RI-URBANS and ACTRIS send recommendations for the revision of the European directive on air quality

  • Both projects have provided feedback on the proposal for reviewing the EC Air Quality Directive published on 26th October 2022
  • The recommendations include seeking more synergies and interoperability between existing infrastructures, maintaining the list of non-regulated pollutants, and defining operating procedures and protocols for the new pollutants

As part of the European Green Deal, the EU is revising the air pollution standards to align them more closely with the recommendations of the World Health Organization. In the Commission adoption, both RI-URBANS and ACTRIS have sent a document with recommendations for the proposal review of the EC Air Quality (AQ) Directive.

All feedback received will be summarised by the European Commission and presented to the European Parliament and Council with the aim of feeding into the legislative debate.

RI-URBANS and ACTRIS recognise that there is a willingness to extend the AQ directive to currently non-regulated pollutants, which may be very relevant for the future development of AQ regulations, the evaluation of the impacts of air pollution on health, the better evaluation of the effects of AQ policies, and ultimately to the well-being of European citizens.

Specifically, RI-URBANS and ACTRIS value positively that:

  • UFP, PNSD, BC, OP, NH3 and PM speciation have been included, as well as the listed PAHs and an extended list of VOCs, in addition to other regulated pollutants;

  • a network of European super-sites is proposed to be created with similar objectives to the one established, with extremely good results, in the US by the US-EPA, to support environmental and scientific policy studies;

  • this is a timely proposal given the currently ongoing developments within ACTRIS and RI- URBANS to demonstrate the added value of observing the non-regulated pollutants for AQ management and the development and testing of innovative tools for AQ monitoring in relation to human health


The feedback provided by RI-URBANS and ACTRIS is summarised in the following points:

Recommendation #1:
It is fundamental to seek synergies with the existing infrastructure in place and ACTRIS in particular.

Recommendation #2:
Maintain the provisional list of non-regulated pollutants in the new directive and add the provision of information on the aerosol vertical profile to be monitored at supersites.

Recommendation #3:
Capitalise, whenever possible, from the measurement metrology outcome from past and current projects, in particular from ACTRIS-1, ACTRIS-2, and RI-URBANS in order to ensure implementation of the most suited operating procedures and interoperability between observations performed by all networks in Europe and beyond.

Recommendation #4:
Advance with the scientific community to define the standard operating procedures for the new pollutants and rely on the already established ACTRIS Topical Centers whenever relevant.

Recommendation #5:
Propose measurement protocols for VOCs species capitalising on the scientific and technical experience of CEN WG13, AQUILA, and ACTRIS.

Recommendation #6:
Ensure a high level of interoperability between the data value chain for responding to AQ and Climate policies. Some of these issues could be resolved with a greater interrelationship between DG. Environment and DG. Research.

Recommendation #7:
Based on the experience gained in ACTRIS and RI-URBANS, and on the scales of regional climate variations, we believe that the number of super-sites proposed in the review of the directive could be reduced by half while keeping in mind the need to cover relevant climatic regions and cities, and keeping at least one of each even in small countries. Likewise, the stations with monitoring atmospheric deposition could be reduced by half.

Recommendation #8:
Ensuring the establishment of supersites recommended in the draft document made through capitalising upon existing facilities, and in particular the ACTRIS National Facilities as rural or urban supersites. RI-URBANS addresses joint exploitation of operations with AQMNs, also including data policies.

Recommendation #9:
Clarify the definition of monitoring sites, and in particular the rural sites, i.e. whether rural stations are located in small towns in rural settings, or do they include regional background stations in rural settings but separated from the rural population? It would be good to define what are the objectives of the measurements in urban and rural environments. For urban sites, the objective seems more obvious, but it is not so clear for rural supersites.

Recommendation #10:
Engage in co-constructing the most appropriate data value chain system supporting the implementation of the EU directive on air quality mobilising the scientific community through the Research Infrastructure ACTRIS, and capitalising from the existing system and the work in RI-URBANS.

Technical recommendation #1:
Accordingly, we recommend following CEN and ACTRIS recommendations and starting measurements of the condensation particle counters (CPC) at 10 nm, but if the supersite is willing to provide data on nucleation mode PNC, complement the CPC with a nano-CPC to obtain by the difference the 3-10 nm size.

Technical recommendation #2:
RI-URBANS recommends starting from 3 nm, at least, in order to independently assess the effect of nucleation mode (<20 nm) on health, and if this effect is not consistent, in the future starting at 10 nm. However, CEN recommendations set the lower limit at 10 nm. ACTRIS recommends 10-800 nm. Only for sites with a focus on sub-10 nm particles, an additional instrument is considered. RI-URBANS recommendation is adding an additional instrument (nano-CPC, Particle Size Magnifier-PSM,…) to evaluate the concentrations of the nucleation mode particles. Thus, we recommend starting measurements with Mobility Particle Size Spectrometers (MPSS) and CPC from 10 nm, following CEN and ACTRIS recommendations and adding an additional instrument to obtain the <10 nm fraction that will give a more complete picture of the nucleation mode fraction.

Technical recommendation #3:
We recommend that a locally obtained MAC is used for each instrument and site, being obtained by in situ co-measuring EC and eBC. When this is not possible, then use the average ACTRIS MAC. However, discussion on the most suitable operating procedures for the determination of (e)BC would start from the recommendation from ACTRIS/RI-URBANS which will soon be published.

Technical recommendation #4:
Make use of the first recommendation from RI-URBANS and engage with the academic community to define the most suited OP techniques and their standard operating procedures before engaging in CEN initiatives.

Technical recommendation #5:
Opt for online NH3 standard technique and engage with the research community to define requirements and the most suited standard operating procedures also including inlet setup, calibration, and routine maintenance in order for datasets to be comparable.


The connection between RI-URBANS and ACTRIS dates back 2 years. In 2021, the European Commission mandated ACTRIS to further develop specific services for urban environments, as part of the EU Green Deal strategy.

The RI-URBANS project, funded by the H2020 programme (2021-2025), has a specific objective to demonstrate how ACTRIS service tools can be adapted and enhanced to better address the challenges and societal needs concerning the air quality in European cities and industrial hotspots.