Respirable Crystalline Silica (RCS) Sampling — MSHA Rule
Mining Operations
Eastern, New Hampshire
Client Challenge
Under Mine Safety and Health Administration’s (MSHA) 2024 Final Rule effective April 8, 2026 (for metal/nonmetal mines), operators must conduct initial respirable crystalline silica (RCS) sampling for all potentially exposed workers —a common occurrence at surface mining operations with moderate dust generation. MSHA mandates require a second sampling round within 3 months. Sampling can be discontinued when two (2) consecutive samplings indicate that miner’s exposures are below the action levels.
Aries Environmental Scientists were retained to assist our client by conducting multiple rounds of RCS personal exposure sampling, preparing a written Silica Exposure Control Plan and Job Hazard Analysis (JHA) at their surface mining operation. Aries expertise with the current regulatory requirements, occupational health imperatives and sampling analysis are a necessary part of assisting clients with health and safety evaluation and controls and maintaining compliance adherence.
Comprehensive Solution
Aries Services
Conduct full-shift personal exposure sampling for respirable crystalline silica.
Confirm initial results through required follow-up sampling within 3 months.
Prepare a findings letter from Aries for each sampling round and compare sampling results with RCS permissible exposure limits (PELs) and action levels (AL).
Conduct JHAs for each job task
Evaluate engineering controls in the employee booths and enclosures.
Document effectiveness of implemented engineering controls
Validate that control modifications successfully reduced exposure to compliant levels
Prepare a Silica Exposure Control Plan identifying miner tasks and appropriate exposure controls, exposure assessment including the findings of personal RCS sampling, suggested corrective actions and regulatory requirements for medical surveillance and training.
Personal Sampling Collection Protocol
Respirable crystalline silica personal exposure samples are collected from full-shift (10-12 hours) individual employee’s breathing zone who represent similar exposure groups (SEGs)
Two field blanks are collected in accordance with the NIOSH method.
Samples are collected on a precipitation-free day
An AIHA and ISO accredited lab is utilized along with sampling media, pumps and lab analysis in accordance with the NIOSH method
Results are compared against established MSHA Action Level (AL) and the Permissible Exposure Limit (PEL)
Beneficial Outcome
Aries professional team conducted personal RCS sampling to evaluate compliance with MSHA new Final Rule regarding PELs and ALs for miner silica exposure. Multiple rounds identified potential exposure exceedances for one SEG, and identified compliance for other miner exposures, with information proved in defensible documentation supporting regulatory compliance. Sampling data, and development of the Silica Exposure Control Plan allowed for focused corrective actions, future worker health protection.