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Discovering Outdoor Sources of Stachybotrys

During the last few month I have run into several homes that are making me rethink one of my opinions about mold contamination and the outdoor environment. Stachybotrys chartarum (atra) is a type of mold that has become well known as a chronic water damage indicator and is a significant problem for indoor environmental quality in homes that have had chronic water damage. In the United States the most common indoor construction material that supports Stachybotrys is the cardboard coating found on gypsum wall board. It is also well known for growing on the backing of carpets manufactured with jute backings. This is a common practice wall to wall carpet manufactured in Europe and for imported area rugs.

The conventional wisdom among experts in building related mold problems has been that Stachybotrys is uncommon in the outdoor environment and does not adversely affect indoor environmental quality in the absence of water damaged materials. In the last months I have had several cases that are beginning to make me rethink this position. In these cases the DNA for Stachybotrys continued to appear inside the building a month or more after remediation had been completed. In most cases such findings would be an indicator that a new or different source of mold growth remained in the building and additional remediation was needed, but in these cases an additional source of the mold growth was not apparent.

After discussion with a colleague in Arizona, I began submitting several samples of outdoor dust that had settled onto non-porous surfaces outside of homes that had these chronic problems. The samples were analyzed for the presence of Stachybotrys DNA after they were collected from surfaces like:

  • a glass patio table top,

  • vinyl chair covers,

  • glass surfaces on solar panel collectors,

  • a ceramic tile food prep counter for an outdoor barbecue

I was surprised to discover that the outdoor levels of Stachybotrys DNA exceeded the levels that were being found inside the problem home. In these cases there is an outdoor source of Stachybotrys coming into the home.

Fortunately this does not appear to be the case with most homes, but for some cases it appears that there may be one or more unknown outdoor sources. I would like to attempt to track these sources down. I know from experience that when cardboard or paper is found on the soil in crawlspaces under homes it frequently develops mold growth and in a number of instances samples collected have shown that the mold is Stachybotrys. A quick internet search for the topic "Using Cardboard As Mulch" identified hundreds of hits for sites discussing ways to use cardboard to help prevent weeds by covering the soil with cardboard or layers of newspapers. Another search identified a technical report from the American Journal of Pediatrics which reported that "moldy horticulture pots made of recycled paper" "had visible black masses of Stachybotrys" and that workers handling these pots developed symptoms (ref 1).

I have announced a new research project on my Indiegogo research crowd-funding website at

Discovering Outdoor Sources of Stachybotrys

Here is a partial list of some of the materials I would like to test:

  • Commercial decorative ground covers such as bark, and mulch.

  • Potting soils and other soil amendments.

  • Compost piles.

  • Cardboard, burlap and carpet sitting on soil (commonly used to control weeds in gardens).

  • Straw used as mulch

  • Leaves in various levels of decay

Once sources of outdoor Stachybotrys are discovered, additional research to identify the distances and methods of distribution for these contaminants will also be important.

If you would like to help crowd fund this research, a contribution of $50 will pay for the DNA analysis of one specimen using Mold Specific Quantitative Polymerase Chain Reaction (MSQPCR). I have inserted and am featuring a special Outdoor Stachybotrys Sources button for contributions earmarked for this study. I am estimating I would like to test approximately 50 different materials commonly found in the outdoor environment. My goal is 50 contributors of $50.00 ($2500.00 total). Of course any contribution will be appreciated.

Thank you for your ongoing support.

John Banta

Reference 1). Lynnette J. Mazur, MD, MPH, Janice Kim, MD, PhD, MPH,, Spectrum of Noninfectious Health Effects From Molds, American Journal of Pediatrics, Volume 118, Number 6, December 2006.


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