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An OSH Inspector’s Perspective: Nano Diesel Particulate Matter in a Single Underground Mine

Lindy Nield MAIOH, MSc, BSc(Hons), Grad. Dip. Occ. Hyg.

OSH InspectorStatewide Health Team

• A Study of Nano Diesel Particulate Matter (nDPM) Behaviour and Physico-chemical changes in Underground Hard Rock Mines of Western Australia (MRIWA PROJECT M495) – final report 13 June 2019

Silvia Black and Ben Mullinshttp://www.dmp.wa.gov.au/Safety/Reports-16199.aspx

• Potential Health Effects on Workers from Exposure to Diesel Engine Exhaust (DEE) in an Underground Gold Mine – to be published peer-reviewed journals

Alison Reid and Ben MullinsPublished separately in peer-reviewed journals

• Critical review of recent diesel exhaust exposure health impact research relevant to the underground hardrock mining industry

Katherine Landwehr, Alex Larcombe, Alison Reid and Ben Mullinshttp://www.dmp.wa.gov.au/Documents/Safety/MSH_nPDM_Study_LitReview.pdf

Independent research commissioned by MIACFunded by DMIRS and MRIWA

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A Study of Nano Diesel Particulate Matter (nDPM) Behaviour and Physico-chemical changes in Underground Hard Rock Mines of Western Australia

• To assess:

− character of nDPM, its behaviour and also size, number and mass-based concentrations in underground hard rock mine environments

− examine the effects of elevated pressures and temperatures (as found in deeper mines) on nDPM formation and evolution

− Whether conventional monitoring (EC / NIOSH 5040) is less relevant to modern engines?

DEEE Characterisation and Exposure Monitoring – Methodology Overview

Over a two week period in October 2017, in a single underground gold mine:

• Part 1 – Tracer gas technology & computational fluid dynamics (CFD)− SF6 tracer gas monitoring as a surrogate for diesel engine exhaust emissions

(DEEE)− CFD – 2 dimensional model

• Part 2 – DEEE exposure monitoring− nDPM in situ real-time and personal exposure monitoring − Components of DEEE mixture

• Part 3 – Deep mine studies− Chamber studies investigating chemical changes under pressure

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Methodology – Part 1 – SF6 simulation

Tracer gas study on the Bogging activity.

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Findings – Part 1 – SF6 simulation

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Findings – Part 1 – SF6 simulation

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Tracer study output

Ventilation conditions

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Findings – Computational Fluid Dynamics (CFD) Studies

Findings – Computational Fluid Dynamics (CFD) Studies

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Findings – Computational Fluid Dynamics (CFD) Studies

Methodology – Exposure Monitoring

Over a two week period in October 2017, in a single underground gold mine:

• Fixed in situ real-time gas and nDPM monitors compared to personal monitoring for:

− nDPM as EC - (NIOSH 5040/EC)

− VOCs

− NOx

− CO and CO2

− SOx

• Comparison of personal exposures of workers conducting specified tasks by underground and on-surface workers

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Particle size monitoring during the Charging activity

Part 2 – Methodology – Deep mine studies

• To investigate generation of “new” or secondary nanoparticles (under elevated pressures) at depth, based on the potential influence elevated pressure and ammonia concentrations may have on the physiochemical characteristics of diesel exhaust particulate matter.

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Experiment flow

Part 2 – Methodology and Findings Deep mine studies

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Part 3 - Findings - DEE exposure

ExposuresUnderground

(median)

Surface

(median)

EC (μg/m3) 56.5 1.4

Total VOCs (μg/m3) 111.5 51.2

NO2 (μg/m3) 0.33 0.02

Particle number (pt/ccm) 52,740 8,763

Particle size (nm) 57.8 50.4

Exposure standards:

EC is 100 μg/m3 8 hour TWA & NO2 is 5600 μg/m3 8 hour TWA

Findings - Highest exposures by job type

Job title

N EC

(median)

(μg/m3)

VOCs

(median)

(μg/m3)

NO2

(median)

(μg/m3)

Particle

number

(median)

(pt/ccm)

Particle size

(median)

(nm)

Service crew 8 89.5 93.8 0.7 85,400 61

Driller / offsider 15 68.9 93.3 0.4 95,100 50

Jumbo operator 7 65.4 192.4 0.3 54,800 66

Bogger operator 9 57.9 136.4 0.7 41,500 65

Nipper 3 41.3 189.9 0.5 82,100 57

Exposure standards: EC is 100 μg/m3 8 hour TWA, NO2 is 5600 μg/m3 8 hour TWA

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Part 4 - Health Study - what participants did

Before work

• Completed a questionnaire

• Provided a urine sample

• Height /weight/ blood pressure/ lung function measured

• Fitted with personal monitoring equipment

After work

• Completed a questionnaire

• Post-exposure urine sample

• Post-exposure lung function test

• Provided a blood sample – DNA methylation analysis

Results for Underground Miners

• Fewer years overall working in the mining industry (7.8 v 12.5 years)

• Higher systolic blood pressure (142.6 mmHg v 135.5 mmHg)

• More current smokers (37.5% v 15%) but difference not statistically

significant

• Body Mass Index – 85% overweight or obese

• No other statistically significant differences in the demographics data

between underground and above ground miners

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Summary of lung function testing results

• Statistical differences in lung function between above and underground miners

• Lung function decreased over the 12 hour shift for underground miners

• The decrease was associated with diesel exposure, and remained after adjusting for smoking, age, height, shift on swing, years in mining

• On average, the decrease was 70 mL.− A ‘normal’ lung function result can vary by 150 mL diurnally

− Hence, reported changes observed were within the normal range of diurnal variation, on average.

Draft manuscript - Association between diesel engine exhaust exposure and lung

function in Australian gold miners

Urine Biomarker and Blood results

• These next results contribute to a general understanding of the effects of workers’ exposure to diesel.

• They don’t provide any information about the current health status of individual workers.

− Use for biological monitoring to detect individual exposure levels is not supported as no strong correlation between exposure to DEE and either of the metrics was shown consistently.

Du M, Mullins BJ, Franklin P, Musk AW, Elliot NSJ, Sodhi-Berry N, Junaldi E, de Klerk NH, Reid A. (2019) Measurement of urinary 1-aminopyrene and 1-hydroxypyrene as biomarkers of exposure to diesel particulate matter in gold miners. Science of the Total Environment. Vol 685;723-728.

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Urinary biomarkers of diesel exposure

Two biomarkers associated with diesel exposure measured:

• 1-hydroxypyrene (1-OHP) and 1-aminopyrene (1-AP)

• 1-OHP is the more commonly used measure, but is more strongly

influenced by smoking and diet

• 1-AP is a ‘better’ measure as it only responds to diesel exposure

• Both measures increased at the end of the 12 hour shift.

• 1-AP is a useful measure of DE uptake and is easy to measure (no

monitoring equipment to wear).

Blood analysis – DNA methylation

• Single blood sample collected at end of shift used to measure DNA

methylation

• After accounting for age and smoking status, we found 41/20,000

genes had reduced methylation (below the average level), which

appeared to be associated with diesel exposure.

• Cigarette smoking also reduces methylation, however to a much

greater extent. Studies in smokers find this is largely reversible after

five years of quitting.

• There is no evidence that the methylation levels found in this study

will lead to any health effects.

Draft manuscript - DNA Methylation following exposure to diesel particulate matter in an underground mine: Relationship to exposure parameters.

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Study recommendations

• Ensure ventilation in place and functioning – especially at dead-ends

• Improve systems around the spraymech to reduce exhaust exposure

• Change cabin air filters regularly

Individual workers

• Keep cab doors and windows closed

• Wear appropriate respirators / RPE when working underground

• Ensure proper respirator fit and regularly maintain it (if not disposable).

Historical DPM results submitted to DMIRS

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The good news …… from DMIRS

• Ventilation Management Plans are in place

− Diesel particulate filters (DPF) on machines have successfully reduced

diesel emission counts since 2006

− 4 out of 100 measurements are too high rather than most.

• Learnings from this study:

− Real-time monitors are now available to measure particle counts

− Alarms can be set to indicate when to switch off or remove vehicles

from an area to make it safer.

− Ventilation models are effective and are recommended to assist

ventilation design at all stages of operations and assessment.

Part 4 – Literature Review - Recommendations

− TWA (8 hour) of <50mg/m3 diesel particles (ultrafine)

− People with respiratory and cardiovascular conditions are the most susceptible to DEE

− The study takes a public health view to protect workers (!?!)

− Based on a lowest adverse observable effect level approach

− 35mg/m3 elemental carbon to limit health effects

− Improve testing of DEE mixture – possibly combining EC and NOx

− Equip diesel engines with after-treatment technology (DPF, Adblue)

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