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PUBLIC HEALTH STATEMENT 

Hexamethylene Diisocyanate (HDI) 

CAS#: 822-06-0 

Division of Toxicology August 1998 

This Public Health Statement is the summary 

chapter from the Toxicological Profile for 

hexamethylene diisocyanate. It is one in a series of 

Public Health Statements about hazardous 

substances and their health effects. A shorter 

version, the ToxFAQsTM is also available. This 

information is important because this substance may 

harm you. The effects of exposure to any hazardous 

substance depend on the dose, the duration, how 

you are exposed, personal traits and habits, and 

whether other chemicals are present. For more 

information, call the ATSDR Information Center at 

1-888-422-8737. 

This public health statement tells you about 

hexamethylene diisocyanate (HDI) 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. 

Hexamethylene diisocyanate 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 HDI 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 hexamethylene diisocyanate, 

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 HDI? 

HDI is the common name for hexamethylene 

diisocyanate. It is also known as 1,6­

hexamethylene diisocyanate, 1,6­

diisocyanatohexane, Mondur HX, and Desmodur H. 

It is a pale yellow liquid with a strong odor. HDI is 

found in hardening agents for automobile paints. 

1.2 WHAT HAPPENS TO HDI WHEN IT 

ENTERS THE ENVIRONMENT? 

HDI is most often found in air near locations where 

spray paints that contain it as a hardening agent are 

used. HDI in the air can enter the soil and water. 

HDI can also enter the soil if products containing it 

are dumped directly onto the soil. HDI can enter 

the water supply by washing out of soil that 

contains it or if products with HDI are dumped 

directly into water. Once it is in soil or water, HDI 

does not easily evaporate, so general air pollution is 

not expected. HDI breaks down very quickly in 

water or sunlight, so it probably will not build up in 

the environment. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

Hexamethylene Diisocyanate (HDI) 

CAS#: 822-06-0 

Division of Toxicology August 1998 

1.3 HOW MIGHT I BE EXPOSED TO HDI? 

The most common products that contain HDI are 

called hardening agents and are used to spray-paint 

cars. The most common way a person can be 

exposed to HDI is by breathing air that contains it 

as a vapor or mist, like that made when spraypainting a car. Most of the people who are exposed 

to HDI work in the automotive painting industry or 

in areas where this is done. If you do this kind of 

work, you can be exposed to more HDI if you do 

not wear the right protective safety equipment such 

as a respirator or mask. If your safety equipment 

does not fit right or does not work properly when 

you are using products that contain HDI, you may 

be exposed to larger amounts. You can probably 

absorb some HDI through your skin. You could 

also accidentally swallow HDI if it is on your hands 

and you do not wash them before eating, drinking, 

or smoking. 

Unless you have been employed in the automobile 

refinishing or other business where painters 

manually mix two-component polyurethane paint 

systems, it is unlikely that you will be exposed to 

large amounts of HDI. 

1.4 HOW CAN HDI ENTER AND LEAVE MY 

BODY? 

The most common way HDI enters your body is by 

breathing air that has it in it. You can probably 

absorb some HDI through your skin, and you can 

also accidentally swallow HDI if it is on your hands 

and you do not wash them before eating, drinking, 

or smoking. Once inside your body, HDI breaks 

down very quickly and is quickly excreted in the 

urine. Some HDI can attach itself to protein in your 

blood, but we do not know how long it takes for this 

form of HDI to break down and be excreted. 

1.5 HOW CAN HDI AFFECT MY HEALTH? 

To protect the public from the harmful effects of 

toxic chemicals and to find ways to treat people 

who have been harmed, scientists use many tests. 

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

learn how the chemical is absorbed, used, and 

released by the body; for some chemicals, animal 

testing may be necessary. Animal testing may also 

be used to identify health effects such as cancer or 

birth defects. Without laboratory animals, scientists 

would lose a basic method to get information 

needed to make wise decisions to protect public 

health. Scientists have the responsibility to treat 

research animals with care and compassion. Laws 

today protect the welfare of research animals, and 

scientists must comply with strict animal care 

guidelines. 

How HDI affects your health depends on how much 

is in the air you breathe. Tests using laboratory 

animals showed that breathing in high 

concentrations of HDI can irritate the nose, eyes, 

and throat. High concentrations have also caused 

pneumonia, difficulty in breathing, and death in 

some animals. Swallowing high concentrations of 

HDI also killed laboratory animals. When placed 

on the skin of these animals, HDI caused redness, 

irritation, and irreversible skin damage. People 

would probably be affected in many of the same 

ways if they were exposed to large amounts of HDI 

in air. 

Many people who breathe in vapors from products 

with small amounts of HDI for many months or 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

Hexamethylene Diisocyanate (HDI) 

CAS#: 822-06-0 

Division of Toxicology August 1998 

many years may develop an allergic, asthma-like 

reaction. Symptoms usually develop very slowly 

over a long time (months or years), but they can 

also develop within a couple of weeks after first 

breathing in HDI. At low concentrations, sensitized 

workers develop a burning sensation and a feeling 

of tightness in the chest, a cough (with and without 

phlegm), fever, and chills. They have a hard time 

breathing during their work day when using a 

product containing HDI. These signs usually are 

not seen on weekends, during vacations, or any time 

the person is not using a product that contains HDI. 

These reactions usually begin again soon after the 

person returns to work and begins to use the product 

with HDI. 

Some studies in laboratory animals showed that, 

when breathed in over a long time, HDI did not 

produce cancer. No studies that show that HDI can 

cause cancer in people have been found. 

1.6 IS THERE A MEDICAL TEST TO 

DETERMINE WHETHER I HAVE BEEN 

EXPOSED TO HDI? 

Before you ask for special medical tests for HDI, 

you should talk with your doctor and tell him you 

work in a place that uses products that contain HDI. 

There are no good medical tests for finding out if 

you have been exposed to HDI. Some tests are 

available that measure the antibodies against HDI 

your body makes after you have been exposed to it. 

However, these blood tests are not very good 

because they can react with other substances that 

look like HDI in your blood. The test can show that 

you have been exposed to HDI when really you 

have not been exposed to it (false positives). Also, 

some people do not develop antibodies to HDI after 

they have been exposed. Another test looks for the 

breakdown products of HDI in the urine. This test is 

only good if you were exposed to HDI within the 

last 12–15 hours. It is not a good test to find out if 

you have been exposed to low amounts of HDI over 

many months or years. 

Unless you have been employed in the automobile 

refinishing or other business where painters 

manually mix two-component polyurethane paint 

systems, it is unlikely that you have been exposed to 

significant amounts of HDI. Your doctor can give 

you more information on medical tests that are 

available for determining if you have been exposed 

to HDI. 

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. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

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PUBLIC HEALTH STATEMENT 

Hexamethylene Diisocyanate (HDI) 

CAS#: 822-06-0 

Division of Toxicology August 1998 

Sometimes these not-to-exceed levels differ among 

federal organizations because of different exposure 

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

of different animal studies, or other factors. 

Recommendations and regulations are also 

periodically updated as more information becomes 

available. For the most current information, check 

with the federal agency or organization that 

provides it. Some regulations and 

recommendations for HDI include the following. 

The EPA proposes to list HDI as a hazardous 

substance that will be required to be reported under 

the Emergency Planning and Community Right-toKnow Act for 1986 and the Pollution Prevention 

Act of 1990. Currently, some owners and operators 

using HDI are required to report every year how 

much HDI they release into the environment. 

The NIOSH-recommended limit for occupational 

exposure is 0.035 milligrams of HDI per cubic 

meter of air (.035 mg/m3), which is the same as 5 

parts per billion (ppb). There is no established 

OSHA permissible exposure limit (PEL) for HDI at 

this time; however, a similar substance, toluene 

diisocyanate (TDI), has a PEL of 5 parts per billion 

(ppb). 

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 F-32 

Atlanta, GA 30333 

Information line and technical assistance: 

Phone: 888-422-8737 

FAX: (770)-488-4178 

ATSDR can also tell you the location of 

occupational and environmental health clinics. 

These clinics specialize in recognizing, evaluating, 

and treating illnesses resulting from exposure to 

hazardous substances. 

To order toxicological profiles, contact: 

National Technical Information Service 

5285 Port Royal Road 

Springfield, VA 22161 

Phone: 800-553-6847 or 703-605-6000 

Reference 

Agency for Toxic Substances and Disease Registry 

(ATSDR). 1998. Toxicological profile for 

hexamethylene diisocyanate (HDI). Atlanta, GA: 

U.S. Department of Health and Human Services, 

Public Health Service. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov