Letter to Task Force Regarding PCB Screening levels

November 16, 2013

Dear Fellow Task Force:

I felt unsettled after the meeting on Nov 14th, about the evaluation criteria we discussed. I am sorry I could not explain well enough what the EPA conveyed to me. So afterwards, I had another conversations with the EPA expert that focuses on PCB’s in soil, air and water. I wanted to share with you what I learned and what the numbers we discussed means to us. In summary, for a school setting, the EPA defaults to the residential guideline of 4.3 ug/m³ for Aroclors and 2.1 ug/m³ (or less) for approximately 12 individual PCB that are highly toxic. This assumes a 1 in 1 million risk factor for cancer.

Please see the following link, it is the current (May 2013) guidelines for essentially all environmental contaminates. The EPA uses this RSL, called
the Regional Screening Level Summary Table (May 2013). We should use this chart to assess the risk for the results of the PCB.

Please look on the bottom of page 9 and the top of page 10 of this RSL. In the green section you will find PBC’s in bold print. This is where the PCB list begins. (these would be the only pages needed to print for now)

* EPA Regional Screening Levels (the health-based concentration for chemicals & contaminants in residential & industrial soils, residential & industrial air, &
water): http://www.epa.gov/reg3hwmd/risk/human/rb- concentration_table/Generic_Tables/docs/master_sl_table_run_MAY2013.pdf

For total PCBs, the screening level is 4.3ng/m³.

Aroclors (the trade name given by Monsanto for their PCB mixtures) are not one of the 209 PCB congeners. Aroclors are a mixture of different PCB congeners. Testing for Aroclors does not test for individual PCB congeners. For example: The soil tested at MHS in 2011 was tested for Aroclors (among other things, but not the 209 individual PCB’s.) This test is widely used. However, when this type of test shows positive for Aroclor, typically you would send the sample back to the lab and test to find the individual congeners to see the specific PCB contaminents (this was not done at MHS).

Let’s remember that Aroclors are a mixture of different PCB congeners (i.e. (this is a completely made up example with no real data) original Aroclor 1111= PCB 1,2,3,4,5). Over time, the environment changes the original makeup of an Aroclor and turns the congeners into a different set of congeners (i.e.: new PCB makeup of the original Aroclor 1111= PCB 1,23,56,77 (again, not real numbers). What happens is lighter PCB congeners may evaporate and other congeners may alter creating different congeners. This change can either cause increased toxicity of the Aroclor or lower toxicity. This means that when we found Aroclor 1254 in our soil, we cannot predict what particular PCB congeners were in our soil. We would actually have to retest the original soil sample and test for all 209 congeners to know what was there. We should consider retesting the soil after we discover the PCB source in the classrooms, to ensure that the soil has no PCBs or other contaminates in it after 3 years.

Testing for the 209 separately is important because some PCB congeners are MUCH more toxic than others. Some PCB congeners are not found to be as toxic. Based on the RSL, the orange section says that congeners 189,167,157,156,169,123,118,105,114,126,77,81 are highly toxic and therefore the guidelines for these are 2.1 ng/m³ or less. Congeners 169,126, 77 and 81 have even lower screening levels (very toxic). This is because the EPA knows they are more toxic and are more likely to cause cancer in the human body with less dosage.

What this means to us is that our evaluation of air testing cannot only be based on a single number. We can look at the total PCBs first, but then must look at the individual congeners to determine what action we will need to take.

In assessing the raw PCB data, the report should come back with the concentration levels in “pg/sample” and it is an easy conversion to ng/m³. We can then check the chart for each congener and know where we stand.

In contrast:
The chart below shows the EPA levels that Mark Katchen originally presented to use for our evaluation criteria. I want to better explain why these levels are too high and not for our situation. The chart below, the numbers assume approx.. 1 in 10,000 cancer risk. To me this risk is not acceptable. If we read it carefully, it says in order to use these numbers one must assume “no significant PCB contamination in building materials and average exposure from other sources”. We have exposure from other sources that was found in the soil in 2010. So this chart and these numbers are not valid for us, in addition, we should not accept a 1 in 10,000 cancer risk for our teachers or our students.

4.3 ng/m³ = 1 in 1 million cancer risk

43 ng/m³ = 1 in 100,000 cancer risk

430 ng/m³ = 1 in 10,000 cancer risk (this should not be acceptable to parents and teachers)

Public Health Levels of PCBs in School Indoor Air (ng/m3)

Assuming a background scenario of no significant PCB contamination in building materials and average exposure from other sources, these concentrations should keep total exposure below the reference dose of 20 ng PCB/kg-day.

Age 1-<2 yr

Age 2-<3 yr

Age 3-<6 yr

6-<12 yr Elementary School

Age 12-<15 yr Middle School

Age 15-<19 yr High School

Age 19+ yr Adult








This 100 ng/m³ = .1ug/m³ (nanogram to microgram conversion).


I hope this helps explain how we look at the air testing results as well as why I have pushed for the EPA guidelines of a 1 in 1 million cancer risk evaluation.

As I said at the meeting Nov 14th, the EPA looks for a non-detect for wipe samples, which equates to the 1 in 1 million cancer risk. If anything is found in the wipes, it equates to a greater than 1 in 1 million cancer risk.

The bulk samples are another issue altogether. The results we receive will show us if the samples are positive or not and to what extent. A conversation for another email :)

I really hope this helps rather than confuse. It’s hard to explain this in writing and make sure it is clear and concise. But if anyone has questions, please feel free to call me and I will do my best to answer them and if I can’t I am willing to do the research and find out.

Best Regards,

Jennifer deNicola