Andreas Mayer’s research while affiliated with University of Bern and other places

Particle number concentration (PN) in vehicle exhaust and ambient air describes the number of ultrafine particles (UFPs) below 500 nm, which are recognized as a toxic and carcinogenic component of pollution and are regulated in several countries. Metal nuclei, ash, and organic matter contribute significantly to the ultrafine particle size fraction and, thus, to the particle number concentration. Exhaust gas filtration is increasingly being used worldwide to significantly reduce this pollution, both on diesel particulate filter (DPF) and gasoline particulate filter (GPF) engines. In recent years, the EU has also funded research projects dealing with the possibilities of retrofitting gasoline vehicles with GPFs. This paper presents the results and compares the PN emissions of different vehicles. An original equipment manufacturer (OEM) diesel car with a DPF is considered as a benchmark. The PN emissions of this car are compared with a CNG car without filtration and with gasoline cars equipped with GPFs. It can be concluded that the currently used GPFs still have some potential to improve their filtration efficiency and that a modern CNG car would still have remarkable possibilities to reduce PN emissions with an improved quality GPF.

Using solid particle number (PN) measurements in the European Periodic Technical Inspection (PTI) of diesel engines equipped with particulate filters was proposed by VERT in 2016 during the Dieselgate Hearing of the Federal Republic of Germany. An international working group developed the standards and instruments for this method over three years under the leadership of TNO and VERT, which were next implemented in four countries, Belgium, the Netherlands, Germany and Switzerland, starting in 2022. PN measurement is now state of the art, enabling rapid and reliable detection of possible failures in particulate filters and the need for their immediate restoration. This paper expands on that successful experience, recommending that PN-counting be used for control of PN emissions from all vehicles during PTI. Five large vehicle fleets, Diesel and Gasoline, Heavy Duty Engines (HDE), Light Duty Vehicles (LDV) and Non-Road Mobile Machinery (NRMM), with and without emission aftertreatment were analyzed. It was observed that, while most vehicles in working fleets are clean (i.e., meet or are below their corresponding emission limits), every fleet however, contains some high emitters, about 4–8% of the fleet hereby termed “dirty tail”. This small fraction dominates the PN emission of the entire fleet and may increase the overall PN emission of its corresponding fleet by up to ten fold over the level of the complient vehicles! Experience indicates that PN emission may be a strong indicator of many different deteriorations in a combustion engine, and thus can be used as a highly sensitive diagnostic signal to detect various engine or emission faults quickly and reliably. This is a new understanding of emission control of vehicle fleets: not by regulations which apply for all vehicles but by selecting the high emitters and consequently repair or replace these relatively few vehicles to the extent desired in terms of emissions policy. Most countries have already implemented strong Periodic Technical Inspection systems. We suggest to expand such tests by additionally measuring the particle number concentration in the exhaust gas of all vehicles for just one minute, thereby detecting the high emitters. With consistent annual monitoring, this procedure will reduce urban particle pollution from combustion engines to one fifth or lower, a significant contribution to reducing local health risks.

Particulate filters are state-of-the-art and are used in internal combustion engines worldwide to eliminate carcinogenic nanoparticles. Health studies estimate that this prevents about one million premature deaths annually. What is less known and often neglected is their equally powerful effect on mitigating global warming. This is because these ultrafine particles form stable aerosols in the atmosphere, absorb sunlight, and heat the atmosphere due to their jet-black color. In addition, once deposited on the ground, they reduce albedo especially when deposited on ice or snow. They also thin clouds and reduce their reflectivity. In this paper, we estimate for the first time the cumulative effect of more than 300 million particulate filters currently installed globally on vehicles, showing that, while they reduce ~ 0.5 Mt of soot per year, their effect on slowing global warming is equivalent to reducing 1 Bt of CO2 per year or about one-third of the CO2 emissions of all European Union Member States combined. Despite its strong potential, this highly efficient, proven, and low-cost technology is not yet regarded as a priority in curbing global warming, even though it is possibly the easiest and quickest to implement. If used in retrofitting more diesel and petrol engines worldwide, it could triple the aforementioned effect. While modern internal combustion engines are on track to be replaced with zero-emission vehicles, it is also crucial, and we strongly suggest that, in the interim, all remaining internal fossil fuel combusting engines be fitted with particulate filters. Evidence is presented in this paper that the potential benefits of such retrofit on climate and human health will be impactful and lasting.

div class="section abstract"> Ultrafine particles, in particular solid sub-100 nm particles pose high risks to human health due to their high lung deposition efficiency, translocation to all organs including the brain and their harmful chemical composition; due to dense traffic, the population in urban environments is exposed to high concentrations of those toxic air contaminants, despite these facts, they are still widely neglected. Therefore, the EU-Commission set up a program for clean and competitive solutions for different problem areas which are regarded to be hotspots of such particles. HORIZON AeroSolfd is an EU project, co-funded by Switzerland that will deliver affordable, adaptable, and sustainable retrofit solutions to reduce exhaust tailpipe emissions from petrol engines, brake emissions and pollution in semi-closed environments. VERT, a Swiss based international industry organization, has a long research history in the field of nanoparticle filtration and it is in charge of reducing tailpipe emissions of gasoline vehicles by using the best available retrofit filtration technology (BAT). VERT will apply the newest high-efficient GPF technology in three high mileage fleets, in Germany, Switzerland and Israel. The project will also serve as a platform to continue research on PN emissions as well as on secondary emissions from GDI and PFI petrol engines. In addition, the “high emitter phenomena” will be further analysed with a NPTI testing campaign of 1000 gasoline vehicles, including GDI, PFI and GPF equipped vehicles. </div

The knowledge about nanoaerosols, their potential health effects, their measurement, limitation and administrative-legal treatment has been developed in the last 3 decades in connection with the exhaust gas cleaning of the combustion engines. Nanofiltration, which has thus become known, almost completely eliminates nanoparticles with filters of high durability, high specific filtration areas, and reasonable costs. On the occasion of the Covid pandemic, NanoCleanAir experimentally proved that the viruses in an automotive filter substrate are separated as well as the combustion particles and are also deactivated. To minimize cross exchange of infectious aerosol, new attention must be paid to flow management in ventilated spaces. Digitized flow analysis has also received significant inspiration from engine technology in the past. This paper provides information on some basic investigations and gives valuable advice based on the experimental and numerical results of a retrofitted classroom.

A substantial amount of traffic-related particle emissions is released by gasoline cars, since most diesel cars are now equipped with particle filters that reduce particle emissions. Little is known about adverse health effects of gasoline particles, and particularly, whether a gasoline particle filter (GPF) influences the toxicity of gasoline exhaust emissions. We drove a dynamic test cycle with a gasoline car and studied the effect of a GPF on exhaust composition and airway toxicity. We exposed human bronchial epithelial cells (ECs) for 6 hours, and compared results with and without GPF. Two hours later, primary human natural killer cells (NKs) were added to ECs to form cocultures, while some ECs were grown as monocultures. The following day, cells were analyzed for cytotoxicity, cell surface receptor expression, intracellular markers, oxidative DNA damage, gene expression, and oxidative stress. The particle amount was significantly reduced due to GPF application. While most biological endpoints did not differ, oxidative DNA damage was significantly reduced in EC monocultures exposed to GPF compared to reference exhaust. Our findings indicate that a GPF has beneficial effects on exhaust composition and airway toxicity. Further studies are needed to assess long-term effects, also in other cell types of the lung.

In the present paper, some results of investigations of nanoparticles from four MPI gasoline cars are represented. The measurements were performed at vehicle tailpipe and in CVS-tunnel. Moreover, two variants of GPF were investigated on a high-emitting modern vehicle, including analytics of PAH. The modern MPI vehicles can emit a considerable amount of PN, which in some cases attains the level of Diesel exhaust gas without DPF and can pass over the actual limit value for GDI (6.0 x 1011 #/km). The GPF-technology offers in this respect further potentials to reduce the PN-emissions of traffic.