29 July 2011

The 15th ETH Conference on Combustion Generated Nanoparticles was held on June 27-29, 2011 in Zurich. The main topics discussed by the delegates included characterization of particle emissions, particle emissions from combustion engines, particulate filters, instrumentation for particle emission measurement, emission regulations, as well as health effects and particle emissions from non-engine sources. The Conference program included about 50 presentations and 53 posters in the poster session.

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Regulations. The European Commission [N. Steininger] is developing a proposal for a particle number (PN) emission limit for positive ignition (gasoline) vehicles, as required by the Euro 5/6 legislation. One of the difficulties in developing a PN limit for gasoline engines is the cost-benefit analysis, as the health effects of PN emissions are difficult to quantify based on existing epidemiological data. Notwithstanding the cost-benefit issue, the Commission intends to propose a PN limit of 6x10^11 for positive ignition vehicles, numerically equal to that already adopted for diesel vehicles. The proposal is to be published this Fall.

Raw engine-out PN emissions from gasoline engines depend on the type of combustion system: in directly injected engines (GDI), PN emissions are typically higher than the Euro 5/6 diesel limit by a factor of 10-20. Hence, if the PN limit is adopted, PN emissions in GDI engines would have to be controlled by either in-cylinder methods or else by gasoline particulate filters (GPF).

PN emissions in port fuel injected (PFI) gasoline engines are generally significantly below the Euro 5/6 diesel limit. However, some studies [J. May, AECC] reported high PN levels from PFI vehicles (in one case, high PM (mass) emissions were measured from a PFI vehicle).

Health Effects. Health effects of particle pollution were discussed in a key lecture that opened the Conference by O. Brandli [Swiss Lung Association]. The speaker focused on the results of the major Swiss cohort study SAPALDIA, conducted over 1991-2011. 40% of Swiss population lives in areas where PM concentrations exceed the Swiss ambient air quality standard of 20 micro-grams/m3. This finding attracted attention to air quality issues in Switzerland. Among other results, the SAPALDIA study confirmed a link between highway traffic and health effects. For example, population that lives within some 200 m from the busy Gotthard highway suffered from more incidents of cough and cold.

The Conference also included a panel discussion on health effects, with the participation of fine medical scholars from Switzerland, The Netherlands, Germany, UK, the United States and other countries. It was apparent from the panel presentations and the following discussion that the medical research continues to be unable to determine which components and/or properties of engine emissions can be correlated with adverse health effects. While a large body of epidemiological research suggests that vehicle emissions are linked to a number of adverse health effects, such as pulmonary and cardiovascular effects, these effects do not always correlate with common metrics of vehicle-derived air pollution such as PM2.5 exposures. In the case of particle pollution, it remains uncertain whether controlling particle mass, particle numbers or particle surface emissions would maximize the public health benefit. However, several of the panel participants seemed to believe that the particle surface may be the most important parameter from the health effects perspective.

Conference website: www.lav.ethz.ch/nanoparticle_conf