Cornwall Air Quality Forum

From the 4th to the 6th of November 2002 forty-two delegates from twelve EU countries attended a conference organised by The Free University of Berlin and the Brandenburg Technical University with the aim of furthering debate and knowledge about particles in the size of 2.5 to 10 microns in urban areas. The European Union is at present debating whether airborne particulate monitoring legislation in Europe should remain focused on PM10s (particulate matter < 10 microns) or change to PM2.5 (particulate matter < 2.5 microns). It is thought that PM2.5 represents a greater threat to human health due to its ability to penetrate further into the lung. PM10 comprises particulate matter in the coarse fraction (10 um – 2.5 um) and PM2.5 comprises fine particulate matter 2.5 um and less, although as the cut off points are not rigid both size fractions contain a percentage of particulates greater than the 10 um and 2.5 um range.

On days one and two, thirty-two oral papers were presented concerning the science of ambient air quality monitoring and modelling in Europe. A poster reception was held on the evening of day one. Day three of the conference was devoted to three working groups, which discussed and collated the conclusions of the delegates.

The conference programme was divided into six oral presentation sessions, a poster session and one workshop:

Day One
Session I: Health
Session II: Chemical and Physical Properties
Session III: Site Measurements
Poster Reception

Day Two
Session IV: Source and Emission
Session V: Dispersion Modelling
Session VI: Abatement

Several interesting points were raised throughout the conference many of which had important implications for the monitoring and modelling of air quality not only in the UK but also more specifically in Cornwall.

Helen ApSimon of Imperial College London and Dr Stefan Jacobi of the European Commission DG Environment gave the opening speeches of the conference.

Helen ApSimon suggested that the coarse contribution to average UK background PM10 levels was 8 ug m-3 and that this amount was comprised of: Resuspension from roads of road abrasion, salting and urban dust Construction and building dust Combustion Natural materials, soil, sea-salt and biological material

Helen ApSimon also stated that coarse particulate matter levels do not necessarily follow vehicle numbers, resuspension of surface material is a function of vehicle speed and road surface condition. In experiments using fluorescent dusts she estimated that only 50% of road dust is resuspended by vehicle movement. She posed the question of what happened to the remaining 50% and suggested that it was removed by rain. Helen also stated that more detailed information is required before effective modelling of pollutants is a reality.

Dr Jacobi, spoke about the 6th Community Environmental Action Programme (EAP) which had been adopted as a Decision of the European Parliament and the European Council in July this year. One of the four areas identified by the Programme was Environmental Health and Quality of Life within which air quality is highlighted as one of the seven thematic strategies. Based on the 6th EAP the CAFÉ Programme was initiated by the European Commission with the specific objectives of:

  • Developing, collecting and validating scientific information relating to the effects of ambient air pollution
  • Supporting the implementation and review of the effectiveness of existing legislation
  • Ensuring that measurements to achieve air quality in Europe are taken at the relevant level through the development of effective structural links with relevant policy areas
  • Determining an overall integrated strategy which defines appropriate air quality objectives for the future
  • Disseminating widely the technical and policy information arising from the implementation of the programme

As for the pollutants considered in the CAFÉ Programme, PM10 has been identifies as one of the key issues. This is mostly due to increasing evidence that fine particles have deleterious effects on human health, causing premature death and reducing quality of life along with the fact that there does not seem to be any concentration threshold below which there are no effects. However, there is still a lack of knowledge e.g. with regard to the importance of health effects of fine and ultra-fine particles versus larger particles in combination with chemical speciation. As one tool in order to address the PM issue properly a CAFÉ working group has been established comprising of experts from different stakeholders (Member States, Industries, NGOs, EEA, WHO). Major tasks of the WG are:

  • To review the current situation with regard to PM10 and other fractions of PM
  • To evaluate possible trends of PM ambient air concentrations
  • To gather information on the attainability of the PM10 limit values set by current legislation
  • To give recommendations on possible future targets for PM, taking into account the WHO review on health effect of air pollution
  • To review the results of the Integrated Assessment Modelling being provided for CAFÉ, with regard to PM.

Session I of the conference was devoted to the health aspects of airborne particulate matter.

Peter Builtjes from the Netherlands gave an “non-expert” view of the health aspects of particulate matter and quoted an article in the Lancet which stated that lung damage caused by PM10 was greater than that caused by ozone by a factor of 10. His impression was that PM10 would not be replaced by PM2.5 as a standard due to the lack of evidence, the possible reason for which was the lack of correlation between PM10 and PM2.5. In the EU the average correlation is assessed as 0.7 but the US Environmental Protection Agency (EPA) give a PM10 / PM2.5 ratio of 0.4. In Spain the ratio is 0.7 in the north of the country and 0.4 in the south where air quality is strongly influenced by Saharan dusts. This incongruity, due to local inputs and diverse monitoring standards and methods, illustrates the difficulty in allocating a universal figure for the contribution of coarse particles to total PM10.

Gabriele Zanini from Italy spoke about “Projetto Benzene” which looked at the determination of polycyclic aromatic hydrocarbons (PAHs) in fractions of airborne particulate matter below 10 um. The study undertook five campaigns in Bologna and Milan during 2001 and 2002. Results of the study indicated that PAHs concentrate in the particulate fraction smaller than 0.4 um. Dr Zanini also stated that, at low speeds, biodiesel fuels and some fuel emulsions (clean fuels) produced a greater concentration of fine particulates than normal diesel.

Session II of the conference concentrated on the chemical and physical properties of airborne pollutants.

In his presentation Hermann Hartmut of the Institut fur Tropspharenforschung, Leipzig stated that that the chemical composition of particles may influence atmospherics and therefore the type of aerosols involved in cloud nucleation was important with regard to climate.

Work by Jurgen Muller of Germany found that combustion sources dominate in the finer fraction of PM10 and the smaller the particle the lower the melting point. Therefore particles became more volatile at smaller sizes and even particles, which at a larger size were not soluble in the lung, became a serious health risk at small sizes (

Session III of the conference looked at site measurements.

In her presentation concerning the marine influence on coarse particle fraction (2.5 – 10 um) to PM10 concentrations Dr Kirsty Smallbone of Brighton University suggested that, on average coarse particles contributed 30.5% to daily PM10 concentrations. Extensive studies by Dr Smallbone and Andy Dyer at Brighton University found that in the SE of the UK marine particles contribute between 10 – 20% of this coarse particle fraction. By tracing back trajectories Dr Smallbone was unable to identify enhanced fine particulate concentration contributions from the EU or inland UK but was able to identify high levels of coarse fraction input when winds were from the south west.

Work by Roy Colvile of Imperial College London indicated that in the urban area a substantial proportion of the coarse fraction of PM10 was derived from non-exhaust emissions by traffic such as resuspension of road dust and abrasion of tyres and road surfaces. Amounts contributed by these sources were dependent on a variety of factors such as the condition of the roads, traffic speed and meteorological conditions. These conclusions drawn from this work have particular relevance for local authorities who have responsibilities to reduce PM10 levels in line with NAQS objectives.

Conclusions from various other presentations were in accordance with the conclusions from the above work although work by Andreas Hainsch of the TU Berlin Department identified sources outside of Berlin as having a dominant effect on urban background airborne particulate matter concentrations. Dr Hainsch stated that as local authority remediation methods can only influence a small proportion of urban PM levels it was necessary to develop a national/international strategy for the reduction on PM10 levels.

Session IV on day two of the conference was entitled Source and Emission and nine speakers from six European countries spoke of the various sources, which input into airborne pollution.

Dr Wilfried Winiwarter spoke about efforts to assess emissions of total suspended particles (TSP) from all anthropogenic sources for Austria. Emissions from industry equipped with efficient PM abatement devices were easy to estimate, but fugitive emissions from industry were more difficult. Emission factors exist for domestic heating and car exhaust emissions, which allowed an estimation of values to be made, and an “unreliable” approach is available for the assessment of resuspension from road traffic. His conclusions were that there was an overall uncertainty with regard to compiling a PM emission inventory, which was determined, almost exclusively by the uncertainty of resuspension.

Dr Goetz Wiegand from Germany suggested that meteorological variables accounted for a major part of the variation in PM10 concentrations and that road traffic had a smaller part to play in those variations.

Work by Denier van de Gon at TNO Environment in the Netherlands sought to apportion input to PM10 from both sea-salts and soil material. Their results suggested that, depending on wind direction, average inputs from soil crustal material to PM2.5 – 10 varied from 2.5 – 6.5 ug m-3 and contributions from sea-salt ranged from 2.7 – 4.2 ug m-3. Therefore total contributions from sea-salt and soil material at four sites in the Netherlands was estimated at at least 64%. This implies that at least a third of the PM2.5 – 10 fraction comes from other, anthropogenic sources. These results complement those of Dr Smallbone (above).

Session V of the conference examined dispersion modelling of pollutants

Michael Memmesheimer from the Universitat Koln in Germany thought that dispersion modelling of airborne pollutants was of use only on a large scale. Localised concentration levels vary due to inputs on a small scale, such as road surface condition and the use of a large-scale model to interpret such data would produce unrealistic values. He suggested that modelling should be extended to the whole northern hemisphere.

The presentations by Ari Karppinen reviewed some of the recent studies at the Finnish Meteorological Institute to model urban particulate matter.

Rainer Stern of the Institute fur Meteorologie in Berlin spoke about the use of models to assess ambient air quality in areas where concentrations are low or where measurements do not give sufficient information to fulfil the requirement of an air quality assessment. He concluded that modelling does not match monitoring, especially in the summer when models greatly underestimate ambient concentrations. Large-scale models were more comparable with observed values than small-scale models.

Session VI of the conference looked at possible abatement measures

Three speakers, Claudio Carnevale from Italy, Zbigniew Klimony from Austria and Martin Lutz from Germany spoke about abatement issues. Claudio Carnevale suggested that a decrease in particulate concentrations was due to the increased use of bio diesel fuels, and that factors such as the evolution of the traffic fleet and the use of CNG busses would lead to an overall decrease in traffic-related pollutants. This work was based on assumptions, which cannot as yet be substantiated. Zbigniew Klimony discussed areas of concern that have been raised identified with respect to availability and quality of data that is needed to establish credible emission inventories and further abatement strategies. He suggested that all future reductions in airborne pollutant levels would be due to legislating against industrial sources and emissions of coarse particles from sources such as transport, construction, fugitive industrial sources, non-exhaust emissions from transport and agricultural activities might increase. All predictions were however based on assumptions such as the replacement of all domestic burners by the best options available. Zbigniew spoke about the use of the RAINS model, which is used to review the current policies to control particulate matter in Europe and assess the future emission reduction potential. Martin Lutz spoke about source apportionment of airborne pollution in Berlin. Monitoring suggested that for sulphur dioxide, lead and carbon dioxide concentrations are well below objective levels. Benzene concentration levels are also low but as there is no safe threshold for benzene it is still important to monitor and work to reduce levels further. Nitrogen dioxide and PM10 concentrations are however still severe as shown by an air pollution episode in January 2001 when concentrations of PM10 reached 150 ug m-3. Monitoring at sites across Berlin showed that background concentration levels followed the same general trends but levels at different sites were influenced by local inputs. Total PM10 concentrations in Berlin were estimated to be comprised of approximately one third local traffic inputs, one third other sources in Berlin and one third from sources outside of Berlin. Approximately half of traffic related inputs were estimated to be caused by tyre abrasion and resuspension of road dusts. Martin Lutz is involved in the EU HEAVEN project which is examining the relationship between noise and traffic.

The poster submission by Hainsch and Rotard supported the above findings, showing that air quality in Berlin was strongly affected by long-range inputs from the east and south-east of Berlin (Poland, Czech Republic etc). Hainsch and Rotard concluded that measures adopted by local authorities could only influence approximately 50% of PM10 concentrations in locations near to traffic. Again it was shown that a national and international approach to air quality is needed.

Day three Working Groups

The consensus of the conference was that the EU is not likely to change the monitoring standard from PM10 to PM2.5 although it is widely considered that it is the 2.5 fraction which is most deleterious to human health. The reasons given for keeping PM10 as standard are:

  • The relationship between PM10 and PM2.5 concentrations is dependant on location, meteorology and various other factor and is therefore not consistent
  • PM10 concentrations have been monitored consistently across Europe and any change would negate the value of this data for comparison.
  • Local Authorities and monitoring bodies across Europe have invested heavily in PM10 monitoring equipment.
  • A large fraction of PM10 is not derived from traffic-related emissions. The coarse fraction of PM10 (20 um – 2.5 um) is sourced by resuspension of road dust, marine sources, opencast mining, construction work, biological sources and transboundary inputs.
  • There was recognition that sources other than traffic impact on air quality. Sea-salt, opencast mining and resuspension of dusts from natural sources such as saharan dusts all have a significant effect on local, national and international air quality.
  • With regard to the modelling of airborne pollutants it was agreed that the production of more accurate modelling programmes would need input from wider sources, i.e;
    • More detailed, localised meteorological data
    • Details of localised air movement, e.g. fluxes and eddies.
    • Road sedimentation values
    • Traffic congestion values
    • Vegetation values
    • Source apportionment of pollutants
    • Road surface data
    • Traffic values and speed of traffic
    • Vertical profiles of pollutants

The conference was felt to have been extremely informative and productive. The atmosphere was congenial and informal and inspired interaction and collaboration between the delegates. This spirit was essential for the success of the working groups.

Abstracts from the conference and WG conclusions will be published on the University of Berlin website and presented to the EU Clean Air for Europe (CAFÉ) Programme.

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