Are there still PCBs in transformers?

What are PCBs and why were they used in transformers?

PCBs, or polychlorinated biphenyls, are synthetic organic chemicals that were widely used in electrical equipment like transformers and capacitors from the 1930s to the 1970s. PCBs have useful properties including chemical stability, low flammability, and high dielectric constants that made them effective coolants and insulating fluids.

Transformers, which convert electrical current from one voltage to another, can generate a lot of heat. Using PCBs as a coolant and dielectric fluid helped prevent transformer fires and short circuits. PCBs were used in many types of transformers including:

  • Pole-top transformers on utility poles
  • Pad-mounted transformers in green boxes
  • Large power transformers at electrical substations
  • Transformers in industrial and commercial buildings

It’s estimated that hundreds of thousands of transformers and capacitors containing PCBs were manufactured before PCB production ceased in the United States in 1979.

Why were PCBs banned?

Despite their useful properties, PCBs were banned due to environmental and health concerns:

  • PCBs are very persistent in the environment and do not readily break down
  • PCBs can bioaccumulate in the food chain
  • PCBs are toxic and are probable human carcinogens
  • PCBs have been linked to adverse health effects on the immune system, reproductive system, nervous system, and endocrine system

The United States banned the manufacture of PCBs in 1979 due to these risks. However, the EPA allowed some existing PCB-containing equipment like transformers to continue being used if it met certain conditions.

Are PCBs still used in new transformers?

No, PCBs have not been used as coolants or dielectric fluids in new transformers manufactured since 1979 in the United States. Alternative non-PCB fluids are now used instead, such as:

  • Mineral oil
  • Silicone fluids
  • Synthetic esters
  • Other less toxic alternatives

So any transformer that was newly manufactured after the PCB ban in 1979 should not contain PCBs. However, many older PCB transformers continued being used after the ban under EPA regulations.

What happened to old transformers that contained PCBs?

When the United States EPA banned PCB production in 1979, it required that PCB transformers be registered and labeled, and that the PCB fluid eventually be removed and disposed of properly. However, the EPA allowed many PCB transformers to continue operating under certain conditions:

  • The transformer is in good condition with no leaks
  • The transformer has PCB levels under 500 ppm
  • The transformer is inspected regularly
  • Combustible materials are kept away from the transformer
  • The transformer is registered with the EPA

Many utilities and building owners chose to continue using PCB transformers that met these conditions to avoid the high costs of immediate replacement. The EPA initially required that all PCB transformers be retired by 1984, but this deadline was extended.

According to EPA regulations, the final deadline for removing all PCB transformers was 1998. After that date, no PCB transformers should remain in use. When removed from service, the PCB fluid must be drained and disposed of properly, and the transformer carcass may also need to be disposed of as PCB waste.

Could any PCB transformers still be in use today?

Legally, there should no longer be any PCB transformers still in operation today in the United States, since the final deadline for removing them was 1998 according to the EPA. All registered PCB transformers should have been retired and properly disposed of by that date.

However, it’s possible that a small number of PCB transformers may have been overlooked and are still in use illegally if they were not properly registered or tracked. The EPA and utilities have made extensive efforts to identify and remove all known PCB transformers, but some could potentially remain off the radar.

Another possibility is that a small number of old transformers could have PCB contamination even if they did not originally contain PCB fluid. This could occur if a non-PCB transformer was serviced or repaired using PCB-contaminated equipment. The EPA does not generally require non-PCB transformers to be tested for PCBs.

Still, the vast majority of transformers still in use today should be PCB-free. Any remaining PCB transformers would be rare exceptions at this point. Most transformers today either were manufactured after the 1979 PCB ban, or have had PCBs removed to comply with EPA regulations.

How can you tell if a transformer contains PCBs?

If you are concerned that a transformer may contain PCBs, there are a few ways to check:

  1. Check for a PCB label: All known PCB transformers were required to be labeled as containing PCBs by the EPA. Look for a label that says something like “Caution: Contains PCBs” or specifies a PCB level such as “525 ppm PCB”. However, a missing or damaged label doesn’t necessarily mean a transformer is PCB-free.

  2. Check the transformer’s nameplate: The nameplate should specify what type of dielectric fluid the transformer contains. If it says a non-PCB fluid like “mineral oil”, it is unlikely to contain PCBs. If the nameplate is missing, damaged, or does not specify the fluid type, further investigation may be warranted.

  3. Check the installation date: If the transformer was newly manufactured and installed after July 1979, it should not contain PCBs. However, the installation date alone does not guarantee a transformer is PCB-free, since an older PCB-contaminated transformer could have been moved and reinstalled at a later date.

  4. Check utility or maintenance records: Utilities and building owners were required to register PCB transformers with the EPA. They may have records on the PCB status of the transformers based on testing or service history. However, these records may be incomplete, especially for very old transformers.

  5. Test the dielectric fluid: The most definitive way to determine if a transformer contains PCBs is to have a sample of the dielectric fluid extracted and tested by a qualified laboratory. Field test kits can also screen for PCB presence, but lab testing is needed to determine the PCB concentration and if regulatory limits are exceeded.

The table below summarizes ways to check if a transformer may contain PCBs:

Method Description
PCB Label Check for label stating PCB content
Nameplate Check if non-PCB dielectric fluid specified
Install Date Pre-1979 transformers more likely to have PCBs
Records Check utility/maintenance records on PCB status
Testing Sample fluid for laboratory PCB analysis

If testing confirms a transformer contains PCBs over 50 ppm, EPA regulations require it to be properly removed, disposed of, and replaced. Professional PCB services should handle sampling, removal, and disposal to avoid further contamination.

What are the risks of PCBs in transformers?

While PCBs are now strictly regulated, those that remain in older electrical equipment still pose environmental and health risks, including:

  • Risk of leaks and spills: As old transformers age and deteriorate, they are at increased risk of leaking PCB oil. A single transformer can contain hundreds of gallons of PCB oil. Leaks and spills can contaminate soil, groundwater, surface water, and the air.

  • Toxic exposures: People can be exposed to PCBs from transformer leaks via skin contact, inhalation, or ingesting contaminated soil or food. PCB exposures have been linked to increased cancer risk and damage to the immune, reproductive, nervous, and endocrine systems. PCBs can also affect childhood development.

  • Fires: Although PCBs are nonflammable, electrical failures in oil-filled transformers can cause ruptures and fires that release PCBs into the environment as toxic smoke and soot. Firefighters and other first responders can have high exposures in these incidents. PCBs can also form even more toxic dioxins and furans when burned.

  • Environmental contamination: PCBs released from leaking transformers can persist in the environment for a long time and contaminate soil, water, plants and animals. These persistent chemicals tend to bioaccumulate up the food chain. Improper disposal of old transformers can also cause PCB contamination.

Because of these risks, the EPA recommends that all PCB transformers be removed from service and their dielectric fluids properly disposed of to eliminate PCBs from the environment as much as possible. Electrical equipment that remains in use should be in good condition and regularly inspected for leaks or damage.


1. How do I know if my transformer has PCBs?

Check the transformer’s labels, nameplates, and maintenance records for any indication it may contain PCBs. If the transformer was made before 1979 and the dielectric fluid type is unknown, it should be assumed to be PCB-contaminated unless testing proves otherwise. Leaking, damaged, or very old transformers are also at higher risk of containing PCBs.

2. I have a transformer that may have PCBs. What should I do?

If you suspect a transformer contains PCBs, contact your utility company or an environmental professional for further guidance. Do not attempt to inspect or service the transformer yourself. If the transformer is found to be leaking or damaged, take measures to restrict access to the area and prevent further contamination until the situation can be addressed.

3. Are PCB transformers still used?

In the United States, the vast majority of known PCB transformers have already been removed and disposed of. The EPA banned the manufacture of new PCB transformers in 1979, and the final deadline for removing old PCB transformers from service was in 1998. While a few rare exceptions may remain, nearly all transformers still in use today should be PCB-free.

4. What replaced PCBs in transformers?

Since PCBs were banned, alternative dielectric fluids have been used in transformers, including mineral oil, silicone fluids, and synthetic esters. These fluids are much less toxic and persistent than PCBs while still providing the necessary cooling and insulating properties. However, they may have other drawbacks such as flammability or shorter lifespans compared to PCBs.

5. How are old PCB transformers disposed of?

Transformers with PCBs must be removed and disposed of according to strict EPA regulations. The PCB oil is drained and either incinerated or chemically treated to destroy the PCBs. The transformer carcass may need to be disposed of as PCB waste as well if internal components are contaminated. Qualified PCB disposal services must handle the removal and disposal to prevent further contamination.