미국의 정부기관인 NIST(National Institute of Standards and Technology)에서 간편한 석면 검출 방법을 찾아 냈다는 내용입니다.
수십년간 미국에서는 주로 TEM를 통해 정확한 석면 검출 여부를 알았으나 고도로 훈련된 직원과 고가인 탓에 특별한 시설에서 운용되었습니다. 또한,위상차현미경이 더욱 쉽고 저렴하지만 정확도에서는 떨어집니다.
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For decades, a laboratory procedure known as transmission electron microscopy (TEM) has been used to test for asbestos in samples taken at construction sites.
In 1989, the U.S. Environmental Protection Agency (EPA) required most schools undergoing asbestos abatement to use TEM to test for the presence of asbestos fibers in air samples before reopening. Several states require or recommend using TEM for testing as part of asbestos removal in commercial buildings.
But TEM must be carried out in a specialized lab by highly trained staff and can be expensive. Another approach, phase contrast microscopy, is easier and cheaper but less precise.
Now, researchers at the National Institute of Standards and Technology (NIST) have determined that a third option, scanning electron microscopy (SEM), can achieve results roughly comparable to TEM. SEM is a “viable alternative to the current regulatory methods for asbestos identification and classification,” the NIST researchers Jason Holm and Elisabeth Mansfield wrote in a new paper published in Analytical Methods.
Since SEM is, in many cases, cheaper and more convenient than TEM, the finding could potentially speed up and reduce the expense of asbestos remediation in the United States, which costs an estimated $3 billion every year.
Asbestos is a naturally occurring mineral whose fibers were used for insulation, weather- and fire-proofing and reinforcing building materials. Its use began declining in the 1970s as researchers became aware of its health risks, including its link to cancer. In March, the EPA banned the last form of asbestos still in use.
As their names suggest, both TEM and SEM are types of electron microscopy. In both methods, technicians focus electron beams on a microscopic amount of material. Electrons interact with the material to produce highly detailed information on the material’s composition, structure and shape.
With TEM, the electrons pass through the sample, whereas with conventional SEM, they are reflected off the surface. This enables TEM to produce more detailed images and probe the surface’s interior. TEM also offers much better spatial resolution — the ability to distinguish between objects very close together — than SEM.
But in recent years, SEM manufacturers have improved the technology’s imaging power and other capabilities. Several companies now produce tabletop SEMs, making it possible to use the technology in the field, while TEM must still be done in a lab. Holm said training to use and operate SEM equipment can be completed in several months, while “expertise in TEM can take years to establish.”
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NIST Researchers Identify a Cheaper, More Convenient Method to Detect Asbestos
