcoholic beverage 

spiked with 4,4 ́-methylenedianiline (Tillmann et al. 1997); his blood cell count and thrombocyte rate 

were normal. The amount of 4,4 ́-methylenedianiline ingested was not known. 

The data in animals are limited to a study that reported no alterations in hemoglobin levels or 

erythrocyte counts in rats treated daily by gavage for 12 weeks with doses of 83 mg 4,4 ́­

methylenedianiline/kg/day (Pludro et al. 1969). 

Musculoskeletal Effects. One female and five males (ages 17-25) complained of muscle and 

joint pain after drinking an alcoholic beverage spiked with 4,4 ́-methylenedianiline (Tillmann et al. 

1997). No further information was located. 

Very limited information was found regarding musculoskeletal effects of 4,4 ́-methylenedianiline in 

animals after oral exposure. No gross or histopathogical alterations were observed in thigh muscle and 

costochondral junction (rib) of rats administered up to 141 mg 4,4 ́-methylenedianiline/kg/day in 

drinking water for 13 weeks or up to 19 mg/kg/day for 103 weeks (Lamb et al. 1986; NTP 1983). 

Similar findings were reported in mice administered up to 116 mg 4,4 ́-methylenedianiline/kg/day in 

the drinking water for 13 weeks or up to 57 mg/kg/day for 103 weeks (Lamb et al. 1986; NTP 1983). 

Hepatic Effects. A local outbreak of jaundice, which was later traced to ingestion of 

4,4 ́-methylenedianiline, occurred in the Epping district of Essex, England, in 1965 (Kopelman et al. 

1966). Eighty-four subjects became ill shortly after eating bread prepared with flour that had been 

contaminated with 4,4 ́-methylenedianiline. Three general types of clinical presentations were 

observed. In a majority of the patients, the illness had an acute onset with severe intermittent pain in 

the upper abdomen and lower chest for 24-36 hours. Over the next few days, the patients in this 

group improved, but then developed a flu-like condition with fever and increasing jaundice. The liver 

was enlarged and tender. After a few days, the liver became smaller, but the jaundice persisted for 

weeks. These patients did not feel completely recovered for a considerable period of time. A second 
METHYLENEDIANILINE 33 

2. HEALTH EFFECTS 

group of patients only showed mild symptoms of upper abdominal discomfort. A week later, however, 

they too developed fever and increasing jaundice, which persisted longer than in the first group. A third 

group, with the least common symptoms, had severe jaundice when first seen, but had minimal preceding 

symptoms. The liver in these patients was often enlarged, but rarely tender. Clinical chemistry tests 

showed increases in serum bilirubin, alkaline phosphatase activity, and glutamic oxaloacetic 

transaminase. Needle biopsy performed in 4 cases within 2-3 weeks of the onset of symptoms showed 

cellular infiltration and cholestasis, and there was evidence of damage to the liver parenchyma and 

biliary tree. This, according to the investigators (Kopelman et al. 1966), is the first documented case of 

human poisoning with 4,4 ́-methylenedianiline. Forty-three of these subjects were evaluated 2 years later 

(Kopelman 1968). Aside from slight abnormalities in single liver tests and complaints of subjective 

nature, there was no evidence of progressive hepatic disease. 

Liver toxicity was also observed in the case of a male subject who accidentally drank an unspecified 

amount of a solution containing 4,4 ́-methylenedianiline, potassium carbonate, and gamma-butyrolactone 

(Roy et al. 1985). Clinical tests conducted 2 days after admission to the hospital showed elevated 

transaminases and hyperbilirubinemia. Slight hepatomegaly developed 6 weeks after admission. One 

year after the accident, serum transaminases still had not returned to normal levels. Although other 

chemicals were involved in this case, the signs and symptoms are consistent with those reported by 

Kopelman et al. (1966) and were most likely caused by 4,4 ́-methylenedianiline. A case of a young man 

who drank an alcoholic beverage spiked with 4,4 ́-methylenedianiline and developed liver toxicity was 

recently described in the literature (Tillmann et al. 1997). The subject thought that the substance was 

methylenedioxyamphetamine, a psychoactive drug. Upon admission to the hospital, 24 hours after 

drinking the beverage, his bilirubin and liver enzyme activities were elevated and increased steadily over 

7 days; he also developed jaundice. By the time he was discharged on day 15, the jaundice had vanished 

and the bilirubin was close to normal. Tillmann et al. (1997) indicates that five other subjects, who also 

drank the spiked beverage, developed a similar picture of liver toxicity. 

Numerous studies of various durations have demonstrated that the liver is a target for 4,4 ́ methylenedianiline toxicity in animals, particularly in rats. A single gavage dose of 25 mg/kg (range tested 25-225 

mg/kg) increased serum alanine aminotransferase activity and relative liver weight in rats (Bailie et al. 

1993). Higher single doses (50-250 mg/kg) induced cholestasis, biliary epithelial injury, bile duct necrosis, 

and periportal hepatocellular necrosis (Bailie et al. 1993, 1994; Kanz et al. 1992; Schmidt et al. 1980). The 

earliest change identified was bile ductular necrosis 4 hours after dosing (Bailie et al. 1993). These single­
METHYLENEDIANILINE 34 

2. HEALTH EFFECTS 

dose studies demonstrated that 4,4 ́-methylenedianiline is selectively toxic to bile duct in rats and that 

hepatic lesions appear after the lesions to the bile ducts (Kanz et al. 1992). The minimal effective 

dose of 25 mg/kg from the Bailie et al. (1993) study is considered a minimal LOAEL and is the basis 

for derivation of an acute oral MRL of 0.2 mg/kg/day. 

Results from intermediate-duration studies support those from single-dose studies. LOAEL values in 

the range of 67-100 mg 4,4 ́-methylenedianiline/kg/day have been identified in rats (Fukushima et al. 

1979, 1981; Hagiwara et al. 1993; Miyamoto et al. 1977; NTP 1983; Pludro et al. 1969). However, in 

many of these studies only one dose level was used. Exceptions are the NTP (1983) study in which 

NOAELs of 35 mg/kg/day and 58 mg/kg/day were identified in rats and mice, respectively, and the 

earlier report by Pludro et al. (1969) that established a NOAEL of 8.3 mg/kg/day in rats. This 

NOAEL, 8.3 mg/kg/day, served as the basis for derivation of an intermediate oral MRL of 

0.08 mg/kg/day. Gavage, drinking water, or diet were used as vehicles in the studies mentioned 

above, which suggests that the method of administration of 4,4 ́-methylenedianiline is not a 

determining factor in liver toxicity. In addition to elevated serum transaminases, the most commonly 

seen liver alterations were hyperplasia of the bile ducts, fatty infiltration, fibrosis, and atrophy of the 

liver parenchyma. In general, it appeared that most of the hepatic lesions were at least partially 

reversible following cessation of treatment. 

Liver dilation, fatty metamorphosis, and focal cellular change were described in rats treated with 9 mg 

4,4 ́-methylenedianiline/kg/day in the drinking water for 103 weeks (Lamb et al. 1986; NTP 1983). In 

the same study, liver degeneration was seen in mice receiving 25 mg/kg/day. Both dose levels 

represent the lowest levels tested. In a study in dogs, all 9 of the treated animals had liver lesions that 

included hepatic cell necrosis, fatty infiltration, and portal fibrosis after treatment with approximately 

2.7 mg 4,4 ́-methylenedianiline/kg/day, 3 days per week for 54-84 months (Deichmann et al. 1978). 

Because of study limitations, such as a small number of animals used and lack of concurrent controls, 

it is not possible to conclusively determine whether dogs are more sensitive than rodents. 

Renal Effects. Only one report was located that described adverse renal effects in humans 

following oral exposure to 4,4 ́-methylenedianiline. In this case report (Roy et al. 1985), a male 

subject accidentally drank an unspecified amount of a liquid containing 4,4 ́-methylenedianiline, 

potassium carbonate, and gamma-butyrolactone. Tests conducted two days after the accident showed 

hematuria and glycosuria. In the presence of normoglycemia, glycosuria indicated renal tubular 
METHYLENEDIANILINE 35 

2. HEALTH EFFECTS 

dysfunction. Because there was simultaneous ingestion of other chemicals, the role of 4,4 ́­

methylenedianiline, if any, cannot be conclusively determined. Proteinuria and erythrocyturia were 

described in a young man who drank an alcoholic beverage spiked with 4,4 ́-methylenedianiline (Tillmann 

et al. 1997). No further information was located. 

Several reports have investigated renal effects of 4,4 ́-methylenedianiline in animals after intermediateand 

chronic-duration exposure. No gross or histopathological alterations have been reported in the kidneys or 

urinary bladder of rats treated with 4,4 ́-methylenedianiline in the range of 83-141 mg/kg/day for periods 

ranging between 8-40 weeks (Pukushima et al. 1979, 1981; NTP 1983; Pludro et al. 1969). Administration 

vehicles included gavage, drinking water, and diet. Similar lack of effects were reported in mice treated 

with up to 116 mg 4,4 ́-methylenedianiline/kg/day in the drinking water for 13 weeks (NTP 1983). In 

contrast, high incidence of kidney mineralization was observed in male rats treated for 103 weeks with dose 

of 16 mg 4,4 ́-methylenedianiline/kg/day in the drinking water (Lamb et al. 1986; NTP 1983). No such 

effect was observed in females treated with a similar dose (Lamb et al. 1986; NTP 1983). A high incidence 

of nephropathy was reported in male and female mice treated with 19-25 mg 4,4 ́methylenedianiline/kg/day 

in the drinking water for 103 weeks (Lamb et al. 1986; NTP 1983). Male mice also exhibited renal papilla 

mineralization at a dose level of 57 mg/kg/day (Lamb et al. 1986; NTP 1983). Various lesions to the kidney 

and urinary bladder were observed in 9 dogs treated with approximately 2.7 mg 4,4 ́­

methylenedianiline/kg/day, 3 days per week for 54-84 months (Deichmann et al. 1978). Kidney 

abnormalities included rough surface, congestion, glomerulonephritis, cloudy swellin,, and thickening of 

the basement membrane. Hyperemia in the urinary bladder was noticed in two dogs, whereas mucosal 

hyperplasia, edema, lymphocytic infiltration, and marked congestion of the urinary bladder were observed 

in another dog. This study has severe limitations, such as a very small number of animals (9 female beagle 

dogs), no concurrent controls, and only one dose level was tested; therefore, the results must be interpreted 

with caution. 

Endocrine Effects. No studies were located regarding endocrine effects in humans after oral 

exposure to 4,4 ́-methylenedianiline. 

Numerous studies in rats have identified the thyroid as a sensitive organ for 4,4 ́-methylenedianiline 

toxicity. Hypertrophy and histopathological alterations of the adrenals and thyroid were reported in 

rats administered doses of 1l0-146 mg 4,4 ́-methylenedianiline/kg/day by gavage for 5- 14 days 
 

METHYLENEDIANILINE 36 

2. HEALTH EFFECTS 

(Tullner 1960). Longer duration studies (8-32 weeks) in rats have established LOAELs for thyroid 

effects in the range of 67-100 mg 4,4 ́-methylenedianiline/kg/day (Fukushima et al. 1981; Hagiwara et 

al. 1993; Hiasa et al. 1984; NTP 1983; Tsuda et al. 1987). The administration vehicle was drinking 

water or food. With the exception of the NTP (1983) study, only one dose level was tested in these 

studies. In the NTP (1983) report, a NOAEL of 35 mg/kg/day was identified for rats and 116 mg/kg/day for 

mice; the latter was the highest dose level tested in mice. The thyroid alterations observed consisted of 

hyperplasia, decrease of colloid in the follicles, reduced follicle size, and slight reduction in serum T3 and 

T2. In addition to thyroid effects, pituitary basophile hypertrophy was noticed in male and female rats that 

received approximately 140 mg 4,4 ́-methylenedianiline/kg/day in the drinking water for 13 weeks (NTP 

1983). Results from chronic-duration studies revealed follicular cysts and follicular cell hyperplasia in the 

thyroid of female rats treated with 19 mg 4,4 ́-methylenedianiline/kg/day in the drinking water for 103 

weeks and thyroid cell hyperplasia in male and female mice treated in the same manner with 57 mg/kg/day 

and 43 mg/kg/day, respectively (Lamb et al.1986; NTP 1983). 

The overall evidence suggests that thyroid, particularly in rats, may be a sensitive organ for 

4,4 ́-methylenedianiline toxicity. However, until other animal species are tested, it is uncertain 

whether rats are the most sensitive species. 

Dermal Effects. Limited relevant dam in humans were located. Roy et al. (1985) described the 

case of a man who developed erythema multiform after accidentally ingesting a solution containing 

4,4 ́-methylenedianiline, potassium carbonate, and gamma-butyrolactone (Roy et al. 1985). This 

finding is consistent with an allergic reaction to 4,4 ́-methylenedianiline (see Section 2.2.3). In a 

recent case report, an 18-year-old male developed a skin rash 7 days after drinking an alcoholic 

beverage spiked with 4,4 ́-methylenedianiline (Tillmann et al. 1997). The rash had cleared by the time 

he was discharged from the hospital on day 15. No further information was located. 

Very limited information was found regarding dermal effects of 4,4 ́-methylenedianiline in animals 

after oral exposure. No gross or histopathogical alterations were observed in the skin of rats 

administered up to 141 mg 4,4 ́-methylenedianiline/kg/day in drinking water for 13 weeks or up to 

19 mg/kg/day for 103 weeks (Lamb et al. 1986; NTP 1983). Similar findings were reported in mice 

administered up to 116 mg 4,4 ́-methylenedianiline/kg/day in the drinking water for 13 weeks or up to 

57 mg/kg/day for 103 weeks (Lamb et al. 1986; NTP 1983). 
METHYLENEDIANILINE 37 

2. HEALTH EFFECTS 

Ocular Effects. Ocular effects were described in the case of a male subject who accidentally 

ingested an unspecified amount of a solution containing 4,4 ́-methylenedianiline, potassium carbonate, 

and gamma-butyrolactone (Roy et al. 1985). Four days after admission to the hospital, his vision 

became blurred and visual acuity was reduced considerably. This condition worsened on subsequent 

weeks and he developed a coarse pigmentary retinopathy similar to that of retinitis pigmentosa. Tests 

conducted later revealed gross malfunction of the retinal pigment epithelium, a condition which 

improved little over the next 18 months. Although the subject ingested a mixture of three 

components, the retina is not known to be a target for gamma-butyrolactone or potassium carbonate 

toxicity. Nevertheless, there is no conclusive evidence that the effects observed were caused by 

4,4 ́-methylenedianiline. 

No studies were located regarding ocular effects in animals after oral exposure to 4,4 ́-methylenedianiline. 

Body Weight Effects. No studies were located regarding body weight effects in humans 

following oral exposure to 4,4 ́-methylenedianiline. 

Oral exposure to 4,4 ́-methylenedianiline in animals usually resulted in dose-related reduction in body 

weight gain, and occasionally, weight loss. Male rats exposed for 14 days in the drinking water to 

235 mg 4,4 ́-methylenedianiline/kg/day had a 31% reduction in final body weight relative to untreated 

controls (NTP 1983). At the lowest dose level tested, 117 mg/kg/day in males and 130 mg/kg/day in 

females, final body weights were reduced by about 11%. In mice treated in the same manner, the 

NOAEL and LOAEL for body weight effects was 220 mg/kg/day and 415 mg/g/day, respectively 

(NTP 1983). Numerous intermediate-duration studies (8-40 weeks) have reported decreased body 

weight gain in rats treated with 4,4 ́-methylenedianiline doses in the range of 84 mg/kg/day to 

141 mg/kg/day (Fukushima et al. 1979, 1981; Hagiwara et al. 1993; Hiasa et al. 1984; Miyamoto et al. 

1977; NTP 1983; Tsuda et al. 1987). The administration vehicle varied between food and drinking 

water. In these studies, final body weights were reduced 27-70% relative to untreated controls. The 

sole exception is a report by Pludro et al. (1969) which identified a NOAEL of 83 mg/kg/day in rats 

treated by gavage for 12 weeks and no explanation is apparent for this discrepancy. In the studies 

mentioned above, except for the NTP (1983) study, only one dose level of 4,4 ́-methylenedianiline was 

tested. The NOAEL for rats in the NTP (1983) report was 70 mg/kg/day. In mice, the NOAEL and 
METHYLENEDIANILINE 38 

2. HEALTH EFFECTS 

LOAEL were 54 mg/kg/day and 108 mg/kg/day, respectively (NTP 1983). None of the studies 

mentioned above provided data regarding food consumption. 

Body weights from rats treated for 103 weeks with up to 19 mg 4,4 ́-methylenedianiline/kg/day in the 

drinking water were not significantly different than untreated controls (Lamb et al. 1986; NTP 1983). 

However, in the same study (Lamb et al. 1986; NTP 1983), final body weight was reduced by 13% in 

male mice treated with 57 mg 4,4 ́-methylenedianiline/kg/day and by 16% in females treated with 

43 mg 4,4 ́-methylenedianiline/kg/day. The NOAEL was about 20 mg/kg/day. Again, food 

consumption data were not provided. 

2.2.2.3 Immunological and Lymphoreticular Effects 

No studies were located regarding immunological and lymphoreticular effects in humans after oral 

exposure to 4,4 ́-methylenedianiline. 

Data in animals are restricted to histopathological examinations of organs of the lymphoreticular 

system, but no information is available regarding possible effects on immunocompetence. Focal 

disintegration of cortical thymocytes was observed in rats 8 hours after a single gavage dose of 

250 mg 4,4 ́-methylenedianiline/kg (Kanz et al. 1992). In some rats, approximately 50% of the 

thymus cortex was necrotic 24 hours after dosing. However, no histopathological alterations were 

observed in the spleen (Kanz et al. 1992). A 13-week drinking water study reported no histopathological 

alterations in the spleen, thymus, and lymph nodes of rats treated with up to 141 mg 

4,4 ́-methylenedianiline/kg/day (NTP 1983). The same findings were reported in mice treated in the 

same manner with up to 116 mg 4,4 ́-methylenedianilinelkglday (NTP 1983). The results from the 

NTP (1983) study are in conflict with those of Pludro et al. (1969) who reported unspecified lesions in 

the spleen in rats treated with daily gavage doses of 8.3 mg 4,4 ́-methylenedianiline/kg. Doses of 

83 mg/kg/day induced hyperplasia in lymphatic nodes. A possible explanation for the discrepancy 

between the results from these two studies is the use of different administration vehicles, drinking 

water in the NTP (1983) and gavage in propylene glycol in the Pludro et al. (1969) study. 

There were no histopathological changes in the spleen, thymus, and lymph nodes from rats treated for 

103 weeks with up to 19 mg 4,4 ́-methylenedianiline/kg/day in the drinking water (Lamb et al. 1986; 

NTP 1983). Similar findings were reported in mice treated with up to 57 mg 4,4 ́-methylene­
METHYLENEDIANILINE 39 

2. HEALTH EFFECTS 

dianiline/kg/day for 103 weeks (Lamb et al. 1986; NTP 1983). In dogs treated for 54-84 months wit1 

approximately 2.7 mg 4,4 ́-methylenedianiline/kg/day (dose given 3 times/week by gavage in a 

capsule) the spleens appeared shrunken and the surface had a granular appearance (Deichmann et al. 

1978). These latter investigators also reported splenitis with thickening and hyalinization of the 

capsule, trabeculae and lymphoid corpuscles. Hemosiderosis and spleen congestion, which were also 

noticed, may have been secondary to hematological effects (not reported) such as hemolytic anemia 

and methemoglobinemia. This study in dogs was poorly conducted and poorly reported; thus, it is 

unclear whether dogs are a particularly sensitive species. 

The highest NOAEL values and all reliable LOAEL values for immunological and lymphoreticular 

effects for each species and duration category are recorded in Table 2-2 and plotted in Figure 2-2. 

2.2.2.4 Neurological Effects 

No studies were located regarding neurological effects in humans after oral exposure to 

4,4 ́-methylenedianiline. 

Information on neurological effects in animals is very limited. No gross or histopathogical alterations 

were observed in the sciatic nerve, brain, and spinal cord of rats administered up to 141 mg 

4,4 ́-methylenedianiline/kg/day in drinking water for 13 weeks or up to 19 mg/kg/day for 103 weeks 

(Lamb et al. 1986; NTP 1983). Similar findings were reported in mice administered up to 116 mg 

4,4 ́-methylenedianiline/kg/day in the drinking water for 13 weeks or up to 57 mg/kg/day for 

103 weeks (Lamb et al. 1986; NTP 1983). No further neurological parameters were evaluated. The 

limited information available suggests that 4,4 ́-methylenedianiline is not a neurotoxicant. The highest 

NOAEL values and all reliable LOAEL values for neurological effects for each species and duration 

category are recorded in Table 2-2 and plotted in Figure 2-2. 

2.2.2.5 Reproductive Effects 

No studies were located regarding reproductive effects in humans after oral exposure to 

4,4 ́-methylenedianiline. 
METHYLENEDIANILINE 40 

2. HEALTH EFFECTS 

Very little information exists regarding reproductive effects of 4,4 ́-methylenedianiline in animals. An 

acute-duration study reported a 71% increase in absolute weight of the uterus in ovariectomized rats 

administered 1l0-146 mg 4,4 ́-methylenedianiline by gavage for 5-14 days (Tullner 1960). 

Histopathological examination of the uterus revealed an atypical folliculoid response in the 

endometrium. No further information was provided in this study. No gross or histopathogical 

alterations were observed in the ovaries, uterus, mammary glands, seminal vesicles, prostate, or testes 

of rats administered up to 141 mg 4,4 ́-methylenedianiline/kg/day in drinking water for 13 weeks or up 

to 19 mg/kg/day for 103 weeks (Lamb et al. 1986; NTP 1983). Similar findings were reported in 

mice administered up to 116 mg 4,4 ́-methylenedianiline/kg/day in the drinking water for 13 weeks or 

up to 57 mg/kg/day for 103 weeks (Lamb et al. 1986; NTP 1983). No further reproductive parameters 

were evaluated. The limited information available is insufficient to determine whether exposure to 

4,4 ́-methylenedianiline may alter reproductive function. 

The highest NOAEL values and all reliable LOAEL values for reproductive effects for each species 

and duration category are recorded in Table 2-2 and plotted in Figure 2-2. 

2.2.2.6 Developmental Effects 

No studies were located regarding developmental effects in humans after oral exposure to 

4,4 ́-methylenedianiline. Only one report was located that provided information on effects in animals. 

In that study (Bourdelat et al. 1983), fetuses from pregnant rats treated by gavage with 37 mg 

4,4 ́-methylenedianiline/kg/day (as the chlorohydrate) on gestation days 14-20 had liver alterations in 

the form of fatty infiltration of the parenchyma. This dose level also caused histological alterations in 

the livers from the dams. Fetuses from 1 of 5 dams administered 219 mg 4,4 ́-methylenedianiline/ 

kgjday on gestation days 7-20 showed delayed closing of the calvaria, enlarged tongue, and an 

abnormally large snout (Bourdelat et al. 1983). The 219 mg/kg/day dose level was lethal to 1 of 

5 pregnant rats. Because of study limitations such as the use of only one female rat as control and 

lack of detailed reporting of the results, this study is not presented in Table 2-2. ­

2.2.2.7 Genotoxic Effects 

No studies were located regarding genotoxic effects in humans after oral exposure to 4,4 ́­

methylenedianiline. 
METHYLENEDIANILINE 41 

2. HEALTH EFFECTS 

Administration of 4, 20, or 50 mg 4,4 ́-methylenedianiline/kg/day by gavage for 3 days to male 

Fischer 344 rats resulted in the dose-related formation of adducts with liver DNA, as detected by 

32Ppostlabeling analysis (Vock et al. 1996). However, DNA isolated from the bladder and from 

lymphocytes from these animals did not show any treatment-related DNA-adducts. 

Other genotoxicity studies are discussed in Section 2.5. 

2.2.2.8 Cancer 

A recent study examined the causes of death (neoplastic and non-neoplastic diseases) in a population 

that had consumed bread contaminated with 4,4 ́-methylenedianiline in 1965 in the Epping district of 

Essex, England (Hall et al. 1992). Liver toxicity was the main adverse effect reported at the time of 

the accident (Kopelman et al. 1966). Of the original 84 cases, 55 people were alive, 18 had died, and 

16 could not be traced. Of those alive, 58% completed a health questionnaire. The causes of death 

were, by and large, unremarkable, with the possible exception of one case of biliary duct carcinoma. 

The observed/expected ratios for cancer and non-neoplastic diseases were well below 1.0. The results 

suggested that there was no obvious link between current health status and the poisoning episode. The 

one case of biliary duct carcinoma was of interest because this tumor, according to the investigators 

(Hall et al. 1992), is very rare in humans. 

The carcinogenic potential of oral administration of 4,4 ́-methylenedianiline has been examined in dogs 

(Deichmann et al. 1978), rats, and mice (Griswold et al. 1968; Lamb et al. 1986; NTP 1983). No 

significant carcinogenic response was reported in rats treated for 30 days with 36 mg 4,4 ́­

methylenedianiline/kg/day by gavage and observed for 9 months (Griswold et al. 1968); however, the 

observation period may have been too short. Dogs that received 5-6.26 grams 4,4 ́-methylenedianilinelkg 

for a period of 54-84 months (the time-weighted dose can be estimated at about 2.7 mg/kg/day) did not 

show a significant increase in bladder or liver tumors (Deichmamr et al. 1978). 

This study has severe limitations such as a very small number of animals (9 female beagle dogs), no 

concurrent controls, and practically only one dose level was tested; therefore, the results must be 

interpreted with caution. In a 2-year bioassay (Lamb et al. 1986; NTP 1983), Fischer 344 rats were treated 

with 4,4 ́-methylenedianiline (as the dihydrochloride) in the drinking water. Doses were 9 and 16 

mg/kg/day in males and 10 and 19 mg/kg/day in females. Clear evidence of carcinogenicity was found. In 

male rats, the incidence of follicular cell carcinomas of the thyroid gland was 0 of 
METHYLENEDIANILINE 42 

2. HEALTH EFFECTS 

49 (controls), 0 of 47 (low dose), and 7 of 48 (high dose); the incidence of neoplastic nodules of the 

liver was 1 of 50 (controls), 12 of 50 (low dose), and 25 of 50 (high dose). In females, the incidence 

of follicular cell adenomas was 0 of 47 (controls), 2 of 47 (low dose), and 17 of 48 (high dose); the 

incidence of C-cell adenomas was 0 of 47 (controls), 3 of 47 (low dose), and 6 of 48 (high dose). 

Tumors were also found in other tissues, but the increased incidence was not statistically significant. 

4,4 ́-Methylenedianiline was also carcinogenic in B6C3F1 mice when administered in the drinking 

water for 103 weeks (Lamb et al. 1986; NTP 1983). The doses were 25 and 57 mg/kg/day for males 

and 19 and 43 mg/kg/day for females. In males, the incidence of follicular adenomas of the thyroid 

gland was 0 of 47 (controls), 3 of 49 (low dose), and 16 of 49 (high dose); carcinomas of the liver 

occurred at an incidence of 10 of 49 (controls), 33 of 50 (low dose), and 29 of 50 (high dose). Also 

in males, the incidence of pheochromocytoma of the adrenal gland was 2 of 48 (controls), 12 of 

49 (low dose), and 14 of 49 (high dose). In females, the following significant increased incidences 

were observed: follicular cell adenomas of the thyroid gland (0 of 50 controls, 1 of 47 low dose, 13 of 

50 high dose), carcinomas/adenomas of the liver (4 of 50 controls, 15 of 50 low dose, 23 of 50 high 

dose), malignant lymphoma (13 of 50 controls, 28 of 50 low dose, 29 of 50 high dose), and 

alveolar/bronchiolar adenoma (1 of 50 controls, 2 of 50 low dose, 6 of 49 high dose). 

Several studies have examined the effects of 4,4 ́-methylenedianiline on post-initiation stage 

carcinogenicity in various organs in rats. For example, administration of 100 mg 4,4 ́-methylenedianiline/ 

kg/day in the diet for 32 weeks following initiation with N-ethyl-N-hydroxyethylnitrosamine 

reduced the incidence of hyperplastic nodules in the liver and neoplastic nodules in the kidney induced 

by the nitrosamine alone (Fukushima et al. 1981). Similar findings were reported regarding neoplastic 

responses in the urinary bladder when 4,4 ́-methylenedianiline (88 mg/kg/day for 34 weeks) followed 

initiation with N-butyl-N-(4-hydroxybutyl) nitrosamine (Fukushima et al. 1981), and regarding 

hepatocellular carcinomas when 4,4 ́-methylenedianiline (100 mg/kg/day for 26 weeks) followed 

initiation with diethylnitrosamine plus 2-acetylamino fluorene (Masui et al. 1986). In these studies, 

4,4 ́-methylenedianiline alone was not carcinogenic. In contrast with the results summarized above, 

the incidence of thyroid tumors in rats initiated with N-bis(2-hydroxypropyl)nitrosamine and then 

treated with 4,4 ́-methylenedianiline (84 mg/kg/day for 19 weeks) was significantly higher (90%) than 

in rats treated only with the initiator (28%) (Hiasa et al. 1984); no tumors were seen in rats treated 

with 4,4 ́-methylenedianiline alone. 
METHYLENEDIANILINE 43 

2. HEALTH EFFECTS 

In a different type of experiment, administration of 100 mg 4,4 ́-methylenedianiline/kg/day for 8 weeks 

to rats followed by treatment with a combination of 3 carcinogens for 4 weeks resulted in a lower 

incidence of follicular cell hyperplasia and adenomas of the thyroid relative to rats treated with only 

the carcinogens (Hagiwara et al. 1993). The incidence of preneoplastic/neoplastic lesions observed in 

other tissues and organs was similar in the two groups. 

The long-term bioassays conducted in rats and mice (Lamb et al. 1986; NTP 1983) provide clear 

evidence of 4,4 ́-methylenedianiline carcinogenicity in rodents. However, no evidence of 

carcinogenicity was found in intermediate-duration studies in the groups of rats that were treated with 

4,4 ́-methylenedianiline alone (Fukushima et al. 1981; Hiasa et al. 1984; Masui et al. 1986). These are 

not necessarily inconsistent results, since exposure duration and observation periods may have been too 

short in the intermediate-duration studies. 

The dose of levels of 9 mg 4,4 ́-methylenedianiline/kg/day for male rats and 19 mg/kg/day for female 

mice from the Lamb et al. (1986) and NTP (1983) studies are listed as Cancer Effect Levels (CEL) in 

Table 2-2 and are plotted in Figure 2-2. 

2.2.3 Dermal Exposure 

2.2.3.1 Death 

No studies were located regarding death in humans following dermal exposure to 4,4 ́-methylenedianiline. 

Very limited information exists regarding death in animals after dermal exposure to 4,4 ́­

methylenedianiline. 

Four of 9 female mice and 1 of 9 males died after having doses of 168 mg 4,4 ́-methylenedianiline/ 

kg/day in methanol applied to the clipped skin 5 days per week for 2 weeks (Holland et al. 

1987). When the solvent was acetone, 3 of 10 males and 3 of 10 females died. The authors indicated 

that using acetone as solvent may have provided inaccurate results since 4,4 ́-methylenedianiline tends 

to form a Schiff base with acetone. The same group of investigators (Holland et al. 1987) reported a 

significant dose-related decrease in survival rate in mice applied ≥5.3 mg 4,4 ́-methylenedianiline/ 

kg/day 3 times per week for 104 weeks. The 24-month survival rate was approximately 60% 
METHYLENEDIANILINE 44 

2. HEALTH EFFECTS 

in untreated controls and 35.9% in treated mice. LOAEL values for death for each species and 

duration category are recorded in Table 2-3. 

2.2.3.2 Systemic Effects 

No studies were located regarding respiratory effects in humans or musculoskeletal effects in humans 

or animals after dermal exposure to 4,4 ́-methylenedianiline. 

The highest NOAEL values and all reliable LOAEL values for systemic effects for each species and 

duration category are recorded in Table 2-3. 

Respiratory Effects. A single study in animals indicates that no gross or histopathological lesions 

were detected in the lungs and trachea of rabbits that received daily skin doses of 12,000 mg 

4,4 ́-methylenedianiline/kg as an aqueous paste for 10 consecutive days (DuPont 1975). No further 

relevant information was located. 

Cardiovascular Effects. A case of a male subject with cardiac abnormalities after dermal 

exposure to 4,4 ́-methylenedianiline was described by Brooks et al. (1979). The 20-year-old subject 

had worked for 2 weeks at a chemical plant where he handled large quantities of 4,4 ́-methylenedianiline. 

Exposure had occurred mostly by dermal contact with uncovered portions of the arms six 

days prior to admission to the hospital. Analysis of the electrocardiogram on admission showed 

normal waves and tests for myocardial damage were unremarkable. However, results from an 

echocardiogram showed reduced septal motion and reduced left ventricular function. Myocardial 

abnormalities were still observed three months after exposure, but not one year after the incident. No 

information was provided regarding possible simultaneous exposure to other chemicals. 

No studies were located regarding cardiovascular effects in animals after dermal exposure to 

4,4 ́-methylenedianiline. 

Gastrointestinal Effects. No studies were located regarding, gastrointestinal effects in humans 

after dermal exposure to 4,4 ́-methylenedianiline. 


METHYLENEDIANILINE 47 

2. HEALTH EFFECTS 

A single study in animals indicate that no gross or histopathological lesions were detected in the 

stomach and intestines of rabbits that received daily skin doses of up to 2,000 mg 4,4 ́­

methylenedianiline/kg as an aqueous paste for 10 consecutive days (DuPont 1975). No further relevant 

information was located. 

Hematological Effects. Very limited information was located regarding hematological effects in 

humans following dermal exposure to 4,4 ́-methylenedianiline. Normal blood counts were reported in 

a man following accidental contact with 4,4 ́-methylenedianiline (Van Joost et al. 1987). A second 

case concerned six men who came in contact with 4,4 ́-methylenedianiline while mixing it with an 

epoxy resin at work (Williams et al. 1974). Four of the six men were reported to have elevated 

eosinophil count, which is consistent with an immunological allergic reaction (although none was 

described) (see Section 2.5). 

No studies were located regarding hematological effects in animals after dermal exposure to 

4,4 ́-methylenedianiline. 

Hepatic Effects. Several studies have described adverse hepatic effects in humans after dermal 

exposure to 4,4 ́-methylenedianiline. Thirteen cases of toxic hepatitis were reported in a factory that 

manufactured hard plastic (McGill and Motto 1974). 4,4 ́-Methylenedianiline was used as a curing 

agent in the process. The illness began between one and three weeks after employment started and all 

the reported signs and symptoms were consistent with liver disease (right upper quadrant pain and 

fever, jaundice, elevated transaminases, hyperbilirubinemia). Similar findings have also been described 

by others (Bastian 1984; Brooks et al. 1979; Williams et al. 1974). All these cases shared common 

signs and symptoms that included pain, elevated serum transaminases, jaundice, and hyperbilirubinemia. 

Although simultaneous exposure to other chemicals cannot be totally ruled out, the overall 

evidence and results from animal studies suggest that 4,4 ́-methylenedianiline was a major contributor 

to liver toxicity. 

Limited data from animal studies suggest that the liver may also be a target for 4,4 ́-methylenedianiline 

after dermal exposure. Mice that received daily applications of 168 mg 4,4 ́-methylenedianilinelkg 

in methanol or acetone 5 days per week for 2 weeks exhibited an increase in liver relative 

to vehicle controls (Holland et al. 1987). No effects were seen at 84 mg/kg/day. Bile duct 

proliferation, portal cirrhosis, and focal parenchymal necrosis were observed in the livers of rabbits 
METHYLENEDIANILINE 48 

2. HEALTH EFFECTS 

which received skin doses of 700 mg 4,4 ́-methylenedianiline/kg/day in ethanol for 10 consecutive
 

days (DuPont 1976a). These changes were not noticed in rabbits treated with ethanol alone. In
 

contrast, no adverse hepatic effects were noticed in the livers of rabbits also treated for 10 consecutive
 

days with up to 2,000 mg 4,4 ́-methylenedianiline/kg/day, but applied as an aqueous paste (DuPont
 

1975), suggesting that the vehicle plays an important role in dermal absorption. No further
 

information was located regarding hepatic effects after dermal exposure.
 

Renal Effects. No studies were located regarding renal effects in humans after dermal exposure to
 

4,4 ́-methylenedianiline.
 

No adverse kidney effects were reported in mice which received up to 168 mg 4,4 ́-methylenedianiline/
 

kg/day in methanol or acetone applied 5 days per week for 2 weeks (Holland et al. 1987).
 

Mild acute glomerulonephritis was reported in rabbits treated with 700 mg 4,4 ́-methylenedianiline/
 

kg/day in ethanol for 10 consecutive days (DuPont 1976a). However, no such effect was
 

noticed when 2,000 mg 4,4 ́-methylenedianiline/kg/day was applied as an aqueous paste (DuPont
 

1975), indicating that the vehicle plays a role in dermal absorption. No further information was
 

located regarding renal effects after dermal exposure.
 

Endocrine Effects. No studies were located regarding endocrine effects in humans after dermal
 

exposure to 4,4 ́-methylenedianiline.
 

The only information regarding endocrine effects in animals is that provided in a study in which no
 

gross or histopathological alterations were seen in the adrenals and thyroid of rabbits which received
 

doses of to 2,000 mg 4,4 ́-methylenedianiline/kg/day as an aqueous paste to the skin for
 

10 consecutive days (DuPont 1975).
 

Dermal Effects. Skin rash was one of the physical findings among a group of 13 individuals who
 

came in contact with 4,4 ́-methylenedianiline at work (McGill and Motto 1974). However, since there
 

was clinical evidence of liver disease, the rash may have been another sign of toxic hepatitis and not
 

due to direct contact with the chemical. A similar clinical picture was described by Brooks et al.
 

(1979) in a male who handled large amounts of 4,4 ́-methylenedianiline at a chemical plant.
 

Dermatitis without evidence of liver damage has also been reported (Emmett 1976; Van Joost et al.
 

1987). It appeared that in these cases dermal sensitization had occurred since patch testing with
 
METHYLENEDIANILINE 49 

2. HEALTH EFFECTS 

4,4 ́-methylenedianiline gave positive reactions. A case of photosensitivity to 4,4 ́-methylenedianiline 

was reported in a male subject who developed erythematous, pruritic dermatitis on his arms and 

forearms during four consecutive summers (Levine 1983). The rash appeared 60 minutes after a 

30 minute exposure to sunlight even if filtered by window glass. Photopatch tests conducted with 

24 contact allergens were positive for 4,4 ́-methylenedianiline. 

No dermal irritation at the application site was observed in mice treated with up to 168 mg 

4,4 ́-methylenedianiline/kg/day in ethanol or acetone 5 days per week for 2 weeks (Holland et al. 

1987). Ten daily doses of 700 mg 4,4 ́-methylenedianiline/kg in ethanol produced acute necrotizing 

dermatitis in rabbits (DuPont 1976a). However, when the test material was applied as an aqueous 

paste, ten doses of 1,000 mg 4,4 ́-methylenedianiline/kg produced only minimal irritation (DuPont 

1975). Application of a single 22 mg 4,4 ́-methylenedianilinelkg in polyethylene glycol to the back of 

guinea pigs produced neither dermal irritation nor sensitization (Leong et al. 1987). In this study, the 

guinea pigs had been previously exposed to an aerosol of 4,4 ́-methylenedianiline intermittently for 

2 weeks in order to determine whether dermal sensitization to 4,4 ́-methylenedianiline occurred across 

routes of exposure. 

Ocular Effects. No studies were located regarding ocular effects in humans after dermal exposure 

to 4,4 ́-methylenedianiline. 

No gross or histopathological lesions were observed in the eyes of rabbits after receiving daily skin 

applications of up to 2,000 mg 4,4 ́-methylenedianiline/kg as an aqueous paste for 10 consecutive days 

(DuPont 1975). Moderate to mild reversible ocular effects were seen in the eyes of rabbits after solid 

4,4 ́-methylenedianiline (3.3 or 33.3 mg/kg) was placed into the conjunctival sac for 20 seconds 

(DuPont 1976b). Effects observed included cornea1 opacity, congestion of the iris, and redness and 

swelling of the conjunctiva. The severity of the effects was dose-related and washing with water for 

3.5 minutes after the 20-second treatment considerably lessened the severity. 

Body Weight Effects. No studies were located regarding body weight effects in humans 

following dermal exposure to 4,4 ́-methylenedianiline. 

No significant alterations in body weight were observed in mice treated 5 days per week for 2 weeks 

with up to 168 mg 4,4 ́-methylenedianiline/kg/day in acetone or ethanol (Holland et al. 1987). Similar 
METHYLENEDIANILINE 50 

2. HEALTH EFFECTS 

results were reported in rabbits treated with up to 2,000 mg 4,4 ́-methylenedianiline/kg as an aqueous 

paste for 10 consecutive days (DuPont 1975). However, when the solvent was ethanol, there was a 

15% reduction in final body weight after 10 days of treatment with 700 mg 4,4 ́-methylenedianiline/ 

kg/day, which suggests that ethanol facilitates dermal absorption of this chemical (DuPont 1976a). 

2.2.3.3 Immunological and Lymphoreticular Effects 

Several cases of dermal sensitization have been described in individuals who came in contact with 

4,4 ́-methylenedianiline in the workplace (Emmett 1976; Levine 1983; Van Joost et al. 1987) (see 

Dermal Effects). However, no information is available regarding possible effects of 4,4 ́­

methylenedianiline on human immunocompetence. 

No dermal sensitization was observed in guinea pigs after a 2-week nose-only exposure period to 

4,4 ́-methylenedianiline aerosol was followed with a single topical application of up to 22 mg 

4,4 ́-methylenedianiline/kg (Leong et al. 1987). Increased spleen weight was reported in mice that 

received topical applications of up to 168 mg 4,4 ́-methylenedianiline/kg/day in ethanol for 2 weeks 

(Holland et al. 1987); no further information was provided in that report. No gross or 

histopathological alterations were observed in the spleen and thymus of rabbits treated dermally with 

2,000 mg 4,4 ́-methylenedianiline/kg as an aqueous paste for 10 consecutive days (DuPont 1975). The 

information available is insufficient to draw any conclusions regarding immunological effects of 

4,4 ́-methylenedianiline after dermal exposure and, therefore, no entries are presented in Table 2-3. 

2.2.3.4 Neurological Effects 

No studies were located regarding neurological effects in humans after dermal exposure to 

4,4 ́-methylenedianiline. 

The information regarding neurological effects in animals is limited to a study that reported no 

treatment-related gross or histopathological alterations in the brains of rabbits after receiving 

10 consecutive daily skin applications of up to 2,000 mg 4,4 ́-methylenedianiline/kg as an aqueous 

paste (DuPont 1975). No further neurological parameters were examined. This brief information is 

not considered a reliable indicator for neurological effect and, therefore, is not listed in Table 2-3. 
METHYLENEDIANILINE 51 

2. HEALTH EFFECTS 

2.2.3.5 Reproductive Effects 

No studies were located regarding reproductive effects in humans following dermal exposure to 

4,4 ́-methylenedianiline. 

The only information regarding reproductive effects in animals is that provided in a study in which no 

gross or histopathological alterations were seen in the testes and epididymis of rabbits which received 

up to 2,000 mg 4,4 ́-methylenedianiline/kg/day applied as an aqueous paste to the skin for 

10 consecutive days (DuPont 1975). No other reproductive parameters were evaluated. Because this 

information is not considered a reliable indicator of reproductive function, it is not listed in Table 2-3. 

2.2.3.6 Developmental Effects 

No studies were located regarding developmental effects in humans or animals after dermal exposure 

to 4,4 ́-methylenedianiline. 

2.2.3.7 Genotoxic Effects 

No studies were located regarding genotoxic effects in humans or animals after dermal exposure to 

4,4 ́-methylenedianiline. Genotoxicity studies are discussed in Section 2.5. 

2.2.3.8 Cancer 

A retrospective assessment of exposure and cancer morbidity was conducted in power generation 

workers exposed to an epoxy resin containing 35% 4,4 ́-methylenedianiline in Sweden (Selden et al. 

1992). The cohort was composed of 550 males and 45 females. Based on company records, the 

individuals were subdivided into three categories: exposed, possibly exposed, and unexposed. 

Information on the cancer incidence of the cohort was obtained by computerized matching with the 

national cancer register for the period 1964-1985. Standardized incidence ratios (SIR) were obtained 

from the ratio of the observed to the expected number of cases. Exposure was considered to be 

primarily by the dermal route. In all three male groups, the observed number of cancers for all sites 

and for urinary bladder cancer was lower than the observed number. The overall SIR was 0.52 based 

on 5 observed cases. In the male exposed subgroup, no single cancer case appeared throughout the 
METHYLENEDIANILINE 52 

2. HEALTH EFFECTS 

observation period; the expected number was 3. Among the female workers, 2 cancer cases were 

identified (none in the urinary bladder); 2.7 cancer cases (all cancers) had been expected from the 

national rates. The authors indicate that the results should be interpreted with caution since the cohort 

was small, the majority of the subjects were quite young and had not reached cancer-prone age, and 

the follow-up period was short and may have not covered the latency period for bladder cancer 

(20 years). 

Additional information is available from a morbidity study of employees who had worked in the gas 

centrifuge process at Oak Ridge Gaseous Diffusion Plant (Cragle et al. 1992). In addition to potential 

exposure to 4,4 ́-methylenedianiline, the workers may have been exposed to m-phenylenediamine, 

bis(2,3-epoxycyclopentylether), diglycidyl ether of bisphenol A, and the solvents trichloroethylene and 

methylene chloride. The cohort consisted of 263 workers who had worked closest to the process for 

the longest amount of time and a comparison group of 271 workers who did not work in the process. 

The most significant finding of the study was the report of five bladder cancers among centrifuge 

workers and none among the comparison worker group. However, interviews with these five workers 

revealed that none of them was working closely with the epoxy resin materials during any part of their 

employment in the process. The authors concluded that no specific agent or job duty could be 

identified as the causative factors for the bladder cancers (Cragle et al. 1992). 

A more recent study followed a group of 10 individuals who had worked at a plant in Ontario, 

Canada, that manufactured an epoxy concrete surfacing material using 4,4 ́-methylenedianiline as a 

hardener (Liss and Guirguis 1994). Between 1967 and 1976 these subjects suffered acute episodes of 

jaundice. The study followed the group from the date of intoxication through the end of 1991 for 

cancer incidence by matching with the Ontario Cancer Registry. At the time of the intoxication the 

length of employment ranged from 7 days to 2.5 months. The results of the follow-up revealed that 

one case of bladder cancer developed among the group; it was diagnosed in 1990, 23 years after the 

intoxication. The standardized incidence ratio for the bladder cancer was 19.3 (95% confidence 

interval 0.5-107; p [one or more cases]=0.051). Liss and Guirguis (1994) suggested that their results 

should be interpreted with caution, given the small number of events, the absence of smoking histories, 

and the presence of other exposures. 

The potential carcinogenicity of 4,4 ́-methylenedianiline by the dermal route was examined in mice 

(Holland et al. 1987). A solution of the test material in ethanol was applied to the clipped skin of 
METHYLENEDIANILINE 53 

2. HEALTH EFFECTS 

male and female C3Hf/Bd mice 3 times per week for 24 months. Positive controls were treated with 

benzo[a]pyrene and negative controls with vehicle alone. Estimated doses were 5.3, 10.7, and 21.3 mg 

4,4 ́-methylenedianiline/kg/day. Treatment with 4,4 ́-methylenedianiline did not produce tumors at the 

application site, but increased the incidence of hepatic tumors in females in a dose-related manner 

(11% vehicle control, 22% low-dose, 25% mid-dose, 85% high-dose); however, a statistical analysis of 

the results was not provided. The incidence of tumors in the spleen, lungs, kidneys, and ovaries/testes 

did not increase relative to negative controls. According to the investigators, the C3Hf/Bd strain of 

mice is unusually susceptible to liver tumors and, therefore, the significance of the findings requires 

further study. Nevertheless, the dose of 5.3 mg 4,4 ́-methylenedianiline/kg/day is listed as a Cancer 

Effect Level in Table 2-3. 

In summary, there is insufficient information to assess the potential carcinogenicity of 4,4 ́­

methylenedianiline by the dermal route of exposure. 

2. 3 TOXICOKINETICS 

Data regarding toxicokinetics of 4,4 ́-methylenedianiline in humans are limited to information from 

cases of accidental ingestion of food contaminated with the chemical and cases of occupational 

exposure in the workplace, where dermal contact with 4,4 ́-methylenedianiline is considered the 

predominant route of exposure. Humans can absorb 4,4 ́-methylenedianiline by the inhalation, oral, 

and dermal routes of exposure. Limited data suggest that in humans the rate of absorption of 

4,4 ́-methylenedianiline through the respiratory tract is faster than dermal absorption. There are no 

data regarding quantitative oral absorption in humans or animals. There are no inhalation data in 

animals. Limited dermal data in animals showed a higher absorption rate in rats than in guinea pigs. 

Furthermore, the absorption rate was a saturable process. No remarkable pattern of accumulation of 

4,4 ́-methylenedianiline occurred in tissues of either species, although the liver seemed to have a 

higher concentration of 4,4 ́-methylenedianiline than other tissues. 4,4 ́-Methylenedianiline may be 

metabolized by cytochrome P-450 to polar metabolites that can undergo conjugation with glutathione; 

this is inferred from data on structurally similar chemicals. 4,4 ́-Methylenedianiline can also be 

acetylated and, in humans and animals, such metabolites have been detected in the urine. Because of 

the limited data available, a physiologically based pharmacokinetic (PBPK) model for 4,4 ́­

methylenedianiline has not been developed. 
METHYLENEDIANILINE 54 

2. HEALTH EFFECTS 

2.3.1 Absorption 

2.3.1.1 Inhalation Exposure 

Only qualitative information is available regarding absorption of 4,4 ́-methylenedianiline by the 

inhalation route in humans. Biological monitoring was used to assess exposure to 4,4 ́-methylenedianiline 

in a cohort composed of 411 men employed in industries that manufactured or used 

4,4 ́-methylenedianiline in the United Kingdom (Cocker et al. 1994). The results showed that when 

exposure to 4,4 ́-methylenedianiline was through inhalation, postshift urine samples had higher 

concentration of 4,4 ́-methylenedianiline than samples taken preshift the next day. This suggested that 

4,4 ́-methylenedianiline is rapidly absorbed through the inhalation route and that peak excretion is 

reached after the end of the shift. In a recent study (Schiitze et al. 1995), 4,4 ́-methylenedianiline was 

found in the urine of 33 workers exposed to low levels of 4,4 ́-methylenedianiline. By using personal 

air samplers to monitor exposure, the authors found that most workers were exposed to <20 μg 

4,4 ́-methylenedianiline/m3, the detection limit. The metabolite of 4,4 ́-methylenedianiline, 

N’-acetylmethylenedianiline, was found in the urine of all but 4 workers. In addition, hemoglobin 

adducts of 4,4 ́-methylenedianiline were found in all blood samples from the exposed workers. The 

possibility of dermal absorption was not discussed. 

Very limited, and only indirect evidence of pulmonary absorption of 4,4 ́-methylenedianiline exists in 

animals. Guinea pigs exposed nose-only to an aerosol of 4,4 ́-methylenedianiline intermittently for 

2 weeks showed retinal lesions, which were attributed to exposure to the test compound (Leong et al. 

1987). This indicates that absorption through the respiratory tract had occurred. No further 

information was located. 

2.3.1.2 Oral Exposure 

In 1965, a group of 84 subjects in Epping, England, developed clinical signs consistent with toxic 

hepatitis shortly after eating bread prepared with flour that was later found to have been contaminated 

with 4,4 ́-methylenedianiline (Kopelman et al. 1966). This was the first documented case of human 

poisoning with 4,4 ́-methylenedianiline and provided clear evidence that the chemical can be absorbed 

from the gastrointestinal tract. No quantitative estimates of absorption were made. A later case report 

described a variety of toxic effects in a man who accidentally ingested a solution containing 
METHYLENEDIANILINE 55 

2. HEALTH EFFECTS 

4,4 ́-methylenedianiline, potassium carbonate, and gamma-butyrolactone (Roy et al. 1985). Although 

in this case there was simultaneous ingestion of other chemicals, some clinical signs were consistent 

with 4,4 ́-methylenedianiline toxicity and provide further evidence of oral absorption in humans. 

Oral absorption of 4,4 ́-methylenedianiline in animals can be inferred from the numerous reports of 

toxic effects after oral administration of 4,4 ́-methylenedianiline summarized in Section 2.2.2. 

Gastrointestinal absorption occurred when 4,4 ́-methylenedianiline was administered by gavage, mixed 

with food, or in the drinking water. However, no quantitative data exist. 

Further evidence of oral absorption is provided in a study in which metabolites of 4,4 ́-methylenedianiline 

were detected in the urine from rats administered a single dose of the test material (Tanaka et 

al. 1985). The extent of absorption was not determined. 

2.3.1.3 Dermal Exposure 

Indirect evidence of dermal absorption of 4,4 ́-methylenedianiline in humans is provided by the various 

reports of adverse health effects observed in individuals exposed to the chemical in the workplace; 

these studies are summarized in Section 2.2.3. It should be mentioned, however, that in some of these 

cases inhalation of dusts of 4,4 ́-methylenedianiline cannot be ruled out. Evidence of dermal 

absorption was also presented by Cocker et al. (1986a, 1994) who detected 4,4 ́-methylenedianiline 

and/or metabolites in the urine of workers exposed primarily by the dermal route. Quantitative data 

were not provided in these studies. A recent study by Bnmmark et al. (1995) showed that 

approximately 28% of a dose of 4,4 ́-methylenedianiline in isopropanol applied in a patch for 1 hour 

to the ventral skin of the forearm of male volunteers was absorbed. In that study, 4,4 ́-methylenedianiline 

reached a peak in hydrolyzed plasma 3-4 hours after initiation of exposure and declined 

thereafter, with a time course consistent with first-order, one compartment kinetics. Additional 

information can be drawn from a study that used human skin in vitro (Hotchkiss et al. 1993). When 

the skin was unoccluded after application of 4,4 ́-methylenedianiline in ethanol, 13% of -the applied 

dose was detected in a receptor fluid at 72 hours. When the skin was occluded, 33% of the applied 

dose appeared in the receptor fluid at 72 hours. It was also observed that a considerable amount of 

4,4 ́-methylenedianiline (23-58% of the applied dose) remained within the skin at the end of the 

experiment. The authors noted that this finding may be of concern in terms of exposure in the 
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workplace, where gloves or clothing may be worn on top of the chemicals after they come in contact 

with the skin. 

Quantitative aspects of dermal absorption have been examined in rats, guinea pigs and monkeys. A 

single dose of 14C-ring labeled 4,4 ́-methylenedianiline (2 or 20 mg/kg) in ethanol/water was applied to 

the back of rats and the area was covered with a cup (El-Hawari et al. 1986). After an exposure of 

6 hours, a total of approximately 12% of the applied radioactivity was recovered in the urine, feces, 

gastrointestinal tract and tissues; 62% was recovered in a wash with soap and water, and 30% 

remained in the application site (total recoveries from radiotracer studies often exceed 100%). A 

24-hour exposure period resulted in a combined 27% of the dose in urine, feces, gastrointestinal tract 

and tissues, 52% in the wash, and 25% in the application site. After a 96-hour exposure period, 55% 

of the dose was accounted for by the combined urine, feces, gastrointestinal tract, and tissues, 25% 

was in the wash and 26% in the application site. The results also showed that after washing, test 

material which remained within the skin continued to be absorbed. Moreover, occlusion facilitated 

absorption. When two dose levels were tested, the amount of radioactivity in tissues was higher after 

the high dose, but the proportion of the applied dose was lower than with the low dose, which 

suggested a dose-dependent absorption rate. Finally, a greater percentage of the dose was absorbed 

when the application site was washed with acetone and water 5 minutes after dosing than when 

washed with soap and water. 

In guinea pigs subjected to the same protocol (El-Hawaii et al. 1986), approximately 3.5% of the 

applied dose (2 or 20 mg/kg) was recovered in the urine, feces, gastrointestinal tract and tissues 

immediately after a 6-hour exposure period; 81% was recovered in the wash and 11% remained in the 

application site. After a 96-hour exposure period, recovery in urine, feces, gastrointestinal tract and 

tissues amounted to 30% of the dose. Occlusion of the exposure site did not significantly affect 

absorption rate. In contrast with the results in rats, washing the area with soap and water prevented 

further absorption. On the other hand, as seen in rats, absorption rate was dose-dependent and a wash 

with acetone and water facilitated absorption relative to washing with soap and water. 

A less comprehensive study was conducted in monkeys (El-Hawari et al. 1986). The treatment 

protocol was similar to that used in rats and guinea pigs, but the dose was kept in place for only 

24 hours, after which time the site was washed with soap and water. As a percentage of the applied 

dose, the cumulative excretion of radioactivity over a 168-hour period was 18.8% in the urine and 
METHYLENEDIANILINE 57 

2. HEALTH EFFECTS 

1.9% in feces. Forty-seven percent was recovered in the wash for a total recovery of about 68 % 

Since tissues from monkeys were not analyzed, a 21% absorption rate represents only a lower limit. 

When the application site was washed with soap and water 5-10 minutes after the 24-hour exposure 

period, 63% was recovered in the wash; when acetone and water were used, recovery was 53%. 

A study with rat skin in vitro showed that after application of 4,4 ́-methylenedianiline in ethanol to an 

unoccluded piece of skin, about 6% of the applied dose reached a receptor compartment at 72 hours 

(Hotchkiss et al. 1993). When the application site was occluded, absorption was enhanced, reaching 

13.3% of the applied dose in 72 hours. These values are lower than those observed in experiments 

with human skin in vitro (Hotchkiss et al. 1993). 

Dermal absorption has not been quantitated in mice, but toxic effects observed after dermal exposure, 

reported in studies summarized in Section 2.2.3, indicate that 4,4 ́-methylenedianiline is absorbed in 

this species. 

2.3.2 Distribution 

2.3.2.1 Inhalation Exposure 

No studies were located regarding distribution of 4,4 ́-methylenedianiline in humans following 

inhalation exposure. 

From the study by Leong et al. (1987) (Section 2.2.1) in which retinal toxicity was reported in guinea 

pigs exposed nose-only to an aerosol of 4,4 ́-methylenedianiline it could be inferred that 

4,4 ́-methylenedianiline (or metabolites) reached the eye after pulmonary absorption. No further 

relevant information was located. 

2.3.2.2 Oral Exposure 

The fact that subjects who ate bread made with flour contaminated with 4,4 ́-methylenedianiline 

developed toxic hepatitis (Kopelman et al. 1966) provides indirect evidence that in humans, 

4,4 ́-methylenedianiline distributes to the liver after oral exposure. In another study (Roy et al. 1985), 

a subject who accidentally drank a solution containing 4,4 ́-methylenedianiline, potassium carbonate, 
METHYLENEDIANILINE 58 

2. HEALTH EFFECTS 

and gamma-butyrolactone showed adverse effects on the liver and kidneys, and also had severe loss of 

visual acuity (Section 2.2.2). This could indicate that 4,4 ́-methylenedianiline (or metabolites) 

distribute to the liver, kidney and eye. However, because other chemicals were involved, the evidence 

is inconclusive. 

Studies regarding quantitative distribution of 4,4 ́-methylenedianiline in tissues and organs from 

animals after oral exposure were not located. Nevertheless, the numerous reports that showed toxic 

responses in various organs after oral administration of 4,4 ́-methylenedianiline (summarized in 

Section 2.2.2) indicate that 4,4 ́-methylenedianiline (or metabolites) can distribute to these organs. The 

organs involved are the liver, kidneys, spleen, thymus, uterus, adrenal glands, and thyroid. 

2.3.2.3 Dermal Exposure 

Case reports of humans who developed hepatitis after dermal contact with 4,4 ́-methylenedianiline in 

the workplace provide indirect evidence that 4,4 ́-methylenedianiline distributes to the liver. No 

further information was located regarding distribution in humans after dermal exposure. 

Quantitative distribution studies have been conducted in rats and guinea pigs after skin application of 

14C-ring-labeled 4,4 ́-methylenedianiline (El-Hawari et al. 1986). Rats were applied a single dose 

(2 and 20 mg/kg) of the test material in ethanol/water and the dose area was covered with a cup. The 

dose was kept on site for 6, 24, or 96 hours. After these times, the skin was washed with soap and 

water and the animals were either sacrificed or returned to the cages for later sacrifice. Organs and 

tissues were prepared for radiochemical analysis. The results showed that the gastrointestinal tract 

contained the highest amounts of radioactivity at 6 (3.8%) and 24 (3%) hours, followed by the liver 

(2% and 1.2%, respectively). After 96 hours, both the gastrointestinal tract and liver had about 0.5% 

of the applied radioactivity. On a per gram basis, the liver had the highest amount of radioactivity at 

all times, followed by the adrenals and kidneys; this was also the case with the high dose. With the 

exception of the liver, preferential accumulation of 4,4 ́-methylenedianiline (or metabolites) was not 

apparent. 

The experimental procedure and dose levels in guinea pigs were the same as in the rat study 

(El-Hawari et al. 1986). The gastrointestinal tract had the highest amount of radioactivity at 6 (1.5%) and 

24 (2.8%) hours followed by the liver (0.4% and 0.5 %, respectively). After 96 hours, both the 
METHYLENEDIANILINE 59 

2. HEALTH EFFECTS 

gastrointestinal tract and liver contained about 0.5% of the applied dose. On a per gram basis, the 

adrenals had the highest amount of radioactivity at all times (about 3 times the liver). The distribution 

pattern did not appear to be dose-dependent and preferential accumulation in organs and tissues was 

not apparent. 

2.3.2.4 Other Routes of Exposure 

The distribution of 4,4 ́-methylenedianiline (or metabolites) has also been studied in rats and guinea 

pigs after a single intravenous injection (El-Hawari et al. 1986). Rats were injected 14C-ring-labeled 

4,4 ́-methylenedianiline (2 mg/kg) in ethanol water and sacrifices were conducted 6, 24, or 96 after 

dosing. After 6 hours, the gastrointestinal tract had the highest amount of radioactivity (24% of the 

dose); this was followed by the liver (9.5%), skin (3.2%), and blood (2.8%). Twenty-four hours after 

the injection, the amount of radioactivity had decreased considerably in all tissues, and the liver and 

gastrointestinal tract had about 4% of the administered dose. Ninety-six hours after dosing, the liver 

had 4 or more times higher radioactivity (0.9%) than any other tissue. On a per gram basis, the liver 

had the highest concentration of radioactivity at all times, followed by the lungs at 6 and 24 hours and 

the spleen at 96 hours. Except for the liver, no preferential accumulation was apparent. 

The guinea pigs were treated the same as the rats except that sacrifices were conducted only 96 hours 

after the injection (El-Hawari et al. 1986). As a percentage of the applied dose, the liver had the most 

radioactivity, about 3 times that found in blood. On a per gram basis, radioactivity was most 

concentrated in the spleen, followed by the liver, and preferential accumulation in these organs was 

suggested. Total recovery as a percentage of the dose, in blood, tissues, and gastrointestinal tract was 

0.55%, 2.4% and 0.61%, respectively. 

2.3.3 Metabolism 

Limited information exists regarding the metabolism of 4,4 ́-methylenedianiline. By inference from 

structurally similar compounds, it has been assumed that 4,4 ́-methylenedianiline is oxidized to 

N-hydroxymethylenedianiline by the monooxygenase system (Cocker et al. 1986a; Farmer and Bailey 

1989). This reaction leads to the formation of potentially toxic derivatives that may bind to cell 

macromolecule. The aryl hydroxylamine can be further oxidized to nitrosomethylenedianiline which 

can then be conjugated with glutathione and excreted in the urine. A different type of reaction is 
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2. HEALTH EFFECTS 

acetylation of 4,4 ́-methylenedianiline to form N-acetylmethylenedianiline and N,N’ diacetylmethylenedianiline. Both the mono- and di-acetylated metabolites have been identified in the urine of exposed 

workers (Robert et al. 1995). N-acetylmethylenedianiline has been identified in the urine from rats 

treated with 4,4 ́-methylenedianiline orally (Tanaka et al. 1985) and in the urine of humans exposed to 

the chemical in the workplace (Cocker et al. 1986a, 1994; Schtitze et al. 1995). This apparently 

represents a detoxification pathway since acetylated metabolites are not mutagenic (Cocker et al. 1986b; 

Tanaka et al. 1985). Results from an in vitro study in which 4,4 ́-methylenedianiline was incubated with 

rabbit liver microsomes showed that three metabolites were formed: azodiphenylmethane, 

azoxydiphenylmethane, and 4-nitroso-4’-aminodiphenylmethane (Kajbaf et al. 1992). According to the 

investigators, the latter may have been formed via a nonenzymatic reaction, whereas the former two were 

produced enzymatically. A schematic diagram of the metabolism of 4,4 ́-methylenedianiline is presented 

in Figure 2-3. 

2.3.4 Elimination and Excretion 

2.3.4.1 Inhalation Exposure 

Data in humans are provided by a study which detected 4,4 ́-methylenedianiline (cl00 nmol/mmol 

creatinine) in the urine of workers exposed through inhalation of solid material or contaminated dust 

(Cocker et al. 1994). A recent study found levels of 4,4 ́-methylenedianiline from 0.013 to 2.76 nmol/L 

in the urine of workers exposed presumably by inhalation to low levels of 4,4 ́-methylenedianiline 

(Schtitze et al. 1995). The urinary concentration of the metabolite N’-acetylmethylenedianiline ranged 

from 0.045 to 23.4 nmol/L. No further information was located. 

No studies were located regarding elimination and excretion of 4,4 ́-methylenedianiline or metabolites in 

animals after inhalation exposure. 

2.3.4.2 Oral Exposure 

No studies were located regarding elimination and excretion of 4,4 ́-methylenedianiline ormetabolites in 

humans after oral exposure. 

Information regarding animals is limited to a report by Tanaka et al. (1985), who demonstrated the 

presence of the N-acetyl and N,N’-diacetyl derivatives of 4,4 ́-methylenedianiline in the urine of rats 

METHYLENEDIANILINE 62 

2. HEALTH EFFECTS 

treated with a single gavage dose of 50 mg/kg of the test material in gum arabic. No quantitative 

information was provided. 

2.3.4.3 Dermal Exposure 

4,4 ́-Methylenedianiline and an N-acetyl conjugate of methylenedianiline have been identified in the 

urine of individuals who had dermal contact with 4,4 ́-methylenedianiline in the workplace (Cocker et 

al. 1986a, 1994). Over 300 urine samples were analyzed and in 81% the concentration of 4,4 ́­

methylenedianiline was below the detection limit for the method (gas chromatography-mass 

spectrometry) (Cocker et al. 1986a). In those found to contain 4,4 ́-methylenedianiline, the 

concentration ranged from 6 to 175 nmol/mmol creatinine; the average was 26 nmol/mmol creatinine. 

N,N’-diacetylmethylenedianiline has also been found in the urine of exposed workers, although at 

much lower concentrations than the monoacetyl derivative (Robert et al. 1995). A recent study 

examined the excretion of 4,4 ́-methylenedianiline in seven male workers from a work site where the 

chemical was used as curing agent for an epoxy resin (Dalene et al. 1995). The study was conducted 

during 4 workdays and one weekend. Exposure was considered to be mainly dermal in spite of 

extensive protection measures. The excretion rate in urine ranged from 0 to 90 μmol/hour and was 

lower after the weekend than after workdays. On workdays, the cumulative excretion ranged from 

0.04 to 1.2 μmol/day; during the weekend, the range was 0.005-0.51 μmol/day. The excretion of 

4,4 ́-methylenedianiline in the urine correlated linearly with its concentration in blood. 4,4 ́-

Methylenedianiline was applied to 5 volunteers in a patch to the ventral forearm for 1 hour; 

excretion of the compound in hydrolyzed urine reached a peak 6-l1 hours after exposure and most of 

the 4,4 ́-methylenedianiline was eliminated within 24 hours (Brunmark et al. 1995). Of the dose 

absorbed, a median of 16% was excreted in the urine. Half-life elimination ranged from 9.2 to 

19 hours in plasma and from 4.6 to 11 hours in urine. In two volunteers who received three dose 

levels, elimination half-lives were not dose-dependent (Brunmark et al. 1995). 

Quantitative information regarding excretion of 4,4 ́-methylenedianiline is available from studies in 

rats, guinea pigs, and monkeys after skin application of 14C-ring-labeled 4,4 ́-methylenedianiline 

(El-Hawari et al. 1986). Rats were applied a single dose (2 or 20 mg/kg) of the test material in 

ethanol/water and the dose area was covered with a cup. The dose was kept on site for 6, 24, or 

96 hours. After these times, the skin was washed with soap and water and the animals were either 

sacrificed or returned to the cages for later sacrifice. Urine and feces were collected at various 
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2. HEALTH EFFECTS 

intervals for up to 96 hours. After a 6-hour exposure, 2.5% and 0.04% of the administered 

radioactivity were recovered in urine and feces, respectively. After a 24-hour exposure, urine and 

feces had 20% and 2.3% of the dose, respectively. The corresponding values for a 96-hour exposure 

were 43 % and 10%. Rats in which the application site was not covered had lower amounts of 

radioactivity in the excreta. The distribution of radioactivity between urine and feces was not dose 

dependent. The results showed that the main excretory route in the rat is the urine. 

In guinea pigs subjected to the same protocol (El-Hawari et al. 1986), 0.35% and 0.1% of the 

administered dose were recovered in urine and feces, respectively. After a 24-hour exposure, the 

recoveries in urine and in feces were 7.8% and 5.7%, respectively. The corresponding values for a 

96-hour exposure were 10.5% and 17.6%. Treatment with the high dose also resulted in similar 

percentages of radioactivity in urine (2.8%) and feces (3.6%). In contrast with results in the rat, both 

urine and feces appear to be main excretory routes in guinea pigs. 

In monkeys, the treatment protocol was similar to that used in rats and guinea pigs, but the dose was 

kept in place for only 24 hours, after which time the site was washed with soap and water (El-Hawari 

et al. 1986). Following dosing, urine and feces were collected for up to 168 hours. As a percentage 

of the applied dose, the cumulative excretion of radioactivity in the urine and feces over the 168-hour 

period was 18.8% and 1.9%, respectively, indicating that in monkeys, the urine is the main excretory 

route for 4,4 ́-methylenedianiline or metabolite(s). 

2.3.4.4 Other Routes of Exposure 

The pattern of excretion of 4,4 ́-methylenedianiline or metabolites was also examined in rats, guinea 

pigs, and monkeys after a single intravenous dose of 2 mg/kg of 14C-ring-labeled 4,4 ́-methylenedianiline 

(El-Hawari et al. 1986). In rats and guinea pigs, urine and feces were collected for up to 96 hours after 

dosing; in monkeys, excreta were collected for 168 hours. In rats, the amount of radioactivity recovered in 

the urine and feces 6 hours after the injection was (as a percentage of the dose) 55% and 0.3%, 

respectively. After 24 hours, the respective percentages were 67.4% and 21.8% and, after 96 hours, 67 % 

and 31%. This indicates that the urine is the main excretory route and that excretion was almost complete 

24 hours after the injection. 
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In guinea pigs, urinary and fecal excretion reached maximums of 34% and 5 1% of the dose, 

respectively, at about 48 hours after dosing, thus indicating that the feces is the main route of 

elimination of 4,4 ́-methylenedianiline in guinea pigs (El-Hawari et al. 1986). 

In monkeys, most of the dose (79%) was excreted in the urine within the first 48 hours; at this time 

6.5% of the dose appeared in the feces (El-Hawari et al. 1986). Total recovery of radioactivity over a 

the 168-hour collection period amounted to 94% of the injected dose. As seen in rats, urine was the 

main route of excretion in monkeys. 

2.3.5 Physiologically Based Pharmacokinetic (PBPK)/Pharmacodynamic (PD) Models 

Physiologically based pharmacokinetic (PBPK) models use mathematical descriptions of the uptake 

and disposition of chemical substances to quantitatively describe the relationships among critical 

biological processes (Krishnan et al. 1994). PBPK models are also called biologically based tissue 

dosimetry models. PBPK models are increasingly used in risk assessments, primarily to predict the 

concentration of potentially toxic moieties of a chemical that will be delivered to any given target 

tissue following various combinations of route, dose level, and test species (Clewell and Andersen 

1985). Physiologically based pharmacodynamic (PBPD) models use mathematical descriptions of the 

dose-response function to quantitatively describe the relationship between target tissue dose and toxic 

end points. 

PBPK/PD models refine our understanding of complex quantitative dose behaviors by helping to 

delineate and characterize the relationships between: (1) the external/exposure concentration and target 

tissue dose of the toxic moiety, and (2) the target tissue dose and observed responses (Andersen et al. 

1987; Andersen and Krishnan 1994). These models are biologically and mechanistically based and 

can be used to extrapolate the pharmacokinetic behavior of chemical substances from high to low 

dose, from route to route, between species, and between subpopulations within a species. The 

biological basis of PBPK models results in more meaningful extrapolations than those generated with 

the more conventional use of uncertainty factors. 

The PBPK model for a chemical substance is developed in four interconnected steps: (1) model 

representation, (2) model parametrization, (3) model simulation, and (4) model validation (Krishnan 

and Andersen 1994). In the early 1990s validated PBPK models were developed for a number of 
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2. HEALTH EFFECTS 

toxicologically important chemical substances, both volatile and nonvolatile (Krishnan and Andersen 

1994; Leung 1993). PBPK models for a particular substance require estimates of the chemical 

substance-specific physicochemical parameters, and species-specific physiological and biological 

parameters. The numerical estimates of these model parameters are incorporated within a set of 

differential and algebraic equations that describe the pharmacokinetic processes. Solving these 

differential and algebraic equations provides the predictions of tissue dose. Computers then provide 

process simulations based on these solutions. 

The structure and mathematical expressions used in PBPK models significantly simplify the true 

complexities of biological systems. If the uptake and disposition of the chemical substance(s) is 

adequately described, however, this simplification is desirable because data are often unavailable for 

many biological processes. A simplified scheme reduces the magnitude of cumulative uncertainty. 

The adequacy of the model is, therefore, of great importance, and model validation is essential to the 

use of PBPK models in risk assessment. 

PBPK models improve the pharmacokinetic extrapolations used in risk assessments that identify the 

maximal (i.e., the safe) levels for human exposure to chemical substances (Andersen and Krishnan 

1994). PBPK models provide a scientifically-sound means to predict the target tissue dose of 

chemicals in humans who are exposed to environmental levels (for example, levels that might occur at 

hazardous waste sites) based on the results of studies where doses were higher or were administered in 

different species. Figure 2-4 shows a conceptualized representation of a PBPK model. 

If PBPK models for 4,4 ́-methylenedianiline exist, the overall results and individual models are 

discussed in this section in terms of their use in risk assessment, tissue dosimetry, and dose, route, and 

species extrapolations. 

Very limited information exists regarding toxicokinetics of methylenedianiline; consequently, a PBPK 

model for 4,4 ́-methylenedianiline has not yet been developed. 

2.4 MECHANISMS OF ACTION 

The mechanism of 4,4 ́-methylenedianiline absorption in the gastrointestinal tract, lungs, or skin is not 

known. Also, no information is available on how 4,4 ́-methylenedianiline is transported in the blood 

METHYLENEDIANILINE 67 

2. HEALTH EFFECTS 

or stored in tissues. 4,4 ́-Methylenedianiline can undergo N-hydroxylation leading to the formation of 

intermediates suspected of being mutagenic and possibly carcinogenic. In contrast, N-acetylation, a 

reaction shown to occur in humans and animals, leads to less toxic derivatives. The liver and thyroid 

are targets for 4,4 ́-methylenedianiline toxicity in animals. Limited data indicate that the liver is also a 

target in humans. The existing information does not suggest route-specific toxicity. 

2.4.1 Pharmacokinetic Mechanisms 

The mechanism of absorption of 4,4 ́-methylenedianiline by the inhalation, oral, and dermal routes is 

not known. Based on the chemical properties of 4,4 ́-methylenedianiline (poorly soluble in water, 

soluble in lipids), a passive transfer process from the aqueous environment of the intestine across cell 

membranes can be anticipated. Limited dermal data in animals suggest that absorption by this route is 

a saturable process (El-Hawari et al. 1986). It was also shown in dermal studies that the 

administration vehicle plays a role in the extent of absorption. For example, 4,4 ́-methylenedianiline 

was more toxic to rabbits when applied in ethanol (DuPont 1976a) than when applied as an aqueous 

paste (DuPont 1975). The results from a study in humans exposed to 4,4 ́-methylenedianiline in the 

workplace suggested that pulmonary absorption is faster than dermal absorption (Cocker et al. 1994). 

No information was located regarding the distribution of 4,4 ́-methylenedianiline in plasma, but it 

would be reasonable to assume that distribution is determined by partition among the various proteins 

according to lipid solubility and concentration. A first-pass effect in the liver can be expected. The 

limited toxicokinetics information available (El-Hawari et al. 1986) suggests that, with the exception of 

the liver, there is no preferential accumulation of 4,4 ́-methylenedianiline or metabolites in tissues or 

organs. No specific mechanism for storage of 4,4 ́-methylenedianiline or metabolites is apparent. 

Based on data from structurally-related compounds and from a study with 4,4 ́-methylenedianiline 

in vitro (Kajbaf et al. 1992), it seems that metabolism of 4,4 ́-methylenedianiline occurs in the liver. 

N-hydroxylation leads to N-hydroxylamine, a potentially toxic intermediate that can bind to 

macromolecule, or can be deactivated by conjugation with glutathione. 

Humans and animals eliminate 4,4 ́-methylenedianiline in the urine (Cocker et al. 1986a, 1994; 

El-Hawaii et al. 1986; Tanaka et al. 1985). Results from a dermal study showed that rats and 

monkeys excrete 4,4 ́-methylenedianiline preferentially in the urine, whereas in guinea pigs both 

excretion routes are of equal importance (El-Hawari et al. 1986). The existing information on 
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2. HEALTH EFFECTS 

4,4 ́-methylenedianiline does not suggest route-dependent toxicity, except for dermal effects which 

may occur after topical application of high concentrations of 4,4 ́-methylenedianiline. 

2.4.2 Mechanisms of Toxicity 

The mechanism of 4,4 ́-methylenedianiline toxicity is not completely understood. Based on 

information on structurally similar compounds, many of the toxic properties of 4,4 ́-methylenedianiline 

have been attributed to a reactive metabolic intermediate, N-hydroxymethylenedianiline, which results 

from the enzymatic oxidation of 4,4 ́-methylenedianiline (Cocker et al. 1986a; Lamb et al. 1986). In 

support of this view is the lack of genotoxicity of 4,4 ́-methylenedianiline in the absence of metabolic 

activation (Section 2.5). On the other hand, metabolic formation of N-acetylmethylenedianiline or 

N,N’-diacetylmethylenedianiline appears to represent a detoxification pathway since these metabolites 

were not mutagenic (Cocker et al. 1986b; Tanaka et al. 1985). 

Results from studies summarized in Section 2.2 strongly s uggest that the liver is a target for 

4,4 ́-methylenedianiline toxicity in humans and animals (Bailie et al. 1993, 1994; Hagiwara et al. 

1993; Kanz et al. 1992; Kopelman et al. 1966; Schmidt et al. 1980) and that the thyroid may also be a 

target for toxicity in animals (Pukushima et al. 1981; Hiasa et al. 1984; NTP 1983; Tsuda et al. 1987). 

Liver toxicity may be caused by a reactive electrophile formed during metabolism (Lamb et al. 1986) 

since the liver has the enzymes necessary for activation. Results from single-dose oral studies have 

shown that biliary epithelial cells are earlier toxicity targets than liver parenchymal cells (Bailie et al. 

1994), but the exact mechanism involved is unknown. A recent study showed that bile is a major 

route of biliary epithelial cell exposure to proximate toxicants of 4,4 ́-methylenedianiline (Kanz et 

al. 1995). This conclusion was based on the fact that rats infused through their common bile duct 

with bile from rats treated with 4,4 ́-methylenedianiline exhibited a much greater percentage of 

necrosis in the common bile duct than rats infused with control bile. The mechanism of thyroid 

toxicity has not yet been resolved. 4,4 ́-Methylenedianiline induced a slight decrease in serum T3 and 

T, in rats (Hiasa et al. 1984). This decrease, according to the investigators (Hiasa et al.1984), may 

have triggered secretion of thyroid stimulating hormone (TSH), which in turn induced thyroid 

hyperplasia. 

4,4 ́-Methylenedianiline was carcinogenic in rats and mice administered via drinking water (Lamb et 

al. 1986; NTP 1983). Although the mechanism of carcinogenicity is not known, some investigators 
METHYLENEDIANILINE 69 

2. HEALTH EFFECTS 

speculated that, at least for the liver, carcinogenicity may be related to the formation of a reactive 

metabolic intermediate which could bind to DNA (Lamb et al. 1986). However, a nongenetic 

mechanism of liver cancer is supported by recent data showing a relatively low potential of 

4,4 ́-methylenedianiline to bind to rat liver DNA in vivo (Schiitze et al. 1996; Vock et al. 1996). As 

for thyroid cancer, some investigators believe that the goitrogenic activity of 4,4 ́-methylenedianiline 

supports a nongenetic mechanism (Lamb et al. 1986). Therefore, the appearance of liver and thyroid 

tumors may be the consequence of chronic tissue-damaging or tissue-stimulating effects, respectively, 

of 4,4 ́-methylenedianiline. 4,4 ́-Methylenedianiline inhibited neoplastic responses in the liver, kidney, 

and urinary bladder in initiated rats (Fukushima et al. 1981; Masui et al. 1986). The mechanism is not 

known but, according to the investigators, it may be related to a reduction in food consumption and, 

consequently, reduced growth. 4,4 ́-Methylenedianiline promoted the development of thyroid tumors 

in rats (Hiasa et al. 1984); the authors speculated that hypersecretion of TSH may have contributed to 

tumor formation in initiated cells. 

2.4.3 Animal-to-Human Extrapolations 

The limited information available shows that N-acetylation of 4,4 ́-methylenedianiline is a metabolic 

reaction shared by humans and animals. N-acetylmethylenedianiline has been detected in the urine of 

rats exposed by the oral route (Tanaka et al. 1985) and in humans exposed to 4,4 ́-methylenedianiline 

in the workplace (Cocker et al. 1986a, 1994). However, an attempt to discuss potential interspecies 

differences or similarities in 4,4 ́-methylenedianiline toxicity based solely on this information seems 

inappropriate at this time. 

2.5 RELEVANCE TO PUBLIC HEALTH 

Overview. 

Most of the information on human health effects of 4,4 ́-methylenedianiline emanates from a case of 

ingestion of contaminated food and several reports of exposure in the workplace. The inhalation and 

dermal routes represent the most likely routes of exposure to 4,4 ́-methylenedianiline in occupational 

settings. Exposure to 4,4 ́-methylenedianiline for the general population seems unlikely. Case reports 

generally have many limitations, including lack of precise exposure data and presence of other 

compounds to which individuals may have been exposed, as well as confounding factors. The 
METHYLENEDIANILINE 70 

2. HEALTH EFFECTS 

presence of liver effects appears to be well established in workers exposed to 4,4 ́-methylenedianiline 

and in subjects who ingested food contaminated with 4,4 ́-methylenedianiline. Dermal effects also have 

been reported in occupationally exposed humans. There are also reports of respiratory, cardiovascular, 

hematological, and renal effects in exposed humans, but the evidence is not strong enough to 

conclusively establish cause-effect relationships. Results from one study were also inconclusive with 

respect to 4,4 ́-methylenedianiline and cancer in humans. 4,4 ́-Methylenedianiline was carcinogenic in 

rats and mice. Studies in animals are consistent and supportive of the human data with regard to liver 

effects. In addition to liver effects, the thyroid also appears to be a target for 4,4 ́-methylenedianiline 

toxicity in animals. No thyroid effects have been reported in humans, but this end point has not been 

appropriately evaluated. Little is known about toxicokinetics of 4,4 ́-methylenedianiline in humans. 

4,4 ́-Methylenedianiline has been detected in the urine of workers exposed to the chemical. Animals can 

absorb 4,4 ́-methylenedianiline through inhalation, ingestion, or skin contact with the chemical. Methods 

are currently being developed to assess exposure by quantitatively determining 4,4 ́-methylenedianiline 

adducts to hemoglobin. Because 4,4 ́-methylenedianiline is a liver toxicant, individuals with 

compromised liver function may be at a greater risk. Based on limited data regarding environmental 

exposure, the most likely exposure route for populations living near hazardous waste sites is the dermal 

route. This route may be of concern to humans since animal studies have shown that 4,4 ́­

methylenedianiline which remains within the skin after washing with soap and water is a potential source 

for later absorption. 

Minimal Risk Levels for 4,4 ́-Methylenedianiline. 

Inhalation MRLs. 

No inhalation MRLs were derived for 4,4 ́-methylenedianiline due to lack of human and animal data. 

Oral MRLs. 

•An MRL of 0.2 mg/kg/day has been derived for acute oral exposure (14 days or less) to 

4,4 ́-methylenedianiline. 

The acute oral MRL is based on a minimal LOAEL of 25 mg/kg for liver toxicity in rats administered a 

single dose of 0 (controls), 25, 50, 75, 100, 125, or 225 mg 4,4 ́-methylenedianiline/kg by gavage in corn 
METHYLENEDIANILINE 71 

2. HEALTH EFFECTS 

oil (Bailie et al. 1993). The minimal effective dose was between 25 and 75 mg/kg. The severity of the 

effects was dose-related. Effects observed included increased serum alanine aminotransferase and 

gamma-glutamyl transferase, increased serum bilirubin, decreased bile flow, and increased relative liver 

weight. All these effects were indicative of hepatic parenchymal injury. A dose of 100 mg/kg caused 

hepatocellular necrosis, bile ductular necrosis, portal edema, and neutrophil infiltration. Bile ductular 

necrosis was observed 4 hours after dosing, and this was the earliest change identified. These finding are 

supported by those of Bailie et al. (1994) and Schmidt et al. (1980), who also observed liver damage in 

rats after a single dose of 50 mg 4,4 ́-methylenedianiline. It has also been shown that the liver is a target 

for 4,4 ́-methylenedianiline toxicity in humans by the oral and dermal routes, and in animals by the 

dermal route. 

•An MRL of 0.08 mg/kg/day has been derived for intermediate oral exposure (15-364 days) to 

4,4 ́-methylenedianiline. 

The intermediate oral MRL is based on a NOAEL of 8.3 mg/kg/day for liver effects in rats administered 

daily doses of 4,4 ́-methylenedianiline by gavage in propylene glycol for 12 weeks (Pludro et al. 1969). 

Effects observed at a higher dose of 83 mg/kg/day included increased relative weight of the liver and 

kidney, atrophy of the liver parenchyma with hyperplasia of the stroma, particularly at portal areas, and 

increased serum beta-globulin and decreased albumin. Many studies have identified LOAELs in the 

range of 67-100 mg/kg/day, which is consistent with the results of Pludro et al. (1969). However, most 

of these studies tested only one dose level. A study conducted by NTP (1983) defined hepatic NOAELs 

of 35 mg/kg/day and 58 mg/kg/day for rats and mice, respectively. 

No chronic oral MRL was derived for 4,4 ́-methylenedianiline. The lowest LOAEL for a number of end 

points was 2.7 mg/kg/day in a study in which dogs were treated for 54-84 months with 4,4 ́­

methylenedianiline in a capsule 3 days per week (Deichmann et al. 1978). However, this study was not 

welldesigned and was poorly reported, which greatly diminished the potential significance of the results. 

No other study in dogs that could support the results of Deichmann et al. (1978) was located. 

Death. No studies were located that reported deaths in humans attributable to exposure to 

4,4 ́-methylenedianiline. In a population that had consumed bread made with flour contaminated with 
METHYLENEDIANILINE 72 

2. HEALTH EFFECTS 

4,4 ́-methylenedianiline in 1965 (Kopelman et al. 1966) the causes of death over the next 20 years 

were unremarkable (Hall et al. 1992). Observed/expected ratios for specific illnesses were well below 

1.0. Data from acute, intermediate, and chronic-duration oral exposure in animals suggest that mice 

are more sensitive than rats (Griswold et al. 1968; Lamb et al. 1986; NTP 1983). Decreased survival 

rates were observed in mice treated with 36 mg 4,4 ́-methylenedianiline kg/day for 30 days (Griswold 

et al. 1968) and in mice treated with 57 mg/kg/day for 103 weeks (Lamb et al. 1986; NTP 1983). 

Mice were also more sensitive to acute dermal doses of 4,4 ́-methylenedianiline than rabbits (DuPont 

1976a; Holland et al. 1987). Although environmental data are limited, it is unlikely that 

4,4 ́-methylenedianiline levels near hazardous waste sites are sufficient to cause death in exposed 

populations after single or few exposures. The limited data in animals are inconclusive in determining 

whether prolonged low-level exposures in humans may represent a health hazard. 

Systemic Effects. 

Respiratory Effects. No respiratory effects were observed in a population that became ill after 

ingesting bread contaminated with 4,4 ́-methylenedianiline (Kopelman et al. 1966), and no studies 

were located that described respiratory effects in subjects exposed to 4,4 ́-methylenedianiline in the 

workplace. The respiratory system was not a target for 4,4 ́-methylenedianiline toxicity in animals by 

the inhalation (Leong et al. 1987), oral (NTP 1983) or dermal (DuPont 1975) route. For populations 

near Superfund sites, the potential for developing adverse respiratory effects from exposure to 

4,4 ́-methylenedianiline seems unlikely. 

Cardiovascular Effects. Lingering myocardial abnormalities were reported in a subject that had 

dermal contact with 4,4 ́-methylenedianiline in the workplace during a period of 2 weeks (Brooks et al. 

1979). However, no information was provided regarding possible simultaneous exposure to other 

chemicals or past medical history. Furthermore, no acute or chronic signs of cardiovascular disease 

were observed in a population that was exposed to 4,4 ́-methylenedianiline by eating contaminated 

bread (Kopelman et al. 1966; Roy et al. 1985). The cardiovascular system was not a target for 

4,4 ́-methylenedianiline toxicity in animals exposed orally in intermediate- or chronic-duration studies 

(Lamb et al. 1986; NTP 1983). There is insufficient evidence to assess the risk of cardiovascular 

disease in populations exposed to low levels of 4,4 ́-methylenedianiline for a prolonged period of time. 
METHYLENEDIANILINE 73 

2. HEALTH EFFECTS 

Gastrointestinal Effects. No acute or chronic signs of gastrointestinal disease were observed in a 

population that ate bread contaminated with 4,4 ́-methylenedianiline (Kopelman et al. 1966; Roy et al. 

1985); however, nausea, abdominal pain, and vomiting were experienced by a subject who ingested 

4,4 ́-methylenedianiline in an alcoholic beverage (Tillmann et al. 1997). Gross abnormalities were 

observed in the stomach of female rats treated with ≥261 mg 4,4 ́-methylenedianiline in the drinking 

water for 14 days (NTP 1983). However, the significance of this finding is unclear since this effect 

was not seen in males treated in a similar manner with doses ≥235 mg/kg/day, although lesions were 

evident at 469 mg/kg/day (NTP 1983). Oral intermediate or chronic-duration studies in animals 

showed no adverse effects in the gastrointestinal tract after administration of 4,4 ́-methylenedianiline. 

The evidence in animals suggest that the gastrointestinal tract is not a target for 4,4 ́-methylenedianiline 

toxicity, but the human data are inconclusive as to the potential effects of prolonged oral 

exposure to 4,4 ́-methylenedianiline. 

Hematological Effects. Eosinophilia was described in a subject who accidentally ingested a solution 

containing 4,4 ́-methylenedianiline (Roy et al. 1985). Other components in the solution were 

potassium carbonate and gamma-butyrolactone. Mild leucocyte elevation was reported in a young man 

who ingested an undetermined amount of 4,4 ́-methylenedianiline mixed in an alcoholic beverage 

(Tillmann et al. 1997). Eosinophilia was also observed in four of six men who became in contact with 

4,4 ́-methylenedianiline at work (Williams et al. 1974). Eosinophilia is a characteristic response 

observed in allergic reactions; therefore, in these cases it was most likely caused by exposure to 

4,4 ́-methylenedianiline, even though other chemicals may have been involved. No significant 

hematological effects have been reported in animals after exposure to 4,4 ́-methylenedianiline; 

however, this system has not been appropriately evaluated. The exact role of eosinophils in the 

allergic immunological reaction is not known. The existing information suggests that eosinophilia may 

develop after exposure to 4,4 ́-methylenedianiline as may occur in populations living near hazardous 

waste sites. 

Musculoskeletal Effects. The only information regarding musculoskeletal effects in humans after 

exposure to 4,4 ́-methylenedianiline is from a case report of a young man who complained of joint and 

muscle pain on admission to the hospital one day after drinking an alcoholic beverage spiked with an 

unknown amount of 4,4 ́-methylenedianiline (Tillmann et al. 1997). Long-term oral studies in both 

rats and mice found no evidence of gross or histopathological alterations in the musculoskeletal system 
METHYLENEDIANILINE 74 

2. HEALTH EFFECTS 

(Lamb et al. 1986; NTP 1983). Based on this limited evidence, no predictions can be made regarding 

musculoskeletal effecIs in populations exposed to 4,4 ́-methylenedianiline. 

Hepatic Effects. It is well established that 4,4 ́-methylenedianiline is a liver toxicant in humans 

(Bastian 1984; Brooks et al. 1979; Kopelman et al. 1966; McGill and Motto 1974; Tillmann et al. 

1997; Williams et al. 1974) and animals (Bailie et al. 1993, 1994; Fukushima et al. 1981; Kanz et al. 

1992; Lamb et al. 1986; NTP 1983) regardless of the route of exposure. In humans that developed 

toxic hepatitis as a result of accidentally ingesting 4,4 ́-methylenedianiline (Kopelman et al. 1966), 

there was no sign of progressive hepatic disease upon examination two years after the poisoning 

episode (Kopelman 1968). No deaths attributed to liver disease were reported among this same 

population over a period of 20 years after the accident (Ball et al. 1992). In animals, the severity of 

the effects was generally dose-related, and results from single dose studies showed that biliary 

epithelial cells are affected earlier than parenchymal liver cells (Bailie et al. 1994) and that the toxicant 

responsible for the damage is present in the bile (Kanz et al. 1995), although its chemical nature has 

not been established. It was also shown that leukocyte infiltration observed in the liver after an oral 

dose of 4,4 ́-methylenedianiline does not contribute to liver damage. Acute-duration studies, mainly in 

rats, identified minimal effective doses around 25 mg/kg/day (Bailie et al. 1993). A NOAEL of 

8.3 mg/kg/day was established in intermediate-duration study in rats (Pludro et al. 1969); LOAELs 

ranged between 67 and 100 mg/kg/day. Chronic LOAELs were 9 and 25 mg/kg/day in rats and mice, 

respectively (Lamb et al. 1986; NTP 1983). A LOAEL of 2.7 mg/kg/day was reported in dogs, but 

this study had severe design limitations (Deichmann et al. 1978). An acute oral MRL of 0.2 mg/kg/day was 

derived based on the results of a study by Bailie et al. (1993). In deriving this MRL, a modifying actor of 

0.5 was used to account for the possibility that the corn oil vehicle might have facilitated the absorption of 

4,4 ́-methylenedianiline in the gastrointestinal tract. An intermediate MRL of 0.08 mg/kg/day was based on 

results from Pludro et al. (1969). The exact mechanism involved in liver toxicity is unknown, but some 

have suggested that it may be related to the formation of a reactive electrophile as a result of metabolic 

activation of 4,4 ́-methylenedianiline (Lamb et al. 1986). The existing evidence indicates that humans 

exposed to elevated levels of 4,4 ́-methylenedianiline, which may be found in the workplace, may be at risk 

of developing liver disease. 

Endocrine Effects. No information was located regarding endocrine effects in humans exposed to 

4,4 ́-methylenedianiline by any route. Results from oral studies in animals suggest that the thyroid is a 

target for 4,4 ́-methylenedianiline toxicity. Gross and histopathological alterations have been described 
METHYLENEDIANILINE 75 

2. HEALTH EFFECTS 

in rats and mice in acute- (Tullner 1960), intermediate- (Fukushima et al. 1981; Hagiwara et al. 1993; 

Hiasa et al. 1984; NTP 1983; Tsuda et al. 1987), and chronic-duration (Lamb et al. 1986; NTP 1983) 

oral studies. The mechanism of thyroid toxicity is not known, but some have speculated that it may 

be related to induced hypersecretion of thyroid stimulating hormone (TSH) which in turn induces 

thyroid hyperplasia (Hiasa et al. 1984). The relevance of the thyroid effects observed in animals to 

human health is unknown. Thyroid function has not been examined in populations with known 

exposure to 4,4 ́-methylenedianiline. 

Renal Effects. Results from clinical tests in a subject who accidentally drank a solution containing 

4,4 ́-methylenedianiline, potassium carbonate, and gamma-butyrolactone were consistent with renal 

tubular dysfunction (Roy et al. 1985), but the role of 4,4 ́-methylenedianiline, if any, is unknown. The 

only other relevant information in humans is a case in which proteinuria and erythrocyturia were 

observed in a young man who drank an alcoholic beverage spiked with 4,4 ́-methylenedianiline 

(Tillmann et al. 1997). No further data in humans were located. Intermediate-duration oral studies in 

animals established NOAELs of 83-141 mg/kg/day (Fukushima et al. 1979, 1981; NTP 1983; Pludro 

et al. 1969). However, in chronic-duration oral studies, high incidence of nephropathy was reported in 

mice at 19-25 mg 4,4 ́-methylenedianiline/kg/day and a high incidence of kidney mineralization was 

seen in male rats at 16 mg/kg/day (Lamb et al. 1986; NTP 1983). A much lower LOAEL of 

2.7 mg/kg/day was reported in dogs, but this study suffered from severe limitations (Deichmann et al. 

1978). The results from these long-term studies in animals suggest that the possibility exists for 

similar effects to occur in humans exposed to low 4,4 ́-methylenedianiline levels for a prolonged 

period of time, such as can occur near Superfund waste sites. 

Dermal Effects. Erythema multiform was observed in a subject who accidentally ingested a liquid 

containing 4,4 ́-methylenedianiline, potassium carbonate, and gamma-butyrolactone (Roy et al. 1985). 

Although more than one chemical was involved in this case, the presence of erythema multiform is 

consistent with an immunological allergic reaction. A recent study reported that a subject who drank 

an alcoholic beverage spiked with 4,4 ́-methylenedianiline developed a skin rash (Tillmann et al. 

1997). Skin rashes have commonly been described in individuals who had dermal contact with 

4,4 ́-methylenedianiline (Brooks et al. 1979; Emmett 1976; McGill and Motto 1974; Van Joost et al. 

1987). Also, a case of photosensitivity to 4,4 ́-methylenedianiline was described (Levine 1983). 

Exposure concentrations were not available. In some cases (Brooks et al. 1979; McGill and Motto 

1974), skin rashes and pruritus could have been a manifestation of the underlying liver disease. 
METHYLENEDIANILINE 76 

2. HEALTH EFFECTS 

However, in other cases (Emmett 1976; Van Joost et al. 1987), proof of dermal sensitization was 

obtained when patch testing with 4,4 ́-methylenedianiline gave positive results. In the case described 

by Van Joost et al. (1987), the patient had no known previous exposure to 4,4 ́-methylenedianiline, but 

had been exposed to other chemicals. This led the investigators to suggest that cross sensitization may 

have occurred, specifically, to agents with substitution in the para position. The possibility of dermal 

sensitization across routes of exposure was examined in guinea pigs and the results were negative 

(Leong et al. 1987). The existing evidence indicates that 4,4 ́-methylenedianiline can cause dermal 

sensitization in humans. 

Ocular Effects. Prolonged and severe loss of visual acuity was reported in a subject who accidentally 

ingested a liquid containing 4,4 ́-methylenedianiline, potassium carbonate, and gamma-butyrolactone 

(Roy et al. 1985). These effects could not, however, be conclusively attributed to 4,4 ́-methylenedianiline. 

No other reports were found regarding ocular effects in humans after exposure to 4,4 ́-methylenedianiline. 

Supporting the findings of Roy et al. (1985) is a report in which guinea pigs exposed nose-only to an 

aerosol of 4,4 ́-methylenedianiline for 2 weeks had serious morphological alterations in the retina (Leong et 

al. 1987). It is assumed that nose-only exposure prevented direct contact of the aerosol with the eye. On the 

other hand, no specific complaints of ocular effects were observed among a group of individuals who ate 

bread contaminated with 4,4 ́-methylenedianiline and developed toxic hepatitis (Kopelman 1968; 

Kopelman et al. 1966). Deposition of solid 4,4 ́-methylenedianiline into the eye of rabbits induced acute 

reversible effects in the cornea, iris, and conjunctiva (DuPont 1976b). The evidence available suggests that 

populations living near Superfund waste sites are not at a greater risk of developing adverse ocular effects 

due to exposure to 4,4 ́-methylenedianiline. However, direct contact with concentrated material, as may 

occur occupationally, can be hazardous. 

Body Weight Effects. No studies were located regarding body weight effects in humans exposed to 

4,4 ́-methylenedianiline by any route. Acute (NTP 1983), intermediate (Fukushima et al. 1979, 1981; 

Hagiwara et al. 1993; Hiasa et al. 1984; Miyamoto et al. 1977; NTP 1983; Tsuda et al. 1987), or chronic 

(Lamb et al. 1986; NTP 1983) oral exposure to 4,4 ́-methylenedianiline in animals usually resulted in a 

reduction in final body weight. Similar results were reported in rabbits exposed dermally for 10 days 

(DuPont 1976a). Food consumption data were not provided in these studies. The relevance of these 

findings to human health is unknown. 
METHYLENEDIANILINE 77 

2. HEALTH EFFECTS 

Immunological and Lymphoreticular Effects. Several cases of dermal sensitization have been 

described in subjects who became in contact with 4,4 ́-methylenedianiline in the workplace (Emmett 

1976; Levine 1983; Van Joost et al. 1987), but no information exists regarding possible effects of 

4,4 ́-methylenedianiline on human immunocompetence. Studies in animals have described 

histopathological alterations in the thymus of rats after single oral doses of 250 mg 4,4 ́­

methylenedianiline/kg (Kanz et al. 1992). No histopathological alterations were seen in organs of the 

lymphoreticular system from rats or mice in intermediate or chronic oral studies (Lamb et al. 1986; 

NTP 1983). Immunocompetence has not been evaluated in animals. There is insufficient information 

to assess the potential immunological effects of prolonged exposure to low levels of 4,4 ́­

methylenedianiline in humans. 

Neurological Effects. No studies were located regarding neurological effects in humans after 

exposure to 4,4 ́-methylenedianiline by any route. Studies in animals provided no evidence of 

neurotoxicity after intermediate or chronic exposure (Lamb et al. 1986; NTP 1983), although a 

complete neurological examination including neurobehavioral testing has not been performed. Because 

4,4 ́-methylenedianiline is a solid with low volatility and because of what is known about structurally 

similar compounds, it is not anticipated that exposures around Superfund sites will cause neurological 

damage in humans. 

Reproductive Effects. No studies were located regarding reproductive effects in humans after 

exposure to 4,4 ́-methylenedianiline by any route. Hypertrophy of the uterus was observed in rats 

treated orally for 5-14 days with 110 mg 4,4 ́-methylenedianiline/kg/day (Tullner 1960). However, no 

such effects were seen after exposure to similar daily doses for 13 weeks (NTP 1983) or to lower 

doses for up to 103 weeks (Lamb et al. 1986; NTP 1983). Endometrial hyperplasia was reported in a 

dogs treated with doses of about 2.7 mg 4,4 ́-methylenedianiline/kg/day for over 54 months, but this 

study had severe design limitations (Deichmann et al. 1978). None of the animal studies examined 

reproductive function. There is not enough information to predict whether reproductive function in 

humans might be affected after exposure to 4,4 ́-methylenedianiline. 

Developmental Effects. No studies were located regarding developmental effects in humans after 

exposure to 4,4 ́-methylenedianiline by any route. A single oral study in rats administered 

4,4 ́-methylenedianiline during gestation showed that doses ≥37 mg/kg/day may cause developmental 

abnormalities in the offspring (Bourdelat et al. 1983). It should be noted, however, that these dose 
METHYLENEDIANILINE 78 

2. HEALTH EFFECTS 

levels also induced maternal toxicity. Furthermore, only one rat was used as control and the results 

were poorly reported. Based on the evidence available, no predictions can be made regarding 

developmental effects in populations exposed to 4,4 ́-methylenedianiline. 

Genotoxic Effects. As seen in Table 2-4, limited information exists regarding genotoxic effects of 

4,4 ́-methylenedianiline in vivo. In rats, a single intraperitoneal injection of approximately 73 mg 

4,4 ́-methylenedianiline/ significantly increased the incidence of DNA fragmentation in liver cells 

(Parodi et al. 1981). In a study in which only two rats were used, intraperitoneal administration of 

approximately 80 mg 4,4 ́-methylenedianiline/kg to one rat increased the amount of DNA adducts in 

the liver relative to the control rat treated with the vehicle only (Endo and Hara 1991). In more recent 

studies, it was shown that 4,4 ́-methylenedianiline has a relatively low DNA binding potency (Schiitze 

et al. 1996). In that study, the total radioactivity bound to liver DNA from rats treated with a single 

intraperitoneal dose of 0.2 or 23 mg of 4,4 ́-methylenedianiline/kg corresponded to 0.06 and 2.7 adducts 

per 10.’ nucleotides, and this put 4,4 ́-methylenedianiline in the range of weakly genotoxic compounds. 

The structure of the adducts was not determined, but it was determined that adduct formation was covalent 

in nature. Similar results were reported in rats after acute oral administration of 4,4 ́-methylenedianiline 

(Vock et al. 1996). In the latter case, no adducts could be detected in the bladder and peripheral 

lymphocytes. Contradictory results were obtained regarding sex-linked recessive lethal mutations in 

Drosophila melanogaster. Foureman et al. (1994) reported a significant increase in the incidence of 

recessive lethal mutations while Ho et al. (1979) reported no significant increase. 

Many studies have examined the genotoxic properties of 4,4 ́-methylenedianiline in vitro in Salmonella 

typhimurium (Andersen et al. 1980; Cocker et al. 1986a; Ho et al. 1979; LaVoie et al. 1979; McCarthy 

et al. 1982; Messerly et al. 1987; Parodi et al. 1981; Rannug et al. 1984; Rao et al. 1982; Takemura 

and Shimizu 1978; Tanaka et al. 1985; Tsuchiya 1995). With few exceptions (see Table 2-5), the 

results showed that 4,4 ́-methylenedianiline is genotoxic after metabolic activation with S-9 systems. 

Although not conclusively established, the genotoxic properties have been attributed to a reactive 

electrophile formed as a result of N-hydroxylation. On the other hand, N-acetylated metabolites have 

been shown to be nonmutagenic (Cocker et al. 1986b; Tanaka et al. 1985). 4,4 ́-Methylenedianiline 

also was shown to be mutagenic in the eukaryotic organism Saccharomyces cerevisiae with and 

without metabolic activation (Ho et al. 1979). 4,4 ́-Methylenedianiline did not increase the incidence 

of sister chromatid exchanges in human leukocytes in vitro when tested with or without activation (Ho 


METHYLENEDIANILINE 81 

2. HEALTH EFFECTS 

et al. 1979), but increased unscheduled DNA synthesis in rat hepatocytes (Mirsalis et al. 1983; Mori et 

al. 1988) and the incidence of forward mutations in L5178Y mouse lymphoma cells (McGregor et al. 

1988). The overall evidence is insufficient to indicate that exposure to 4,4 ́-methylenedianiline may 

cause genetic damage in humans. 

Cancer. Limited information exists regarding potential carcinogenicity of 4,4 ́-methylenedianiline in 

humans. No association was found between deaths from cancers and 4,4 ́-methylenedianiline in a 

group of 84 subjects who ate bread contaminated with 4,4 ́-methylenedianiline (Hall et al. 1992). The 

evaluation was conducted over a period of 20 years following the accident. However, the cohort is 

quite small for drawing any firm conclusions. Similar lack of association was reported for a cohort of 

550 male and 45 female Swedish workers exposed to 4,4 ́-methylenedianiline (predominantly by 

dermal contact) (Selden et al. 1992). The exposure period was not clearly established. It was noted, 

however, that the subjects were quite young and had not reached cancer-prone age, and that the 

follow-up period was short and may not have covered the latency period for some cancers, in 

particular bladder cancer, which has a latency of about 20 years. Two additional studies also provided 

inconclusive evidence of increased incidence of bladder cancer among workers exposed to 

4,4 ́-methylenedianiline; studies were inconclusive mainly because of simultaneous exposure to other 

chemicals (Cragle et al. 1992; Liss and Guirguis 1994). 

Results from a 2-year drinking water bioassay provided clear evidence of carcinogenicity in rats and 

mice (Lamb et al. 1986; NTP 1983). Under the conditions of the study, 4,4 ́-methylenedianiline 

caused significantly increased incidences of thyroid follicular cell carcinomas in male rats, thyroid 

follicular cell adenomas in female rats and both male and female mice, C-cell adenomas of the thyroid 

gland in female rats, neoplastic nodules in the liver of male rats, hepatocellular carcinomas in male 

and female mice, adenomas of the liver and malignant lymphomas in female mice, and adrenal 

pheochromocytomas in male mice. It should be mentioned, however, that considerable debate exists 

on whether adenomas result in, or are a precursor to, malignant neoplasms. 

4,4 ́-Methylenedianiline was not a promoter of liver, kidney, or urinary bladder tumors in rats 

(Fukushima et al. 1981; Masui et al. 1986); in fact, it inhibited the neoplastic response induced by the 

carcinogens alone. It was postulated that the mechanism may be related to a decreased food 

consumption and reduced growth (Fukushima et al. 1981; Masui et al. 1986). In contrast, 
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2. HEALTH EFFECTS 

4,4 ́-methylenedianiline promoted the formation of thyroid tumors in rats initiated with 

N-bis(2-hydroxypropyl)nitrosamine (Hiasa et al. 1984). 

The mechanism of 4,4 ́-methylenedianiline carcinogenicity is not known. It has been suggested that a 

reactive intermediate resulting from metabolic activation may be responsible for the liver 

carcinogenicity by binding to cell macromolecules, and that a nongenetic mechanism may be involved 

in thyroid carcinogenicity (Lamb et al. 1986). Based on recent data regarding the low potential of 

4,4 ́-methylenedianiline to bind to rat liver DNA (Schiitze et al. 1996), a nongenotoxic mechanism of 

liver carcinogenicity would also appear likely. Based on inadequate evidence of carcinogenicity in 

humans and sufficient evidence in experimental animals, the International Agency for Research on 

Cancer (IARC 1987) has designated 4,4 ́-methylenedianiline a Group 2B carcinogen and possibly 

carcinogen in humans. 

2.6 BIOMARKERS OF EXPOSURE AND EFFECT 

Biomarkers are broadly defined as indicators signaling events in biologic systems or samples. They 

have been classified as markers of exposure, markers of effect, and markers of susceptibility 

(NAS/NRC 1989). 

Due to a nascent understanding of the use and interpretation of biomarkers, implementation of 

biomarkers as tools of exposure in the general population is very limited. A biomarker of exposure is 

a xenobiotic substance or its metabolite(s), or the product of an interaction between a xenobiotic agent 

and some target molecule(s) or cell(s) that is measured within a compartment of an organism (NRC 

1989). The preferred biomarkers of exposure are generally the substance itself or substance-specific 

metabolites in readily obtainable body fluid(s) or excreta. However, several factors can confound the 

use and interpretation of biomarkers of exposure. The body burden of a substance may be the result 

of exposures from more than one source. The substance being measured may be a metabolite of 

another xenobiotic substance (e.g., high urinary levels of phenol can result from exposure to several 

different aromatic compounds). Depending on the properties of the substance (e.g., biologic half-life) 

and environmental conditions (e.g., duration and route of exposure), the substance and all of its 

metabolites may have left the body by the time samples can be taken. It may be difficult to identify 

individuals exposed to hazardous substances that are commonly found in body tissues and fluids (e.g., 
METHYLENEDIANILINE 83 

2. HEALTH EFFECTS 

essential mineral nutrients such as copper, zinc, and selenium). Biomarkers of exposure to 

4,4 ́-methylenedianiline are discussed in Section 2.6.1. 

Biomarkers of effect are defined as any measurable biochemical, physiologic, or other alteration within 

an organism that, depending on magnitude, can be recognized as an established or potential health 

impairment or disease (NAS/NRC 1989). This definition encompasses biochemical or cellular signals 

of tissue dysfunction (e.g., increased liver enzyme activity or pathologic changes in female genital 

epithelial cells), as well as physiologic signs of dysfunction such as increased blood pressure or 

decreased lung capacity. Note that these markers are not often substance specific. They also may not 

be directly adverse, but can indicate potential health impairment (e.g., DNA adducts). Biomarkers of 

effects caused by 4,4 ́-methylenedianiline are discussed in Section 2.6.2. 

A biomarker of susceptibility is an indicator of an inherent or acquired limitation of an organism’s 

ability to respond to the challenge of exposure to a specific xenobiotic substance. It can be an 

intrinsic genetic or other characteristic or a preexisting disease that results in an increase in absorbed 

dose, a decrease in the biologically effective dose, or a target tissue response. If biomarkers of 

susceptibility exist, they are discussed in Section 2.8, Populations That Are Unusually Susceptible. 

2.6.1 Biomarkers Used to Identify or Quantify Exposure to 4,4 ́-Methylenedianiline 

Exposure to 4,4 ́-methylenedianiline in manufacturing and use has been assessed by monitoring 

4,4 ́-methylenedianiline in the urine (Cocker et al. 1986a, 1994; Dalene et al. 1995; Schtitze et al. 

1995). A metabolite of 4,4 ́-methylenedianiline, N-acetylmethylenedianiline, also has been quantified 

in urine (Cocker et al. 1986a; Schtitze et al. 1995). Quantification of these substances is performed by 

gas chromatography-mass spectrophotometry. Cocker et al. (1994) was able to show that when 

exposure to 4,4 ́-methylenedianiline occurred through inhalation, postshift urine samples contained 

higher concentrations of 4,4 ́-methylenedianiline than samples taken preshift next day. When exposure 

was thought to be through the dermal route, urine collected preshift next day had higher-concentration 

of 4,4 ́-methylenedianiline than samples taken immediately postshift on the day of exposure. These 

results suggested that pulmonary absorption is relatively fast such that peak excretion is reached at the 

end of the shift. In contrast, absorption through the skin was slower and maximum excretion occurred 

the next morning. N,N’-diacetylmethylenedianiline has also been found in the urine of exposed 

workers, but at a much lower concentration than the monoacetylated metabolite (Robert et al. 1995). 
METHYLENEDIANILINE 84 

2. HEALTH EFFECTS 

Little is known about the pharmacokinetics of 4,4 ́-methylenedianiline in humans, but data in animals 

suggest that it is eliminated fairly rapidly and does not accumulate. This is consistent with what has 

been found in occupationally exposed humans. In a study involving 411 exposed workers, 42% of the 

urine samples had no detectable 4,4 ́-methylenedianiline (Cocker et al. 1994). In another study of 

111 exposed workers, the concentration of 4,4 ́-methylenedianiline in 81% of over 300 urine samples 

was below the detection limit for the method (Cocker et al. 1986a). This suggests that monitoring 

urinary 4,4 ́-methylenedianiline may not be sensitive enough in cases of brief or single exposures to 

low levels of the chemical. Furthermore, only an indication of recent exposure would be obtained. In 

contrast with the results from Cocker et al. (1986a), a recent study by Schtitze et al. (1995) found 

4,4 ́-methylenedianiline in the urine from workers exposed to low levels of the chemical (<20 pg/m3

). 

Thirty-three workers were examined and 4,4 ́-methylenedianiline was detected in the urine 

(0.013-2.76 nmol/L) from all of them. Urinary levels of the metabolite N-acetylmethylenedianiline 

ranged from 0.045 to 23.4 nmol/L. 

Recent studies have examined the formation of adducts of 4,4 ́-methylenedianiline with hemoglobin as 

a means for monitoring exposure (Bailey et al. 1990; Farmer and Bailey 1989; Schiitze et al. 1995). 

In the recent study by Schiitze et al. (1995), the authors showed that there was a good correlation 

(r=0.77) between adduct levels in hemoglobin and 4,4 ́-methylenedianiline released after acid treatment 

of urine. The following mechanism of adduct formation has been postulated (Farmer and Bailey 

1989). N-hydroxymethylenedianiline resulting from the enzymatic oxidation of 4,4 ́-methylenedianiline 

is further oxidized to nitroso compounds, which may react with sulfhydryl groups in hemoglobin. This 

yields N-hydroxy sulphenamides, which then rearrange to more stable sulphinamides. Hydrolysis of the 

sulphinamides under mild acidic or basic conditions releases the parent amine, which may be extracted and 

quantitated. This approach has a clear advantage over directly monitoring 4,4 ́-methylenedianiline because 

the adduct is stable in vivo and its elimination is related to the lifespan of the erythrocytes, which in 

humans is 120 days (Farmer and Bailey 1989). In addition, there is an advantage over DNA adducts which 

are subjected to DNA repair reactions. Although no data exist yet in humans, studies in rats showed that 

4,4 ́-methylenedianiline and N-acetylmethylenedia.niline formed adducts with hemoglobin and that a doseresponse relationship could be established over the range of oral doses used (1-12 mg/kg) (Bailey et al. 

1990). 
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2.6.2 Biomarkers Used to Characterize Effects Caused by 4,4 ́-Methylenedianiline 

There are no specific biomarkers of effects for 4,4 ́-methylenedianiline. Studies summarized in 

Section 2.2 indicate that exposure to 4,4 ́-methylenedianiline causes adverse liver effects in humans 

(Kopelman et al. 1966; McGill and Motto 1974; Williams et al. 1974). However, exposure to many 

other chemicals, not even necessarily of a structure similar to 4,4 ́-methylenedianiline, can produce a 

similar clinical picture. Also, the properties of dermal sensitizer are not unique to 4,4 ́-methylenedianiline, 

and a positive patch testing response to 4,4 ́-methylenedianiline may also be obtained in cases of previous 

contact with chemicals substituted in the para-position (cross sensitization) (Van Joost et al. 1987). 

For more information on biomarkers for renal and hepatic effects of chemicals see the ATSDR/CDC 

Subcommittee Report on Biological Indicators of Organ Damage (1990); for information on 

biomarkers for neurological effects, see OTA (1990). 

2.7 INTERACTIONS WITH OTHER CHEMICALS 

No information was located regarding the influence of other chemicals on the toxicity of 4,4 ́­

methylenedianiline in humans. Limited data in animals showed that pretreatment of rats with the 

monooxygenase function inhibitor aminobenzotriazol, ameliorated the hepatic effects of 4,4 ́­

methylenedianiline (Bailie et al. 1993). However, pretreatment with the inhibitor SKF-525A had 

no effect. Based on these results, the investigators proposed that 4,4 ́-methylenedianiline requires 

metabolic activation for its toxicity and that activation is carried out by an isozyme of cytochrome 

P-450 that is inhibited by aminobenzotriazol, but not SKF-525A (Bailie et al. 1993). 

4,4 ́-Methylenedianiline inhibited the formation of liver, kidney, and urinary bladder tumors when 

administered orally to rats following initiation with various carcinogens (Fukushima et al. 1981; Masui 

et al. 1986). The mechanism for this interaction is not known. Some have suggested that a reduction 

in food consumption and, consequently, in growth, induced by 4,4 ́-methylenedianiline, may play a 

role (Fukushima et al. 1981). A different possibility that has been offered is that 4,4 ́-methylenedianiline 

may alter the activities of enzymes involved in carcinogen metabolism, resulting in reduced 

biotransformation of the carcinogens (Tsuda et al. 1987). 4,4 ́-Methylenedianiline has been shown to 

alter the activities of several biotransformation enzymes in rats (Wu et al. 1989). 
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2. HEALTH EFFECTS 

2.8 POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE 

A susceptible population will exhibit a different or enhanced response to 4,4 ́-methylenedianiline than 

will most persons exposed to the same level of 4,4 ́-methylenedianiline in the environment. Reasons 

may include genetic makeup, age, health and nutritional status, and exposure to other toxic substances 

(e.g., cigarette smoke). These parameters may result in reduced detoxification or excretion of 

4,4 ́-methylenedianiline, or compromised function of target organs affected by 4,4 ́-methylenedianiline. 

Populations who are at greater risk due to their unusually high exposure to 4,4 ́-methylenedianiline are 

discussed in Section 5.6, Populations With Potentially High Exposure. 

In the review of the literature regarding toxic effects of 4,4 ́-methylenedianiline, no information was 

located on any population that might be unusually sensitive to 4,4 ́-methylenedianiline. However, 

based on the knowledge of the primary toxic effect of 4,4 ́-methylenedianiline (liver toxicity), a 

number of groups may be proposed as being potentially highly sensitive to this chemical. Some of 

these groups include very young children who have an immature hepatic detoxification system and 

individuals with impaired liver function (i.e., liver cirrhosis). In addition, people who develop 

dermatitis following exposure to 4,4 ́-methylenedianiline in the workplace may become hypersensitive 

to subsequent exposure to the chemical or to structurally related chemicals (Van Joost et al. 1987). 

Also, since the enzyme N-acetyltransferase exhibits polymorphism, slow acetylators will be prone to 

more toxic insult of 4,4 ́-methylenedianiline than fast acetylators, assuming that acetylation represents 

a true detoxification pathway. 

2.9 METHODS FOR REDUCING TOXIC EFFECTS 

This section will describe clinical practice and research concerning methods for reducing toxic effects 

of exposure to 4,4 ́-methylenedianiline. However, because some of the treatments discussed may be 

experimental and unproven, this section should not be used as a guide for treatment of exposures to 

4,4 ́-methylenedianiline. When specific exposures have occurred, poison control centers and medical 

toxicologists should be consulted for medical advice. 

No texts were found that provided specific information about treatment following exposures to 

4,4 ́-methylenedianiline. 
METHYLENEDIANILINE 87 

2. HEALTH EFFECTS 

2.9.1 Reducing Peak Absorption Following Exposure 

4,4 ́-Methylenedianiline can be absorbed through the skin, by inhalation of fine dust or vapor, or by 

ingestion. The only recommendation found in the literature to reduce peak absorption after ingestion 

was induction of vomiting (Allied Chemical 1978). Removing the patient to fresh air is suggested if 

inhalation occurs, and washing with soap and water is recommended after contact with the skin (Allied 

Chemical 1978; NIOSH 1997). NIOSH (1997) further recommends immediately washing the eyes 

with large amounts of water, occasionally lifting the lower and upper lids. A recent study examined 

the efficacy of either 100% ethanol, 100% water, or 1% or 10% soap solution in removing 

4,4 ́-methylenedianiline from human and rat skin in vitro (Hewitt et al. 1995). The results showed that 

all solutions were equally effective in removing the chemical from the human skin surface, with 

2 l-47% of the applied dose removed at 72 hours. In contrast, 100% ethanol or 10% soap solution 

were significantly more effective in removin, 0 4,4 ́-methylenedianiline from the rat skin than 100% 

water or 1% soap solution. The results also showed that washing the skin surface 3 or 30 minutes 

after dosing significantly reduced absorption (2- to 3-fold) compared with control unwashed skin. 

Washing after 72 hours following application of the compound did not significantly reduce absorption. 

Data from an in vivo study in a groups of rats and guinea pigs and in a monkey showed that washing 

the application site with soap and water was more effective in removing 4,4 ́-methylenedianiline from 

the skin than washing with acetone and water (El-Hawaii et al. 1986). 

2.9.2 Reducing Body Burden 

No information was located regarding reducing the body burden after exposure to 4,4 ́-methylenedianiline. 

2.9.3 Interfering with the Mechanism of Action for Toxic Effects 

The mechanism of 4,4 ́-methylenedianiline toxicity is not lmown. Information on structurally related 

chemicals suggests that the toxicity of 4,4 ́-methylenedianiline is due to the formation of a reactive 

intermediate that can bind covalently to cell macromolecule. The reactive intermediate is produced by 

the enzymatic N-oxidation of 4,4 ́-methylenedianiline (Lamb et al. 1986). A different metabolic 

pathway, which has been demonstrated in humans, is N-acetylation (Cocker et al. 1986a, 1994). This 

pathway seems to represent a detoxification route since N-acetylmethylenedianiline and 
METHYLENEDIANILINE 88 

2. HEALTH EFFECTS 

N,N’-diacetylmethylenedianiline, in the presence of activating systems, were not genotoxic in 

mutagenicity assays (Cocker et al. 1986b; Tanaka et al. 1985). This was in contrast with a strong 

mutagenic effect of the parent compound with activation. Therefore, it would appear that if the 

acetylation pathway could be favored over the N-oxidation route, some toxic effects attributed to 

4,4 ́-methylenedianiline might be diminished. 

2.10 ADEQUACY OF THE DATABASE 

Section 104(i)(5) of CERCLA, as amended, directs the Administrator of ATSDR (in consultation with 

the Administrator of EPA and agencies and programs of the Public Health Service) to assess whether 

adequate information on the health effects of 4,4 ́-methylenedianiline is available. Where adequate 

information is not available, ATSDR, in conjunction with the National Toxicology Program (NTP), is 

required to assure the initiation of a program of research designed to determine the health effects (and 

techniques for developing methods to determine such health effects) of 4,4 ́-methylenedianiline. 

The following categories of possible data needs have been identified by a joint team of scientists from 

ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that if met would 

reduce the uncertainties of human health assessment. This definition should not be interpreted to mean 

that all data needs discussed in this section must be filled. In the future, the identified data needs will 

be evaluated and prioritized, and a substance-specific research agenda will be proposed. 

2.10.1 Existing information on Health Effects of 4,4 ́-Methylenedianiline 

The existing data on health effects of inhalation, oral, and dermal exposure of humans and animals to 

4,4 ́-methylenedianiline are summarized in Figure 2-5. The purpose of this figure is to illustrate the 

existing information concerning the health effects of 4,4 ́-methylenedianiline. Each dot in the figure 

indicates that one or more studies provide information associated with that particular effect. The dot 

does not necessarily imply anything about the quality of the study or studies, nor should-missing 

information in this figure be interpreted as a “data need.” A data need, as defined in ATSDR’s 

Decision Guide for Identifying Substance-Specific Data Needs Related to Toxicological Profiles 

(ATSDR 1989), is substance-specific information necessary to conduct comprehensive public health 

assessments. Generally, ATSDR defines a data gap more broadly as any substance-specific 

information missing from the scientific literature. 

METHYLENEDIANILINE 90 

2. HEALTH EFFECTS 

Data regarding health effects of 4,4 ́-methylenedianiline in humans result from a few studies involving 

accidental acute oral exposure to 4,4 ́-methylenedianiline, and from cases of dermal exposure in the 

workplace. No information was located regarding inhalation exposure in humans. No information is 

available regarding neurological, reproductive, or developmental effects in humans by any route of 

exposure. 

Most of the data regarding the health effects of 4,4 ́-methylenedianiline in animals were obtained from 

studies in which 4,4 ́-methylenedianiline was administered orally. A single study was located 

concerning health effects in animals following inhalation exposure, and few reports on dermal 

exposure to 4,4 ́-methylenedianiline were located. The available information from animal studies is 

insufficient to determine with certainty whether the effects of 4,4 ́-methylenedianiline are route- or 

species-specific, or age-dependent. Information on the dermal route of exposure would be useful 

because of the potential exposure via this route for workers in industry. Because of its low volatility, 

inhalation of 4,4 ́-methylenedianiline appears less likely than dermal contact, but cannot be completely 

ruled out. Although there are limited environmental data regarding 4,4 ́-methylenedianiline, the 

dermal route of exposure appears to be the most relevant for humans living near hazardous waste sites 

where 4,4 ́-methylenedianiline might be found. 

2.10.2 Identification of Data Needs 

Acute-Duration Exposure Populations living in the vicinity of hazardous waste sites may be 

exposed to 4,4 ́-methylenedianiline for a short time. Exposure would probably occur via the dermal 

route, but oral exposure, particularly by children ingesting contaminated soil, cannot be excluded. 

The liver is the major target of 4,4 ́-methylenedianiline toxicity in humans following acute exposure by 

any route (Brooks et al. 1979; Kopelman et al. 1966; McGill and Motto 1974; Roy et al. 1985; 

Tillmann et al. 1997). The same was seen in rats (Bailie et al. 1993, 1994; Kanz et al. 1992; Schmidt 

et al. 1980), but other animal species have not been studied. An acute oral MRL was derived based 

on liver effects in rats identified in the Bailie et al. (1993) study. The mechanism of liver toxicity has 

not been elucidated, but it seems that the biliary tree epithelium is affected before the liver 

parenchyma (Bailie et al. 1994). Further studies are necessary to corroborate this finding and possibly 

identify the chemical entity responsible for the liver toxicity. In addition, studies providing 

quantitative estimates of excretion of 4,4 ́-methylenedianiline and/or metabolites in the bile would help 
METHYLENEDIANILINE 91 

2. HEALTH EFFECTS 

establish a possible relationship between this excretory route and bile duct toxicity. The existing 

information also showed that 4,4 ́-methylenedianiline can cause adverse dermal reactions in humans 

(Emmett 1976; Van Joost et al. 1987; Williams et al. 1974). Intermediate- and chronic-duration 

studies in animals suggest that the thyroid is also a target for 4,4 ́-methylenedianiline toxicity, but this 

end point has not been examined in acute-duration studies. Reproductive function has not been 

examined in acute-duration studies by any route; such studies could provide valuable information on 

possible effects of 4,4 ́-methylenedianiline on that system. Based on its chemical structure, 

4,4 ́-methylenedianiline does not appear to be a neurotoxicant, but the nervous system has not been 

examined in acute-duration studies. A limited number of acute dermal studies in animals have 

suggested that the administration vehicle plays a role in the toxicity of 4,4 ́-methylenedianiline, 

possibly by influencing absorption (DuPont 1975, 1976a). Further dermal studies with different 

vehicles and also oral studies with 4,4 ́-methylenedianiline in different soils would provide valuable 

information for those living near hazardous waste sites where 4,4 ́-methylenedianiline may be found. 

Intermediate-Duration Exposure. No studies were located on intermediate-duration exposure to 

4,4 ́-methylenedianiline in humans by any route. The preponderance of data is available from rats 

exposed to 4,4 ́-methylenedianiline in the diet (Fukushima et al. 1979, 1981; Hagiwara et al. 1993; 

Hiasa et al. 1984; Miyamoto et al. 1977), by gavage (Pludro et al. 1969), or through the drinking 

water (NTP 1983). Results from these studies indicate that the liver and the thyroid are targets for 

4,4 ́-methylenedianiline toxicity. An intermediate oral MRL was derived based on liver effects in rats 

reported by Pludro et al. (1969). Studies in other species would provide information on whether these 

end points are sensitive targets across species. The mechanism of thyroid toxicity is not known; 

therefore, research aimed to investigate this subject would be helpful. Neurological, reproductive, and 

developmental effects have not been appropriately studied in oral intermediate-duration studies, and no 

information is available regarding the inhalation and dermal routes of exposure. Pharmacokinetic data 

to help identify potential target organs after exposure by any route were not located. 

Chronic-Duration Exposure and Cancer. No studies were located following chronic-duration 

inhalation or oral exposure to 4,4 ́-methylenedianiline in humans. Data were available concerning 

dermal exposure to 4,4 ́-methylenedianiline in the workplace. Results from one study confirmed that 

the liver is a target for 4,4 ́-methylenedianiline toxicity (Bastian 1984). A skin reaction triggered by 

exposure to sunlight was described in another study (Levine 1983). Research regarding the 

mechanism involved in photosensitivity to 4,4 ́-methylenedianiline would be helpful. Examination of 
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2. HEALTH EFFECTS 

subjects occupationally exposed (presumably long-term exposure) revealed that 4,4 ́-methylenedianiline 

can be absorbed through the lungs and the skin and that the parent compound and metabolites can be 

excreted in the urine (Cocker et al. 1986a, 1994; Schiitze et al. 1995). A limited number of oral 

studies in animals showed that the liver, thyroid, and perhaps the kidney are targets for 

4,4 ́-methylenedianiline toxicity (Deichmann et al. 1978; Lamb et al. 1986; NTP 1983). One of these 

studies, Deichmann et al. (1978), was conducted in dogs and the results suggested that dogs may be a 

particularly sensitive species for liver and kidney effects. However, this study was not well designed 

(only 9 dogs were tested and no concurrent controls were used), and therefore, the results are 

inconclusive. The inadequacies of this study precluded derivation of a chronic oral MRL. A well 

conducted chronic oral study in dogs could remove the uncertainty regarding dogs as very sensitive 

species for 4,4 ́-methylenedianiline toxicity. A comprehensive clinical evaluation of individuals 

exposed to low levels of 4,4 ́-methylenedianiline for many years in the workplace may provide 

evidence on less recognizable subtle effects of 4,4 ́-methylenedianiline. Neither immunocompetence 

nor reproductive function has been examined in animals after chronic exposure to 4,4 ́-methylenedianiline 

by any route of exposure. Such studies after low-level chronic exposure by the oral and 

dermal routes would be of value to determine whether exposures via these routes could cause toxicity 

in populations living near hazardous waste sites, or in those exposed in industries where this chemical 

is used. 

Two-year cancer bioassays have been performed following oral and dermal exposure. In a well designed 

2-year drinking water bioassay, there was clear evidence of carcinogenicity in rats and mice 

(Lamb et al. 1986; NTP 1983). An oral bioassay in dogs showed no evidence of carcinogenicity, but, 

as previously mentioned, the study was poorly designed and therefore, the results are inconclusive 

(Deichmamr et al. 1978). A dermal bioassay in mice found 4,4 ́-methylenedianiline to be a liver 

carcinogen, but it appears that the strain of mice used may have been particularly susceptible to liver 

tumors; therefore, the results are also inconclusive (Holland et al. 1987). A follow-up study on a 

group of individuals who had accidentally ingested 4,4 ́-methylenedianiline and contracted toxic 

hepatitis did not find increased incidences of cancer (Hall et al. 1992). A similar conclusion was 

reached in a small group of power generation workers exposed to an epoxy resin containing 

4,4 ́-methylenedianiline (Selden et al. 1992). Two additional occupational studies found inconclusive 

evidence of bladder cancer in workers who were also exposed to other chemicals (Cragle et al. 1992; 

Liss and Guirguis 1994). Follow-up and other epidemiological studies are needed to adequately assess 

the carcinogenicity of 4,4 ́-methylenedianiline in humans. 
METHYLENEDIANILINE 93 

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Genotoxicity. The only information in humans was provided by Ho et al. (1979), who reported 

that incubation of human leukocytes with 4,4 ́-methylenedianiline did not increase the incidence of 

sister chromatid exchanges. Existing genotoxicity studies indicate that 4,4 ́-methylenedianiline was 

mutagenic in Salmonella (Andersen et al. 1980; Cocker et al. 1986b; LaVoie et al. 1979; McCarthy et 

al. 1982; Parodi et al. 1981; Rao et al. 1982; Tanaka et al. 1985) with metabolic activation. 

4,4 ́-Methylenedianiline also induced DNA damage in rat hepatocytes (Mirsalis et al. 1983; Mori et al. 

1988) in vitro and formed adducts with rat liver DNA (Endo and Hara 1991; Schiitze et al. 1996; 

Vock et al. 1996). Cytogenic analysis of human populations exposed to 4,4 ́-methylenedianiline in 

occupational settings would provide an opportunity to assess the genotoxic potential of this chemical 

in humans. 

Reproductive Toxicity. No studies were located regarding reproductive effects in humans after 

exposure to 4,4 ́-methylenedianiline by any route. A small number of studies provided information on 

the gross and histopathological appearance of reproductive organs in animals after acute (Tullner 

1960), intermediate (NTP 1983), and chronic (Deichmann et al. 1978; NTP 1983) oral exposure to 

4,4 ́-methylenedianiline. Hypertrophy of the uterus in rats was described in an acute study (Tullner 

1960), and endometrial hyperplasia was reported in dogs after chronic treatment with relatively low 

4,4 ́-methylenedianiline doses (Deichmann et al. 1978). However, the latter study has severe 

limitations (small number of animals and no concurrent controls) and the results should be interpreted 

with caution. A single acute dermal study found no alterations in the testes and epididymis from 

rabbits after treatment with 4,4 ́-methylenedianiline (DuPont 1975). Since none of these studies 

examined reproductive function, additional studies are necessary to adequately evaluate this parameter. 

A multi-generational study would provide valuable information. Examination of clinical records from 

women exposed for prolonged periods of time to low levels of 4,4 ́-methylenedianiline at work may 

provide information on reproductive outcome for this population. Oral and dermal studies in animals 

would provide information on susceptibility by these routes. The dermal route is of particular concern 

in individuals exposed to 4,4 ́-methylenedianiline in the workplace. 

Developmental Toxicity. No studies were located regarding developmental effects in humans 

after exposure to 4,4 ́-methylenedianiline by any route. A single study in rats showed that exposure to 

4,4 ́-methylenedianiline during, gestation may result in adverse developmental effects (Bourdelat et al. 

1983). The study, however, was of limited scope and was not well conducted. Further well-designed 

studies in animals exposed during pregnancy would provide information on the potential effects of 
METHYLENEDIANILINE 94 

2. HEALTH EFFECTS 

4,4 ́-methylenedianiline on the developing organism. Studies by the dermal route are of particular 

interest since this route is of concern in occupational settings and to people living near hazardous 

waste sites where 4,4 ́-methylenedianiline might be found. 

Immunotoxicity. Information in humans indicates that dermal contact with 4,4 ́-methylenedianiline 

may trigger allergic dermal reactions in some individuals (Emmett 1976; McGill and Motto 1974; Van 

Joost et al. 1987). In one case, a reaction was triggered by exposure to sunlight (Levine 1983). 

Animal studies have provided limited information. An acute oral study found histopathological 

alterations in the thymus from rats (Kanz et al. 1992). Intermediate oral studies found no 

histopathological alterations in organs of the lymphoreticular system from rats and mice (NTP 1983). 

Similar findings were reported in chronic oral studies in rats and mice (NTP 1983). The NTP (1983) 

study did not evaluate blood components. A chronic oral study in dogs reported spleen effects at a 

relatively low dose (Deichmann et al. 1978); however, because of study limitations, the results must be 

interpreted with caution. Two acute dermal studies provided information on spleen weight in mice 

(Holland et al. 1987) and on histopathology of spleen and thymus in rabbits (DuPont 1975). None of 

the studies in animals examined immunocompetence. Studies that examine antibody levels and 

responses to bacterial and viral infections after exposure to 4,4 ́-methylenedianiline would provide 

valuable information on the immune system. Some immune parameters (e.g., serum immunoglobulin 

levels, response to mitogen stimulation) have been found to be quite sensitive to chemical insult. 

Also, evaluation of morbidity among individuals exposed to 4,4 ́-methylenedianiline in the workplace 

may provide important indirect evidence regarding their immune status. 

Neurotoxicity. No studies were located regarding neurotoxicity in humans after exposure to 

4,4 ́-methylenedianiline by any route. An acute dermal study in rabbits (DuPont 1975) and 

intermediate and chronic oral studies in rats and mice (Lamb et al. 1986; NTP 1983) found no gross or 

histopathological lesions in tissues from the peripheral and central nervous system. However, more 

sensitive neurological end points have not been examined. Laboratory animal studies that focus on 

subtle neurological effects following acute, intermediate, or chronic exposure via oral and dermal 

routes would help estimate potential neurotoxic effects in humans living near hazardous waste sites 

and in workers who might be exposed in certain occupational settings. Furthermore, evaluation of 

neurological end points in offspring from animals exposed during gestation would provide information 

that may be relevant to children of pregnant women exposed to 4,4 ́-methylenedianiline in the 

workplace. 
METHYLENEDIANILINE 95 

2. HEALTH EFFECTS 

Epidemiological and Human Dosimetry Studies. A retrospective study investigated the 

relationship between deaths caused by neoplastic and non-neoplastic diseases and accidental ingestion 

of 4,4 ́-methylenedianiline in a cohort originally composed of 84 subjects (Hall et al. 1992). The 

study period covered approximately 20 years after the accident occurred. The results showed no 

obvious link between ingestion of 4,4 ́-methylenedianiline and any particular cancer or non-neoplastic 

disease. Another study conducted a retrospective assessment of exposure to 4,4 ́-methylenedianiline 

and cancer morbidity in power generation workers in Sweden (Selden et al. 1992). An overall 

standardized cancer incidence ratio of 0.52 indicated no increased incidence of cancer due to exposure 

to 4,4 ́-methylenedianiline, but several study limitations were identified (small size and young age of 

the cohort, and short follow-up period). These limitations should be addressed in additional wellconducted 

epidemiology studies in occupational settings. This information would provide valuable 

data on possible adverse effects in humans. There is evidence that 4,4 ́-methylenedianiline may be 

released from certain medical devices made of polyurethane such as plasma separators and artificial 

dialyzers (Shintani 1991). This suggests a potential health risk for uremic patients or patients who 

receive frequent blood transfusions. Because of the known hepatic effects of 4,4 ́-methylenedianiline, 

liver tests should be periodically conducted in these patients as well as in occupationally exposed 

individuals for early detection of liver toxicity. 

Biomarkers of Exposure and Effect. 

Exposure. Exposure to 4,4 ́-methylenedianiline may be assessed by determining levels of 

4,4 ́-methylenedianiline or N-acetylated metabolites in urine (Cocker et al. 1986a, 1994; Dalene et al. 

1995; Robert et al. 1995; Schfitze et al. 1995). However, no quantitative estimates of exposure have 

been provided. In a study of 411 individuals occupationally exposed, 42% of urine samples examined 

had no detectable 4,4 ́-methylenedianiline (Cocker et al. 1994). In another study of 111 workers 

exposed to 4,4 ́-methylenedianiline, 81% of over 300 urine samples had concentrations of 

4,4 ́-methylenedianiline below 5 nmol/mmol creatinine, which was below the detection limit of 

50 nmol/L (Cocker et al. 1986a). A preferred method for assessing exposure may be bpmeasuring 

hemoglobin adducts. Studies in rats have shown that 4,4 ́-methylenedianiline can form adducts with 

hemoglobin which are stable in vivo and persist for the life span of the erythrocyte-120 days in 

humans (Bailey et al. 1990; Farmer and Bailey 1989). Similar findings have recently been reported in 

humans (Schiitze et al. 1995). 4,4 ́-Methylenedianiline can be released from the adduct and 

quantitated. The advantage of this method is that it provides information that is not restricted to recent 
METHYLENEDIANILINE 96 

2. HEALTH EFFECTS 

exposure. Preliminary results in rats showed that a dose-response can be established. Further studies 

on this subject would provide valuable information that could lead to early detection of 

4,4 ́-methylenedianiline exposure. 

Effect. There are no specific biomarkers of effects for 4,4 ́-methylenedianiline. Many different 

classes of chemicals are liver toxicants or may cause dermal sensitization. Further studies to identify 

specific biomarkers of effects of 4,4 ́-methylenedianiline would facilitate medical surveillance leading 

to early detection of potentially adverse health effects and possible treatment. 

Absorption, Distribution, Metabolism, and Excretion. There is no quantitative information 

on the rates of absorption of 4,4 ́-methylenedianiline in humans following inhalation or oral exposure. 

A study in volunteers showed that a maximum of approximately 28% of a dose of 4,4 ́-methylenedianiline 

applied dermally for one hour was absorbed (Brunmark et al. 1995). Limited data from 

workers exposed to 4,4 ́-methylenedianiline su,, Ooested that absorption by inhalation is faster than 

dermal absorption (Cocker et al. 1994). There is also no information on absorption rates in animals 

following inhalation or oral exposure. Dermal data are available in rats, guinea pigs, and monkeys 

(El-Hawari et al. 1986). Obtaining additional quantitative data in animals via inhalation and oral 

routes, and using different vehicles, would be helpful for estimating absorption in humans. 

There are no distribution data in humans. Data on distribution via the inhalation and dermal routes for 

animals were not located. There is limited information describing distribution following acute dermal 

exposure to 4,4 ́-methylenedianiline in animals. Studies indicate that it is distributed among all tissues 

(El-Hawari et al. 1986). Additional studies regarding repeated dermal exposure would help elucidate 

the distribution pattern of 4,4 ́-methylenedianiline. The dermal route appears to be the most likely 

route of exposure near hazardous waste sites. Dermal contact is also the most likely route of exposure 

in manufacturing and process industries. 

No information was located regarding metabolism of 4,4 ́-methylenedianiline in humans-following 

inhalation or oral exposure. Data from humans exposed primarily by dermal contact showed that 

4,4 ́-methylenedianiline can be acetylated in vivo to form N-acetylmethylenedianiline (Cocker et al. 

1986a; Robert et al. 1995) and to a small extent, N,N’-diacetylmethylenedianiline (Robert et al. 1995). 

Acetylation has been demonstrated in rats exposed orally (Tanaka et al. 1985). No information was 

located regarding metabolism in animals exposed by inhalation or dermally. Information on 
METHYLENEDIANILINE 97 

2. HEALTH EFFECTS 

metabolism after dermal exposure in animals would be useful because the potential exists for exposure 

to occur in humans via this route. 

Workers and volunteers exposed to 4,4 ́-methylenedianiline by inhalation or by skin contact excreted 

4,4 ́-methylenedianiline and/or acetylated metabolites in the urine (Brunmark et al. 1995; Cocker et al. 

1986a, 1994; Dalene et al. 1995). There is no information regarding excretion in humans after oral 

exposure. Acute dermal studies in animals showed that urinary excretion is a major excretory 

pathway, but fecal excretion also occurs (El-Hawari et al. 1986). Only one study was located that 

provided excretion data in animals following oral exposure (Tanaka et al. 1985); no inhalation data 

were located. Further examination of excretion patterns in animals following repeated dermal 

exposures would provide valuable information relevant to humans exposed continuously in the 

workplace. 

Comparative Toxicokinetics. There is insufficient information to determine possible differences 

or similarities in toxicokinetic patterns for 4,4 ́-methylenedianiline between humans and animals. The 

limited data suggest that 4,4 ́-methylenedianiline can be acetylated by humans and animals, and that 

the resulting metabolite is excreted in the urine. Studies have also demonstrated that the liver is a 

target for 4,4 ́-methylenedianiline toxicity in humans and the animal species tested. Acute dermal 

studies in animals showed some qualitative differences in excretory patterns between species. The 

urine was the main excretory route in rats and monkeys, whereas guinea pigs excreted similar amounts 

of 4,4 ́-methylenedianiline (or metabolites) in urine and feces (El-Hawari et al. 1986). Physiologically 

based pharmacokinetic models for 4,4 ́-methylenedianiline have not been developed. Further studies 

are necessary to determine which species might be a suitable animal model. 

Methods for Reducing Toxic Effects. The mechanism by which 4,4 ́-methylenedianiline enters 

the bloodstream in humans is not known, and there are no established methods for reducing absorption 

after inhalation and oral exposure other than minimizing exposure. A study of dermal absorption 

through human skin in vitro provided information on decontamination procedures that could potentially 

be used in vivo (Hewitt et al. 1995). Further studies of decontamination strategies by using different 

washing solutions would be valuable. Animal studies using gastrointestinal sorbents such as activated 

carbon and resins, which can bind amines, might give insight into additional methods for reducing 

systemic absorption of this chemical. Suggested methods for treating the effects of acute exposure to 

4,4 ́-methylenedianiline are generally supportive. Toxic hepatitis that developed after exposure to 
METHYLENEDIANILINE 98 

2. HEALTH EFFECTS 

4,4 ́-methylenedianiline has been treated conventionally. There are no established methods for 

reducing body burdens in humans. It is assumed that metabolism of 4,4 ́-methylenedianiline leads to 

the formation of highly reactive and potentially toxic derivatives. Thus, additional studies examining 

the feasibility of favoring metabolic pathways leading to the formation of nontoxic metabolites 

(N-acetylation pathway) would be valuable. 

2.10.3 Ongoing Studies 

Dr. Mary Kanz from the Department of Pathology, University of Texas at Galveston, is conducting 

research aimed to understand how and why 4,4 ́-methylenedianiline causes early, selective injury to 

bile duct cells. She is focusing the research on 4,4 ́-methylenedianiline metabolites excreted in bile 

and their capacity to damage biliary epithelial cells (FEDRIP 1997). 
METHYLENEDIANILINE 99 

3. CHEMICAL AND PHYSICAL INFORMATION 

3.1 CHEMICAL IDENTITY 

Methylenedianilines are diphenylmethane compounds with an amino group added to each benzene 

ring. Depending on the position of the amino group, methylenedianilines can exist in six isomeric 

forms: 2,2’-methylenedianiline; 2,3’-methylenedianiline; 2,4’-methylenedianiline; 3,3’-methylenedianiline; 

3,4’-methylenedianiline; and 4,4 ́-methylenedianiline. Of the six isomers, 2,2’-methylenedianiline 

and 2,4’-methylenedianiline are produced on a small scale as research chemicals (HSDB 

1996). The isomer 4,4 ́-methylenedianiline is produced in the United States for industrial use. 

Therefore, this profile will limit its discussion to 4,4 ́-methylenedianiline. Information regarding the 

chemical identity of 4,4 ́-methylenedianiline is presented in Table 3-l. 

3.2 PHYSICAL AND CHEMICAL PROPERTIES 

Information regarding the physical and chemical properties of 4,4 ́-methylenedianiline is presented in 

Table 3-2. Exposure of 4,4 ́-methylenedianiline to air and light results in polymerization and oxidation 

of the compound, as evidenced by darkening of color and polymerization leading to the formation of 

polymeric amines (IARC 1986; Moore 1978). When heated to decomposition, 4,4 ́-methylenedianiline 

emits toxic fumes of aniline and nitrogen oxides (NIEHS 1994). It is a weak base (pH 7.7, Allied 

Chemical Corp. 1978), but its experimentally determined pka value was not located in the literature. 

The estimated pka for this compound is 4.88 (EPA 1995). Since 4,4 ́-methylenedianiline is a base, it 

forms dihydrochloride salts with hydrochloric acid (IARC 1986). The dihydrochloride of 

4,4 ́-methylenedianiline or other salts of the compound with strong inorganic acids will be more water 

soluble than the free base. The dihydrochloride salt is soluble in water (NIEHS 1994). 



METHYLENEDIANILINE 103 

4. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 

4.1 PRODUCTION 

4,4 ́-Methylenedianiline is produced by the condensation of formaldehyde with aniline in the presence 

of an acid catalyst. The reaction produces a mixture of di-, tri-, and poly-methyleneanilines. Aniline 

is removed from the reaction mixture by distillation. The percentage of 4,4 ́-methylenedianiline in the 

mixtures manufactured varies from producer to producer. 4,4 ́-Methylenedianiline can be isolated 

from the residual mixture by crystallization with a suitable solvent (IARC 1986; Merck 1989; Moore 

1978). 4,4 ́-Methylenedianiline commercially available in bulk quantities contains approximately 96% 

4,4 ́-methylenedianiline, 3% other isomeric amines, and traces of aniline (IARC 1986). 

The quantity of 4,4 ́-methylenedianiline produced by six manufacturers was approximately 230 million 

pounds (104 million kg) in 1981 (CMA 1982). In 1982, approximately 90-180 million kg 

(200-400 million pounds) of 4,4 ́-methylenedianiline was produced in the United States by a total of 

seven manufacturers (NIEHS 1994; NIOSH 1986). According to data in Toxics Release Inventory 

(TRI), four companies produced 4,4 ́-methylenedianiline in the United States in 1994 for distribution 

and sale, as well as their own use, captively or otherwise (TR194 1996): Dow Chemicals, U.S.A., La 

Porte, Texas; an unidentified company in New Martinsville, West Virginia; Rubicon, Inc., Geismar, 

Louisiana; and Uniroyal Chemical Co., Inc., Naugatuck, Connecticut. Another report indicates three 

companies producing 4,4 ́-methylenedianiline in the United States (SRI 1994): Dow Chemicals, 

U.S.A., La Porte, Texas; Bayer Corporation, Polymers Division, New Martinsville, West Virginia; and 

Uniroyal Chemical Co., Inc., Naugatuck, Connecticut. 

The data on production capacity or the amount of 4,4 ́-methylenedianiline produced in the United 

States in recent years are not available. Table 4-l lists the facilities in each state that manufacture or 

process 4,4 ́-methylenedianiline, the intended use, and the range of maximum amounts of 

4,4 ́-methylenedianiline that are stored on site. The data listed in Table 4-l are derived from the 

Toxics Release Inventory (TR194 1996). Only certain types of facilities were required to report; 

therefore, this is not an exhaustive list. 


 

 

 

METHYLENEDIANILINE 106 

4. PRODUCTION, IMPORT/EXPORT, USE, AND DISPOSAL 

4.2 IMPORT/EXPORT 

The exports of 4,4 ́-methylenedianiline from the United States to other countries in 1989, 1990, 1991, 

1992 and 1993 were 13.1 million kg (28.9 million pounds), 13.5 million kg (29.8 million pounds), 

5.8 million kg (12.8 million pounds), 7.1 million kg (15.7 million pounds), and 4.5 million kg 

(9.9 million pounds), respectively (NTDB 1994). There was a marked decrease in amounts of 

4,4 ́-methylenedianiline exported to other countries during the period 1990-1993. The imports of 

4,4 ́-methylenedianiline from other countries to the United States in 1989, 1990, 1991, 1992, and 1993 

were 1.5 million kg (3.3 million pounds), 1.3 million kg (2.9 million pounds), 1.1 million kg 

(2.4 million pounds), 0.9 million kg (2.0 million pounds), and 0.5 million kg (1.1 million pounds), 

respectively (NTDB 1994). These figures indicate a continual and gradual decrease in the amounts of 

4,4 ́-methylenedianiline imported into the United States from other countries from 1989 to 1993. 

4.3 USE 

Over 90% of 4,4 ́-methylenedianiline produced in the United States is used captively for the 

production of 4,4 ́-methylenedianiline diisocyanate and other polymeric isocyanates (IARC 1986). 

These di- or poly-isocyanates are used in a variety of polymer and resin production, including 

polyurethane foam, isocyanate resins and elastomer (e.g., Spandex® fiber). Small amounts of 

4,4 ́-methylenedianiline are used as an azo dye intermediate; as a chemical reagent for the 

determination of tungsten and sulfates; as a corrosion inhibitor; as an antioxidant and curative agent in 

rubber; as a raw material in the production of resins; and as an epoxy-resin hardening agent in 

adhesives, encapsulants, coatings, filament windings and binders (CMA 1982; IARC 1986; Lewis 

1993; Tucker et al. 1993). 

4.4 DISPOSAL 

Incineration is one of the feasible methods for disposal of wastes containing 4,4 ́-methylenedianiline. 

Gas-fired incinerators in which first-stage combustion takes place with a less than stoichiometric 

airfuel ratio, followed by a second-stage combustion with excess air, are suitable for disposal of 

4,4 ́-methylenedianiline wastes (HSDB 1996). The temperature and the residence time inside the 

combustion zone of the incinerators should be such that they ensure complete destruction (>99.99%) of 

the compound (HSDB 1996). 
METHYLENEDIANILINE 107 

5. POTENTIAL FOR HUMAN EXPOSURE 

5.1 OVERVIEW 

4,4 ́-Methylenedianiline is released to air and water during industrial production and use of this 

compound (IARC 1986). 4,4 ́-Methylenedianiline may also be released in water as a result of 

hydrolysis of treated and untreated 4,4 ́-methylenediphenyl diisocyanate wastewater discharged into 

surface water or public sewers. However, there are no monitoring data that confirm the presence of 

4,4 ́-methylenedianiline in waste effluents from the plants that manufacture and use 4,4 ́­

methylenedianiline, or in natural waters where the treated or untreated wastewaters from these plants are 

discharged. 4,4 ́-Methylenedianiline may be found in soils of controlled or uncontrolled hazardous 

waste sites as a result of disposal of wastes containing either 4,4 ́-methylenedianiline or products such 

as 4,4 ́-methylenediphenyl diisocyanate. 4,4 ́-Methylenedianiline may also be released to soil as a 

result of accidental spillage during storage or transport. Smaller amounts of 4,4 ́-methylenedianiline 

may be released to water and soil as a result of terrestrial and hydrospheric precipitation and 

scavenging of atmospheric 4,4 ́-methylenedianiline. However, very few monitoring data are available 

that confirm the presence of 4,4 ́-methylenedianiline in soil. 

Experimental data on the environmental fate of 4,4 ́-methylenedianiline are scarce. Most conclusions 

about the environmental fate and transport of 4,4 ́-methylenedianiline are estimated, based on its 

physical and chemical properties. In air, the compound will primarily exist as particulate matter and 

will be removed from the atmosphere by dry deposition and scavenging by rain and snow. The small 

amount of 4,4 ́-methylenedianiline present in the vapor phase in the atmosphere will be transformed by 

reaction with hydroxyl radicals with an estimated half-life of 1.6 hours. In water and soil, the material 

will be degraded primarily via biodegradation. The estimated half-lives of biodegradation in surface 

water, groundwater and soil are l-7 days, 2-14 days, and l-7 days, respectively. 4,4 ́-Methylenedianiline 

will covalently bind with humic materials in soil and water. As a result, it will be present 

predominantly in the bound form in sediment and suspended solids in water, and its leaching from 

most soils will not be important. Three factors indicate that 4,4 ́-methylenedianiline will neither 

bioconcentrate in aquatic organisms nor biomagnify in terrestrial or aquatic food chains: (1) the 

experimental bioconcentration factor in carp (Caprinus carpio); (2) the estimated bioconcentration 

factor and octanol/water partition coefficient (indicator of lipid solubility), and (3) the fact that it is 

metabolized quickly in higher trophic level animals. 
METHYLENEDIANILINE 108 

5. POTENTIAL FOR HUMAN EXPOSURE 

No monitoring data exist on the levels of 4,4 ́-methylenedianiline in ambient air, surface water, 

industrial effluents, soil or any fruits and vegetables. Levels of the compound in occupational air have 

been measured; and the levels rarely exceed the American Conference of Governmental Industrial 

Hygienists (ACGIH) threshold limit value of 0.8 mg/m3

 for an 8-hour weighted average concentration. 

4,4 ́-Methylenedianiline and its metabolites have also been measured in urine of workers. The 

maximum urinary 4,4 ́-methylenedianiline concentration of 6,871 nmol/mmol cretinine was detected in 

a worker at a manufacturing plant in Britain (Cocker et al. 1994). 

4,4 ́-Methylenedianiline has been found in none of the 1,445 current or former EPA National Priorities 

List (NPL) hazardous wastes sites (HazDat 1997). However, the number of sites evaluated for 

methylenedianiline is not known. 

5.2 RELEASES TO THE ENVIRONMENT 

Anthropogenic releases of 4,4 ́-methylenedianiline are primarily to the soil via underground injection. 

According to the Toxics Chemical Release Inventory, in 1994, a total of 36,531 pounds of 

4,4 ́-methylenedianiline were released to the environment (air, water, soil) from 27 large processing 

facilities (TR194 1996). Table 5-l lists the amounts released from these facilities. In addition, an 

estimated 1,889 pounds of 4,4 ́-methylenedianiline were released by these manufacturing and 

processing facilities to publicly owned treatment works (POTWs), and an estimated 184,458 pounds 

were transferred off-site (TR194 1996). The data listed in the TRI should be used with caution 

because only certain types of facilities are required to report (EPA 1996). This is not an exhaustive 

list. Manufacturing and processing facilities are required to report information to the Toxics Release 

Inventory if they employ 10 or more full-time employees; if their facility is classified under Standard 

Industrial Classification (SIC) codes 20 through 39; and if their facility produces, imports, or processes 

25,000 or more pounds of any TRI chemical or otherwise uses more than 10,000 pounds of a TRI 

chemical in a calendar year (EPA 1996). 

5.2.1 Air 

4,4 ́-Methylenedianiline is released to the air during the industrial production of this compound (IARC 

1986). It is also released into the air during industrial production processes that use 4,4 ́-methylenedianiline 

as a component. For example, it is released to the air during the production of reinforced 


METHYLENEDIANILINE 111 

5. POTENTIAL FOR HUMAN EXPOSURE 

plastics, during encapsulation of instruments with polyurethane mixture, and during coremaking of iron 

and steel foundries where 4,4 ́-methylenedianiline polymers are used as binders in molding (IARC 

1986). 

According to the Toxics Chemical Release Inventory (TRI) in 1994, releases of 4,4 ́-methylenedianiline 

to the air from 27 large processing facilities were 9,742 pounds (4,419 kg) (TR194 1996). 

Release to the air constituted 26.7% of the total environmental release. Table 5-l lists amounts 

released from these facilities. The TRI data should be used with caution because only certain types of 

facilities are required to report. This is not an exhaustive list (EPA 1996). 

5.2.2 Water 

4,4 ́-Methylenedianiline is released to water as aqueous effluents from industries that produce or use it, 

for example, from methylenediphenyl diisocyanate manufacturing plants. The source of 

4,4 ́-methylenedianiline in treated and untreated waste water from methylenediphenyl diisocyanate 

plants may be due to release of the starting material (4,4 ́-methylenedianiline) in waste water or from 

the hydrolysis of methylenediphenyl diisocyanate. Small amounts of 4,4 ́-methylenedianiline may also 

be released to surface water via storm water runoff from waste sites containing this compound. 

However, there is no monitoring data that confirm the presence of the compound in waste effluents 

from the plants that manufacture and use it, or in natural waters where the treated or untreated 

wastewaters from these plants are discharged. 

According to the TRI, in 1994 releases of 4,4 ́-methylenedianiline to water from the 27 large 

processing facilities totaled 725 pounds (329 kg) (TR194 1996). Release to water constituted 2% of 

the total environmental release. An additional 1,889 pounds (857 kg) were released indirectly to 

POTWs and some of this volume ultimately may have been released to surface waters. Table 5-l lists 

amounts released from these facilities. The TRI data should be used with caution because only certain 

types of facilities are required to report. This is not an exhaustive list (EPA 1996).III 

5.2.3 Soil 

4,4 ́-Methylenedianiline may be found in soils of controlled or uncontrolled hazardous waste sites as a 

result of disposal of wastes containing either 4,4 ́-methylenedianiline or reaction products, such as 
METHYLENEDIANILINE 112 

5. POTENTIAL FOR HUMAN EXPOSURE 

methylenediphenyl diisocyanate. Products such as polyurethane foams which contain the reactant 

diphenylisocyanate moiety (NIOSH 1976) can break down into 4,4 ́-methylenedianiline either 

chemically or biologically in soil. 4,4 ́-Methylenedianiline may also be released to soil as a result of 

accidental spillage during storage or transport. However, very few monitoring data are available that 

confirm the presence of 4,4 ́-methylenedianiline in soil. 

According to the TRI, in 1994 there were no releases of 4,4 ́-methylenedianiline to soil from the 

27 large processing facilities (TR194 1996). However, an additional 26,064 pounds (11,818 kg) was 

released by underground injection. These releases represent 71% of all environmental releases. 

Table 5-l lists amounts released from these facilities. The TRI data should be used with caution 

because only certain types of facilities are required to report. This is not an exhaustive list (EPA 

1996). 

5.3 ENVIRONMENTAL FATE 

5.3.1 Transport and Partitioning 

The vapor pressure of 4,4 ́-methylenedianiline at 25 o

C has been estimated to be 2.82x10-l0 atm 

(2.15x10-7 mm Hg) by multiplying its water solubility of 5.04 moles/m3

 by its Henry’s law constant 

(II) of 5.6x10-11 atm-m3

/mole (H = vapor pressure/water solubility) (Thomas 1990a). This is 

comparable to an estimated vapor pressure of 1.5x10-7 mm Hg at 25 o

C (NIOSH 1986). Organic 

compounds with a vapor pressure of 2.15x10-7 mm Hg will exist in the air mostly as an aerosol and 

partly in the vapor phase (Eisenreich et al. 1981). In a test atmosphere generated by vaporization of 

epoxy resin containing 4,4 ́-methylenedianiline hardener, no difference in the sample collection 

efficiency for 4,4 ́-methylenedianiline was observed when sulfuric acid-coated glass-fiber filters and 

simple Teflon filters were used (Gunderson and Anderson 1988). This indicates that 4,4 ́­

methylenedianiline will exist primarily in the aerosol phase in the atmosphere and, like other atmospheric 

aerosol, will be removed from the atmosphere by rain/snow scavenging and dry deposition (Bidleman 

1988). 

4,4 ́-Methylenedianiline has an estimated Koc value of 174 (see Table 3-2). It will be weakly to 

moderately adsorbed to suspended solids and sediment in water (Swarm et al. 1983), and a large 

percentage of 4,4 ́-methylenedianiline may exist in water in the dissolved state where it is susceptible 
METHYLENEDIANILINE 113 

5. POTENTIAL FOR HUMAN EXPOSURE 

to degradation via chemical/biological processes. As the water solubility of amine salts is higher than 

the free base, the concentration of dissolved 4,4 ́-methylenedianiline will increase in natural waters as 

the pH decreases below 7. However, aromatic amines, particularly primary aromatic amines, 

covalently and irreversibly bind to humic substances present in most natural waters (Parris 1980). 

Therefore, in deference to moderate/low physical adsorption, 4,4 ́-methylenedianiline will become 

strongly bound (through covalent bonds) to humic materials in suspended solids and sediment present 

in most waters. Therefore, the percentage of 4,4 ́-methylenedianiline present in water may be much 

lower than is expected from simple physical adsorption of the compound. Organic compounds with 

Henry’s law constants <3.7x10-7 atm-m3

/mole are essentially non-volatile in water (Thomas 1990b). 

Therefore, 4,4 ́-methylenedianiline, with an estimated H of 5.99x10-11 atm-m3

/mole (see Table 3-2), 

will remain essentially non-volatile in water. 

Based on a value of 1.59 for log Kow and a regression equation (Bysshe 1990), the estimated 

bioconcentration factor for 4,4 ́-methylenedianiline in fathead minnow, bluegill sunfish, rainbow trout, 

and mosquitofish is 9.5. Therefore, 4,4 ́-methylenedianiline will not bioconcentrate in aquatic 

organisms. Carp (Cyprinus carpio) were grown in a model river consisting of natural river water, 

0.5% volume per volume (v/v) river bottom sludge, and 0.1 mg/L methylene-di-p-phenylene 

isocyanate (MDI) in an outdoor stainless steel tank for 8 weeks with water flowing in the tank at rates 

of 4-14 cm/sec (III 1981). Neither MD1 nor its decomposition product, 4,4 ́-methylenedianiline, was 

detected (detection limit <0.1 mg/kg) in the whole body of fish. It was concluded that MD1 and 

4,4 ́-methylenedianiline do not bioaccumulate in carp (III 1981). No data were located in the literature 

that would suggest that 4,4 ́-methylenedianiline will biomagnify in animals of higher trophic level via 

food chain biotransfer (e.g., bioaccumulation in algae < bioaccumulation in fish < bioaccumulation in 

human). This is not surprising, considering the low Kow value (indicative of low accumulation in 

lipids) and easy metabolism of the compound (Cocker et al. 1994) in higher trophic level animals. 

The estimated Koc value of 174 indicates that the mobility of 4,4 ́-methylenedianiline in soils having 

low organic carbon content will be moderate to high (Swarm et al. 1983). However, besides the 

physical adsorption to organic matter in soils, the compound will also become bound to organic matter 

(humates) by stronger covalent bonds (Parris 1980). In soils that exhibit this covalent bonding 

behavior, the mobility of 4,4 ́-methylenedianiline will be low and the rate of leaching from soil to 

groundwater will not be important. 
METHYLENEDIANILINE 114 

5. POTENTIAL FOR HUMAN EXPOSURE 

5.3.2 Transformation and Degradation 

5.3.2.1 Air 

Reactions with hydroxyl radicals, ozone and nitric acid may be important for 4,4 ́-methylenedianiline 

in the atmosphere (Atkinson 1985). The rate constant for the homogeneous vapor phase reaction of 

4,4 ́-methylenedianiline with hydroxyl radicals at 25 o

C is estimated to be 2.4lx 10-10 cm3/molecule-sec 

(HSDB 1996). The estimated value is in conformity with a value of 1.18x10-10 for reaction of aniline 

with hydroxyl radicals (Atkinson 1985). Assuming the atmospheric concentration of hydroxyl radicals 

to be constant at 5x10-5 molecules/cm3

, the half-life of 4,4 ́-methylenedianiline for this pseudo first 

order reaction is 1.6 hours. However, since the compound will be present predominantly in the 

aerosol phase (see Section 5.3.1), the importance of the heterogeneous reaction of particulate 

4,4 ́-methylenedianiline with gas phase hydroxyl radicals cannot be ascertained. Based on the rate 

constants for the reactions of primary amines with ozone (Atkinson and Carter 1984), the atmospheric 

reaction of 4,4 ́-methylenedianiline with ozone will not be important. On the other hand, based on the 

reaction of amines with atmospheric nitric acid (Atkinson 1985), the reaction of 4,4 ́-methylenedianiline 

with gas phase nitric acid may be an important loss process in urban atmospheres (where the 

concentration of atmospheric nitric acid is much higher than the concentration of nitric acid in rural 

atmospheres). But the importance of the heterogeneous reaction of particulate 4,4 ́-methylenedianiline 

with gas phase nitric acid in the atmosphere cannot be quantitatively ascertained. 

5.3.2.2 Water 

The ultraviolet absorption spectra of 4,4 ́-methylenedianiline solution in methanol shows an absorption 

maximum at 243 nm, and a much weaker maximum at 289 nm (Sadtler 1974). The weaker absorption 

extends well into wavelengths >290 nm. Therefore, solutions of 4,4 ́-methylenedianiline in water will 

absorb some sunlight (wavelength >290 nm) and may undergo photolysis in water. In water with 

pH <7, the absorption maximum shifts from 289 nm to a lower wavelength (261 nm), with little 

absorption at wavelengths 2290 nm (Sadtler 1974). Therefore, in water with pH <7, photolysis of 

4,4 ́-methylenedianiline will not occur. Even in natural surface waters having pH ≥7, photolysis may 

not be important because 4,4 ́-methylenedianiline will be present predominantly in the adsorbed form 

in the sediment (see Section 5.3.1). 
METHYLENEDIANILINE 115 

5. POTENTIAL FOR HUMAN EXPOSURE 

The hydrolysis of 4,4 ́-methylenedianiline in water will not be important because aromatic amines are 

generally resistant to hydrolysis (Harris 1990). Aromatic amines react with hydroxyl and peroxy 

radicals present in most waters found in the environment, and the pseudo-first-order half-lives of 

4,4 ́-methylenedianiline due to these reactions are estimated to be upwards of 2.6 days (Howard et al. 

1991). Based on aqueous screening test data for toluidines, the half-lives for biodegradation of 

4,4 ́-methylenedianiline in surface waters under aerobic and anaerobic conditions have been estimated 

to be 1-7 days and 4-28 days, respectively (Howard et al. 1991). Similarly, the half-life for biodegradation 

of 4,4 ́-methylenedianiline in groundwater has been estimated to be 2-14 days (Howard et al. 1991). In an 

experimental biodegradation study in water, it was concluded that 4,4 ́-methylenedianiline (concentration 

1.35 mg/L) was not biodegradable in 87 days with activated sludge alone (III 1986). Biodegradation 

occurred when the sludge was adapted with aniline and 4,4 ́-methylenedianiline and the rate of 

biodegradation was maximum when the adaptation period was >200 days. The biodegradation of 4,4 ́­

methylenedianiline was concluded to be a co-metabolic process (III 1986) and the adapted sludge 

biodegraded 4,4 ́-methylenedianiline from its initial concentration of 12.7 mg/L to undetectable levels 

(detection limit <0.02 mg/L) in 8 days (III 1987). Under aerobic conditions, the nitrogen in 4,4 ́­

methylenedianiline oxidized to ammonia and finally to nitrate (III 1987). There was some evidence of 

phenol formation, but this could not be confirmed. The degradation of 4, 4’-methylenedianiline in water 

was studied in a model river system (for a description of the model river, see Section 5.3.1). Methylene-dip-phenylene isocyanate (MDI) was first added to the water; it degraded to form 4,4 ́-methylenedianiline at 

an initial concentration of 0.1 mg/L. After 4 days, the concentration of 4,4 ́-methylenedianiline was below 

the analytical methods detectable limit (<0.02 mg/L) (III 1980). It was concluded that 4,4 ́­

methylenedianiline will biodegrade rapidly in most natural bodies of water. The main drawbacks of the 

International Isocyanate Institute (III 1980) study are inadequacy of the performed control tests, failure to 

identify the products of biodegradation, and failure to provide any mass balance of the original substrates 

with the products formed. 

5.3.2.3 Sediment and Soil 

No data, either experimental or estimated, were located for the rate of 4,4 ́-methylenedianiline loss 

from soil by reaction with oxidants and natural sunlight. The importance of photolysis beyond the 

surface layer of soil can be ruled out because of lack of light availability. The reaction of 

4,4 ́-methylenedianiline with nitric acid (see Section 5.3.2.1) in soil, particularly in soil having pH <7, 

is an interesting subject that needs investigation. The pseudo-first-order aerobic biodegradation half­
METHYLENEDIANILINE 116 

5. POTENTIAL FOR HUMAN EXPOSURE 

life of 4,4 ́-methylenedianiline in soil has been estimated to be l-7 days (Howard et al. 1991). In 

deeper soil or sediment where there is a lack of oxygen, 4,4 ́-methylenedianiline may be degraded by 

anaerobic biodegradation, but the rate of this reaction was not located in the literature. 

5.4 LEVELS MONITORED OR ESTIMATED IN THE ENVIRONMENT 

5.4.1 Air 

No monitoring data for the levels of 4,4 ́-methylenedianiline in ambient air were located in the 

literature. 

5.4.2 Water 

No data regarding the level of 4,4 ́-methylenedianiline in surface water, industrial effluents, 

groundwater, or drinking water were located in the literature. 

5.4.3 Sediment and Soil
 

No data were located on the level of 4,4 ́-methylenedianiline in contaminated soil or sediment.
 

5.4.4 Other Environmental Media
 

No data were located in the literature on the levels of 4,4 ́-methylenedianiline in edible fish or aquatic 

organisms from contaminated water, fruits, or vegetables grown on contaminated land, and in other 

related environmental media. No residue of MD1 or 4,4 ́-methylenedianiline was found at a detection 

limit of 0.01 mg/kg (fresh weight) in tomato, cucumber, melon, and lettuce grown on soilless 

reconstituted polyurethane foam with or without nutrient solutions (Rouchaud et al. 1992). 

5.5 GENERAL POPULATION AND OCCUPATIONAL EXPOSURE 

The consumption of bread accidentally contaminated with 4,4 ́-methylenedianiline led to an outbreak 

of 84 cases of jaundice in Eppin, England, in the early 1960s (Kopelman et al. 1966). Six young 

people developed acute jaundice and may have suffered severe liver damage when they ingested an 
METHYLENEDIANILINE 117 

5. POTENTIAL FOR HUMAN EXPOSURE 

alcoholic beverage spiked with 4,4 ́-methylenedianiline, which they assumed was the psychometric 

drug methylendioxyamphetamine; both have the same abbreviation, MDA (Tillmann et al. 1997). 

Consumer products that contain 4,4 ́-methylenedianiline are polyurethane foam, Spandex® fiber, and 

epoxy-containing products (see Section 4.3). Under normal use conditions, very little 4,4 ́­

methylenedianiline is present in the free state in these consumer products. Potential consumer exposure 

may occur via dermal contact with trace amounts of free 4,4 ́-methylenedianiline found in automobile 

cushioning or epoxy-containing products (NIEHS 1994). It has been reported that the levels of the 

compound in food, food additives, and food packaging are so low that the potential daily intake via 

food is virtually zero (NIEHS 1994). With the exception of certain medical devices, there is no 

documentation of exposure to 4,4 ́-methylenedianiline from any consumer products. Polyurethane is 

widely used in such medical devices as potting materials for components of plasma separators and 

artificial dialyzers (Shintani 1991). Although polyurethane in these materials contains methylene 

diphenyldiisocyanate, polyurethane releases free 4,4 ́-methylenedianiline during sterilization by gamma 

irradiation or autoclaving (Shintani 1991). Therefore, there is a potential risk of exposure to 

4,4 ́-methylenedianiline for patients with kidney disease or patients who receive frequent blood 

transfusions (Shintani 1991). The relative potential of sterilization methods to release 4,4 ́­

methylenedianiline and mutagenic compounds from polyethylene foam potting material has been studied 

(Shintani 1995a). Gamma-ray irradiation sterilization at 2.5 Mrad produced a few ppm of the 

compound, but more importantly, produced unknown compounds which proved to be mutagenic in the 

absence of metabolic activity. On the other hand, no formation of 4,4 ́-methylenedianiline was 

observed in autoclaved thermosetting polyurethane potting material (heated at 12 l°C for 60 minutes) 

and smaller amounts of mutagenic compounds were determined. Thus, autoclave sterilization is more 

appropriate, provided materials can withstand the process. Another sterilization technique, ethylene 

oxide gas, produced the least amount of 4,4 ́-metbylenedianiline and other compounds, but the residue 

of ethylene oxide gas is itself problematic (Shintani 1995b). 

Occupational exposure to 4,4 ́-methylenedianiline can occur during its production; during its use in the 

manufacture of insulation materials (e.g., plastic insulating materials and polyurethane), eoremaking in 

iron and steel foundries, and encapsulation of instruments with polyurethane mixture; and during use 

of epoxy resins in the construction of nuclear power plants (NIOSH 1976). The major routes for 

occupational exposure to 4,4 ́-methylenedianiline are dermal and inhalation (Cocker et al. 1994; 

Peterson et al. 1991). The occupational exposure to 4,4 ́-methylenedianiline can be assessed both by 

air monitoring and biological monitoring of urinary 4,4 ́-methylenedianiline and its metabolites in 
METHYLENEDIANILINE 118 

5. POTENTIAL FOR HUMAN EXPOSURE 

workers. However, air monitoring alone would underestimate occupational exposure to the compound 

by failing to consider exposure from skin absorption (Peterson et al. 1991). There is some evidence 

which showed that when exposure to 4,4 ́-methylenedianiline was via inhalation, postshift urine 

samples of workers had higher concentrations of the compound than samples taken preshift next day 

(Cocker et al. 1994). When the exposure was mostly via the dermal route, urine samples taken 

preshift the next day had higher concentrations of 4,4 ́-methylenedianiline than urine samples collected 

immediately postshift (Cocker et al. 1994). Therefore, urine collection strategies may provide some 

clue about the route of entry into the body. Workers’ exposure to 4,4 ́-methylenedianiline used in an 

epoxy mixture to insulate electrical cables was monitored by analysis of the compound in blood and 

urine (Dalene 1995). At the end of the workday, workers removed material from their skin with a 

cleaning solution containing mainly butyl acetate. Some results suggested that using such cleaning 

solutions may enhance the absorption of 4,4 ́-methylenedianiline (compared to washing with soap and 

water). 

Occupational exposure to 4,4 ́-methylenedianiline has been assessed by monitoring workplace air, 

analysis of the substance collected on dermal pads, and analysis of urine. The concentrations of 

4,4 ́-methylenedianiline in the air of working areas for some of these industries are given in Table 5-2. 

A concentration of ≤29 mg/m3

 was detected in the occupational air of a facility where workers were 

blending and bagging a hardener containing 4,4 ́-methylenedianiline (Shuker et al. 1986). In a survey 

conducted in Britain, postshift urine samples were taken from 111 workers at 5 factories that used 

4,4 ́-methylenedianiline (Cocker et al. 1986a). The urinary concentrations (both free and conjugated 

4,4 ́-methylenedianiline) in 77.2% of the samples were below the detection limit (<5 nmol 

4,4 ́-methylenedianiline/mmol creatinine) and the concentration range was 6- 175 nmol 4,4 ́­

methylenedianiline/mmol creatinine in the rest of the samples. In a more recent survey (1989-1990) by the 

same group, 960 preshift and postshift urine samples from 411 workers from 45 factories that 

manufactured or used 4,4 ́-methylenedianiline were analyzed for total 4,4 ́-methylenedianiline (Cocker 

et al. 1994). The compound was not detected in 57% of postshift and 42% of the preshift urine 

samples. The concentrations of 4,4 ́-methylenedianiline in about 95% of urine samples were below 

100 nmol/mmol creatinine. However, the concentration of 4,4 ́-methylenedianiline in 3 postshift urine 

samples exceeded 1,300 nmol/mmol creatinine and the concentration in one sample was 

687 1 nmol/mmol creatinine. The maximum urinary 4,4 ́-methylenedianiline levels were found among 

manufacturers and formulators. In a Swedish study of 8 epoxy resin workers, the urinary total 

4,4 ́-methylenedianiline concentrations (not standardized with creatinine level in urine) were in the 

METHYLENEDIANILINE 120 

5. POTENTIAL FOR HUMAN EXPOSURE 

range of l0-3,026 nmol/L (2-600 μg/L) (Tiljander et al. 1989). 4,4 ́-Methylenedianiline was detected 

(detection limit < 1.7 nmol/mmol creatinine) in <20% of urine samples from more than 160 workers at 

10 industrial sites in the United States at a concentration range of 1.7-119.8 nmol 4,4 ́-methylenedianiline/ 

mmol creatinine (2.9-210 μg/g creatinine) (Peterson et al. 1991). The National Occupational 

Exposure Survey (NOES) conducted by NIOSH during 1981-83 estimated that a total of 

15,178 workers in different industries are potentially exposed to 4,4 ́-methylenedianiline (NIOSH 

1989). However, the NOES database does not contain data on the frequency, duration, concentration, 

or route of exposure of workers to 4,4 ́-methylenedianiline (or any other chemical). German 

researchers (Sepai 1995) found that a hemoglobin adduct of an acetylated metabolite of 

4,4 ́-methylenedianiline can be detected after occupational exposure to MDI. The authors consider this 

evidence for the biological availability of 4,4 ́-methylenedianiline from in vivo hydrolysis of MDI. 

5.6 POPULATIONS WITH POTENTIALLY HIGH EXPOSURES 

Within the general population, there are a few groups that are potentially exposed to 4,4 ́­

methylenedianiline at higher levels than the background population. In addition to individuals exposed to 

the compound in the workplace, these groups include: patients with kidney disease, patients who receive 

frequent blood transfusions (Shintani 1991), and people who live in the vicinity of 4,4 ́-methylenedianiline 

disposal facilities. With the exception of occupational groups, the levels of exposure in other 

potentially high exposure groups have not been documented either by measuring levels in the 

contaminated media (e.g., air, transfused plasma) or the levels in tissues or body fluids of the exposed 

persons. 

5.7 ADEQUACY OF THE DATABASE 

Section 104(i)(5) of CERCLA, as amended, directs the Administrator of ATSDR (in consultation with 

the Administrator of EPA and agencies and programs of the Public Health Service) to assess whether 

adequate information on the health effects of 4,4 ́-methylenedianiline is available. Where adequate 

information is not available, ATSDR, in conjunction with the NTP, is required to assure the initiation 

of a program of research designed to determine the health effects (and techniques for developing 

methods to determine such health effects) of 4,4 ́-methylenedianiline. 
METHYLENEDIANILINE 121 

5. POTENTIAL FOR HUMAN EXPOSURE 

The following categories of possible data needs have been identified by a joint team of scientists from 

ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that if met would 

reduce the uncertainties of human health assessment. This definition should not be interpreted to mean 

that all data needs discussed in this section must be filled. In the future, the identified data needs will 

be evaluated and prioritized, and a substance-specific research agenda will be proposed. 

5.7.1 Identification of Data Needs 

Physical and Chemical Properties. Data on physical and chemical properties are available for 

4,4 ́-methylenedianiline (HSDB 1996; IARC 1986; Moore 1978), although some of these data (vapor 

pressure, pb, and Henry’s law constant) are estimated by reliable methods. The available data will 

permit the prediction of environmental fate processes for 4,4 ́-methylenedianiline. Therefore, a data 

need has not been identified. 

Production, Import/Export, Use, Release, and Disposal. Five companies that manufacture 

4,4 ́-methylenedianiline for sale and/or distribution also utilize the predominant amount of 

manufactured material captively for the production of other products (IARC 1986; TR194 1996). 

Therefore, data on recent production volumes or the trend in yearly production volume for 

4,4 ́-methylenedianiline remain unavailable. The availability of this data could be important, because 

it provides indirect evidence of environmental release. Information regarding the recent trend in 

import/export volumes and its use is well documented in the literature (IARC 1986; NTDB 1994). 

Since medical devices such as plasma separators or artificial dialyzers are often fabricated with 

polyurethane as a potting material, they release 4,4 ́-methylenedianiline during sterilization (Shintani 

1991). This is one of the documented sources of consumer exposure to the compound. Although 

some information regarding the method of disposal is available (HSDB 1996), it would be helpful to 

obtain more information on the methods currently used by industries for the disposal of 

4,4 ́-methylenedianiline wastes that are transferred off-site. 4,4 ́-Methylenedianiline itself is used to 

prepare other chemicals or products; it is not used in the home or the general environment and thus, 

would not contaminate any home or environmental media. No literature data were found on 

4,4 ́-methylenedianiline as a food contaminant. Levels of the compound in food, food additives, and 

food packaging are so low that potential daily intake via these routes is virtually zero (NIEHS 1994). 

No residue of the compound was found on vegetables grown on soilless reconstituted polyurethane 

foam with or without nutrient solutions (Rouchaud et al. 1992). Consumer products that contain 
METHYLENEDIANILINE 122 

5. POTENTIAL FOR HUMAN EXPOSURE 

4,4 ́-methylenedianiline are polyurethane foam, Spandex fiber, and epoxy-containing products (see 

Section 4.3). Under normal use conditions, very little 4,4 ́-methylenedianiline is present in the free 

state in such products. 

According to the Emergency Planning and Community Right-to-Know Act of 1986, 42 U.S.C. Section 

11023, industries are required to submit chemical release and off-site transfer information to the EPA. 

The Toxics Release Inventory (TRI), which contains this information for 1992, became available in 

May of 1994. This database will be updated yearly and should provide a list of industrial production 

facilities and emissions. 

Environmental Fate. Experimental data on the fate of 4,4 ́-methylenedianiline in air, water, and 

soil are scarce. Homogeneous reaction of vapor-phase 4,4 ́-methylenedianiline with the hydroxyl 

radical in the atmosphere is known to be an important removal mechanism (half-life estimated at 

1.6 hours). However, 4,4 ́-methylenedianiline exists in the atmosphere predominantly as either a solid 

aerosol or adsorbed on other particles. Very little is known about the reaction mechanisms, rate of 

removal, or degradation products formed when 4,4 ́-methylenedianiline reacts heterogeneously with 

hydroxyl radical or gas-phase nitric acid. Based on its low estimated vapor pressure of 2.15x10-7 mm Hg at 

25 o

C, and its ability of form covalent bonds with humic substances present in soil and sediment (Parris 

1980), 4,4 ́-methylenedianiline will partition into sediment of surface water and in soil. The strong binding 

of the compound with humic substances in soil will retard its mobility, resulting in low leachability in most 

soils. However, it would be important to verify experimentally the sorption behavior of 4,4 ́­

methylenedianiline in sediment and soil. The half-lives of 4,4 ́-methylenedianiline due to biodegradation in 

aerobic soil and anaerobic sediment/soil are predicted to be l-7 days and 4-28 days, respectively (Howard et 

al. 1991). Therefore, the compound will persist in deeper soil and sediment where there is a lack of oxygen. 

However, these estimated halflives and the prediction that biodegradation will be the most important fate of 

4,4 ́-methylenedianiline in water and soil need further experimental verification. 

Bioavailability from Environmental Media. People who live in the vicinity of disposal 

facilities may be exposed to 4,4 ́-methylenedianiline by inhalation of airborne dust, ingestion of soil 

(children), and dermal contact with soil (children). However, no monitoring data on levels of the 

compound in air, water, or sediment and soil were located in the literature search. Analyses of fish 

and vegetables have been conducted, but no residues were found at the detection limits attained (see 
METHYLENEDIANILINE 123 

5. POTENTIAL FOR HUMAN EXPOSURE 

Section 5.4). Thus, no information on the absorption of 4,4 ́-methylenedianiline from contaminated air, 

water, soil, or plant material is available. In order to estimate the uptake of the substance as a result 

of exposure, it is important that the bioavailability of 4,4 ́-methylenedianiline from each route of entry 

be known. The bioavailability may not depend entirely on the sorption coefficient of 4,4 ́­

methylenedianiline on soil or air particles, but may also depend on the pH of the media of contact. Because 

4,4 ́-methylenedianiline is a weak base, its bioavailability may increase as the medium becomes more 

and more acidic. Since no data on the bioavailability of 4,4 ́-methylenedianiline from contaminated air 

and soil are available, it would be helpful to develop this information. 

Reliable monitoring data for the levels of 4,4 ́-methylenedianiline in contaminated media at hazardous 

waste sites are needed so that the information obtained on levels of 4,4 ́-methylenedianiline in the 

environment can be used in combination with the known body burdens of 4,4 ́-methylenedianiline to 

assess the potential risk of adverse health effects in populations living in the vicinity of hazardous 

waste sites. 

Food Chain Bioaccumulation. Both the experimentally determined K, value (HSDB 1996) and 

the estimated bioconcentration value indicate that 4,4 ́-methylenedianiline will not bioconcentrate in 

lipids and will not bioconcentrate in aquatic organisms or animals. Experimental study also supports 

this conclusion (III 1981). No data located in the literature suggest that 4,4 ́-methylenedianiline will 

biomagnify in animals of higher trophic levels through aquatic or terrestrial food chains. Since 

experimental data on the bioaccumulation and biomagnification potential of 4,4 ́-methylenedianiline are 

lacking, it would be helpful to develop these data in both aquatic and terrestrial food chains. 

Exposure Levels in Environmental Media. Other than in occupational air, measured values for 

the levels of 4,4 ́-methylenedianiline in ambient air, water, soil, plant materials, and foodstuffs have 

not been reported. Consequently, no estimate of human intake of the compound from various 

environmental media was located in the literature. Reliable monitoring data for the levels of 

4,4 ́-methylenedianiline in contaminated media at hazardous waste sites are needed so that the 

information obtained on levels in the environment can be used in combination with the known body 

burden of the substance to assess the potential risk of adverse health effects in populations living in 

the vicinity of hazardous waste sites. 
METHYLENEDIANILINE 124 

5. POTENTIAL FOR HUMAN EXPOSURE 

Reliable monitoring data for the levels of methylenedianiline in contaminated media at hazardous 

waste sites are needed so that the information obtained on levels of 1,4-dichlorobenzene in the 

environment can be used in combination with the known body burdens of 1,4-dichlorobenzene to 

assess the potential risk of adverse health effects in populations living in the vicinity of hazardous 

waste sites. 

Exposure Levels in Humans. Data on the levels of 4,4 ́-methylenedianiline in urine of 

occupationally exposed workers are available (Cocker et al. 1994; Peterson et al. 1991; Tiljander et al. 

1989). No data were located on the levels in other tissues or body fluids of exposed or unexposed 

people. Similarly, no biological monitoring study has been conducted for populations in the vicinity 

of hazardous waste sites. This information is necessary for assessing the need to conduct health 

studies on these populations. 

Exposure Registries. No exposure registries for 4,4 ́-methylenedianiline were located. This 

substance is not currently one of the compounds for which subregistry has been established in the 

National Exposure Registry. The substance will be considered in the future when chemical selection is 

made for subregistries to be established. The information that is amassed in the National Exposure 

Registry facilitates the epidemiological research needed to assess adverse health outcomes that may be 

related to exposure to this substance. 

5.7.2 Ongoing Studies 

A search of the Federal Research in Progress (FEDRIP) database did not identify any ongoing studies 

that could be useful in filling the data gaps discussed in Section 5.7.1. 
METHYLENEDIANILINE 125 

6. ANALYTICAL METHODS
 

The purpose of this chapter is to describe the analytical methods that are available for detecting, and/or 

measuring, and/or monitoring 4,4 ́-methylenedianiline, its metabolites, and other biomarkers of 

exposure and effect to 4,4 ́-methylenedianiline. The intent is not to provide an exhaustive list of 

analytical methods. Rather, the intention is to identify well-established methods that are used as the 

standard methods of analysis. Many of the analytical methods used for environmental samples are the 

methods approved by federal agencies and organizations such as EPA and the National Institute for 

Occupational Safety and Health (NIOSH). Other methods presented in this chapter are those that are 

approved by groups such as the Association of Official Analytical Chemists (AOAC) and the 

American Public Health Association (APHA). Additionally, analytical methods are included that 

modify previously used methods to obtain lower detection limits, and/or to improve accuracy and 

precision. 

6.1 BIOLOGICAL SAMPLES 

Methods are available for the determination of 4,4 ́-methylenedianiline in blood and urine. 

Representative methods are summarized in Table 6-l. Most methods involve an extraction step, 

purification and fractionation procedures, and analysis, usually by gas chromatography (GC) or high 

performance liquid chromatography (HPLC). 

The determination of 4,4 ́-methylenedianiline in blood, serum, or urine requires special precautions 

because the compound and some of its metabolites are heat labile (Cocker et al. 1988; Shintani 1992). 

During sample treatment, care should be taken to assure that no loss of 4,4 ́-methylenedianiline or its 

metabolites has occurred during evaporative steps used for the concentration in organic solutions and 

during hydrolysis of urine (Cocker et al. 1988; Shintani 1992). 

Determination of 4,4 ́-methylenedianiline in blood/serum requires pretreatment steps involving 

deproteinization with a suitable reagent (e.g., perchloric acid), centrifugation for separation of 

4,4 ́-methylenedianiline from the precipitate, and concentration (Shintani 1992). Determination of 

4,4 ́-methylenedianiline in urine often uses solvent extraction and multiple clean-up steps (Avery 

1989). An improved method uses solid phase extraction columns (octadecyl bonded silica) for the 

METHYLENEDIANILINE 127 

6. ANALYTICAL METHODS 

separation of 4,4 ́-methylenedianiline from interfering components in blood and hydrolyzed urine 

(Peterson et al. 1991; Shintani 1992). 

Due to the polar nature of 4,4 ́-methylenedianiline, derivatization of the amine groups is required to 

produce a species which can be analyzed by GC without peak tailing. This derivatization may not be 

necessary if HPLC is used (Peterson et al. 1991). The common derivatizing agents are trifluoroacetic 

anhydride, pentafluoropropionic anhydride (PFPA), and heptafluorobutyric anhydride (HFBA). 

The commonly used HPLC techniques include ultraviolet absorbance detection (UV) (Brumnark et al. 

1992; Tiljander et al. 1990; Tiljander and Skarping 1990) and electrochemical detection (Peterson et 

al. 1991; Shintani 1992). Generally, the detection limit of 4,4 ́-methylenedianiline with 

electrochemical detection is in the range of 2-3 ng/mL (Peterson et al. 1991; Shintani 1992). This 

method is approximately two orders of magnitude better than the HPLC/UV method, which has a 

detection limit of 150 ng/mL (Shintani 1992). However, with special techniques, such as precolumn 

separation of derivatized 4,4 ́-methylenedianiline and microliquid chromatography, it is possible to 

lower the detection limits with UV in the range 0.4 ng/mL-8.0 ng/mL (Brunmark et al. 1992; 

Tiljander and Skarping 1990; Tiljander et al. 1990). Interferences from biological materials may 

co-elute with 4,4 ́-methylenedianiline, so confirmation is recommended. A second wavelength has 

been used with UV detection (Tiljander and Skarping 1990) and GC/mass spectrometry (Peterson et al. 

1991). 

GC may be used with electron capture detection (ECD) (Tortoreto et al. 1983), thermionic specific 

detection (Skarping et al. 1983), and mass spectrometry (MS) (Avery 1989; Cocker et al. 1988). 

Detection limits in the range of l-10 ng/mL are attainable by GC/MS (Avery 1989; Cocker et al. 

1986a, 1988). For urine and serum, a detection limit of ≤1 ng/mL was obtained with solid phase 

extraction, derivatization, and GC/negative-ion chemical ionization MS (Avery 1989). The detection 

limit for GC/ECD is l-10 ng/mL (Skarping et al. 1983; Tortoreto et al. 1983). Although the detection 

limit with the thermionic specific detectors is about 10 times higher than electron capture detection 

(Skarping et al. 1983), both thermionic specific detector and MS detectors are more selective for 

4,4 ́-methylenedianiline determination (Cocker et al. 1986a; Skarping et al. 1983). 

Besides the parent 4,4 ́-methylenedianiline, N-acetyl-, N,N’-diacetyl-, and the N-glucuronide of 

4,4 ́-methylenedianiline may also be present in urine as metabolites (Cocker et al. 1986a, 1988; 
METHYLENEDIANILINE 128 

6. ANALYTICAL METHODS 

Peterson et al. 1991). N-acetyl-4,4 ́-methylenedianiline has been identified in human urine (Cocker 

1986a). Three metabolites have been identified in rabbit liver microsomal incubations: 

azodiphenylmethane (azo), azoxydiphenylmethane (azoxy), and 4-nitroso-4’-aminodiphenylmethane 

(nitroso) compounds (Kajbaf et al. 1992). The formation of metabolites is shown schematically in 

Figure 2-3. Methods that can be used for the determination of metabolites are included in Table 6-l. 

It is possible to determine the free amine (4,4 ́-methylenedianiline) and the total 4,4 ́-methylenedianiline 

(free, acetylated, and conjugated) in urine. The treatment of urine with strong base or strong 

acid hydrolyzes acetylated and conjugated 4,4 ́-methylenedianiline to the free 4,4 ́-methylenedianiline 

(Cocker et al. 1988; Tiljander and Skarping 1990). Therefore, the determination of free and total 

4,4 ́-methylenedianiline is possible by determining the amount of 4,4 ́-methylenedianiline in 

unhydrolyzed and hydrolyzed urine (Peterson et al. 1991). Methods for the determination of free and 

total 4,4 ́-methylenedianiline are included in Table 6-l. 

Biological monitoring for 4,4 ́-methylenedianiline and its metabolites is used to assess exposure to 

4,4 ́-methylenedianiline. Available methods are summarized in Table 6-2. The methods are similar to 

the methods described in Table 6-1, except that very sensitive and specific MS techniques are used for 

analysis. In addition, the monitoring strategy must take into account the route of exposure (Cocker et 

al. 1994). The corresponding hemoglobin adducts have also been measured. Adducts are analyzed by 

GC/MS after hydrolysis, extraction and derivatization of hemoglobin precipitated from lysated red 

blood cells (Bailey et al. 1990; Schutz et al. 1995). Very low detection limits have been reported; 

however, little other performance information is available (Bailey et al. 1990; Schutz et al. 1995). 

6.2 ENVIRONMENTAL SAMPLES 

Analytical methods available for the determination of 4,4 ́-methylenedianiline in environmental 

samples are listed in Table 6-3. As in the case of biological samples, 4,4 ́-methylenedianiline in 

environmental samples has been determined by HPLC/UV (Emes and Hanshumaker 1983; Gunderson 

and Anderson 1988; Mazzu and Smith 1984), HPLC/electrochemical detection (Concialini et al. 1983), 

and GC/thermionic detection (Audunsson and Mathiasson 1983). Although analysis of 

4,4 ́-methylenedianiline by HPLC does not require derivatization, analysis of environmental samples is 

frequently performed after derivatization to reduce amine reactivity on HPLC column packing 


METHYLENEDIANILINE 131 

6. ANALYTICAL METHODS 

materials (Emes and Hanshumaker 1983; Gunderson and Anderson 1988; Mazzu and Smith 1984). 

Because of lower matrix interference environmental samples (air or water), the detection limits can be 

an order of magnitude lower than those achieved for biological samples (Avery 1989). The available 

analytical methods are capable of detecting 4,4 ́-methylenedianiline in air at concentrations lower than 

the ACGIH threshold limit value of 0.08 mg/m3

 (10 ppb) (for time-weighted average for 8 hours) and 

a short-term exposure limit of 0.8 mg/m3

 (100 ppb) (Audunsson and Mathiasson 1983; Boeniger 

1984a; Gunderson and Anderson 1988). 

Special precautions should be taken during sampling of workplace air for 4,4 ́-methylenedianiline. 

The compound can be present in workplace air, both in the vapor and particle phase. Therefore, air 

sampling methods must be able to collect 4,4 ́-methylenedianiline present in both phases. Glass fiber 

filter/silica gel sampling tubes (Boeniger 1984a) or acid-impregnated glass fiber filters (Gunderson and 

Anderson 1988) are capable of collecting 4,4 ́-methylenedianiline in both phases. In certain workplace 

environments, such as polyurethane industries that produce methylenediphenyl diisocyanate (MDI) or 

polymeric MDI, the air may contain both 4,4 ́-methylenedianiline and MDI. Sampling methods that 

use impingers containing acids (Audunsson and Mathiasson 1983) or acid-coated glass fiber filters 

(Gunderson and Anderson 1988) would hydrolyze MD1 to 4,4 ́-methylenedianiline (Audunsson and 

Mathiasson 1983; Gunderson and Anderson 1988). Therefore, if a distinction is to be made between 

4,4 ́-methylenedianiline and MDI, either MD1 or 4,4 ́-methylenedianiline should be determined in the 

sample alone and could be subtracted from the total (following acid hydrolysis) for the determination 

of individual MD1 and 4,4 ́-methylenedianiline concentrations. Methods for such determinations are 

available (Audunsson and Math&son 1983; Boeniger 1984a). 

6.3 ADEQUACY OF THE DATABASE 

Section 104(i)(5) of CERCLA, as amended, directs the Administrator of ATSDR (in consultation with 

the Administrator of EPA and agencies and programs of the Public Health Service) to assess whether 

adequate information on the health effects of 4,4 ́-methylenedianiline is available. Where adequate 

information is not available, ATSDR, in conjunction with the NTP, is required to assure the initiation 

of a program of research designed to determine the health effects (and techniques for developing 

methods to determine such health effects) of 4,4 ́-methylenedianiline. 
METHYLENEDIANILINE 132 

6. ANALYTICAL METHODS 

The following categories of possible data needs have been identified by a joint team of scientists from 

ATSDR, NTP, and EPA. They are defined as substance-specific informational needs that if met would 

reduce the uncertainties of human health assessment. This definition should not be interpreted to mean 

that all data needs discussed in this section must be filled. In the future, the identified data needs will 

be evaluated and prioritized, and a substance-specific research agenda will be proposed. 

6.3.1 Identification of Data Needs 

Methods for Determining Biomarkers of Exposure and Effect. The total amount of 

4,4 ́-methylenedianiline (free and conjugated) in urine is used as an indicator of 4,4 ́-methylenedianiline 

exposure in workers (Bnmmark et al. 1995; Cocker et al. 1994). Total MDA in plasma is 

also an appropriate method for biological monitoring of 4,4 ́-methylenedianiline. Methods for the 

determination of total 4,4 ́-methylenedianiline in human urine and blood by alkaline hydrolysis of 

urine are available and shown in Table 6-1. However, no quantitative correlation has been established 

between level of workplace exposure and urinary level of free and/or conjugated 4,4 ́-methylenedianiline. 

Adducts of 4,4 ́-methylenedianiline with hemoglobin can also be used as an indicator of 

exposure (Bailey et al. 1990; Schutz et al. 1995). These methods are suitable for the monitoring of 

occupational exposure. It would be helpful to assess whether the existing analytical methods are 

capable of detecting the compound in biological samples at levels at which biological effects might 

occur. 

There is no specific biomarker of effect that can be attributed to 4,4 ́-methylenedianiline exposure. 

Exposure to the compound is usually associated with occurrence of jaundice, bile duct inflammation, 

suppression of bile excretion, and clinical hepatitis (NIOSH 1986). However, none of these effects is 

specific to 4,4 ́-methylenedianiline exposure. It would be useful to establish that a certain effect could 

be specifically attributed to 4,4 ́-methylenedianiline exposure. 

Methods for Determining Parent Compounds and Degradation Products in 

Environmental Media. Few methods are available for analysis of 4,4 ́-methylenedianiline in 

environmental media. Methods are available for determination in occupational air (Audunsson and 

Mathiasson 1983; Boeniger 1984a; Gunderson and Anderson 1988). Analytical methods of sufficient 

sensitivity, precision, and accuracy are available for the determination of 4,4 ́-methylenedianiline in 

occupational air at levels at least an order of magnitude lower than the ACGIH level of 0.8 mg/m3 
METHYLENEDIANILINE 133 

6. ANALYTICAL METHODS 

(Hoeniger 1984a; Gunderson and Anderson 1988). However, the compound has not been measured in 

ambient air. Methods are also available for the determination of extractable 4,4 ́-methylenedianiline in 

polyurethanes (Emes and Hanshumaker 1983; Mazzu and Smith 1984). Standardized analytical 

methods for the determination of 4,4 ́-methylenedianiline in water, soil, and other environmental media 

are not available. Therefore, it would be most useful to develop standardized analytical methods of 

sufficient sensitivity, precision, and accuracy for its determination, at least, in contaminated 

environmental media. Most important, analytical methods should be developed to determine the 

concentrations of 4,4 ́-methylenedianiline in soil and groundwater at Superfund waste disposal sites. 

Experimental data on the environmental fate of 4,4 ́-methylenedianiline are very scarce. Consequently, 

the environmental degradation products of the compound have not been identified. Therefore, before 

the evaluation of this data need, it would be more important to conduct more studies to assess the 

environmental fate of 4,4 ́-methylenedianiline. 

6.3.2 Ongoing Studies 

No ongoing studies involving methods for determination of 4,4 ́-methylenedianiline were located. 

METHYLENEDIANILINE 135 

7. REGULATIONS AND ADVISORIES
 

The international, national, and state regulations and guidelines regarding 4,4 ́-methylenedianiline in 

air, water, and other media are summarized in Table 7-1. 

ATSDR has derived an acute oral MRL of 0.2 mg/kg/day based on a minimal LOAEL for liver effects 

observed in rats treated with a single dose of 4,4 ́-methylenedianiline (Bailie et al. 1993). 

ATSDR has derived an intermediate oral MRL of 0.08 mg/kg/day based on a NOAEL for liver effects 

observed in rats treated daily with gavage doses of 4,4 ́-methylenedianiline for 12 weeks (Pludro et al. 

1969). 

Neither a reference dose nor a reference concentration for 4,4 ́-methylenedianiline is available at this 

time. 

The International Agency for Research on Cancer (IARC) has classified 4,4 ́-methylenedianiline as 2B, 

probably carcinogenic to humans, based on limited evidence of carcinogenicity in humans but 

sufficient evidence of carcinogenicity in animals (IARC 1987). The EPA and the National Toxicology 

Program (NTP) have not classified the chemical for carcinogenicity. The National Institute for 

Occupational Safety and Health (NIOSH) has identified 4,4 ́-methylenedianiline as a potential 

occupational carcinogen and recommends that occupational exposures to the compound be limited to 

the lowest feasible concentration (NIOSH 1994). 

4,4 ́-Methylenedianiline is on the list of chemicals appearing in The Emergency Planning and 

Community Right-to-Know Act of 1986 (EPCRA) (EPA 1987). Section 313 of Title III of EPCRA 

requires owners and operators of certain facilities that manufacture, import, process, or otherwise use 

the chemicals on this list to report annually their release of those chemicals to any environmental 

media. 

OSHA requires employers of workers who are occupationally exposed to 4,4 ́-methylenedianiline to 

institute engineering controls and work practices to reduce and maintain employee exposure at or 

below permissible exposure limits (PEL). Except as provided by specific clauses within the standard 

given at 29 CFR 1910.1050 (e.g., products not capable of releasing MDA in excess of the action level; 
METHYLENEDIANILINE 136 

7. REGULATIONS AND ADVISORIES 

conditions where no dermal exposure to MDA can occur, materials in any form containing less than 

0.1% MDA by weight or volume, and construction work) for all occupational exposures to MDA, the 

employer must use engineering and work practice controls, if feasible, to reduce exposure to or below 

an 8-hour time-weighted average (TWA) of 10 ppb (OSHA 1992a, 1992b). The short term exposure 

limit (STEL), as determined by any 15minute sampling period is 100 ppb (OSHA 1992a, 1992b). 

The OSHA standard for construction work is given in 29 CFR 1926.60; however, the PEL for these 

activities is the same as that for all other occupational exposures. The action level for occupational 

exposure to airborne 4,4 ́-methylenedianiline, including construction work, is 5 ppb, based on an 

8-hour time-weighted average (OSHA 1992a, 1992b). The OSHA standard for construction work is 

applicable, but not limited, to activities such as alteration, repair, maintenance, or renovation of 

structures or substrates that contain 4,4 ́-methylenedianiline (OSHA 1992a, 1992b). Respirators must 

be provided and used during the time period necessary to install or implement feasible engineering and 

work practice controls (OSHA 1992a, 1992b). 




___________________ 

METHYLENEDIANILINE 141 

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METHYLENEDIANILINE 155 

9. GLOSSARY
 

Acute Exposure-Exposure to a chemical for a duration of 14 days or less, as specified in the 

Toxicological Profiles. 

Adsorption Coefficient (Koc)-The ratio of the amount of a chemical adsorbed per unit weight of 

organic carbon in the soil or sediment to the concentration of the chemical in solution at equilibrium. 

Adsorption Ratio (Kd)-The amount of a chemical adsorbed by a sediment or soil (i.e., the solid 

phase) divided by the amount of chemical in the solution phase, which is in equilibrium with the solid 

phase, at a fixed solid/solution ratio. It is generally expressed in micrograms of chemical sorbed per 

gram of soil or sediment. 

Bioconcentration Factor (BCF)-The quotient of the concentration of a chemical in aquatic organisms 

at a specific time or during a discrete time period of exposure divided by the concentration in the 

surrounding water at the same time or during the same period. 

Cancer Effect Level (CEL)-The lowest dose of chemical in a study, or group of studies, that 

produces significant increases in the incidence of cancer (or tumors) between the exposed population 

and its appropriate control. 

Carcinogen- A chemical capable of inducing cancer. 

Ceiling Value-A concentration of a substance that should not be exceeded, even instantaneously. 

Chronic Exposure-Exposure to a chemical for 365 days or more, as specified in the Toxicological 

Profiles. 

Developmental Toxicity-The occurrence of adverse effects on the developing organism that may 

result from exposure to a chemical prior to conception (either parent), during prenatal development, or 

postnatally to the time of sexual maturation. Adverse developmental effects may be detected at any 

point in the life span of the organism. 

Embryotoxicity and Fetotoxicity-Any toxic effect on the conceptus as a result of prenatal exposure 

to a chemical; the distinguishing feature between the two terms is the stage of development during 

which the insult occurred. The terms, as used here, include malformations and variations, altered 

growth, and in utero death. 

EPA Health Advisory-An estimate of acceptable drinking water levels for a chemical substance 

based on health effects information. A health advisory is not a legally enforceable federal standard, but 

serves as technical guidance to assist federal, state, and local officials. 

Immediately Dangerous to Life or Health (IDLH)-The maximum environmental concentration of a 

contaminant from which one could escape within 30 min without any escape-impairing symptoms or 

irreversible health effects. 
METHYLENEDIANILINE 156 

9. GLOSSARY 

Intermediate Exposure-Exposure to a chemical for a duration of 15-364 days, as specified in the 

Toxicological Profiles. 

Immunologic Toxicity-The occurrence of adverse effects on the immune system that may result from 

exposure to environmental agents such as chemicals. 

In vitro-Isolated from the living organism and artificially maintained, as in a test tube. 

In vivo-Occurring within the living organism. 

Lethal Concentration(LO) (LCLO)-The lowest concentration of a chemical in air which has been 

reported to have caused death in humans or animals. 

Lethal Concentration(50) (LC50)-A calculated concentration of a chemical in air to which exposure for 

a specific length of time is expected to cause death in 50% of a defined experimental animal 

population. 

Lethal Dose(LO) ( LDLO)-The lowest dose of a chemical introduced by a route other than inhalation that 

is expected to have caused death in humans or animals. 

Lethal Dose(50) (LD50)-The dose of a chemical which has been calculated to cause death in 50% of a 

defined experimental animal population. 

Lethal Time(50) (LT50)-A calculated period of time within which a specific concentration of a 

chemical is expected to cause death in 50% of a defined experimental animal population. 

Lowest-Observed-Adverse-Effect Level (LOAEL)-The lowest dose of chemical in a study, or group 

of studies, that produces statistically or biologically significant increases in frequency or severity of 

adverse effects between the exposed population and its appropriate control. 

Malformations-Permanent structural changes that may adversely affect survival, development, or 

function. 

Minimal Risk Level-An estimate of daily human exposure to a dose of a chemical that is likely to be 

without an appreciable risk of adverse noncancerous effects over a specified duration of exposure. 

Mutagen-A substance that causes mutations. A mutation is a change in the genetic material in a body 

cell. Mutations can lead to birth defects, miscarriages, or cancer. 

Neurotoxicity-The occurrence of adverse effects on the nervous system following exposure to 

chemical. 

No-Observed-Adverse-Effect Level (NOAEL)-The dose of chemical at which there were no 

statistically or biologically significant increases in frequency or severity of adverse effects seen 

between the exposed population and its appropriate control. Effects may be produced at this dose, but 

they are not considered to be adverse. 
METHYLENEDIANILINE 157 

9. GLOSSARY 

Octanol-Water Partition Coefficient (Kow)-The equilibrium ratio of the concentrations of a chemical 

in n-octanol and water, in dilute solution. 

Permissible Exposure Limit (PEL)-An allowable exposure level in workplace air averaged over an 

8-hour shift. 

q1*-The upper-bound estimate of the low-dose slope of the dose-response curve as determined by the 

multistage procedure. The ql* can be used to calculate an estimate of carcinogenic potency, the 

incremental excess cancer risk per unit of exposure (usually μg/L for water, mg/kg/day for food, and 

pg/m3

 for air). 

Reference Dose (RfD)-An estimate (with uncertainty spanning perhaps an order of magnitude) of the 

daily exposure of the human population to a potential hazard that is likely to be without risk of 

deleterious effects during a lifetime. The RfD is operationally derived from the NOAEL (from animal 

and human studies) by a consistent application of uncertainty factors that reflect various types of data 

used to estimate RfDs and an additional modifying factor, which is based on a professional judgment 

of the entire database on the chemical. The RfDs are not applicable to nonthreshold effects such as 

cancer. 

Reportable Quantity (RQ)-The quantity of a hazardous substance that is considered reportable under 

CERCLA. Reportable quantities are (1) 1 pound or greater or (2) for selected substances, an amount 

established by regulation either under CERCLA or under Sect. 3 11 of the Clean Water Act. Quantities 

are measured over a 24-hour period. 

Reproductive Toxicity-The occurrence of adverse effects on the reproductive system that may result 

from exposure to a chemical. The toxicity may be directed to the reproductive organs and/or the 

related endocrine system. The manifestation of such toxicity may be noted as alterations in sexual 

behavior, fertility, pregnancy outcomes, or modifications in other functions that are dependent on the 

integrity of this system. 

Short-Term Exposure Limit (STEL)-The maximum concentration to which workers can be exposed 

for up to 15 min continually. No more than four excursions are allowed per day, and there must be at 

least 60 min between exposure periods. The daily TLV-TWA may not be exceeded. 

Target Organ Toxicity-This term covers a broad range of adverse effects on target organs or 

physiological systems (e.g., renal, cardiovascular) extending from those arising through a single limited 

exposure to those assumed over a lifetime of exposure to a chemical. 

Teratogen-A chemical that causes structural defects that affect the development of an organism. 

Threshold Limit Value (TLV)-A concentration of a substance to which most workers can be exposed 

without adverse effect. The TLV may be expressed as a TWA, as a STEL, or as a CL. 

Time-Weighted Average (TWA)-An allowable exposure concentration averaged over a normal 

8-hour workday or 40-hour workweek. 

Toxic Dose (TD50)-A calculated dose of a chemical, introduced by a route other than inhalation, 

which is expected to cause a specific toxic effect in 50% of a defined experimental animal population. 
METHYLENEDIANILINE 158 

9. GLOSSARY 

Uncertainty Factor (UF)-A factor used in operationally deriving the MRL or RfD from experimental 

data. UFs are intended to account for (1) the variation in sensitivity among the members of the human 

population, (2) the uncertainty in extrapolating animal data to the case of human, (3) the uncertainty in 

extrapolating from data obtained in a study that is of less than lifetime exposure, and (4) the uncertainty in 

using LOAEL data rather than NOAEL data. Usually each of these factors is set equal to 10. 
METHYLENEDIANILINE A-1 

APPENDIX A
 

ATSDR MINIMAL RISK LEVEL
 

The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) [42 U.S.C. 

9601 et seq.], as amended by the Super-fund Amendments and Reauthorization Act (SARA) [Pub. L. 

99-4991, requires that the Agency for Toxic Substances and Disease Registry (ATSDR) develop 

jointly with the U.S. Environmental Protection Agency (EPA), in order of priority, a list of hazardous 

substances most commonly found at facilities on the CERCLA National Priorities List (NPL); prepare 

toxicological profiles for each substance included on the priority list of hazardous substances; and 

assure the initiation of a research program to fill identified data needs associated with the substances. 

The toxicological profiles include an examination, summary, and interpretation of available 

toxicological information and epidemiologic evaluations of a hazardous substance. During the 

development of toxicological profiles, Minimal Risk Levels (MRLs) are derived when reliable and 

sufficient data exist to identify the target organ(s) of effect or the most sensitive health effect(s) for a 

specific duration for a given route of exposure. An MRL is an estimate of the daily human exposure 

to a hazardous substance that is likely to be without appreciable risk of adverse noncancer health 

effects over a specified duration of exposure. MRLs are based on noncancer health effects only and 

are not based on a consideration of cancer effects. These substance-specific estimates, which are 

intended to serve as screening levels, are used by ATSDR health assessors to identify contaminants 

and potential health effects that may be of concern at hazardous waste sites. It is important to note 

that MRLs are not intended to define clean-up or action levels. 

MRLs are derived for hazardous substances using the no-observed-adverse-effect level/uncertainty 

factor approach. They are below levels that might cause adverse health effects in the people most 

sensitive to such chemical-induced effects. MRLs are derived for acute (I-14 days), intermediate 

(15-364 days), and chronic (365 days and longer) durations and for the oral and inhalation routes of 

exposure. Currently, MRLs for the dermal route of exposure are not derived because ATSDR has not 

yet identified a method suitable for this route of exposure. MRLs are generally based on the most 

sensitive chemical-induced end point considered to be of relevance to humans. Serious health effects 

(such as irreparable damage to the liver or kidneys, or birth defects) are not used as a basis for 










METHYLENEDIANILINE B-6 

APPENDIX B 

Chapter 2 (Section 2.5) 

Relevance to Public Health 

The Relevance to Public Health section provides a health effects summary based on evaluations of 

existing toxicologic, epidemiologic, and toxicokinetic information. This summary is designed to 

present interpretive, weight-of-evidence discussions for human health end points by addressing the 

following questions. 

1. What effects are known to occur in humans? 

2. What effects observed in animals are likely to be of concern to humans? 

3. What exposure conditions are likely to be of concern to humans, especial1 around hazardous 

waste sites 

The section covers end points in the same order they appear within the Discussion of Health Effects
 

by Route of Exposure section, by route (inhalation, oral, dermal) and within route by effect. Human
 

data are presented first, then animal data. Both are organized by duration (acute, intermediate,
 

chronic). In vitro data and data from parenteral routes (intramuscular, intravenous, subcutaneous, etc.)
 

are also considered in this section. If data are located in the scientific literature, a table of
 

genotoxicity information is included.
 

The carcinogenic potential of the profiled substance is qualitatively evaluated, when appropriate, using
 

existing toxicokinetic, genotoxic, and carcinogenic data. ATSDR does not currently assess cancer
 

potency or perform cancer risk assessments. Minimal risk levels (MRLs) for noncancer end points (if
 

derived) and the end points from which they were derived are indicated and discussed.
 

Limitations to existing scientific literature that prevent a satisfactory evaluation of the relevance to
 

public health are identified in the Data Needs section.
 

Interpretation of Minimal Risk Levels
 

Where sufficient toxicologic information is available, we have derived minimal risk levels (MRLs) for
 

inhalation and oral routes of entry at each duration of exposure (acute, intermediate, and chronic).
 

These MRLs are not meant to support regulatory action; but to acquaint health professionals with
 

exposure levels at which adverse health effects are not expected to occur in humans. They should
 

help physicians and public health officials determine the safety of a community living near a chemical
 

emission, given the concentration of a contaminant in air or the estimated daily dose in water. MRLs
 

are based largely on toxicological studies in animals and on reports of human occupational exposure.
 

MRL users should be familiar with the toxicologic information on which the number is based.
 

Chapter 2.5, “Relevance to Public Health,” contains basic information known about the substance.
 

Other sections such as 2.7, “Interactions with Other Substances,” and 2.8, “Populations that are
 

Unusually Susceptible” provide important supplemental information.
 

MRL users should also understand the MRL derivation methodology. MRLs are derived using a
 

modified version of the risk assessment methodology the Environmental Protection Agency (EPA)
 

provides (Barnes and Dourson 1988) to determine reference doses for lifetime exposure (RfDs).
 
METHYLENEDIANILINE B-7 

APPENDIX B 

To derive an MRL, ATSDR generally selects the most sensitive endpoint which, in its best judgement, 

represents the most sensitive human health effect for a given exposure route and duration. ATSDR 

cannot make this judgement or derive an MRL unless information (quantitative or qualitative) is 

available for all potential systemic, neurological, and developmental effects. If this information and 

reliable quantitative data on the chosen endpoint are available, ATSDR derives an MRL using the 

most sensitive species (when information from multiple species is available) with the highest NOAEL 

that does not exceed any adverse effect levels. When a NOAEL is not available, a lowest-observedadverseeffect level (LOAEL) can be used to derive an MRL, and an uncertainty factor (UF) of 10 

must be employed. Additional uncertainty factors of 10 must be used both for human variability to 

protect sensitive subpopulations (people who are most susceptible to the health effects caused by the 

substance) and for interspecies variability (extrapolation from animals to humans). In deriving an 

MRL, these individual uncertainty factors are multiplied together. The product is then divided into the 

inhalation concentration or oral dosage selected from the study. Uncertainty factors used in 

developing a substance-specific MRL are provided in the footnotes of the LSE Tables.