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Public Health Statement for Toluene Diisocyanate and Methylenediphenyl Diisocyanate

(Tolueno Diisocianato / Metilendifenil Diisocianato)

CAS#: 584-84-9, 584-84-9

Public Health Statement PDF PDF Version, 281 KB


This Public Health Statement is the summary chapter from the Toxicological Profile for Toluene. It is one in a series of Public Health Statements about hazardous substances and their health effects. A shorter version, the ToxFAQs™, is also available. This information is important because this substance may harm you. The effects of exposure to any hazardous substance depend on the dose, the duration, how you are exposed, personal traits and habits, and whether other chemicals are present. For more information, call the ATSDR Information Center at 1-888-422-8737.


This Public Health Statement summarizes the Division of Toxicology and Human Health Science's findings on toluene diisocyanate (TDI) and methylenediphenyl diisocyanate (MDI), tells you about them, the effects of exposure, and describes what you can do to limit that exposure.

The U.S. 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 sites targeted for long-term federal clean-up activities. U.S. EPA has found toluene diisocyanate in at least 1 of the 1,699 current or former NPL sites. Methylenediphenyl diisocyanate was not found in any of the current or former NPL sites. The total number of NPL sites evaluated for toluene diisocyanate and methylenediphenyl diisocyanate is not known. But the possibility remains that as more sites are evaluated, the number of sites at which toluene diisocyanate and methylenediphenyl diisocyanate are found may increase. This information is important; these future sites may be sources of exposure, and exposure to toluene diisocyanate and methylenediphenyl diisocyanate may be harmful.

If you are exposed to toluene diisocyanate or methylenediphenyl diisocyanate, many factors determine whether you'll be harmed. These include how much you are exposed to (dose), how long you are exposed to it (duration), and how you are exposed (route of exposure). You must also consider the other chemicals you are exposed to and your age, sex, diet, family traits, lifestyle, and state of health.

What Are Toluene Diisocyanate and Methylenediphenyl Diisocyanate?

TDI and MDI do not occur naturally in the environment. TDI is a clear, colorless to pale yellow liquid. MDI is a light yellow crystalline solid. There are several forms of TDI and MDI, which are called isomers. The two most common TDI isomers are 2,4-TDI and 2,6-TDI. The most common isomer of MDI is 4,4'-MDI.

TDI and MDI are used to make many household products. They combine with other chemicals to produce various polyurethanes. Some of the products made with these polyurethanes include foam for furniture cushions and carpet padding and waterproof sealants.

What Happens To Toluene Diisocyanate and Methylenediphenyl Diisocyanate When They Enter the Environment?

TDI and MDI can be released into the air, water, and soil at places where they are produced or used. TDI and MDI are extremely reactive chemicals and are not likely to stay in the environment. In air, TDI and MDI have half-lives of less than 1 day (half -life is the amount of time needed for the amount of TDI or MDI in air to be reduced by one-half). TDI and MDI rapidly react with water to form other compounds in a process called hydrolysis. The half-lives of TDI and MDI in water range from a few minutes to a few hours. Significant concentrations are not likely to be found in moist soil or sediment due to the rapid hydrolysis of these compounds; however, small amounts may be detected near point sources such as industrial waste streams and hazardous waste sites. TDI and MDI will not bioaccumulate in the food chain and are therefore not expected to be found in significant concentration in fish and foods.

How Might I Be Exposed To Toluene Diisocyanate and Methylenediphenyl Diisocyanate?

TDI and MDI are used to make a number of different types of polyurethane products that are used by consumers ranging from foams for insulation, foam cushions, and sealants. In products such as cushions, the diisocyanates are cured meaning that they are not reactive. It is unlikely that consumers would be exposed to diisocyanates from cured products. However, you can be exposed to TDI and MDI in the air from uncured polyurethane products such as adhesives, sealants, coatings, paints, craft materials, and insulating foams. Workers involved in the manufacture or cured and uncured polyurethane products or involved in other industries using diisocyanates may be exposed to higher levels. You are unlikely to be exposed to TDI or MDI in food or water.

How Can Toluene Diisocyanate and Methylenediphenyl Diisocyanate Enter and Leave My Body?

When you breathe air containing TDI or MDI, some will enter your body through your lungs, but there is limited information on how much and how fast these compounds enter the body. TDI may enter your body through the digestive tract if you ingest it. There are no data on whether MDI will enter your body after ingestion. If your skin comes in contact with TDI or MDI, it is possible that a small amount may enter the body through the skin. Once TDI or MDI enters your body, it binds to other substances and is widely distributed throughout the body. TDI that is ingested can also be converted to another compound called toluene diamine. TDI and MDI primarily leave the body in the feces; a small amount also leaves the body in the urine.

How Can Toluene Diisocyanate and Methylenediphenyl Diisocyanate Affect Your Health?

The health effects of TDI and MDI depend on how much you are exposed to and the length of that exposure. Respiratory effects, including a decrease in lung function, have been reported in workers exposed to TDI or MDI. Some workers have become sensitized to TDI and/or MDI; they are particularly sensitive to the toxicity of TDI and MDI and may experience adverse effects at much lower concentrations than the concentrations that may affect non-sensitized individuals. Asthma and symptoms of asthma, such as wheezing and shortness of breath, have been observed in some individuals who are particularly sensitive to the toxicity of TDI and MDI.

An excess of lung cancer has been observed in some workers at a polyurethane foam manufacturing plant. However, it is not known if exposure to TDI was the cause. A study in animals orally exposed to TDI reported increases in tumors in the pancreas, mammary gland, and liver. The National Institute of Environmental Health Sciences (NIEHS) considers TDI as reasonably anticipated to be a human carcinogen. EPA has not classified the carcinogenicity of TDI. EPA notes that the carcinogenicity of MDI cannot be determined, but there is suggestive evidence that raises concern for carcinogenic effects.

How Can Toluene Diisocyanate and Methylenediphenyl Diisocyanate Affect Children?

We do not have any information on the effects of TDI or MDI in children. We expect that the effects in children will be similar to those seen in adults; exposure to TDI or MDI in the air could result in lung damage. A delay in bone growth has been observed in offspring of animals exposed to high levels of TDI in air that also caused decreases in body weight gain or respiratory effects in the mothers. Exposure to MDI in air during gestation also resulted in bone effects in the offspring; the MDI concentration causing these effects also resulted in decreased food consumption in the mothers.

How Can families Reduce the Risk Of Overexposure To Toluene Diisocyanate and Methylenediphenyl Diisocyanate?

You are unlikely to be exposed to TDI and MDI from food, drinking water, contaminated groundwater, or soil.

TDI and MDI are used to make many products; however, most of these products are cured and should not have unreacted diisocyanates remaining in them. Primary users and bystanders should be made aware of the potential risks and appropriate precautions to take when uncured TDI or MDI products (such as spray foam or sealants) are being used because use of these products can result in exposure to TDI or MDI.

Are There Medical Tests To Determine Whether I Have Been OverExposed To Toluene Diisocyanate and Methylenediphenyl Diisocyanate?

TDI and MDI and their hydrolysis products can be measured in blood and urine. However, the detection of TDI and MDI or their hydrolysis products cannot predict the kind of health effects that might develop from that exposure. Because TDI and MID and their hydrolysis products leave the body fairly rapidly (within days), the tests need to be conducted soon after exposure. For more information on the hydrolysis products of TDI and MDI and on tests to detect these substances in the body, see Chapters 3 and 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 as "not-to-exceed" levels; that is, levels of a toxic substance in air, water, soil, or food that do not exceed a critical value usually based on levels that affect animals; levels are then adjusted to help protect humans. Sometimes these not-to-exceed levels differ among federal organizations. Different organizations use different exposure times (an 8-hour workday or a 24-hour day), different animal studies, or emphasize some factors over others, depending on their mission.

Recommendations and regulations are also updated periodically as more information becomes available. For the most current information, check with the federal agency or organization that issued the regulation or recommendation.

OSHA has set a legal ceiling limit of 0.02 parts per million (ppm) for TDI and MDI in air; these are "not-to-exceed" levels. NIOSH has set a recommended limit of 0.005 ppm for monomeric 4,4'-MDI in air for workers exposed 10 hours/day during a 40 hour/day workweek. The EPA has not recommended any drinking water guidelines for TDI or MDI.

Where can I get more information?

If you have questions or concerns, please contact your community or state health or environmental quality department or:

For more information, contact:
Agency for Toxic Substances and Disease Registry
Division of Toxicology and Human Health Sciences
1600 Clifton Road NE, Mailstop F-57
Atlanta, GA 30333
Phone: 1-800-CDC-INFO · 888-232-6348 (TTY)
Email: Contact CDC-INFO

ATSDR can also tell you the location of occupational and environmental health clinics. These clinics specialize in recognizing, evaluating, and treating illnesses resulting from exposure to hazardous substances.

Contact Us:
  • Agency for Toxic Substances and Disease Registry
    4770 Buford Hwy NE
    Atlanta, GA 30341
  • 800-CDC-INFO
    (800-232-4636)
    TTY: (888) 232-6348
  • New Hours of Operation
    8am-8pm ET/Monday-Friday
    Closed Holidays
    Contact CDC-INFO
USA.gov: The U.S. Government's Official Web PortalDepartment of Health and Human Services
Agency for Toxic Substances and Disease Registry, 4770 Buford Hwy NE, Atlanta, GA 30341
Contact CDC: 800-232-4636 / TTY: 888-232-6348

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