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PUBLIC HEALTH STATEMENT 

CHLORODIBENZOFURANS (CDFs) 

Division of Toxicology May 1994 

This Public Health Statement is the summary 

chapter from the Toxicological Profile for 

Chlorinated Dibenzofurans (CDFs). 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 Statement was prepared to give you 

information about chlorinated dibenzofurans 

(CDFs) and to emphasize the human health effects 

that may result from exposure to them. The 

Environmental Protection Agency (EPA) has 

identified 1,350 hazardous waste sites as the most 

serious in the nation. These sites comprise the 

"National Priorities List" (NPL). Those sites which 

are targeted for long-term federal cleanup activities. 

CDFs have been found in at least 57 of the sites on 

the NPL. However, the number of NPL sites 

evaluated for CDFs is not known. As EPA evaluates 

more sites, the number of sites at which CDFs is 

found may increase. This information is important 

because exposure to CDFs may cause harmful 

health effects and because these sites are potential 

or actual sources of human exposure to CDFs. 

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. You may be exposed by breathing, 

eating, or drinking substances containing the 

substance or by skin contact with it. 

If you are exposed to substances such as CDFs, 

many factors will determine whether harmful health 

effects will occur and what the type and severity of 

those health effects will be. These factors include 

the dose (how much), the duration (how long), the 

route or pathway by which you are exposed 

(breathing, eating, drinking, or skin contact), the 

other chemicals to which you are exposed, and your 

individual characteristics such as age, gender, 

nutritional status, family traits, life-style, and state 

of health. 

1.1 WHAT ARE CDFs? 

CDFs are a family of chemicals known as 

chlorinated dibenzofurans. These chemicals contain 

one to eight chlorine atoms attached to the carbon 

atoms of the parent chemical, dibenzofuran. The 

CDF family contains 135 individual compounds 

(known as congeners) with varying harmful health 

and environmental effects. Of these 135 

compounds, those that contain chlorine atoms at the 

2,3,7,8-positions of the parent dibenzofuran 

molecule are especially harmful. Other than for 

laboratory use of small amounts of CDFs for 

research and development purposes, these 

chemicals are not deliberately produced by industry. 

Most CDFs are produced in very small amounts as 

unwanted impurities of certain products and 

processes utilizing chlorinated compounds. Only a 

few of the 135 CDF compounds have been 

produced in large enough quantities so that their 

properties, such as color, smell, taste, and toxicity 

could be studied. The few CDF compounds that 

have been produced in those quantities are colorless 

solids. They do not dissolve in water very easily. 

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 

CHLORODIBENZOFURANS (CDFs) 

Division of Toxicology May 1994 

There is no known use for these chemicals. CDFs 

are often found in association with dibenzo-pdioxins (CDDs), which cause similar toxic effects. 

1.2 WHAT HAPPENS TO CDFs WHEN THEY 

ENTER THE ENVIRONMENT? 

Small amounts of CDFs can enter the environment 

from a number of sources. Accidental fires or 

breakdowns involving capacitors, transformers, and 

other electrical equipment (e.g., fluorescent light 

fixtures) that contain polychlorinated biphenyls 

(PCBs) are known to release high levels of CDFs 

formed by thermal degradation. A fire involving a 

transformer containing PCBs contaminated the 

State Office Building in Binghamton, New York, 

with CDFs. Accidents of a different kind involving 

heated PCBs occurred in Japan (Yusho incident) 

and Taiwan (Yu-Cheng incident). These incidents 

involved exposure to CDFs-contaminated PCBs that 

were used as a heat exchanger fluid for processing 

rice oil and which accidentally leaked into the oil. 

CDFs are also produced as unwanted compounds 

during the manufacture of several chlorinated 

chemicals and consumer products, such as wood 

treatment chemicals, some metals, and paper 

products. When the waste water, sludge, or solids 

from these processes are released into waterways or 

soil in dumpsites, they become contaminated with 

CDFs. CDFs also enter into the environment from 

burning municipal and industrial waste in 

incinerators. The exhaust from cars that use leaded 

gasoline, which contains chlorine, releases small 

amounts of CDFs in the environment. Small 

amounts of CDFs may also enter into the 

environment from burning of coal, wood, or oil for 

home heating and production of electricity. Many of 

these chemicals or processes that produce CDFs in 

the environment are either being slowly phased out 

or strictly controlled. 

CDFs in air are present mostly as solid particles and 

to a much lesser extent as vapor. Some of the CDFs 

present in air return to the land and water by 

settling, snow, and rainwater. An amount of CDFs 

in the vapor phase is destroyed by reacting with 

certain chemical agents (called hydroxyl radicals) 

naturally present in the atmosphere. CDFs may 

remain in air for an average of more than 10 days 

depending on the CDF compound. Once in the air, 

CDFs can be carried long distances. They have been 

found in air and waters and at the bottom of lakes 

and rivers in areas far away from where they were 

released into the environment. CDFs tend to stick to 

suspended particles and settled particles in lakes 

and rivers and can remain at the bottom of lakes and 

rivers for several years. Sediment acts as a medium 

where CDFs that are present in air or water 

eventually settle. CDFs can build up in fish, and the 

amount of CDFs in fish can be tens of thousands 

times higher than the levels in water. The CDFs in 

water can get into birds or other animals and 

humans that eat fish containing CDFs. CDFs bind 

strongly to soil and are not likely to move from the 

surface soil into groundwater. In some instances, 

CDFs from some waste landfills may reach 

underground water. CDFs are more likely to move 

from soil to water or other soils by soil erosion and 

flooding. The breakdown or loss of CDFs in soil 

occurs over years, so CDFs remain in soil for years. 

Most CDFs found in plants are probably deposited 

by air. Cattle that eat plants on which CDFs have 

been deposited will build up some of the CDFs in 

their bodies. Some of the CDFs will enter the milk 

and meat of cattle. 

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 

CHLORODIBENZOFURANS (CDFs) 

Division of Toxicology May 1994 

1.3 HOW MIGHT I BE EXPOSED TO CDFs? 

CDFs are found at very low levels in the 

environment of industrial countries and at even 

lower levels in nonindustrial countries. People are 

exposed to very small levels of CDFs by breathing 

air, drinking water, and eating food, but most 

human exposure comes from food containing CDFs. 

The levels of CDFs in air are usually higher in city 

and suburb areas than in rural areas. The 

concentration of CDFs in city and suburb areas 

ranges from less than one femtogram (fg) (one 

quadrillionth of a gram, that is 

1/1000,000,000,000,000th of a gram) to a few 

picograms (pg) in a cubic meter (m3) of air. The 

levels in rural air are usually so low that 

measurements are not possible. The levels of CDFs 

in most drinking waters are also below the level that 

can be measured. CDFs were found in drinking 

water of one of the 20 water supplies in New York 

State at a concentration of 3.4 parts of CDF in a 

quadrillion part of water. CDFs are not found in 

soils that have not been polluted. CDFs have been 

detected in the stack emissions and ash from certain 

industries and processes that are sources of these 

compounds in air at levels that are thousands of 

times higher than the levels in the air that we 

usually breathe. Once emitted in the air from stacks, 

CDFs are dispersed by the cleaner air and the level 

of CDFs drops substantially. Similarly, the levels of 

CDFs in waste waters from certain industries and in 

soil at dumpsites can be thousands to millions times 

higher than the levels found in clean water and soil. 

Some products you use, such as paper towels, 

coffee filters, tampons, and milk cartons, can 

contain extremely low levels of CDFs. The intake 

of CDFs from these sources is very low. Since 

CDFs tend to concentrate in the fat, and milk 

contains fat, mother's milk can be a source of CDFs 

for babies. But considering the small amounts of 

CDFs in milk and the other beneficial effects of 

human milk to a baby and the length of time a baby 

uses mother's milk, scientists believe that mother's 

milk, on balance, is still beneficial to babies. Cow's 

milk and formula usually contain lower amounts of 

CDFs than human milk. Children playing in 

dumpsites may come in contact with CDFs through 

their skin and by eating dirt. It has been estimated 

that over 90% of the total daily intake of CDFs (on 

the order of a few pg per day) for the general adult 

population occurs from eating food containing 

them. The rest comes from air, consumer products, 

and drinking water. Meat and meat products, fish 

and fish products, and milk and milk products 

contribute equally to intake of CDFs from food, 

while intake from vegetable products contributes 

much less. Eating large amounts of fatty fish from 

water containing CDFs may increase your daily 

intake of CDFs from food. 

People in certain occupations may be exposed to 

higher levels of CDFs than the general population. 

Exposure in the workplace occurs mostly by 

breathing air and touching substances that contain 

CDFs. Workers involved with cleaning up after 

transformer fires, workers in the pulp and papermill 

industry, workers in municipal incinerators, and 

workers in sawmills may be exposed to higher 

levels of CDFs than the general population. Contact 

with CDFs at hazardous waste sites can happen 

when workers breathe air or touch soil containing 

CDFs. 

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 

CHLORODIBENZOFURANS (CDFs) 

Division of Toxicology May 1994 

1.4 HOW CAN CDFs ENTER AND LEAVE MY 

BODY? 

If you breathe air that contains CDFs, they can enter 

your body through your lungs and pass into the 

bloodstream, but we do not know how fast this 

occurs or how much of the CDFs will pass into the 

bloodstream. If you swallow food, water, or soil 

contaminated with CDFs, most of the CDFs will 

probably enter your body and pass from the 

stomach into the bloodstream, but we do not know 

how fast this occurs. If you touch soil containing 

CDFs, which might occur at a hazardous waste site, 

some of the CDFs will pass through your skin into 

the bloodstream, but we do not know how fast this 

occurs. Most commonly, CDFs enter your body 

when you eat food contaminated with CDFs, in 

particular fish and fish products, meat and meat 

products, and milk and milk products containing 

CDFs. Exposure from drinking water is less than 

that from food. For people living around waste sites 

and for people who work with or around other 

chemicals that produce CDFs when heated, skin 

contact with contaminated soil or breathing CDF 

vapors are the most likely ways CDFs will enter the 

body. Once CDFs are in your body, some may 

change into breakdown products called metabolites. 

We do not know whether these metabolites are 

harmful. Some metabolites and some unchanged 

CDFs may leave your body mainly in the feces and 

in very small amounts in the urine in a few days, but 

other unchanged CDFs may stay in your body and 

be stored for years in your body fat. CDFs build up 

in milk fat and can enter the bodies of infants 

through breast feeding. CDFs can also enter the 

bodies of unborn babies through the placenta. 

1.5 HOW CAN CDFs AFFECT MY HEALTH? 

Much of what we know about the health effects of 

CDFs comes from studies of accidental poisonings 

in Japan and Taiwan in the 1960s and 1970s, where 

many people ate food cooked in contaminated rice 

oil for several months. In both of these incidents, 

the rice oil was contaminated with PCBs that 

contained CDFs. The amounts of CDFs that these 

people accidentally ate were much higher than those 

normally found in your diet. Skin and eye 

irritations, especially severe acne, darkened skin 

color, and swollen eyelids with discharge, were the 

most obvious health effects of the CDF poisoning. 

However, these effects did not develop in some 

people until weeks or months after exposure and 

might not have occurred at all in other people. 

CDFs also caused vomiting and diarrhea, anemia (a 

blood disease), more frequent lung infections, 

numbness and other effects on the nervous system, 

and mild changes in the liver, but there were no 

permanent liver changes or definite liver damage in 

the people who accidentally ate the CDFs. The 

children born to the poisoned mothers also had acne 

and other skin irritations. Young children of these 

mothers also had some trouble learning, but we do 

not know if this effect was permanent. It is 

unknown whether these health effects were caused 

by CDFs alone or CDFs and PCBs in combination. 

We know nothing about the health of people who 

are exposed to low levels of CDFs by breathing, 

skin contact, or for long periods of time. 

Many of the same health effects that occurred in the 

people accidentally exposed also occurred in 

experimental or laboratory animals that ate CDFs. 

Animals fed CDFs also had severe body weight 

loss, and their stomachs, livers, kidneys, and 

immune systems were seriously injured. Some fed 

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 

CHLORODIBENZOFURANS (CDFs) 

Division of Toxicology May 1994 

high doses died. CDFs also caused birth defects and 

testicular damage in animals, but we do not know if 

CDFs make males or females infertile. Most of the 

effects in animals occurred after they ate large 

amounts of CDFs for short periods or smaller 

amounts of CDFs for several weeks or months. 

Nothing is known about the possible health effects 

in animals from eating CDFs over a lifetime. Only 

one study tested animals exposed to CDFs by skin 

contact. The health effects were similar to those that 

occurred in animals that ate CDFs. We do not know 

the possible health effects in animals of breathing in 

CDFs. The amounts of CDFs that caused health 

effects in animals were far greater than the levels 

normally found in the environment. 

We do not definitely know if CDFs caused cancer 

in any of the accidentally poisoned people. There 

are no cancer studies in animals that ate or breathed 

CDFs. One study found that CDFs alone did not 

cause skin cancer in animals when they were 

applied to the skin for several months. However, 

when researchers applied another carcinogen to the 

animals' skin before applying CDFs, skin cancer 

developed. Although skin cancer developed in these 

animals, the Department of Health and Human 

Services, the International Agency for Research on 

Cancer, and the Environmental Protection Agency 

have not classified the carcinogenicity of CDFs. 

1.6 IS THERE A MEDICAL TEST TO 

DETERMINE WHETHER I HAVE BEEN 

EXPOSED TO CDFs? 

There are tests to find out if CDFs are in blood, 

body fat, and breast milk; however, these are not 

routinely done. High levels of CDFs in these body 

fluids and in fat will show that you have been 

exposed to high levels of CDFs. However, these 

measurements cannot show the exact amount or 

type of CDFs you were exposed to or for how long 

you were exposed. These tests do not predict 

whether you will experience harmful health effects. 

Blood tests can detect recent exposures to CDFs, 

but are not always the easiest, safest, or best 

method. Fat biopsies (small amounts of fat taken 

with a needle and syringe) may be less traumatic to 

a small child or very sick person and more 

diagnostic than blood tests. Nearly everyone in the 

United States and other industrial countries has 

been exposed to CDFs because they are found 

throughout the environment, and nearly all people 

are likely to have some CDFs in their blood, fat, and 

breast milk. 

1.7 WHAT RECOMMENDATIONS HAS THE 

FEDERAL GOVERNMENT MADE TO 

PROTECT HUMAN HEALTH? 

There are no federal guidelines or recommendations 

for protecting human health from exposure to 

CDFs. CDFs are, however, listed as hazardous 

waste components by the EPA. 

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 

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 

CHLORODIBENZOFURANS (CDFs) 

Division of Toxicology May 1994 

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). 1994.. Toxicological profile for 

chlorinated dibenzorufans (CDFs). 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