Before beginning this post we at OTO want to express our deepest sympathies to the individuals and families who experienced losses in the wake of the horrible Boston Marathon bombing.  We also want to extend our gratitude to the medical teams that helped the injured and to our local, state and federal law enforcement officers who worked tirelessly to bring order back to the Commonwealth.

PCBs in Soil around Buildings

One of the questions that often come up after soil is tested for PCBs in the vicinity of a building is: why are there higher concentrations of PCBs in the soil right around building foundations?  There has been a tendency for investigators to shrug their shoulders and answer: it must be from the degradation of PCB containing caulk or paint used on the outside of the building.  Frequently there is no direct evidence to support this claim, but it seems like the only reasonable explanation that is consistent with the findings.  Well here is another explanation that might also make sense. 

PCBs in Pesticide Formulations

In the 1950s and ‘60s it was common to treat the soil volume immediately around building foundations with pesticides to control or prevent infestations of soil dwelling insects (like termites, ants etc.).  Solutions of pesticides were pumped into the ground under pressure until the surface soil became wetted.  Among the pesticides commonly used in this way were lindane and several of the other chlorinated pesticides.  Since the chlorinated pesticides were very effective and more persistent in the subsurface environment than other options, they were often the pesticide of choice for this purpose.

Although pesticide registrations are now overseen by the USEPA, before there was an EPA (pre-1970) it was handled by the US Department of Agriculture (USDA).  The USDA has generally had a more “congenial” relationship with farmers and other agricultural enterprises than the EPA has had with farmers and the rest of US industry.  During the period when USDA regulated pesticides it was not out of the ordinary for the USDA to make recommendations on the more effective use of pesticides including pesticides for the control of soil dwelling insects.

One of the ways that pesticides lose their potency (even in the ground) is through the volatilization of the active component into air and via the solublization of the  pesticide into water percolating through the soil.   USDA researchers discovered that the addition of certain oils and/or chemicals to a pesticide formulation prior to its application could inhibit the volatilization and solublization of pesticides thereby increasing the amount of time a single application would remain effective.  Further, it was discovered that one of the very best additives for extending the useful duration of a pesticide applications was polychlorinated biphenyls (PCBs).  PCBs did not modify the pesticide’s mode of toxic action, but they did extend the effective duration of a pesticide application up to ten times over a control application that contained no such additive.

This meant that the addition of a relatively small amount of PCBs to a pesticide formulation could significantly increase the value of a single application.  This obviously presented a significant economic incentive for the inclusion of PCBs into pesticide formulations.  The use of PCBs in this manner was actually encouraged by the USDA because it reduced the total amount of pesticide required to control insects in any given situation.

All that Remains

The last pesticide application that included PCBs likely occurred more than 40 years ago.

While it is possible that some detectable trace of the active pesticide ingredient still remains where it was applied, it is more likely that simple volatilization and the aggressive soil biochemical environment has attenuated the pesticide concentrations so they are too low to measure.  However, it is likely that the PCBs used in that long ago application are still present in the soil and can still be readily measured.

For help understanding how PCBs entered soil at a property please contact me at

In a regulatory reinterpretation with far significant implications, the USEPA clarified the definition of “Excluded PCB Products” as used in the PCB regulations and signaled its intention to deemphasize the regulation of low concentration PCBs in commercial products.  Excluded PCB products are defined as commercial products containing PCBs originating from Aroclor or non-Aroclor sources where the PCBs are present at less than 50 ppm.

The excluded product reinterpretation was the result of a request by the Institute of Scrap and Recycling Industries, Inc. (ISRI) which was seeking clarification on the management of plastic residue from automobile shredding and recycling.  This plastic residue sometimes contains low levels (less than 50 ppm) PCBs.  Managing the material as a PCB remediation waste limited the recycling industry’s ability to reuse this plastic and increased the cost of the recycling operations.  If it was clearly understood to be an excluded product, then the regulatory burden would be less.

There is often confusion about whether a PCB containing product with less than 50 ppm PCBs should be classified as an Excluded PCB Product or as a PCB Remediation Waste.  The responsibility for making this decision rests with the waste generator, but complicating the assessment is the sometimes variable guidance between EPA regions.   Remediation waste must be managed in accordance with regulatory requirements, excluded product waste is effectively deregulated.  For generators the differences in the management costs and potential long term liabilities between the classifications can be large.

The reinterpretation establishes guidance from EPA headquarters that should assist generators in making the decision.  EPA restated its policy that most materials containing less than 50 ppm PCB are not regulated by the PCB regulations.  The reinterpretation also seems to lessen the burden of proof for generators who claim their material should be classified as an excluded product.  Here is a key quote from the reinterpretation:

“In promulgating the excluded PCB product rule, EPA described the provision as follows:

“EPA is adopting the generic 50 ppm exclusion for the processing, distribution in commerce, and use, based on the Agency’s determination that the use, processing, and distribution in commerce of products with less than 50 ppm PCB concentration will not generally present an unreasonable risk of injury to health or the environment. EPA could not possibly identify and assess the potential exposures from all the products which may be contaminated with PCBs at less than 50 ppm. . . . EPA has concluded that the costs associated with the strict prohibition on PCB activities are large and outweigh the risks posed by these activities. 53 FR 24210 (June 27, 1988).

“EPA has further stated, with respect to the excluded PCB products rule: “These amendments have excluded the majority of low-level PCB activities (less than 50 ppm) from regulation” (Ref. 4). Given the difficulty of determining the precise source of PCBs, EPA believes the purpose of excluding “old” PCBs under the excluded products rule is best effectuated in these circumstances by treating < 50 ppm materials entering a shredder as excluded PCB products unless there is information specifically indicating that the materials do not qualify”.

The reference to the “excluded PCB product rule” refers to a 1988 PCB regulation amendment that confirmed EPA’s intention to not regulate most PCBs at concentrations less than 50 ppm.  The history behind he excluded product rule is a story unto itself (maybe for another post).

Over the past few years the relevance of the 1988 excluded product rule has been cast in some doubt.  However, with this new interpretation EPA has affirmed its decision to not regulate most PCBs at concentrations less than 50 ppm and has clearly reiterated its long standing position “that the use, processing, and distribution in commerce of products with less than 50 ppm PCB concentration will not generally present an unreasonable risk of injury to health or the environment”.

For help with PCB waste classifications please contact Jim Okun at