In my last post I discussed my invitation to speak about PCB exposures at the 2015 American Industrial Hygiene Association (AIHA) conference in Salt Lake City. In this post I want to review a fascinating remedial technology presented during the conference’s PCB session by Professor Cherie Yestrebsky from the University of Central Florida.
Zero Valent Metal PCB Treatment
Working with her graduate students, Dr. Yestrebsky developed a technology that effectively destroys PCBs on non-porous surfaces, such as metal sheet and pipes. The specific chemical reaction at the heart of her approach, sometimes referred to as “zero valent metal” chemistry, reduces PCB molecules by removing the chlorine atoms from the PCB molecules. Note that this technology has also been referred to as the “NASA method”.
In practice the technique involves the application of a specially prepared paste (containing a suspension of zero valent metal) to a PCB contaminated non-porous surface; the paste consists entirely of non-hazardous materials. Typically PCBs on non-porous surfaces are the result of their inclusion in the paint or other coating used on the surface. The paste softens the PCB containing coating and brings the PCBs into proximity with the zero valent metal. The chemical reaction between the metal and the PCBs is allowed to proceed for a period of time. The reaction takes place at room temperature, and no toxic gases or fumes are released during or after the reaction. The spent waste is not a listed or characteristically hazardous waste.
In addition to its effectiveness on non-porous surfaces, zero valent metal technology shows some promise for significantly reducing concentrations of PCBs absorbed into porous building materials like coated and non-coated concrete. When applied to non-coated concrete the mode of action is different because no surface coating is present. However, it appears that the paste is able to penetrate some distance into the concrete and destroy PCBs close to the surface. PCBs that have penetrated more deeply into the concrete matrix are not affected.
PCBs sorbed into concrete is an especially troublesome problem, particularly in occupied buildings like schools and residences. The technical solutions currently available to reduce or eliminate these PCBs are very limited and typically require the removal and replacement of the contaminated concrete. Removal of PCB contaminated concrete is usually expensive and often impossible without jeopardizing the structural integrity of the building.
Clearly the zero valent metal approach would be a welcomed addition to the PCB remediation tool kit for non-porous and porous surfaces. However, there looks to be an obstacle in the way of getting this technology into the remedial tool kit, namely the PCB regulations.
Do the PCB Regulations Stifle Innovative Remedial Solutions?
Subpart D of the PCB regulations describes in exhausting detail the permitted methods for PCB disposal. The language is so dense and the cross-references so convoluted that some have suggested EPA subcontracted the writing of Subpart D to the IRS, just joking. Subpart D does contain provisions that seem to create a regulatory path for the development of innovative PCB disposal methods.
However, the requirements for traversing this regulatory path are significant (read “abandon all hope ye who go this way”). I have heard presentations by USEPA scientists whose research into alternative PCB destruction methods came to an abrupt halt when they ran into the Subpart D regulations. If EPA’s own scientists can’t meet the Subpart D requirements, what chance does a non-federal government entity have?
Back to the zero valent metal technology. From the data I have seen the approach is 80% to 100% effective on non-porous surfaces and 40% to 80% effective on porous surfaces. On porous surfaces the effectiveness depends a lot on how deeply into the matrix the PCBs have migrated.
What standards do the PCB regulations require for alternative disposal technologies? Either equivalent to the PCB incinerator standards (aka 99.9999% effective – the “six-nine” standard) or possibly equivalent to a “high efficiency boiler” (aka 99.9% effective – the Herman Cain standard?). Of course an applicant wouldn’t know what would be acceptable until submitting an application to EPA, and you can’t submit an application until you have the data demonstrating that the technology meets the standard. Catch 22.
The Real Alternative Technology: Don’t Ask – Don’t Test
What it comes down to is this: EPA has set the bar so high for the introduction of an alternative remedial technology for PCB disposal/destruction that investing in the development of a potentially useful new technology is just too risky. Particularly in the case of PCBs in building materials a technology that provided significant concentration reduction (say greater than 50%) would seem to be very attractive even if it’s not 99.9% or 99.9999% effective. But the regulations do not permit that option.
And so the real alternative is often “don’t ask – don’t test”. Since there is no published data linking PCBs in building materials to adverse health effects, and since there are few practical approaches to removing PCBs from buildings, many have concluded it is better not to know if PCBs are present. They may just be right.