1.1 What are CDFs? |
1.2 What happens to CDFs when they enter
the environment? |
1.3 How might I be exposed to CDFs? |
1.4 How can CDFs enter and leave my body? |
1.5 How can CDFs affect my health? |
1.6 Is there a medical test to determine
whether I have been exposed to CDFs? |
1.7 What recommendations has the federal
government made to protect human health? |
1.8 Where can I get more information? |
References |
|
|
|
May 1994 |
Public Health Statement |
for |
Chlorodibenzofurans (CDFs) |
|
|
This Public Health Statement is the
summary chapter from the Toxicological
Profile for chlorodibenzofurans (CDFs). 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 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. There is
no known use for these chemicals. CDFs are often found
in association with dibenzo-p-dioxins (CDDs), which
cause similar toxic effects.
|
back to top |
|
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.
|
back to top |
|
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.
|
back to top |
|
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.
|
back to top |
|
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 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.
|
back to top |
|
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.
|
back to top |
|
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.
|
back to top |
|
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
|
back to top |
|
References |
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.
|
back to top |
|
|
|