ATSDR TOXZINE

PBBs

Polybrominated Biphenyls

CONTENTS

1 . . . . . . . . . . . . . . . . . . . . . . . . . . PBBs Overview

2 . . . . . . . . . . . . . . . PBBs and the Environment

4 . . . . . . . . . . . . . . . . . . . . . . . . Exposure to PBBs

6 . . . . . . . . . . . . . . . . . . . . . . . PBBs and the Body

8 . . . . . . . . . . . . . . . Health Effects of Exposure

10 . . . . . . . . . . . . . . . . . . . . . . . PBBs and Children

12 . . . . . . . . . . . . . . . Reducing Risk of Exposure

13 . . . . . . . . . . . . . . . . . . . . . . . . . Exposure Testing

14 . . . . . . . . Governmental Recommendations

15 . . . . . . . . . . . . . . . . . . . Additional Information

1

POLYBROMINATED 

BIPHENYLS (PBBs) OVERVIEW 

Polybrominated biphenyls (PBBs) are chemicals that were 

added to plastics used in a variety of consumer products to 

make them difficult to burn. 

These products include items such as computer monitors, televisions, textiles, 

and plastic foams. Because PBBs were mixed into plastics rather than bound to 

them, they were able to leave the plastic and find their way into the environment.

Commercial production of PBBs began in the 1970s. Manufacture of PBBs was 

discontinued in the United States in 1976. Concern regarding PBBs is mainly related 

to exposures resulting from an agriculture contamination episode that occurred in 

Michigan over a 10-month period during 1973–1974.

 There are no known natural sources of PBBs in the environment. PBBs are solids 

and are colorless to off-white. PBBs enter the environment as mixtures containing 

a variety of individual brominated biphenyl (for PBBs) components, known as 

congeners. Some commercial PBB mixtures are known in the United States under 

the industrial trade name, FireMaster®. However, other flame retardant chemicals 

also may be identified by this name. PBBs are no longer used in North America 

because the agriculture contamination episode that occurred in Michigan in 1973–

1974 led to the cessation of its production. ◆

There are 

no known 

natural sources 

of PBBs in the 

environment
2

PBBs AND THE 

ENVIRONMENT 

In the past, PBBs entered the air, water, and soil during their 

manufacture and use.

In addition, animal feed was accidentally mixed with 500– 1,000 pounds of PBBs 

in lower Michigan in 1973. This contamination of the food chain affected millions 

of farm animals and humans living in Michigan at this time. PBBs entered the 

environment during the disposal of contaminated animal feed and animal products 

during the agriculture contamination episode. PBBs also entered the environment 

from PBB-containing wastes that manufacturers disposed of in waste sites. Small 

quantities of PBBs also entered the environment from accidental spills during 

transport. PBBs are no longer manufactured in North America, but very small 
3

amounts of PBBs may be released into the environment from poorly maintained 

hazardous waste sites and improper incineration of plastics that contain PBBs. ◆
4

EXPOSURE TO 

PBBs

PBBs are no longer produced or used in the United States.

Thus, the general population exposure to PBBs will only be from past releases. For 

people living in the lower peninsula of Michigan, especially near PBB contaminated 

areas, exposure to PBBs may still be occurring today. However, environmental levels 

have decreased since the 1970s and current exposure, if any, will be at low levels.

For other regions of the United States, the levels of exposure will either be very low 

or none.

Measured data in air, water, soil, and food, as well as body burden data (blood, urine, 

breast milk, and body fat), indicate that most people within the state of Michigan 

who were exposed to PBBs received very low levels of PBBs. The levels from exposure 

were slightly higher for people living in the lower peninsula of Michigan and highest 

among people living on contaminated dairy farms. Consumption of contaminated 

meat and dairy products caused the higher levels of PBBs in the body. Monitoring 

Exposure 

in workplaces 

is no longer likely 

because PBBs 

are no longer 

manufactured.
5

of the workplace environment, as well as the blood, urine, and body fat of workers 

indicated that those in PBB industries were exposed to higher levels of PBBs than the 

general population. These workers were exposed to PBBs by breathing contaminated 

workplace air and by skin contact with PBBs. Occupational exposure also could have 

occurred from the incineration of materials containing PBBs. Exposure in workplaces 

is no longer likely because PBBs are no longer manufactured. People who live near 

hazardous waste sites that contain PBBs may be exposed primarily by breathing air 

that contains PBBs. ◆
6

PBBs AND 

THE BODY 

If you breathe air that contains PBBs, or swallow food, water, or 

soil contaminated with PBBs, they can enter your body through 

your lungs and stomach and pass into the bloodstream. 

 We don’t know how much of the PBBs will pass into the blood from the lungs; 

although most will probably pass into the blood from the stomach and intestines.

If you touch soil containing PBBs, it is highly unlikely that PBBs would pass through 

your skin into the bloodstream. It is not known how fast PBBs enter the blood from 

the lungs or stomach. There are no known current sources of PBBs because they 

are no longer produced and used in North America. They are rarely found in air and 

drinking water away from production plants and contaminated sites. Once PBBs are 

in your body, they can partially change into breakdown products called metabolites.

Some metabolites and unchanged PBBs could leave your body, mainly in the feces 
7

and in very small amounts in the urine, within a few days. Other unchanged PBBs 

might stay in your body for many years. PBBs are stored mainly in your body fat, tend 

to concentrate in breast milk fat, and can enter the bodies of children through breast 

feeding. PBBs also can enter the bodies of unborn babies through the placenta. ◆

There are no known 

current sources 

of PBBs because they are 

no longer produced 

and used in 

North America.
8

HEALTH EFFECTS

OF EXPOSURE 

Much of what is known about the health effects of PBBs in 

people comes from studies of ingestion in Michigan in the earlyto-mid 1970s, where feed for farm animals was accidentally 

contaminated with a fire retardant containing PBBs.

People were exposed to PBBs for several months when they ate meat, milk, and eggs 

from the contaminated animals. After news of the contamination episode became 

widespread, many Michigan residents complained of various health problems, 

including nausea, abdominal pain, loss of appetite, joint pain, fatigue, 

and weakness. However, it could not be clearly established that any of 

the problems were caused by eating the food contaminated with PBBs.

PBBs also did not cause any definite changes in the livers or immune 

systems of the Michigan residents. However, some people who ate 

the contaminated food developed skin disorders, such as acne and 

hair loss. It is likely that PBBs caused the skin problems because other 

chemicals similar to PBBs also cause these effects. Workers who were 

exposed to PBBs for a few days to months by breathing and skin 

contact also developed acne, although not all persons exposed to 

PBBs developed acne. Very little is known about the health of people 

who are exposed to low levels of PBBs for long periods by eating, 

breathing, or skin contact.

 Laboratory animals fed PBBs had body weight loss, skin disorders, and nervous system 

effects, and their livers, kidneys, thyroid glands, and immune systems were seriously 

injured. Some animals fed high amounts died. PBBs also caused birth defects in animals, 

but it is not known for sure whether PBBs make males or females infertile. Most of the 

effects in animals occurred after they ate large amounts of PBBs for short periods or 

smaller amounts for several weeks or months. Body weight loss and effects on the livers, 

kidneys, and thyroid glands were observed. A few studies tested animals exposed to 

PBBs by skin contact. These animals had injuries to the liver and skin. Only one study 

tested animals exposed to PBBs by breathing, and no health effects were observed.

The International 

Agency for Research 

on Cancer (IARC) 

has determined that 

PBBs are probably 

carcinogenic 

to humans.
9

We do not know if PBBs caused or will cause cancer in people who ate food 

contaminated with PBBs. Rats developed cancer in their livers after eating a large 

amount of a PBB mixture only once. The babies of exposed rats developed cancer 

in their livers after eating a large amount of the same PBB mixture only once. Liver 

cancer also developed in rats and mice that ate smaller amounts of the PBB mixture for 

several months. Mice that had skin contact with a small amount of a PBB mixture for 

several months did not develop skin cancer. There are no cancer studies in animals that 

breathed PBBs. Because animals fed PBBs did develop cancer, the National Toxicology 

Program (NTP) of the Department of Health and Human Services (DHHS) determined 

that PBBs may reasonably be anticipated to be carcinogens. Similarly, the International 

Agency for Research on Cancer (IARC) has determined that PBBs are probably 

carcinogenic to humans. The EPA has not classified the carcinogenicity of PBBs.

 We do not know whether the effects found in animals exposed to PBBs would 

also occur in people exposed in the same way. The amounts of PBBs that caused 

health effects in animals are much greater than levels of PBBs normally found in the 

environment. Long-term exposure to these chemicals has a greater potential to cause 

health effects than does short-term exposure to low levels because they tend to build 

up in your body over many years. ◆
10

PBBs AND

CHILDREN 

Children are exposed to PBBs in generally the same way as 

are adults, mainly by eating contaminated food. 

Because of their smaller weight, children’s intake of PBBs per kilogram (or pound) of 

body weight may be greater than that of adults. The most likely way that infants will 

be exposed is from breast milk that contains PBBs, although fetuses in the womb are 

also exposed. Children who live near hazardous waste sites might accidentally eat 

some PBBs by putting dirty hands or other soil/dirt covered objects in their mouths, 

by eating without washing their hands, or similar behavior. Some children also eat 

dirt on purpose. It is not possible that children could be exposed to PBBs following 

transport of the chemical on clothing from the parent’s workplace to the home 

because PBBs are no longer being produced or used. 

Some information on health effects of PBBs in children is available from studies of 

the Michigan contamination episode. Symptoms of ill health were not associated 

with increased exposure to PBBs, and general neurological examinations did not 

show any abnormalities. More detailed studies of physical and neuropsychological 

development showed no effects that were clearly related to PBBs among Michigan 
11

children exposed during the episode. Changes in nerve and brain function have 

been seen in animals that were exposed to PBBs in the womb and by nursing. Animal 

studies also found that exposure to PBBs during pregnancy or lactation caused 

changes in thyroid hormone levels in the newborn animals and, at high doses, 

increases in prenatal death and structural birth defects.

As indicated above, children can be exposed to PBBs before birth and from breast 

milk. PBBs are stored in the mother’s body and can be released during pregnancy, 

cross the placenta, and enter fetal tissues. Because PBBs dissolve readily in fat, they 

can accumulate in breast milk fat and be transferred to babies and young children.

PBBs have been found in breast milk; however, in most cases, the benefits of breastfeeding outweigh any risks from exposure in mother’s milk. You should consult your 

health care provider if you have any concerns about PBBs and breast feeding. Because 

the nervous system and thyroid are still developing in the fetus and child, the effects 

of PBBs on these target systems might be more profound from exposure before and 

soon after birth. That could mean fetuses and children are more susceptible to PBBs 

than are adults. ◆
12

If your doctor finds that you have been exposed to significant 

amounts of PPBs, ask whether your children might also be 

exposed. Your doctor might need to ask your state health 

department to investigate.

Because PBBs are no longer produced or used, the risk of exposure to these 

compounds is limited. You and your children could be exposed to PBBs by eating fish 

or wildlife caught from contaminated locations. Children who live near hazardous 

waste sites should be discouraged from playing in the dirt near these sites because 

they could still contain PBBs. Children should also be discouraged from eating the 

dirt, and careful hand-washing practices should be followed. ◆

REDUCING RISK 

OF EXPOSURE 
13

EXPOSURE 

TESTING 

Special tests can determine whether PBBs are in the blood, 

body fat, and breast milk.

These are not regular or routine clinical tests, but could be ordered by a doctor to 

detect PBBs in people exposed to them in the environment and at work. If your PBB 

levels are higher than the normal levels, this will show that you have been exposed 

to high levels of the chemicals. However, these measurements cannot determine the 

exact amount or type of PBBs that you have been exposed to, or how long you have 

been exposed. Although these tests can indicate whether you have been exposed to 

PBBs to a greater extent than the general population, they do not predict whether 

you will be harmed. Blood tests are the easiest, safest, and probably the best method 

for detecting recent or past exposures to large amounts of PBBs. Results of such tests 

should be reviewed and carefully interpreted by physicians with a background in 

environmental and occupational medicine. ◆
14

GOVERNMENTAL 

RECOMMENDATIONS 

Recommendations and regulations are updated periodically 

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 PBBs include the following: 

At present, there are no federal guidelines or recommendations for 

protecting human health from exposure to PBBs.
15

ADDITIONAL INFORMATION 

If you have any more questions or concerns, please contact 

your community or state health or environmental quality 

department or contact ATSDR at the address and phone 

number below. 

Agency for Toxic Substances and Disease Registry

Division of Toxicology and Human Health Sciences

1600 Clifton Road NE, Mailstop F-57

Atlanta, GA 30329-4027

Toll-free information and technical assistance:

1-800-CDCINFO (1-800-232-4636)
something like: A publication from the Centers for 

Disease Control and Prevention

ATSDR TOXZINE A publication of CDC/ATSDR

CS252396-A