PCB Research Supports Safer Schools
EPA researchers help answer questions about potential exposures in schools
EPA researchers recently completed five studies to answer questions about polychlorinated biphenyls, or “PCBs,” in schools. What they are learning is providing information to help minimize exposures and better protect students, teachers, and others.
PCBs are a group of manmade chemicals that were widely used from 1950 until the late 1970s. Congress banned their use and manufacture in 1976 in the face of growing evidence linking PCB exposure with adverse human health effects, including cancer, reproductive problems, and neurological development.
Because they are heat and flame resistant, they were used in schools and other buildings constructed during that time. For example they were a component of fluorescent light fixtures and were added to paints, adhesives, and caulking.
While PCB exposures have been greatly reduced after they were banned, they are persistent by design and may still be present in or near places where they were used. Buildings, including schools, built or renovated between 1950 and 1970 may contain PCBs, particularly in or around window caulking or in older fluorescent lighting fixtures.
In response to concerns raised by the public about PCBs in schools, in the fall of 2009 EPA announced a series of steps that building owners and school administrators should take to reduce exposure to PCBs that may be found in caulk and other materials in buildings constructed during this timeframe. Also in 2009, EPA scientists also began researching PCB sources, evaluating potential routes and pathways of exposure, and studying mitigation and remediation methods.
EPA released the results of this research in five studies and a literature review. A summary of the study findings follow.
- Study 1 confirmed that emissions from old caulk causes elevated PCBs in the surrounding air. Old fluorescent light ballasts were also tested for PCB emissions. The emission rates for fluorescent light ballasts containing PCBs were small at room temperature for non-leaking light ballasts but increased significantly at temperatures similar to those reached during operation. Fluorescent lighting fixtures that still contain their original PCB-containing light ballasts have exceeded their designed lifespan, and the chance for rupture and emitting PCBs is significant.
- Study 2 concluded that some building materials (e.g., paint and masonry walls) and indoor dust can absorb PCB emissions and become potential secondary sources for PCBs. Once the primary PCB-emitting source is removed, the secondary sources are likely to begin emitting PCBs on their own. Although the rate of emissions is typically lower than emissions from the primary sources, these secondary sources can have large surface areas. These secondary sources may make mitigation more complex. A remediation plan must consider the potential effects of secondary sources.
- Study 3 described an emission containment method called “encapsulation,” where PCB sources are coated with a coating material that separates the source from its surrounding environment to reduce PCB emissions.
EPA scientists found encapsulation to be a solution to the PCB emissions issue, but it is only effective at reducing air concentrations to desirable levels when PCB content in the source is low. Selecting high-performance coating materials is key to effective encapsulation. Multiple layers of coatings enhance the performance of the encapsulation. Ten commercially available coatings are ranked in the report for effectiveness.
Encapsulating sources that contain high levels of PCBs may still be beneficial, but may not be sufficient to reduce the air concentration to the desirable level. Thus, encapsulating old caulk can only be used as a temporary measure before the caulk is removed.
- Study 4 evaluated another method to reduce exposure to PCBs called Active Metal Treatment System (AMTS), developed by NASA and its collaborators.
AMTS eliminates PCBs by dechlorination and can remove PCBs from paint, up to several thousand parts per million, using a form of chemical scrubbing.
Results from the study show that the current AMTS can remove PCBs from paint effectively but the method tested is less effective in removing PCBs from thicker sources such as caulk and concrete, because of its limited penetration ability.
The AMTS method that was tested in this study is not designed to remove PCBs from these other sources. However, NASA recently developed an improved method that could be tested to see if it works to remove PCBs from these other sources.
- Study 5 generated limited data for characterizing real-world PCB sources and environmental levels in six schools that were built or renovated from the 1950s to the 1970s.
EPA exposure scientists collected air, dust, soil, and surface wipe samples from one old school building scheduled for demolition. From this same school, scientists also collected samples from building materials like caulk, tile, and paint. In addition, scientists used environmental and building material PCB measurement data provided by EPA Region 2 (New Jersey, New York, the U.S. Virgin Islands and eight tribal nations) that was gathered from five schools by the New York City School Construction Authority.
The measurement data collected from the five schools included measurements from the schools before mitigation methods were implemented and after mitigation methods were implemented.
A model was used to predict exposures that a typical student might experience based on the PCB measurement data. The measurements collected from the five New York City schools following PCB mitigation actions were put into the model and it predicted that less than 1% of the students would have exposures exceeding the reference dose following mitigation. Not surprisingly, the identified sources of PCBs were caulk and light ballasts containing PCBs—similar to the sources identified by the EPA laboratory study (see above).
In November 2012, EPA used the results of this research to update its PCB guidance about how to reduce exposures to PCBs that may be found in schools. As EPA researchers gain new information they will make further recommendations on how to best prevent harmful PCB exposure in schools.
Polychlorinated Biphenyls (PCBs)