Superfund Research Program
This webinar series focused on polychlorinated biphenyls (PCBs) in schools and featured SRP grantees, as well as EPA and international partners. During the first session, EPA Regional Risk Assessment Coordinator Mark Maddaloni gave a brief overview of PCBs and the issue of PCBs in the environment, particularly in schools. Following his introduction, Kent Thomas, an EPA Research Physical Scientist, discussed the sources and levels of PCBs in indoor environments, and Peter Thorne, a professor and SRP researcher at the University of Iowa, discussed human exposure to PCBs, routes of exposure, and reducing exposures. During the second session, Gabrielle Ludewig, a professor and SRP researcher at the University of Iowa, gave an overview of the mechanisms of toxicity; Geniece Lehmann, an EPA Toxicologist, discussed evaluating the noncancer health risks from inhaled PCBs; and Niklas Johansson of the Swedish Environmental Protection Agency gave an international perspective on PCB inventory, remediation, and outcomes.
Session I - PCBs in Schools: Overview and Exposure Assessment
April 21, 2014, 2:00-4:00 p.m. EDT
An archive of this webinar is available on the Environmental Protection Agency's (EPA) Clu-in Training & Events Webpage.
- Introduction and Moderation: Mark Maddaloni , Regional Risk Assessment Coordinator, U.S. EPA Region 2
- Presenter 1: Kent Thomas, Research Physical Scientist, Human Exposure and Atmospheric Sciences Division, Exposure Measurements and Analysis Branch, U.S. EPA
- Presentation Title: Sources and Levels of PCBs in Indoor Environments
- Abstract: PCBs in buildings have been studied in recent years to identify and characterize sources, measure indoor concentrations, and assess exposure. The goal of this research is to inform risk-management decision making, particularly in schools and other buildings where children are present. Sealants and light ballasts are common PCB sources in older buildings, while absorption of PCBs by other materials may create secondary sources. PCBs are measured in indoor air, on surfaces, and in dust and soil, often with considerable within- and between-building variability resulting from differences in source, ventilation, or other factors. Different approaches for environmental sampling and analysis of PCBs as Aroclors, homologs, or individual congeners have implications for exposure assessment, indoor modeling, and informing cost-effective remediation.
- Presenter 2: Peter Thorne, Professor and Head, Department of Occupational and Environmental Health, University of Iowa
- Presentation Title: Human Exposure and Disposition
- Abstract: Recent child cohort and school measurement studies have shed new light on the importance of indoor air exposures arising in homes and schools. Modeling of children's exposures in schools with PCB sources shows >80% of the estimated absorbed dose results from inhalation with the remainder from ingestion of dust/soil and dermal contact. Active and passive sampling with measurement of all 209 PCB congeners demonstrates inhalation exposures are most prominent for the mono- to penta-chlorinated PCBs. Biomonitoring of exposures by analysis of blood samples for parent PCB congeners and selected hydroxy metabolites has emerged as a means to estimate body burden. Challenging this approach are the low levels of PCBs in the blood as compared to other body compartments. Animal inhalation exposure studies to a Chicago Air Mixture demonstrate rapid disposition and metabolism of inhaled PCBs from the lung to the blood, liver, brain, and adipose tissue with half-lives less than 20 hours. We suggest that for most people, inhalation presents the primary route of PCB exposure, and public health efforts should be directed toward monitoring and reducing these exposures, particularly among children.
Session II – PCBs in Schools: Identifying and Reducing Health Risks
April 28, 2014, 2:00-4:00 p.m. EDT
An archive of this webinar is available on the Environmental Protection Agency's (EPA) Clu-in Training & Events Webpage .
- Introduction and Moderation: Gabriele Ludewig, Professor, Department of Occupational and Environmental Health, University of Iowa
- Presentation Title: Overview of Mechanisms of Toxicity
- Abstract: The number and placement of chlorine atoms on individual PCBs determine their physical properties (solubility/lipophilicity, vapor pressure, melting point, planarity, chirality) and their biologic/toxicologic characteristics (binding to receptors, induction, repression and inhibition of xenobiotic metabolism, resistance to metabolic attack, activation to electrophilic species, and propensity for secretion/excretion). Airborne PCBs are more volatile and more readily metabolically activated. For this latter group of lighter PCBs and their metabolites, sensitive toxic endpoints may include genotoxic endpoints (point mutations, chromosome breaks and loss, sister chromatid exchanges, polyploidizations, telomere shortening) and interference with vitamin and hormone transport, especially thyroid hormone availability. Several of the above effects have been observed at nanomolar concentrations in vitro. The challenge for the toxicologist will be to identify those operative in vivo for those persons exposed to airborne PCBs at levels found in school environments.
- Presenter 2: Geniece Lehmann, Toxicologist, U.S. EPA
- Presentation Title: Evaluating Noncancer Health Risks from Inhaled PCBs
- Abstract: In some buildings, indoor air PCB concentrations can be up to one or more orders of magnitude higher than ambient outdoor concentrations. In some indoor settings and for some age groups, inhalation may contribute more to total PCB exposure than any other route of exposure. In recognition of this particular route of exposure, efforts have been made to assess the potential health risk posed by inhaled PCBs. PCB exposure has been associated with human health effects, but data specific to the inhalation route are insufficient to support exposure response assessment. For this purpose, it is critical that future investigations of the health impacts of PCB inhalation carefully consider certain aspects of study design, including characterization of the PCB mixture present. This presentation described critical areas of research needed to reduce some of the uncertainty in evaluating risks for inhaled PCBs. The views expressed in this presentation are those of the author and do not necessarily reflect the views or policies of the U.S. Environmental Protection Agency.
- Presenter 3: Niklas Johansson, Swedish Environmental Protection Agency
- Presentation Title: International Experience: Inventory, Remediation, and Outcomes
- Abstract: During the 1950s up to the late 1970s—or, in some countries, even later—PCBs were used in considerable amounts in buildings and other construction, mainly as plasticizer and stabilizer in caulk, flooring materials, paint, and glue. There are only rough estimates of the total amounts that were used in buildings and construction and even more uncertain information on remaining amounts. It has been shown that PCBs in these open applications are continuously volatilizing into both outdoor and indoor air and that the elevated levels in indoor air can cause elevated concentrations in the blood of inhabitants in such buildings. Based on the information that PCBs can cause negative health effects in both humans and the environment, many countries in the 1970s introduced legal restrictions on the production and use of PCBs. Many countries have launched specific programs to remove PCBs also in open applications. Sweden has issued an "Order of PCBs etc." that contains specific legislation on nationwide identification, removal, and destruction of PCBs in open applications like buildings and construction. International actions to reduce human and environmental exposure to PCBs have also been taken. The most important international agreements are the Stockholm Convention on POPs and the Convention on Long-range Transboundary Air Pollution (CLRTAP) that includes a Protocol on Persistent Organic Pollutants (POPs). Experiences from these national and international activities were summarized, and some important recommendations were discussed.