‘Nuisance’ PM: visible dust monitoring and assessment

A presentation for IAQM

Hugh DatsonDustScan Ltd

14 April 2011

Contents

• Dust definitions and context• Dust sources and examples• Passive dust monitoring• Deposition by mass• Flux by mass• Deposition by soiling• Flux by soiling• Custom & practice limits• A need for greater consistency?

Dust definitions 1

• BS6069 Part 2: particulate matter < 75µm diameter

• Specific fractions (size/composition dependent)– Public health (e.g. PM10)

– Workplace exposure (e.g. Inhalable convention)

– Specific minerals (e.g. Asbestiforms)

• Limits agreed (NAQS, WELs)

• ‘Active’ (powered) monitoring methods

Dust definitions 2

• ‘Nuisance dust’ (not size/composition dependant)– Poorly defined: visible dust; annoyance; soiling

– Short-term (acute)

– Long-term (chronic)

• Limits not agreed (custom and practice)• ‘Passive’ (unpowered) monitoring methods• Some misconceptions and misapplications

over limits and methods

Short-term dust event: acute

• Dust clouds generated by vehicle traffic on a site access road…

Long-term dust impact: chronic

• …can lead to soiling of vegetation and signage next to the road

Or both…

• Dust soiling within about 2 hours of parking near a secondary aggregates site

Dust sources

• ‘Natural’ background dust• Fugitive industrial dust: common

processes, different sources, different impacts?– Construction and demolition – Roads and transport– Surface mining and minerals– Waste transfer and landfill– Land remediation– Secondary aggregates– Agriculture

• Different public perceptions and reactions

Construction & demolition

• Relatively short term, varied intensity, may have neighbour issues (especially during a major redevelopment scheme)?

Roads and transport

• Track-out from industrial sites can affect neighbours: where do the impacts start and end?

Secondary aggregates/recycling

• May have significant impacts on neighbouring land users – and a range of competing dust sources?

Surface mining & minerals

• Drilling, blasting, materials handling and haulage: long-term potential for impacts but often located away from major settlements

Waste transfer & landfill

• Scale of impacts will vary considerably depending on location: wide range of effects from materials handling and treatment

Agriculture

• Seasonal, generally remote from major habitation but can have significant local impacts

Dust measurement

• Source – pathway – receptor relationships• Fugitive dust generation, dispersion and

settlement• Dust flux: the horizontal passage of dust

past a point• Dust deposition: the vertical passage of

dust to a surface or the ground• Flux and deposition: different phases of

the same material?• The distinction between dust flux and dust

deposition is ‘frequently misunderstood’

Other considerations

• Monitoring strategy, aims and objectives– Whose dust is it, how much is there, what’s in

it?– Public perceptions, reactions (and fears?)

• Distinguish between site and background:– Weather data– Directionality– Geochemical analyses– Sampler locations– Site activity logs– Modelling– Data evaluation

Passive dust monitoring methods

• Range of approaches– dust deposition or dust flux– dust mass or dust soiling

• Data not interchangeable– mass vs. soiling– flux vs. settlement

• No one method is ideal: whichever method is specified or used, use correctly– Deposition monitoring ideally at receptor/proxy

receptor locations– Flux monitoring ideally at boundary/pathway

locations

Deposition monitoring by mass

Deposition monitoring by mass

• Mass/area/time (mg m-2 day-1)• Frisbee gauge ≈30% more efficient than BS1747

Part 1 gauge (Vallack, 1995); c. 5° displacement from horizontal reduces collection efficiency by 40% (Hall and Upton, 1998)

• Different versions in use• Different measurement methods also in use: BS

1747 Part 1 (inappropriate) and SEI-Y (appropriate) for Frisbee

• Other mass deposition methods include Bergerhoff & NILU (ISO). BS 1747 Part 1 gauge effectively discontinued

Flux monitoring by mass

Flux monitoring by mass

• Mass/area/time (mg m-2 day-1) BUT NOT INTERCHANGEABLE WITH DEPOSITION GAUGES – ‘There is a popular misconception that these gauges

measure dust deposition whereas they attempt to measure dust flux…adding the flux from the four collecting heads does not magically convert this directional gauge into a deposit gauge as some practitioners imagine’ (Ian Hanby, 2010)

• BS 1747 Part 5 gauge: obscuration or mass– Directionality good for coarse dust/grit but up to 25%

from downwind side (Ralph and Hall, 1989)– Closed container samplers ‘fundamentally unsuitable’ for

flux sampling (Hall et al, 1993)• Warren Spring wedge dust flux gauge...(not in

production)• ‘directional Frisbee’ – see Metdust?• Modified Wilson and Cooke gauge (MWAC)

Deposition monitoring by soiling

Deposition monitoring by soiling

• Shorter sampling intervals than dust mass gauges (days not weeks)

• Glass slides (Brooks & Schwar, 1987) Loss of gloss % method; reported as soiling units (s.u.)

• Sticky pads (Beaman & Kingsbury, 1981) Effective area coverage (EAC %); emulates smoke stain reflectometry

• Results not interchangeable - although some correspondence found when sampling indoors (Adams et al, 2001)

Flux monitoring by soiling

Flux monitoring by soiling

• Sticky pads–Beaman & Kingsbury (1983); EAC%–DustScan (Farnfield & Birch, 1997)

absolute area coverage (AAC%); EAC% (Datson and Birch, 2006)

Custom & practice criteria…

• Frisbee gauge (SEI-Y method): ≥ 3.5 ×median local background (minimum 12 months data) or 200 mg m-2 day-1

(residential areas and outskirts of towns) ‘complaints likely’

• Glass slides: 20 – 25 soiling units/week (4-week average) ‘limit of acceptability’

• Sticky pads: 5% EAC day-1 ‘serious complaints’; AAC% and EAC% ‘risk matrix’

…and comments

• Very limited research on public reaction to ‘nuisance’ dust published (QUARG, 1996)

• Site-specific criteria that take local conditions into account more likely to be effective for site operator and the local community (Brimblecombe and Grossi, 2005)

• Unlike NAQS, are site-specific thresholds more appropriate? – one size doesn’t fit all

• Are the appropriate methods and criteria being applied?

Monitoring and application guidance

• Hence the need for consistent guidance … and terminology

• Regulatory guidance is getting outdated–e.g. EA M9 (2000)

• Differences between industry sectors–EA M17 (2004)–BRE (2003), London BPG (2006)–Arup Environmental (1996), AEA (2010)

Conclusion

• ‘Nuisance’ PM: poorly defined and unspecified by particle size or composition

• Wide range of sources, difficult to quantify at source

• Acute and chronic impacts (dust flux or dust deposition)

• Affects quality of life, if not public/personal health• Impacts depend on perception/experience, thus

difficult to quantify (and will change)• Very different sampling systems and techniques

(deposition or flux, mass or soiling)• Custom and practice criteria (limited evaluation)• Some misconceptions about sampling and criteria• There is a need for greater clarity and clearer

guidance (and terminology)