monitoring of diesel exhaust particulate (dep) · hsl: hse’s health and safety laboratory ©...

Health and Safety Executive

© Crown Copyright, HSE 2016 HSL: HSE’s Health and Safety Laboratory

Monitoring of Diesel Exhaust Particulate (DEP)

28th September 2016

James Forder

HSL: HSE’s Health and Safety Laboratory © Crown Copyright, HSE 2016

Introduction

• What is Diesel exhaust particulate (DEP)? – Constituent of diesel engine exhaust emissions,

alongside, CO, CO2, NOx, aldehydes, PAHs – 2 main components, organic carbon (OC) and

elemental carbon (EC) – Nanoscale particles which agglomerate into clumps

and chains

• Why monitor DEP? – IARC classify it as a definite human carcinogen – More specific and correlated with diesel engine

exhaust emissions than the other main constituents.

HSL: HSE’s Health and Safety Laboratory © Crown Copyright, HSE 2016 © Crown Copyright, HSE 2016

Super short summary of a literature review commissioned by HSE

• Acute – respiratory/eye irritation, rare for exposures below 100 µg/m3 EC

• Persistent - lung cancer, rhinitis and cardiac illness. Evidence is currently insufficient to establish links with adult onset asthma and COPD.

Health effects


Super short summary of a literature review commissioned by HSE

• Transport, typically < 50 µg/m3 EC

• Mining, 100 – 600 µg/m3 EC

• Construction, main exposures in tunnelling works

Occupational exposures (from IARC monograph, 2013)


Super short summary of a literature review commisioned by HSE

• EC mass by combustion is the most appropriate measurement to assess exposure to DEEEs

• Biomonitoring of nitro- and amino-pyrenes

• Increase in ultrafines (<40 nm) in modern biodiesel engines. Particulate mass (EC) may underestimate health effects

Measurement


Elemental Carbon

• EC is favoured as a marker for DEP

– Thought to be highly specific to diesel exhaust

– Other carbon sources can be removed by size selection at the inlet

– Some evidence that the nanoscale physical nature of the particles are a cause of observed health effects

Image courtesy of Tomas E Baquero Rincon, University of

Sheffield


Established methods

• The standard method is codified in EN14530:2004 and NIOSH method 5040.

• The methods are not equivalent but incorporate the same key stages.

– Sample on to quartz fibre filters with cyclonic samplers,

– Heat the filter to temperature 1, measure the evolved CO2 = OC.

– Increase the temperature, measure the evolved CO2 = EC


Established methods

• Being a carbonaceous soot DEP is black, therefore the degree of staining can be used to quantify exposure.

• Historically, for on-site monitoring the “blackness” of sample filters has been measured using the Bosch meter.

• Blackness can be converted to EC.


Previous work at HSL

• Alternatives to the Bosch meter

• 3 techniques analogous to measuring “blackness” – Difference gloss meter (DR-Lange) – Scanner/photo software – OT21 transmissometer (Magee

Scientific)

• Filters collected form – Mobile crane exhaust – Ambient air in a mine

• All 3 methods could replace the Bosch meter. In principle any optical technique could be used.


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Earlier work at HSL

• Charts were prepared showing the correlations between each instrument and EC.

• Functions were derived to convert the instrument results to EC.

– Difference gloss meter EC = 10(-0.0244x + 0.3196)

– Scanner (greyscale) EC = 10(-0.0065x + 1.9672)

– OT21 transmissometer EC = 10(0.2x - 0.0795)

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EC

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Difference gloss meter

Mine airCrane exhaust

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1 3 5 7 9 1113151719212325272931333537394143454749515355

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B

Modernising & Improving

• Results post shift is good but wouldn’t results during a shift be better?

– Highlight specific

exposure sources

– Facilitate and

encourage

immediate

interventions

– Empower workforce

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1 3 5 7 9 1113151719212325272931333537394143454749515355

ABCD


Real-time monitoring

• Incorporate pump, sampler and measurement in one device. Several options.

– General particle counters • Readily available • Non-specific, result is number of particles not mass of

EC

– FLIR Systems Airtec • Developed to replicate NIOSH 5040 • Light absorption measurement technique • Result given is EC based on a calibration study

– AethLabs AE51 microaeth • Developed for ambient air measurement • Miniaturised version of OT21 measurement technique • Result is Black carbon


Real-time monitoring

• HSL has been studying the performance of the µAeth and Airtec in parallel sampling tests with filters analysed by EN14530.

• A controlled atmosphere of diesel exhaust has been prepared and measured in the laboratory.

• In addition the instruments have been tested in field trials in a variety of workplaces. – RO-RO ferries – Vehicle test station – Underground non-metal mines


Laboratory measurements

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BC 95% CI


On site measurements

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Airtec

Mine Airtec


Instrument performance

y = 1.0845x + 42.245 R² = 0.9099

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Air Concentration of EC by EN14530 method µg.m-3

µAeth (BC)

1:1 Relationship

y = 1.185x - 40.147 R² = 0.7417

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Air Concentration of EC by EN14530 method µg.m-3

Airtec EC

1:1 Relationship

• µAeth AE51

• Airtec


Usefulness of gas monitoring

• Measured CO, CO2, NO, NO2 alongside particulates.

• HSG 187 states that if CO2 is <1000 ppm DEEE exposures are likely to be low. This should not be relied upon.

• CO - unmeasurable.

• CO2 – confounding sources, low resolution

• NO and NO2 – low resolution, can correlate with particulates, urban background often more significant



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BC


Real-time monitoring - Conclusions

AE51 microAeth

• Advantages

– Low detection limits

– Quick response

• Limitations

– Short monitoring period at high concentrations

– Does BC = EC?

– Separate device required to view results in real-time

Airtec

• Advantages – Can sample for a full

shift at high concentrations

– On board display

• Limitations – Slow response time –

not truly real time – High limit of detection,

especially for short term sampling


Summary

• Diesel exhaust is unhealthy

• Most UK occupational exposures are low

• Levels in the general environment are also significant

• Real-time monitoring is possible using black carbon as a proxy.

• Research interest globally


Improved microAeth instruments

• Now in 3 formats, two personal monitors, one static

• tape filter drive (for extended sampling and analysis),

• multi wavelength capabilities (allowing assessment of organic carbon, brown carbon e.g.woodsmoke/tobacco derived carbon in addition to black carbon)

• dual spot sampling (internal correction of self absorption)

• GPS and Wifi/Bluetooth capabilities (for data transfer to PC/Tablet/phone etc.)

• Weather-proof version for fenceline/lamp post/static sampling (unattended monitoring for up to 3 months)


Acknowledgements/Further reading

• This work was funded by the Health and Safety Executive. Its contents, including any opinions/conclusions expressed, are those of the author alone and do not necessarily reflect HSE policy.

• HSE RR994, available from the HSE website

• Simply Scan published in the Annals of Occupational Hygiene, 2014, vol 58, 889-898

• AethLabs AE51 µAeth - www.aethlabs.com/microaeth

• FLIR Airtec - www.flir.com/airtec/


HSL – HSE’s Health and Safety Laboratory

HSL is the commercial arm of the Health and Safety Executive, HSE. Our commercial work delivers high quality science to meet the needs of industry and government in the UK and overseas. Our commercial customers can commission services and research using our state-of-the- art scientific laboratory in Buxton, as well as analytical expertise from other parts of HSE’s science base.

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