The other day I got an email asking a good, basic question about the federal PCB regulations: “Where did the 50 ppm regulatory cut-off for PCBs come from?”  Is it a science based number? Or did the 50 ppm number just get pulled out of the air?

The more I thought about it, the more consequential the question seemed.  Thus a new PCB blog post seemed to be in order.  As you’ll read, the 50 ppm level wasn’t exactly science based, but then it wasn’t totally pulled out of the air either.

What does TSCA say?

Congress passed and the president signed the Toxic Substances Control Act (TSCA) in 1976.  This statute directed EPA to develop two sets of PCB regulations that became known as: (1) the 1978 PCB Disposal and Marking Rule; and (2) the 1979 PCB Ban Rule.  TSCA does not specify a PCB concentration cut-off limit to let EPA (or the rest of us) know exactly what Congress had in mind as to how concentrated PCBs had to be for them to fall into the regulatory net.

Wise legislators must have agreed that setting a regulatory cut-off limit is a decision best left to the professional staff at the regulatory agency. (I will leave the question of whether the phrase “wise legislators” is an oxymoron for a more politically oriented blog).  So TSCA is silent on the issue of PCB cut-off concentrations.  This was something EPA needed to figure out.

What does EPA say about the 50 ppm cutoff?

In the draft public comment version of what became the Disposal and Marking Rule, EPA proposed a 500 ppm cut-off limit for the regulation of PCBs.  But, by the time the final rule was published in the Federal Register (February, 1978), EPA was already getting cold-feet about this high a limit.  The agency warned in the preamble to the Rule that they would likely soon reduce the cut-off level to something in the neighborhood of 50 ppm, but needed to go through a more prolonged regulation development process before they did so.  Quoting from the preamble:

“The Agency is aware that adverse health and environmental effects can result from exposure to PCB’s (sic) at levels lower than 500 ppm; however, at this time the Agency is not establishing a level based on health effects or environmental contamination but rather a level at which regulated disposal of most PCB’s can be implemented as soon as possible”.

EPA goes on to explain that they had only recently acquired the additional scientific information needed to support a lower cut-off level, and that this information was not available in time to include in the administrative record or hearings for the Disposal and Marking Rule.  More from the Rule’s preamble:

“As a consequence, the 500 ppm definition for a PCB mixture, as proposed, is included in this final rule making.  However, the Agency plans to propose a lower concentration of PCB’s, possibly in the range of 50 ppm or below, to define PCB mixture in the forthcoming . . . regulations”.

In accordance with EPA’s warning, the preamble to the May, 1979 PCB Ban Rule explains that EPA had in fact decided to adopt the 50 ppm cut-off level.  This was after the Agency considered cut-off levels of 1 ppm, 10 ppm, 50 ppm and 500 ppm.  EPA concluded that reducing the cut-off level to 10 ppm was impractical because it would bring far too much physical material and too many unrelated chemical processes into the PCB regulatory net.  EPA pointed out that a 1 ppm cut-off level would obviously be even more impractical than the 10 ppm level.

So the 50 ppm level was chosen as the happy medium.  It was a concentration that could be “administered” by EPA (presumably unlike the lower 10 ppm and 1 ppm levels) and yet would capture hundreds of thousands of pounds of PCBs that would have gone unregulated with a 500 ppm cut-off level.

So, that is the story of where the 50 ppm PCB cut-off concentration came from.  It wasn’t rocket science, one could argue it was barely science at all.  In retrospect it was a compromise between those interested in controlling as much PCB as possible and those whose focus was on what could realistically be accomplished.

Now some might wonder why it is that under the 1998 PCB Mega Rule there is a 1 ppm cut-off concentration for PCB remediation waste, but that’s a question for another blog post.