Asbestos contamination may be found in dust from a variety of sources. The asbestos may be present due to a poorly performed remediation in the past or from decaying building materials, but regardless of the cause asbestos in dust can be a major source for concern. The asbestos found in dust generally presents itself in very small unbound fibers, which can be released into the air when the dust is disturbed. An alternative for dust sampling may be aggressive air testing which is not always a practical solution.
There are two commonly used ASTM methods available for sampling settled dust for asbestos analysis. These methods are used to sample and analyze settled dust from a given area:
- ASTM D5755 (Micro-vacuum Method)
- ASTM D6480 (Wipe Method).
- It is important to note that TEM is the only worthwhile choice for analysis, PLM is not an appropriate analytical approach.
- TEM filtration can provide a presence/absence on either of the stated sampling techniques while this is not EMSL’s recommended analytical choice it can be a useful tool when you are unable to measure the area sampled, or you are using the qualitative result as confirmation of a suspected positive result.
- Sampling media is crucial for proper analysis, fiber interferences will occur if using improper media. Use of baby wipes, paper towels or tape would severely impact the ability to provide acceptable results.
- While these ASTM methods have been used in the asbestos industry for years there is no set action There are some industry accepted levels for concern as well as other sampling comparisons techniques (inside work area compared to outside) that are used.
- Results are provided in structures per square centimeter (Str/cm2) regardless of the unit of measure used to sample.
- These methods are designed for dust; dust is different from debris. If you believe that your sampling area consists of debris, please contact the lab for alternative analysis options.
The summaries of both methods are relatively similar. The sampled dust is introduced into an aqueous solution of a known volume. The aqueous solution is then portioned into aliquots and filtered on to membrane filters. A subsection of the filter is collapsed on to a TEM grid. The samples are then analyzed via TEM wherein structures are counted, measured, and identified using SAED and EDXA at a significant magnification. The methods were designed for a sampling area of 100cm2; however, a smaller area can be sampled for a location with heavy dust accumulation, or for a location with extremely light dust a larger area can be sampled. Ideally, a location with visible dust should be sampled, but not a location where the dust has formed an opaque layer. It is important to always provide the sampling area sizes on the chain of custody as they are used in calculations.
Asbestos in Settled Dust Sampling Instructions