CLARIFICATION OF LAYERED ASBESTOS SAMPLES
So, what does “layering of asbestos” really mean when it comes to the analysis of bulk asbestos samples? Section 220.127.116.11 of the EPA Test Method states that “if the sample is heterogeneous due to the presence of distinct layers or two or more distinct building materials, each layer or distinct material should be analyzed and results reported. Total asbestos content may also be stated in terms of a relative percentage of the total sample.” New York State and EPA interpret this statement differently, which has led to considerable confusion as to how to analyze multilayered samples collected in New York State as well as those following EPA and NESHAP methods, procedures, and requirements. Our clarification of the regulations is stated below.
In New York State, friable bulk materials with distinct and separable layers must be analyzed as separate samples. For example, a puffy insulation with a paper layer will be two samples and reported as such.
EPA and NESHAP asbestos regulations state that all multilayered systems, except for wall systems where joint compound was used, must be analyzed as separate layers. Results are not allowed to be combined to determine average asbestos content. For example, a wall plaster sampled from an area where joint compound is suspected can be analyzed as one layer. A wall plaster from a nonsuspected area with add-on materials must be broken into layers and reported as such. The possible presence of joint compound is a field observation and cannot be determined by the labouratory. In this instance, unless the client specifies where sampling took place or that there are add-on materials present, all plasters can be analyzed as one layer.
In New York State, nonfriable organically bound (NOB) samples, specifically tar, roofing materials, mastic, glue, and floor tiles, must be analyzed by the DOH ELAP Gravimetric Reduction Method (NYS DOH ELAP Manual Item 198.1 Section 4.2) Detection of asbestos used in these types of samples (especially vinyl asbestos tile) is often extremely difficult because of the small fibres used during manufacture, the organic matrix used as a coating, and possible pulverization during sample preparation.
Polarized light microscopy is not consistently reliable in detecting asbestos in floor coverings and similar non-friable organically bound materials. Quantitative transmission electron microscopy is currently the only method that can be used to determine if this material can be considered or treated as non-asbestos containing.
For NOB samples reported as non detect the EPA strongly recommends that gravimetric reduction be used for NOBs, but it is not a requirement.
Under NESHAP (40 CFR Part 61), any source sending multilayered bulk samples to a lab may request that certain samples be considered as composites for analysis. If this happens, then the following requirements must be followed: to analyze the composite sample, the procedure in the Test Method, EPA/600-93/116 “Method for the Determination of Asbestos in Bulk Building Materials” Section 2.3 (Gravimetry), must be used.
Additionally, the recommendations in Appendix D (Special Case Building Materials) of the method must be followed.