Question
We recently bought a house and are finding a number of issues since move in. Today, we found a huge mold spore growing under a brick. It's slightly bigger than a pie pan in diameter and about 4 inches thick. It had black tar like fluid on it as well. When we bought this house, the previous owner had the front and back yard landscaped with very little grass. It only has rock, flower beds and mulch. Under all that we have found indoor carpet. We asked the next door neighbor and he said, when she replaced the carpet with in the house, she used the old carpet as an underlay out side. Is this going to cause a problem? should we removed the carpet and redo the yard? is this safe for my family? Thanks for your help!

Answer
Hi Cara - Congratulations on a new home!  First, the mold question.  From your description, it actually sounds like you have a type of mushroom, also a type of fungus.  Fungi kingdom includes mushrooms, molds, mildew, yeast, lichen, rust, and truffles.  According to several sources, only about 10% of the population is sensitive to mold exposure, producing an allergic reaction (eye & respiratory irritation), typically of those already compromised or sensitive to allergens - asthmatics, chemo patients, seasonal allergy sufferers, people with chemical hyper-sensitivity, etc.   According to the American College of Occupational & Environmental Medicine there is little evidence that breathing in mycotoxins (the airborne parts of a fungus) are a health hazard, and are naturally occurring in such things as coffee and fruit.  More people are affected by bacterial, protozoan, and viral sources, than fungal diseases.

Having said that, however, excessive mold growth in your garden should be controlled in an appropriate manner.  There are EPA guidelines for indoor mold control (http://www.epa.gov/iedmold1/moldguide.html), but molds are ubiquitous in the outdoor environment.  

As I am not an epidemiologist (one who studies disease patterns in populations), but a landscape architect, your brick mold issue in my opinion is aesthetic, as molds will discolor walkway brick and concrete over time.  Here is a product specific to outdoor mold eradication:  http://www.concrobium.com/concrobium-products/.  

If you still have concerns, the Colorado Department of Health has specific mold information that may be of help:  
http://www.rmrpehsu.org/Portals/24/docs/Mold%20Info%20Sheet_PEHSU%20Site.pdf

As to using old carpet as a weed blocker, I have seen it done. Usually it is flitted over, with carpet side down and woven backing facing up.  As you have discovered it is unsightly as it decomposes. Also, it traps moisture, becomes heavy, smelly, and takes a long time to break down as it is a synthetic product.  Since you said your yard is only rocks, flower beds, and mulch, if you plan on increasing the amount of landscape, then pull it up in areas that will receive new plants and trees.  It should be limited to being placed under pathways and areas that will not receiving plants as it is tough to dig through for plant holes, and once plant roots adhere into it, becomes difficult to remove.  

If it is not unsightly and buried under rocks and gravel, I抎 leave it alone.  As to a hazard, no, I don抰 think it poses a health risk.  Again, it is aesthetics for me. Sorry that the previous owner didn抰 want to pay to have it hauled to a dump, but perhaps you can re-frame it as a positive, that it has been re-purposed for an adaptive re-use and not taking up landfill space.

All the best to you. ~m