Polychlorinated
Biphenyls (PCBs)

The following has been extracted from
EPA document number EPA/540/s-93/506.

PCBs, also referred to by the trade names Aroclor, Phenoclor and Kanechlor [5, p.2], encompass a class of chlorinated compounds that includes up to 209 variations, or congeners, with different physical and chemical characteristics [6]. Most PCBs are oily liquids whose color darkens and viscosity increases with rising chlorine content. PCBs with fewer chlorine atoms are more soluble, more amenable to chemical and biological degradation, and less persistent in the environment that those PCBs with more chlorine atoms. PCBs are thermally stable and excellent electrical insulators [1, p.173].

PCBs are very persistent, hydrophobic, and generally do not migrate. However, there are some site characteristics that may have some bearing on the potential of PCBs to migrate. For example, PCBs in oil will be mobile if the oil itself is present in a volume large enough to physically move a significant distance from the source. Soil or sediment characteristics that affect the mobility of the PCBs include soil density, particle size distribution, moisture content, and permeability. Additionally, meteorological and chemical characteristics such as amount of precipitation, organic carbon content, and the presence of organic colloids also affect PCB mobility [4, p.33] Determination of these characteristics during the Remedial Investigation/Feasibility Study (RI/FS) activities will aid in estimating the mobility of PCBs at the site.

Because of the stability of PCBs, many exposure routes must be considered: dermal exposure, ingestion of PCB-contaminated soil, water and food; and inhalation of ambient air contaminated with PCBs. PCBs have a high potential for bioaccumulation, which is an important factor to consider due to their ability to accumulate in aquatic environments such as lakes rivers, and harbors [5, p.1]. Although not very common, volatilization and other transport mechanisms may remove PCBs from contaminated soil or sediment or entrain them into the air. Remedies involving excavation may create short-term exposures to workers and surrounding communities from inhalation of dust emissions.

Chronic exposure of animals to PCBs can lead to disrupted hormone balances, reproductive failures, teratomas, or carcinomas. Plants, however, do not appear to exhibit detectable toxicity responses to PCBs [4, p.37]. A more significant health impact of PCBs may be caused by their incomplete combustion during thermal treatment processes. Incomplete oxidation of PCBs may form polychlorinated dibenzofuran (PCDF) emissions [7]. These are of concern due to their toxicological and lethal effects on laboratory animals.

References

1.Amend, L. and P. Lederman. "Critical Evaluation of PCB Remediation Technologies." Environmental Progress, Volume 11. August 1992. pp.173-177

4. Guidance on Remedial Actions for Superfund Sites with PCB Contamination. EPA/540/G-90/007, U.S. Environmental Protection Agency. August 1990.

5. Development of Advisory Levels for Polychlorinated Biphenyl (PCBs) Cleanup. Project Summary. EPA/600/S6-86/002, US Environmental Protection Agency. June 1987.

6. A Guide On Remedial Actions at Superfund Sites with PCB Contamination. Quick Reference Fact Sheet. US Environmental Protection Agency. August 1990.

7. Federal Register. Polychlorinated Biphenyls; Exclusions, Exemptions and Use Authorizations; Proposed Rule 52 FR 25849-50. Office of the Federal Register, Washington, DC. July 8, 1987.

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