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Sealing Pentachlorophenol (PCP)-Treated Wood

MSVA | Posted in General Questions on

I have a 50s era house.  Found random places in my crawlspace, for example, under front door sill, that look like they were painted with pentachlorophenol.  Is there a good way to ‘seal’ this in?
Does anyone know how toxic this is after 70+ years?


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  1. Expert Member


    Are you positive that it's PCP? If so you'll need some sort of oil based product to seal it with. I'm not sure how long the toxicity lasts, but there are numbers out there than you can call and ask.

    I'm no expert, but it looks like a lot of the risk was exposure during treatment, IE the plant workers where it was produced or applied. If there's minimal contact I'm not sure the risk is all that great.

    1. MSVA | | #3

      Thank you! I'm not positive - no...I have contacted a lab to see if they can test a sample. I'm not sure if that's possible. Thanks though for the link to CDC - I will ask them about toxicity. The problem is the house was 'retrofitted' with central air in the early 70s. One of the vents goes through an area near the front door, that upon more inspection, looks like it's painted with PCP or something like that. I grew up next to this house and always remember a peculiar smell near the front door. I never questioned it. Now I live in this house. There is still a bit of smell but it's more of an 'old/moldy' smell but no mold so I did some looking around and found the 'painted' areas in the crawlspace next to front concrete/cinderblock porch. I also found this link....

  2. Expert Member
    BILL WICHERS | | #2

    It looks like the biggest issue is if you ingest (eat) the stuff, and breathing it is also bad if the concentration is high. You probably don't have much to worry about, but a few coats of a serious primer/sealer like BIN would probably help a little BUT I would check that first: You don't want to put a coating over something nasty if the solvent in the new coating will reactivate the nasty stuff! You may be better off just leaving it alone completely. The EPA info at the link below seems to imply that old materials treated with this stuff aren't a big deal (it says they can usually be disposed of in the regular trash, etc.):

    If you need more info, contract an enviornment remediation company and see what they say. I would NOT just randomly paint over the stuff without getting some assurance that the old stuff won't react with the new coating.


    1. MSVA | | #4

      Thank you! I did contact a lab and we'll see once they get back in touch with me. My reply to Kyle above gives some background as to why I ask. We sealed around the vents, the HVAC system is new and sealed, but I still would like to make sure the stuff isn't still toxic.

      1. Expert Member
        BILL WICHERS | | #5

        Keep in mind that something can be "toxic" but still not be a hazard to you. Think of rat poison as an example: it will kill you if you eat it, but a pile of it sitting in the corner for years won't hurt you. Asbestos is like this too: you don't want to breath the dust, but if it's encapsulated or undisturbed, it won't hurt you. The bad stuff you found, even if the lab tests it and finds that it really is "bad stuff", doesn't necassarily mean it's a problem IF you leave it undisturbed. The nice thing about it being 70+ years old is that it's probably not offgassing anything anymore, but the lab will be able to tell you for certain.

        If the lab confirms the bad stuff is bad, ask if they can advise as to if you need to worry about it or if you're safe just leaving it alone. Since crawlspaces are usually not places you often go, you might be fine just leaving the bad stuff alone.


        1. MSVA | | #6

          Thank you! I'll follow up with what I find out.

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