Case Study: Respirable Dust Monitoring Program for Mining Operations

Client: Hard Rock Mining Operation, Western Australia

A mid-sized hard rock gold mining operation in the Goldfields region of Western Australia operated a surface open pit mine with underground decline access. The operation employed approximately 220 personnel and conducted:

Open pit mining (excavation, blasting, loading)
Underground development mining (drilling, blasting, mucking)
Ore crushing and milling
Site infrastructure and maintenance

The operation had been in production for 12 years. Whilst the company had conducted occasional air monitoring in response to regulatory inspections, they had never implemented a systematic dust monitoring and health monitoring program covering all risk areas.

The Challenge

In mid-2023, the mining company’s internal safety audit and a regulator inspection identified significant gaps:

No baseline data: The company had no documented exposure profile for any work areas, making it impossible to assess whether the WorkExposure Standard (0.05 mg/m³ RCS) was being met
No health monitoring program: No workers had occupational health screening (chest X-rays, lung function tests) despite many having 10+ years tenure in the mining operation
Uncontrolled high-risk areas: Underground mining activities (drilling, blasting, mucking) had no dust suppression or ventilation controls beyond general mine ventilation
Regulatory pressure: The regulator indicated that a monitoring program, results, and health monitoring plan would be expected within 12 months
Worker concern: An informal survey revealed that some long-serving workers were worried about their lung health after years of mining without formal surveillance

The mining company engaged Anitech Group to design and implement a comprehensive dust and health monitoring program.

Our Approach

1. Comprehensive Hazard and Risk Assessment

Anitech conducted a site-wide occupational hygiene audit identifying all dust-generating activities:

Open pit operations:
– Excavator operation and bucket handling (dust from ore)
– Loading into haul trucks
– Blasting fragmentation and secondary breaking
– Site roads and traffic

Underground mining:
– Percussion drilling (development and definition holes)
– Blasting and re-entry
– Mucking (load haul dump [LHD] operation and manual mucking)
– Ventilation adequacy assessment

Processing:
– Primary and secondary crushing
– Milling and grinding
– Concentrate handling
– Dust exposure from ore transport between areas

High-risk roles identified (for personal monitoring priority):
– Underground drill operators
– Underground LHD operators
– Mine mucking crews
– Excavator operators (surface)
– Crusher operators
– General mine workers

2. Baseline Monitoring Program Design

Anitech designed a two-phase baseline program:

Phase 1: Quick Assessment (Weeks 1–6)
– Personal air sampling of 3–4 workers per high-risk area
– Static monitors in processing areas and underground zones
– Real-time dust screening in underground operations

Phase 2: Comprehensive Baseline (Weeks 7–16)
– Extended personal sampling (2–4 week campaigns) in each major operational area to capture typical work variation
– Seasonal variation assessment (baseline conducted in winter; summer monitoring to follow to account for ventilation and environmental differences)
– Task-specific sampling (distinguish between high-intensity drilling vs. lower-intensity development tasks)

3. Control Baseline Assessment

Before designing controls, Anitech documented what was already in place:

Existing controls found:
– Mine ventilation system (primary control in underground areas)
– Some water suppression on open pit loadout
– Dust collector on the crushing plant
– Minimal personal protective equipment (PPE) protocol

Key finding: The operation had basic passive controls but minimal active dust suppression. Underground areas relied entirely on general mine ventilation, which was designed for heat/gas exchange, not optimised for dust control.

4. Health Monitoring Program Design

In parallel with air monitoring, Anitech designed an occupational health monitoring program:

Baseline occupational health assessments: All underground workers and long-serving surface workers (≥5 years tenure) were offered baseline assessments consisting of:
Chest X-ray (compared to international standard reference films to screen for silicosis)
Spirometry (lung function testing)
Occupational health questionnaire (respiratory symptoms, smoking history, previous exposures)
Medical consultation with an occupational physician (not on-site; telehealth available)
Surveillance protocol: Workers with significant underground exposure would undergo repeat health monitoring every 2 years; surface workers every 3–4 years
Access and engagement: Health assessments were conducted at the mine site (X-ray mobile unit, spirometry equipment brought in) to maximise participation; offered to workers on paid time during shifts

Key Findings

Phase 1 Baseline Results (Weeks 1–6)

Rapid assessment identified major exposure variability:

Activity	Location	Worker Role	TWA Result (mg/m³)	% of WES
Drilling	Underground	Drill operator	0.28	560%
Mucking	Underground	LHD operator	0.15	300%
Blasting	Underground	General worker (post-blast re-entry)	0.32	640%
Crushing	Surface	Crusher operator	0.08	160%
Excavation	Open pit	Excavator operator	0.04	80%
Haul truck	Open pit	Truck driver	0.02	40%

Critical finding: Underground activities substantially exceeded the WES. Open pit and processing were closer to compliance but still elevated.

Immediate actions:
– Work halted on high-risk underground tasks for emergency control design
– Drilling operations temporarily restricted to short shift durations (rotating crews, reducing individual exposure)
– Blasting protocols modified: extended re-entry delay (allowing dust to settle) and additional ventilation run time

Phase 2 Comprehensive Baseline (Weeks 7–16)

Extended monitoring across seasonal and task variation:

Underground drilling: 0.22–0.35 mg/m³ across multiple trials (high variability depending on rock type and hole depth)

Underground mucking: 0.12–0.18 mg/m³

Post-blast re-entry: 0.28–0.42 mg/m³ (worst-case scenarios during hot re-entry without extended ventilation)

Crushing: 0.06–0.10 mg/m³ (seasonal variation; higher in dry summer)

Open pit excavation and haulage: 0.02–0.05 mg/m³ (already at or near compliance)

Key insight: The operation had a two-tier exposure problem: underground activities were severely non-compliant, whilst open pit was marginal. This informed a prioritised control strategy.

Health Monitoring Baseline Results

Occupational health assessments were offered to 156 workers; 134 (86% uptake) participated.

Findings:
– Abnormal baseline X-rays: 8 workers (5.9%) showed early-stage silicosis (simple pneumoconiosis category 1/1). All were underground workers with >10 years tenure
– Reduced lung function: 23 workers (17.2%) had spirometry results showing reduced FVC (forced vital capacity) or FEV1, consistent with early occupational lung disease
– Respiratory symptoms: 42 workers (31.3%) reported chronic cough, shortness of breath, or chest tightness
– Smoking confounders: 38 of the 134 workers were current smokers; smoking status was documented and controlled for in interpretation

Clinical significance: The results indicated that workers had been accumulating silica-related disease during the operation’s 12-year history. The 8 workers with radiographic silicosis required:
– Immediate notification and medical counselling
– Worker compensation assessment and claims support
– Job modifications to reduce future exposure
– Repeat X-ray and spirometry at 6-month intervals

Regulatory notification: These results were reported to the mining regulator as required. The company was not subjected to enforcement action but was required to implement a remediation plan.

Outcomes

Control Improvements (Months 2–6)

Based on baseline findings, the operation implemented:

Underground:
– Installed water suppression on all percussion drills (mist sprays at drill collar and boom)
– Enhanced ventilation: upgrade to secondary fan capacity, optimised air routing through drill and muck areas
– Modified drilling procedures: slower penetration rates (reducing instantaneous dust generation), more frequent ventilation pauses
– Engineered dust collector on underground haul truck paths
– Extended post-blast ventilation time (30 minutes minimum before re-entry, vs. previous ~5 minutes)
– RPE protocol: supplied all underground workers with P3 (high-efficiency) respirators; fit-testing and training implemented

Surface:
– Enhanced water suppression on excavator loadout areas
– Upgraded dust collection on primary crusher (improved airflow, HEPA filter replacement frequency)
– Site road watering programme (daily watering during dry season)

Estimated capital investment: Approximately AUD $320,000 for ventilation upgrades, dust collection, and water suppression infrastructure.

Post-Control Monitoring (Months 8–14)

After controls were fully operational, monitoring was repeated:

Activity	Location	Worker Role	New TWA Result (mg/m³)	% of WES	Reduction
Drilling	Underground	Drill operator	0.06	120%	79% ↓
Mucking	Underground	LHD operator	0.04	80%	73% ↓
Blasting	Underground	General worker	0.05	100%	84% ↓
Crushing	Surface	Crusher operator	0.035	70%	56% ↓

Key outcome: All activities moved significantly closer to the WES. Underground drilling and blasting remained above the limit but were now in range where combined controls (engineering + RPE) could achieve compliance.

Sustained Compliance Program (Months 14 onwards)

The operation established a standing monitoring program:

Frequency: Quarterly personal air sampling of high-risk roles; annual static monitoring at all areas
Health monitoring: All underground workers on a 2-yearly health surveillance cycle; surface workers every 3 years
Real-time feedback: A handheld dust monitor was deployed for daily screening (not compliance assessment, but for process control and early warning)
Training: All workers received induction training on dust hazards, controls, and monitoring; annual refresher training

Compliance rate: In the 12 months post-control implementation, 94% of personal samples were ≤ 0.05 mg/m³. The remaining non-compliant samples (6%) occurred during unusually high-risk tasks or control failures (e.g., temporary water suppression malfunction); all non-compliant workers were notified, controls were immediately corrected, and re-sampling showed return to compliance.

Health Outcomes

Repeat occupational health assessments at 12 months (post-control):

No new radiographic cases of silicosis identified in the repeat cohort
Lung function: 3 of 23 workers with previously reduced function showed improvement (attributed to reduced exposure)
Respiratory symptoms: 28 workers (26.3% of repeat cohort) reported symptoms, down from 31.3% (suggesting improvement in air quality perception, though not statistically significant in one year)

The workers with baseline silicosis diagnoses remained under specialist medical follow-up and were transitioned to lower-exposure roles (e.g., supervisor, technical roles not requiring underground time).

Regulatory and Business Outcomes

Regulator satisfaction: The comprehensive baseline, rapid control implementation, sustained monitoring, and health program satisfied the regulator. No enforcement action was taken; the operation was commended for transparency and remediation efforts
Worker relations: Workers responded positively to the health monitoring and transparent communication of results. Retention improved; several workers reported increased confidence in the company’s commitment to safety
Competitive positioning: The operation became a model for the region. Future recruitment was easier based on the demonstrated WHS commitment; the company won industry awards for occupational health excellence
Insurance and liability: The documented program, baseline data, and remediation efforts created a defensible record in the event of future workers’ compensation claims

Lessons and Takeaways

Baseline data is essential: Without knowing where exposure stood, the operation couldn’t prioritise controls. The rapid Phase 1 baseline (weeks 1–6) immediately identified the crisis (underground exposure 5–6x the WES) and triggered emergency response.
Health monitoring reveals hidden disease: The operation had accumulated silicosis cases over 12 years with no knowledge. Early health monitoring detection allowed intervention before disease progressed; several workers were preventable from further disease progression through role modification.
High-risk activities require combined controls: Underground drilling couldn’t be brought to compliance with water suppression alone; ventilation, procedure change, and RPE were all necessary.
Sustained monitoring is non-negotiable: A single baseline is insufficient; quarterly monitoring caught control failures and ensured compliance was maintained, not just achieved once.
Transparency builds workforce engagement: Workers who understood baseline findings, saw visible control improvements, and received health monitoring results were engaged partners in the safety program.

Anitech Supports Mining Operations Across Australia with Comprehensive Dust Monitoring Programs—Get in Touch

Mining operations face the highest silica exposure risks of any industry. Baseline monitoring, health surveillance, and sustained compliance programs are essential. Whether you’re a new operation building a WHS framework or an established mine needing program review, Anitech’s occupational hygienists have extensive mining experience.

IMAGE_REQUIREMENTS

FEATURE: 1200x630px. Underground mining operation: close-up of a percussion drill in operation with visible water suppression mist in action around the drill collar; tungsten lighting of underground tunnel visible; dust particles visible in air but controlled by mist; professional, realistic underground mining scene.
BODY_1: 800x450px. Occupational health assessment in progress: a worker sitting for spirometry testing (lung function equipment visible), occupational health nurse operating the equipment; portable X-ray mobile unit visible in background at the mine site; shows the health monitoring program in action.