Poisonous Plaster?

By: Bill Kibbel , Contributing Writer
In: Old House Construction

Old-house folklore — I hear it everywhere.  Unfortunately, some home owners believe it if they hear it from people that hold themselves out to be professionals.

In a Canadian newspaper, the Toronto Star, a home inspector was interviewed as the sole source for a piece titled “Take a careful look at older homes.”  On the topic of hazardous materials he states:

“In older homes in the plaster they used horse hair to bond the plaster together and horse hair was treated with arsenic.”

If asked, I don’t think he, or anyone else, could cite a credible source that would substantiate that horse hair in plaster was ever treated with arsenic.  I don’t know of any research, study or testing that would indicate any type of poison would have been mixed into plaster on walls of historic buildings.  I haven’t read about any plasterer, remodeling contractor or homeowner ever getting poisoned from old walls.

There is only one time that I’ve ever heard of someone trying to link arsenic and plaster.  A geologist, studying environmental issues with tanneries in the mid-Atlantic, found receipts indicating small quantities of horsehair from one tannery was sold to plasterers. He also found the tannery used lime (not the kind prepared to be suitable for plaster) and arsenic in processing hides. It was then implied that there might be arsenic in plaster. It seems that this was picked up by a periodical, thus creating a perceived link between what was “discovered” and a possible health risk.

There are only two instances, from credible sources, that have indicated arsenic in building products.  I can no longer recall those sources, but one was about arsenic in pigment used in very expensive wallpaper.  Another source indicated some rare instances of trace amounts of arsenic of iron furnace slag ground up and used for aggregate in mortar.

There are some very real health risks, well studied and documented, that old-house owners deal with regularly.  I don’t think being poisoned by our walls has made it on that list.


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  1. 6 Responses  to “Poisonous Plaster?”

  2. Shereta
    Nov 12, 2015
    Ok, so the issue you speak of, just happen to a friend of ours that was working installing meters and was jabbed with a piece of this horsehair and went to the ER.. this finger was infected and was hospitalized for 5 days due to the fact of arsenic in the horse hair. This just happen in 2015 in Yonkers NY
  3. Aug 29, 2011
    I plaster occasionally although not full time. I am well aware of asbestos etc in artex but arsenic is a new one on me. THanks for the info. Too many people have bad lungs by not taking Health and safety seriously.
  4. Aug 29, 2011
    Just to follow on, its not only old houses, asbestos was used in most construction compound up until 1993!!
  5. Aug 29, 2011
    Very interesting blog. Thanks for the information. Sounds like this guy has either misunderstood the information or is just trying to get more work by twisting the truth.
  6. karen gerald
    Aug 29, 2011
    my son has come down with a serious illness that is unknown and rare. he bought a home built in the 1800's and has been taking it apart to restore. i am looking into everythig possible to find a cure for him. i am his mother. he is 30 yrs old and has always been healthy. it is a blood disease: "ITP" with EVANS SYDROME on top of it. there has got to be some explanation to me, so i have been looking at his home. the house has horse hair plaster in it with many other things i do not know of.
  7. Aug 29, 2011
    Artex can also be hazardous. Older artex can contain asbestos.