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.
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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
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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)
HSL: HSE’s Health and Safety Laboratory © Crown Copyright, HSE 2016 © Crown Copyright, HSE 2016
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
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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
HSL: HSE’s Health and Safety Laboratory © Crown Copyright, HSE 2016
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
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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.
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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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0
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0 100 200 300Scanner
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
(µ
g o
n f
ilte
r)
Difference gloss meter
Mine airCrane exhaust
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0 200 400 600OT21
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1 3 5 7 9 1113151719212325272931333537394143454749515355
A
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
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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
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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
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Laboratory measurements
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co
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g/m
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d a
ir c
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g/m
3)
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Airtec 95% CI
BC 95% CI
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On site measurements
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BC
/EC
(µ
g/m
^3)
Time
1 min comparison
µAeth
Airtec
Mine Airtec
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Instrument performance
y = 1.0845x + 42.245 R² = 0.9099
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co
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f µ
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th B
C
µg.
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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
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irte
c EC
µ
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Air Concentration of EC by EN14530 method µg.m-3
Airtec EC
1:1 Relationship
• µAeth AE51
• Airtec
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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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Usefulness of gas monitoring
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NO2(ppm)(Max)
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CO2(ppm)(Max)
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Usefulness of gas monitoring
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12:56 13:04 13:12 13:21 13:29 13:37 13:46 13:54 14:02 14:11 14:19
BC
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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
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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
HSL: HSE’s Health and Safety Laboratory © Crown Copyright, HSE 2016
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)
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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 © Crown Copyright, HSE 2016 © Crown Copyright, HSE 2016
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