The Institute of Air Quality Management (IAQM) has published new guidance on odour assessment for planning.
The National Planning Policy Framework (NPPF) requires the effects of pollution on health, the natural environment or general amenity to be taken into account in planning decisions. The NPPF definition of pollution specifically includes odour.
However, until now, there has been little guidance on how best to carry out an odour impact assessment; and none on how to assess the significance of the effects for planning purposes. The IAQM guidance, released on 20th May, addresses both of these areas.
Dr Jon Pullen, Operational Director at RPS` Brighton office, was a co-author of the guidance and has prepared a brief summary of some essential points:
The National Planning Policy Framework (NPPF) requires the effects of pollution on health, the natural environment or general amenity to be taken into account in planning decisions. The NPPF definition of pollution specifically includes odour. There are two general scenarios where an assessment of the impact of odour may be required for planning applications:
a) When the proposed land-use activity is itself a potentially significant source of odours (e.g. wastewater treatment, waste management, food and drink, industrial and agricultural activities); or
b) When a sensitive use (e.g. residential development) is being proposed near to an existing odorous activity and may be affected by it.
However, until now, there has little guidance on how best to carry out an odour impact assessment; and none on how to assess the significance of the predicted effects for planning purposes. The Institute of Air Quality Management (IAQM) – the only UK professional body specifically for air quality practitioners – has issued guidance that addresses both of these needs.
Good practice for assessment of odour impacts
The air quality section of the NPPG advises that “Assessments should be proportionate to the nature and scale of development proposed and the level of concern about air quality, and because of this are likely to be locationally specific.” The IAQM guidance helps put some flesh on these bones by summarising:
i. what an odour impact assessment for planning purposes should cover; and
ii. the different assessment tools that can be used, highlighting their applications and limitations. Typical assessment tools include qualitative predictive assessments, detailed atmospheric dispersion modelling, and odour monitoring by “Sniff Tests”.
The IAQM guidance requires the air quality professional to justify that the assessment approach used is suitable and proportionate.
Guidance on odour-sensitive receptors
Properly categorising receptor sensitivities is therefore crucial to a robust assessment of odour effects. Hitherto there has been little official guidance on this; the IAQM has therefore developed a sensitivity classification scheme based on the concept of reasonable expectation of amenity.
Judging the significance of odour effects
For something as subjective as odour, the significance of the effect is a matter of judgement that cannot easily be defined by scientific methods alone and ideally requires a wider societal or stakeholder consensus to be arrived at. The IAQM guidance proposes a general framework of descriptors for the magnitude of effects resulting from the odour impact on a receptor of a particular sensitivity. This framework will be kept under review to benefit from the feedback of affected or interested parties, be they air quality practitioners, EIA specialists, planners, or communities.