Asbestorama's photostream  

Dual image: asbestiform mineral found in "non-asbestos" vermiculite plaster sample; sample of amphibole asbestiform mineral fragment shown on U.S. penny for scale.

Left image shows a few asbestiform mineral fragments at approx. 100x magnification through a simple light microscope, collected from a sample of a 1960's-era structure wall plaster material containing vermiculite aggregate. What may look like tiny slivers and grains are actually compacted bundles of innumerable microscopic fibers found mixed within the wall plaster material sample, along with gold-brown vermiculite and fine-grained sand mix. Interestingly, this particular plaster material was tested multiple times via PLM by a reputable NVLAP-accredited laboratory and asbestos content was reported as "none detected". Which makes one wonder.

In fact, over the course of several years and through using a variety of microscopy laboratories, hundreds of similar vermiculite-containing wall and ceiling plaster samples from numerous decades-old buildings and dwellings have all been reported as "none detected" (not even "trace" amount) regarding asbestos content. But, how could this be, especially considering the tremendous quantity of Zonolite aggregate used in plastering applications in the past, a vermiculite product known to be contaminated with amphibole asbestos? The US-EPA's website indicates, " ...over 70 percent of all vermiculite sold in the U.S....was contaminated with asbestos..."

So, a split-sample of "no asbestos detected" vermiculite-plaster was thoroughly visually examined by yours truly under the HEPA-hood. Suspicions confirmed: several tiny bundles of asbestiform amphibole mineral, after looking at only one sample. Based on this, how much microscopic asbestiform mineral fiber would an entire building structure contain within its suspected "Zonolite" vermiculite-containing fireproofing or plaster walls, ceilings, floors, and roof decks? A concerning thought when conducting renovation or demolition activities which impact such materials.

Special considerations for modification of sampling and testing measures should be given if dealing with vintage materials containing vermiculite. A couple of important points to consider regarding vermiculite plaster testing would be: collecting larger-sized samples and thoroughness of microscopic examination.

One of these days will have to get better micrographic imaging equipment, but for now putting the camera up to the microscope ocular eyepiece at least helps demonstrate a point.

Painted, fibrous asbestos felt laminate on exterior metal siding panels, shown peeling and in poor condition from the damaging effects of weathering. Exposed friable asbestos is susceptible to erosion from water and wind across a large surface area of the structure's exterior walls.

Painted, fibrous asbestos felt laminate on exterior metal siding panels, shown peeling and in poor condition from the damaging effects of weathering. Exposed friable asbestos is susceptible to erosion from water and wind across a cumulative large surface area of the structure's exterior walls.

Painted, fibrous asbestos felt laminate on exterior metal siding panels, shown in poor condition and flaking off from the damaging effects of weathering. Exposed friable asbestos is susceptible to erosion from water and wind across the large surface area of the structure's exterior walls.