New NIOSH Software Measures Silica Exposure FAST
Overexposure to silica dust can cause a number of potentially fatal health issues. Therefore, it’s imperative to measure and control exposure to hazardous respirable crystalline silica (RCS).
Traditionally, measuring RCS levels meant sending samples to a lab and waiting for the results to be returned.
“[Silica dust sampling] is required for each task and set of conditions,” said David Rigsbee, CEO of Chemtek Inc., Morrisville, North Carolina. Each sample must then be sent to a lab for testing, which takes around three weeks to return results and can be cost-prohibitive, especially for smaller contractors, he added.
“Many contractors have not addressed this problem and are still trying to understand how to tackle [the new requirement],” Rigsbee said.
That’s why the National Institute for Occupational Safety and Health (NIOSH) launched a new software program to monitor workers’ exposure to RCS much faster than traditional methods allow.
The NIOSH program, dubbed Field Analysis of Silica Tool (FAST), was launched in October. It works alongside commercially available portable Fourier Transform Infrared (FTIR) analyzers to monitor a worker’s exposure to RCS dust and provides detailed results immediately after a worker’s shift. Although the program is meant for coal mining operations, it can also be used to monitor and approximate silica dust exposure in other industries.
“We began with coal mining because there are minimal mineral confounders in coal mines, which can affect measurements,” said Dr. RJ Matetic, Director for the Pittsburgh Mining Research Division. “But that doesn’t mean the approach can’t be used in other industries as long as the limitations are understood.”
Samples collected in other environments should be considered approximations. The reliability of these estimates can be ascertained by comparing field results to results obtained from an accredited laboratory. The FTIR method is non destructive, which allows these comparisons.
How It Works
The FAST software works alongside NIOSH’s new monitoring approach, which relies on portable FTIR instruments to analyze dust collected on sampling cassettes. Each dust sampling cassette contains a PVC filter that collects airborne dust for later measurement and analysis. The FTIR analyzers scan the infrared spectrum to identify and measure the amount of crystalline silica present in the dust collected on the filter.
“We haven’t changed the way dust samples are collected,” said NIOSH engineer Dr. Emanuele Cauda; however, there are certain benefits to using the dust cassette developed by NIOSH that is commercially available from Zefon International.
By employing this method, the user can then import the data from the FTIR analyzers into the FAST software, which takes around 20 seconds. The FAST software translates the data to estimate silica levels, based on sampler type, flow rate, sampling time, and other factors. The estimations are available within two minutes.
“A traditional cassette could be used for this application, but you would need to take the filter out of the cassette and handling the filter may introduce errors to the estimate,” Cauda said. “Here, the cassette does it all in the analyzer. It’s more user friendly in the field.”
This process also doesn’t degrade the dust sampling cassette, so it is possible to then send it off for lab analysis for verification, in addition to monitoring the situation with NIOSH’s FAST software.
Estimation vs. Approximation
Although NIOSH’s FAST software may offer more accurate estimations of silica dust for industries besides coal mining in the future, Rigsbee has reservations about its use at present.
“I think approximations are dangerous, as they quickly move from guess to fact as they proliferate,” Rigsbee said.
Cauda mentions that there are several points in the software with disclaimers reminding the user that these are estimations. NIOSH also field-tested the FAST software nationally and internationally before releasing the beta version.
It is possible to use the FAST software on other mined commodities by selecting “other” commodity within the software, but NIOSH warns that the presence of other minerals from other types of mines or locations could decrease the accuracy of the system.
“We have to explain to the public that there are limitations when using the software, but that shouldn’t hold people back from using it as long as they understand those limitations,” Matetic said. “Use of the software may indicate a change in the RCS environment that needs to be addressed while waiting for the lab results to come back.”
In the future, NIOSH plans to launch industry-specific software for other commodities within the mining industry.
Although NIOSH already has large databases for mining operations, including metal mines and rock quarries, in addition to coal mines it hopes to expand its sample datasets for industries outside of mining. “That’s our first step,” Cauda said. They will also be creating calibration samples to train the software’s model to address the presence of other minerals automatically. “It may be a few years before we are at that point.”
They are also working on a publication that will outline best practices on how to implement this monitoring approach, expected for publication in the first half of 2019.
“Our main focus for this research is mining, but if it’s applicable to other industries, that’s win-win for everyone,” Matetic said.
The beta version of FAST is available now, with a full version to be made available after the software completes NIOSH’s testing process. Feedback on the software can be sent to firstname.lastname@example.org.
CPWR Estimates Common Hazards
The Center for Construction Research and Training, or CPWR, has also launched an Exposure Control Database to help predict exposure to common hazards on the job site, including silica.
“We started developing the database in close collaboration with NIOSH researchers, trade unions and other industry partners,” said Babak Memarian, CPWR’s director of exposure control technologies research. “The database is a web-based searchable tool that estimates worker exposure to four major hazards…using objective exposure data based on construction operations, not lab data or from simulations.”
The free tool allows users to select from four hazards: silica, noise, welding fumes or lead. For example, if the user selects silica as the hazard, he or she will be prompted to input data specific to the situation, including task, tool/equipment, material, control method, environment and project type. If the user chooses milling pavement of asphalt with a milling machine using water to control the silica dust in an outdoor environment, they can click submit and the tool will return an expected exposure based on the average of the data CPWR used to build the tool, as well as a list of useful resources.
The dropdown menus change depending on the hazard selected. For example, noise requires the user to input tool, manufacturer, model, material, task duration and other tools. If the dropdown menus do not include the option for your specific situation, CPWR’s Sara Brooks recommends checking back at a later date. “We will be adding new data regularly,” she said.
Although the tool can be useful in estimating whether or not employees are at risk of these four hazards, when asked if a regulatory body would be satisfied that employees were not at risk for overexposure based on the results of the tool, the short answer is no.
“The database is not meant to be a regulatory tool,” Brooks said. “Your PPE and control method decisions should be governed using an abundance of caution. [The tool] is not necessarily something a regulatory body would abide by.”
She added that the data can not be used as a substitute for an exposure assessment. “It is an assistive tool,” Brooks said. “The gold standard is to perform an exposure assessment on the task being performed.”
The free tool is publicly available here and will be added to the CPWR website in the near future.