Respirable crystalline silica, or silica dust, is a common occupational hazard for metal/nonmetal (MNM) miners including those at aggregate mining sites. Silica dust is released through many mining and milling operations, including cutting, drilling, excavating, sanding, and crushing. To reduce miner exposures to silica dust and other airborne hazards, the Mine Safety and Health Administration (MSHA) issued a final rule entitled “Lowering Miners’ Exposure to Respirable Crystalline Silica and Improving Respiratory Protection.” MNM mine operators must come into compliance by April 8, 2026. One requirement of the new rule is for mine owners to perform personal air sampling for silica of each task performed at the mine prior to the new rule taking effect. If levels of silica exceed an action level the new rule also requires repeated personal air sampling to document workers exposures.
Additional information from MSHA is available here.
MSHA New Silica Rule – Initial Exposure Monitoring Requirements
- What/Who’s exposure to sample?
- What about portable crushing crews that move to multiple mine sites?
- How is sampling performed?
- Where can I get the pumps and filters to do sampling?
- How many filters do I need?
- How long do I need to sample a worker?
- Where do I send my samples for analysis?
- What laboratory procedure/analysis do I request?
- Who pays for the analysis?
- What do I do with the results?
- Do I need to do anything else?
- Approved AIHA LAP Labs for Silica Analysis
Rent an MSHA Pump Kit from AGC
Each kit contains three personal air sampling pumps with all the equipment needed to calibrate and use the pumps for personal air sampling. The pump is rented for a duration of five business days. For questions, please email silicapumps@agc-oregon.org.
What/Who’s exposure to sample?
All Mine Safety and Health Administration (MSHA) Part 56 surface pit mine sites are required to perform an initial evaluation involving personal air sampling for silica for every job task performed at the mine site by April 2026. Sampling must be performed twice, with the second sampling session performed no more than 90 days from the first sampling session. For example, if an employer sampled on July 1 for three different tasks, they would need to resample the same three tasks within 90 days or before September 30.
Examples of tasks that should be sampled include personnel operating large powered haulage equipment (haul trucks, bulldozers, scalers, front end loaders); small power haulage equipment (bobcat, forklifts); crushing equipment (operators and workers); conveyors (belt cleaners, crew); drilling equipment (diamond drill, wagon drill, and helpers); kilns, dryers, ball mill, and pelletizers; or truck loading stations (dump operator and loader), as well as mobile workers (laborers, mechanics, electricians, supervisors, stone cutting operators, and package equipment operators).
Where multiple miners perform the same tasks/same shift/same work area, the employer can sample a representative fraction (at least two) of these miners—pick the ones expected to have the highest exposure.
If you have a small mine site with just a few miners who operate multiple equipment or perform multiple tasks, for example a site that runs with just two miners on site, then sample all miners on site the day you sample and keep track of the tasks/equipment they operated for your report.
When re-sampling, the same miner who was sampled during the first site evaluation does not need to be used; different miners performing the same task can be sampled. Ensure if multiple miners are doing the same task on site at least two in the task are sampled.
What about portable crushing crews that move to multiple mine sites?
MSHA’s silica rule requires ALL mine operators, including portable operations, to conduct exposure monitoring.
If portable operators move to a different site before the second sampling is performed (within the three-month window), then they need to perform the second sampling at the next site.
How is sampling performed?
A personal air sampling pump approximately 4x4x3 inches is worn on the belt or placed in a pocket of the miner. Tubing runs from the pump to the miner’s collar where a small filter is placed. The miner wears the pump, tubing, and filter for the entire work shift. At the end of the shift the filter is sent to a laboratory for analysis.
Learning to set up and operate the pump is not difficult. AGC has guides to show you how to sample.
Where can I get the pumps and filters to do sampling?
AGC has a pump rental service which also includes how-to guides, sampling filters, and phone/text support with one of the AGC industrial hygienists to assist you with any questions. Click here for details.
How many filters do I need?
Normally only one filter is needed per miner for an eight-hour work shift (including breaks and lunch). If the job is very dusty (working outside most of the day or cleaning crews) or the shift will be nine hours or more, it is recommended you use two filters and change the first filter used during the day for a second one half-way through the shift. If you change out a filter, make sure you record the start and stop time for each filter.
For quality control, you are required to submit one “blank” (unused) filter with your sample filters to the laboratory you use.
How long do I need to sample a worker?
Sampling must be performed over the miner’s full shift. You can pause sampling at lunch, but sampling must resume after lunch through the end of their workday. If the miner works an extended (e.g., 10-hour) shift, silica sampling must be conducted over the entire shift—in the case of this example, 10 hours.
Where do I send my samples for analysis?
Respirable dust samples must be analyzed for respirable crystalline silica analysis at an accredited laboratory that meets the international standard, ISO/IEC 17025 “General Requirements for the Competence of Testing and Calibration Laboratories.” Many industrial hygiene laboratories in the United States receive accreditation through the American Industrial Hygiene Association Laboratory Accreditation Program (AIHA LAP). At the end of this document, you will find a list of approved AIHA LAP labs.
Prior to sampling, you need to make arrangements with an industrial hygiene laboratory. The lab will want you to establish an account with them and use their chain of custody. Send samples to the lab within a reasonable time after collection—usually within 10 days.
What laboratory procedure/analysis do I request?strong>
At a minimum you should request analysis for respirable silica (quartz and cristobalite combined) and respirable dust (total dust). For a more complete understanding of the miner’s exposure, request analysis for quartz, cristobalite, and tridymite with respirable dust.
Who pays for the analysis?
Each member is responsible for paying for their laboratory analysis. Silica analysis generally costs around $100 per sample for analysis.
What do I do with the results?
An AGC representative will send an email with resource information on interpreting your results once you rent equipment. In the email, there will be a guide to help you interpret your results from the laboratory and determine if your samples exceeded the MSHA action level or permissible exposure limit. AGC IH’s can also help you review your data—we are just a phone call away.
Based on the results, MSHA will require certain actions if the workers’ personal silica levels were above the MSHA action level or permissible exposure limit.
Do I need to do anything else?
Yes, you are required by the new MSHA silica rule to conduct a qualitative (eyes only) evaluation every six months to see if any new exposures or changes to work activities that could increase worker exposure have occurred. If changes have occurred, MSHA will expect you to do more exposure monitoring.
Approved AIHA LAP Labs for Silica Analysis
- SGS Galson – New York: SGS Galson – Industrial Hygiene Lab for Sampling and Analysis, 888-432-LABS (5227)
- NVL Laboratory Inc – Washington: NVL Lab Services | NVL Labs, 888-685-5227
- EMSL Analytical – California: EMSL Analytical, Inc.- Microbiology & Environmental Testing, 866-798-1089
- LA Testing Huntington Beach – California: California Indoor Air Quality, Materials, Environmental, Microbiology and Industrial Hygiene Testing (latesting.com), 800-755-1794
- ALS Environmental – Utah: Industrial and Occupational Hygiene Services USA | Technical Consultation and ISO 17025:2017 Accredited Laboratories | ALS (alsglobal.com), 801-266-7700
- A&B Environmental Services – Texas: Industrial Hygiene Testing | Respirable Crystalline Silica Testing in Texas (ablabs.com), 713-453-6060
- Bureau Veritas North America, Inc. – Illinois: Industrial Hygiene Analysis (bvna.com), 888-357-7020
- Wisconsin Occupational Health Laboratory – Wisconsin: WOHL | Wisconsin State Laboratory of Hygiene, 800-446-0403
- Liberty Mutual – Massachusetts: Industrial Hygiene Laboratory | Liberty Mutual Business Insurance, 800-230-6263
- Travelers Industrial Hygiene and Forensics Laboratory – Connecticut: Industrial Hygiene Laboratory | Travelers Insurance, 800-842-0355
- RJ Lee Group: 800-860-1775
Rent an MSHA Pump Kit from AGC
Each kit contains three personal air sampling pumps with all the equipment needed to calibrate and use the pumps for personal air sampling. The pump is rented for a duration of five business days. For questions, please email silicapumps@agc-oregon.org.