Polychlorinated Biphenyls (PCBs)

Polychlorinated Biphenyls (PCBs)

Polychlorinated biphenyls (PCBs) are a group of human-made chemicals that were commonly used in building materials and electrical equipment before 1980. Caulk, paint, glues, plastics, fluorescent lighting ballasts, transformers and capacitors are examples of products that may contain PCBs. The U.S. Environmental Protection Agency (EPA) banned manufacturing and certain uses of PCBs in 1979.

In recent years, PCBs have been found in schools in Vermont, New York City, Massachusetts and Connecticut. Lighting ballasts in older fluorescent lighting fixtures and caulk are the common sources of PCBs in school buildings. 

What are the health effects of PCBs?

PCBs can cause serious health problems. The potential for health effects from PCBs, as with other chemicals, depends on how much, how often, and how long someone is exposed to them.

In order to understand the potential health effects of chemicals on humans, they are first tested on animals. In animal studies, PCBs have been shown to have effects on the immune system, reproductive system, nervous system and endocrine (hormone) system. This means that PCBs could also have the same effects on these systems in humans. PCBs have also been shown to cause cancer in animals.

There have been a number of human studies on the health effects of PCBs. These studies plus the animal studies have shown that exposure to PCBs can affect the immune system, reproductive system, nervous system and endocrine system of humans. In addition, PCBs are classified as probable human carcinogens. This means that exposure to PCBs can likely cause cancer in humans.

Additionally, the different health effects of PCBs may be interconnected. This means that if one system of the body is affected by PCBs, it may have significant effects on the other systems of the body, which can lead to many serious health problems.


The EPA has studied the health effects of PCBs and concluded that PCBs are probable human carcinogens. This means that exposure to PCBs can likely cause cancer in humans.

Immune System

The immune system is critical for fighting infections. Diseases of the immune system can have very serious effects on human health. Exposure to PCBs can suppress the immune system, which can lead to other health problems.

Nervous System

Proper development of the nervous system is critical for early learning and can have significant effects on the health of people throughout their lives. Exposure to PCBs can lead to significant losses in neurological development, including visual recognition, short-term memory and learning.

Endocrine System

PCBs can affect thyroid hormone levels in humans. Thyroid hormone levels are critical for normal growth and development, and can have significant health effects if levels are altered.

Reproductive System

Exposure to PCBs can lead to decreased birth weight and can cause babies to be born too early.

Learn more about the health effects of PCBs from the EPA

How could I come in contact with PCBs?

PCBs continue to be widespread in our soil, air, water and food because of past use and disposal. PCBs break down very slowly and can remain in the environment for a long time. Most people have low levels of PCBs in their bodies because of the widespread presence of PCBs in the environment. In general, however, PCB levels in people have been going down since they were banned.

Food is the main source of exposure to PCBs for most people. PCBs are found in meat, dairy products and fish (especially fish caught in polluted waters).

In schools, the common sources of PCBs are old lighting ballasts and caulk. As the ballasts age, the PCB oil can leak onto nearby surfaces or produce vapors in the air. As caulk containing PCBs deteriorates, PCBs may be released into the dust or air. Students and staff may be exposed to PCBs by:

  • Breathing in dust or vapors that contain PCBs
  • Getting dust containing PCBs on their hands and then swallowing it while eating or drinking
  • Skin contact with materials that contain PCBs
What are the Vermont school action levels for PCBs in indoor air?

The school action levels are different depending on the lowest grade of students in the school. They are:

  • 30 ng/m3 for pre-K
  • 60 ng/m3 for kindergarten to 6th grade
  • 100 ng/m3 for 7th grade to 12th grade

ng/m3 = nanograms per cubic meter

PCBs in Indoor Air of Schools, Development of School Action Levels

Why does Vermont have a screening level and different action levels for PCBs in the indoor air of schools?

Vermont’s screening level for PCBs in the indoor air of schools is 15 ng/m3. This level is close to the background levels of PCBs that we would expect to find in indoor air. When indoor air levels of PCBs are only slightly higher than the screening level it may be difficult to find and get rid of sources of PCBs. This is because sources of PCBs inside schools may constantly absorb and emit PCBs back into the air.

The State recognized that acceptable school action levels need to protect the health of the students and staff while considering how common PCBs are in our environment and the challenges of removing them. The fact that the school action levels are higher than the screening level makes it more likely that the sources of PCBs will be found and levels in indoor air will be lowered.

PCB Testing in Schools

In 2021, a new Vermont law passed (Act 74) requiring all schools built or renovated before 1980 to test their indoor air for PCBs by July 2024.

Learn more about PCB testing in schools

More Information

Questions? Please email SOV.PCBSampling@vermont.gov.