Healthy Indoors Magazine
Issue link: https://hi.healthyindoors.com/i/815664
COVER STORY—March/April 2017 14 sion Electron Microscope (TEM) analysis ac- cording to the method. The preparation process can be quite lengthy depending on the amount of contamination and the number of dilutions the laboratory must perform to make a suitable mount of the dust. The analyst will analyze the sample on the TEM at a magnification of approximately 20,000X. Asbestos structures will be classified and counted using the same counting criteria as standard AHERA air clearance samples. The laboratory will provide results in number of asbestos structures per square centimeter area sampled (S/cm 2 ). The report will also tell you what type or types of asbestos were identified in the sample which may be helpful in discovering the source of the asbestos contamination. But what do you do with this data? Local, state, and federal governments really have not defined any limits for asbestos in settled dust. This leads us into an ethics debate. If the gov- ernment doesn't provide us with an acceptable limit for the asbestos in settled dust, do we need to collect the samples? If we, as ethical environmen- tal professionals do not investigate this potential contamination concern, this means that asbestos may still be present in dust deposits. Doesn't this increase our liability? What will happen to the dust after the abatement crew has left? Will the dust be disturbed and the asbestos become airborne? Won't other construction trades disturb the depos- its when completing their portion of the project? Won't occupants of the building return and clean up any dust left in their work area? So what are you going to do? Jeff Mlekush has over twenty years of experience in asbestos, lead, industrial hygiene and indoor air quality. He is currently the Vice President of Quan- TEM Laboratories, LLC. He joined QuanTEM in 2000 as the Asbestos Laboratory Manager and, over time, has taken on progressively more respon- sibility for the management and business direction of QuanTEM. Prior to joining QuanTEM his experi- ences included: environmental training and consult- ing, environmental sampling and inspection, project oversight and laboratory management. • Vacuum sampler capable of maintaining a minimum flow rate of 2 liters per minute, • Masking tape or template for demarcating sample area, • 1/4 inch diameter tubing for connecting cas- sette to vacuum sampler and constructing vacuum nozzle. • Sampling log for recording data (area sam- pled, location of sample etc.) Constructing the nozzle: • Cut a 1 to 1 ½ inch length of tubing, • Cut one end of the tubing at a 45o angle. The sampling technician demarcates an area to sample using a template or masking tape; ASTM recommends 100 cm 2 for the sample area but the area can be more or less depending on the amount of visible dust present. Cleaner surfaces may require larger sample areas, while dirtier surfaces may re- quire smaller sample areas. Remove the end plug from the cassette and place the nozzle on the cas- sette. Calibrate the vacuum sampler to draw at least 2 liters per minute using standard industrial hygiene practices; make sure to calibrate the vacuum with the sample cassette on the tubing. Vacuum the sam- ple area for at least two minutes by moving the noz- zle left to right across the entire area and then front to back across the entire area. Once the sample is collected, point the nozzle upward, turn off the vac- uum, remove the nozzle and place it inside the cas- sette, and replace the plug in the cassette endcap. Make sure to label the cassette with an appropriate identifier, fill out a chain of custody, and submit the sample to the laboratory for analysis. The laborato- ry will need to know the exact area vacuumed for the sample so please send that information with the sample. As a side note, the ASTM sampling meth- od described can be used in other scenarios. It has been successfully used to collect mold samples from surfaces, determine extent of asbestos contamina- tion from inadvertent damage of asbestos material, and collect dust for forensic particle analyses. Once the laboratory receives the sample, they will prepare it by rinsing all of the dust out of the cassette and prepare the sample for Transmis-