Construction dust risk assessment under IAQM guidance

A construction dust assessment follows the Institute of Air Quality Management method: screen the site against distance thresholds, size the dust emission magnitude for each of four activities, judge the sensitivity of the surrounding area, combine the two into a risk category, then set mitigation to match. Councils across England expect that structure, and an assessment that skips the screening step or jumps straight to a list of mitigation measures usually comes back with a request for the missing stages.

The method is proportionate by design. A small infill site with no neighbours within 350 m can screen out in a page. A demolition and basement scheme next to a primary school cannot.

Screening: does the assessment need to happen at all

The first question is whether any receptor sits close enough to be affected. The IAQM guidance sets the screening distances by receptor type and by pathway.

Human receptors are screened in where they lie within 350 m of the site boundary, or within 50 m of the routes used by construction vehicles on the public highway, up to 500 m from the site entrance. Ecological receptors use a tighter 50 m from the boundary and 50 m from the route, again up to 500 m from the entrance.

If nothing falls inside those distances, the guidance allows the assessment to stop there, with the reasoning written down. Say which receptors you looked for, name the designated sites you checked on the relevant national datasets, and show the search radii on a plan. That short section is the part officers actually read.

The four activities and their emission magnitude

Where screening does not clear the site, the guidance splits the works into demolition, earthworks, construction and trackout, and assigns each one a dust emission magnitude of large, medium or small.

Trackout is the one most often underestimated. The guidance treats more than 50 outward heavy duty vehicle movements a day as a large magnitude, 10 to 50 as medium and fewer than 10 as small, so a modest scheme with a long muck-away phase can sit in a higher band than the building volume alone suggests. Earthworks scale by area, with sites above roughly one hectare falling into the largest band.

Take the volume and area thresholds from the current version of the guidance rather than from an older report. The document has been revised, and the bands are the part most often quoted out of date.

Judging the sensitivity of the area

Sensitivity is assessed separately for three effects: dust soiling of surfaces and property, human health effects from PM10, and effects on ecological receptors.

For dust soiling and health, the guidance asks for the number of receptors within given distance bands and their sensitivity. Housing, schools, hospitals and care homes are high sensitivity. Offices and retail are medium. Footpaths, playing fields and industrial premises are low. For the health element you also need the existing annual mean PM10 concentration, which comes from the Defra background maps or from local monitoring published by the council in its air quality annual status report.

Ecological sensitivity depends on the designation and on how dust-sensitive the habitat is. A Site of Special Scientific Interest with a lichen or bryophyte interest is far more sensitive than an ordinary local wildlife site.

The combination of emission magnitude and area sensitivity produces a risk category for each activity and each effect: negligible, low, medium or high. Set it out as a matrix in the report so the officer can follow the logic without recalculating it.

Mitigation that matches the risk category

The guidance gives mitigation by risk category, and the difference between low and high risk is real rather than cosmetic. Highly visible measures apply everywhere: hoarding and screening, damping down, sheeting of loads, no burning on site, wheel washing, and a named site contact for complaints displayed at the boundary.

Higher risk sites add more:

1. Real-time PM10 monitoring at the boundary with agreed trigger and action levels, reported to the council on request.
2. Dust deposition gauges or directional sticky pad monitoring where soiling of property is the concern.
3. Water suppression on cutting, grinding and crushing, with cutting done off site where the design allows.
4. Enclosed chutes and covered skips for demolition arisings, and no drop heights above what the method statement allows.
5. Hard surfacing and regular mechanical sweeping of haul routes and the site entrance.
6. Restrictions on non-road mobile machinery emission standards, which apply in Greater London under the Mayor's requirements and increasingly appear as conditions elsewhere.

Write the measures as commitments with a responsible role attached, rather than as a list of things that are generally good practice. Conditions are drafted from your wording.

Reporting the residual effect

The IAQM approach expects the assessment to conclude on residual effects after mitigation. For the overwhelming majority of sites, properly mitigated construction dust is not significant in air quality terms, and the guidance says so directly. That conclusion only holds if the mitigation is secured, which is why the mitigation schedule must be capable of being conditioned.

Two things undermine it. Mitigation described in general terms that a contractor could interpret away, and a monitoring commitment with no trigger levels or action plan attached.

Where the site sits inside an Air Quality Management Area, or where the scheme also generates operational traffic emissions, the dust chapter sits within a wider Air Quality Assessment rather than standing alone. Dust from construction and emissions from completed development are different questions with different methods, and merging them confuses both.

Illustrative example. A scheme demolishing a two storey warehouse and building 40 flats on a 0.6 hectare site, with 30 lorry movements a day during the muck-away phase and terraced housing 20 m from the boundary, lands in the medium magnitude band for earthworks and trackout against a high sensitivity area. The result is a medium risk category, boundary monitoring, a hard surfaced haul route and a wheel wash. This example is illustrative only.

Where the mitigation ends up

Planning conditions rarely refer to the dust assessment itself. They refer to a management document, and the drafting matters.

A Construction Management Plan is the usual home for dust control, working hours, noise limits referencing BS 5228, waste handling and neighbour liaison. Vehicle routing, wheel washing and delivery management sit in the Construction Traffic Management Plan. Some councils also ask for a standalone dust management plan, which is a document a suitably experienced air quality consultant prepares and which PlanScope does not produce.

On larger schemes the dust assessment feeds the air quality chapter of an Environmental Statement, and the screening opinion for Environmental Impact Assessment should be settled before the dust work starts, because the EIA Regulations 2017 require the Environmental Statement to be prepared by competent experts. A PlanScope draft is a starting point for that specialist, never a replacement for them.

One honest limitation. The IAQM method is a risk-based screening tool rather than a predictive model, and it does not tell you how much dust will be deposited on a particular window ledge. Where a neighbour has already complained, monitoring data does more than a risk matrix.

This is general guidance, not legal advice. Councils usually expect a suitably qualified author for air quality work, and professional review is strongly advised before submission.

Browse the PlanScope report types to see which environmental documents your site is likely to need.

PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.