PCBs in Schools Research - Questions and Answers
Why is EPA conducting research on PCBs in schools?
Caulk containing polychlorinated biphenyls (PCBs) was used in some buildings, including schools, between about 1950 to the 1979. Generally, schools and buildings built after 1979 do not contain caulk with PCBs. In September 2009, EPA announced guidance for school administrators and building managers for managing PCBs in caulk in order to help minimize possible exposure. In response to public concern, EPA scientists began researching PCB sources, studying methods to reduce PCB emissions and evaluating exposures in school buildings. Although some data are available, it is not known how widely and at what levels PCBs are present in air, dust, and on surfaces. EPA is helping to fill these information gaps to improve the understanding of exposure to PCBs and to evaluate methods that can be used to cost-effectively reduce PCBs in schools.
What are the results of the PCBs studies?
In total, EPA has released five studies and a literature review. In November 2012, EPA released research results from 3 of the studies and the literature review and in January 2013 EPA released two additional studies. All of the research results are described below.
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 that was gathered from five schools by the New York City School Construction Authority. The measurement data collected from these 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 inputted 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).