It also need to be mentioned that in other sectors, such as the household and commercial/institutional sector, legislative initiatives have been undertaken with less frequency and with lower ambitions than in road transport. One of the few examples of legislative action in the residential and commercial area is from Germany, where new, small firing installations, such as stoves, are subject to regulatory requirements, and where the same legislative framework requires the modernization of existing installations of the same kind.

Thus to improve the quality of air around us more attention must be given to the primary PM emitters.

—“Diesel Engines Exhausts: Myths and Realities”

The paper, which focused on the European Union, North America, and Japan, had a number of objectives:

• to offer a balanced view on the on‐going debate about the harmful effects of diesel engine exhaust emissions on human health and the environment;

• to take stock of recent studies on the harmful effects of diesel exhausts to public health;

• to provide information about diesel emissions by different economic sectors including inland transport;

• to overview the recent policy developments on the reduction of pollutant emissions to address health and environmental concerns; and

• to overview any technological developments in diesel engines that reduce or even eliminate the harmful effects to public health.

The primary conclusions of the review and assessment were:

• Diesel engines emissions in the air are carcinogenic to humans based on scientific research evidence; the emission of particulate matters is the most dangerous for humans health; the danger is the highest in closed areas, such as in‐door and in areas with inadequate ventilation;

• Diesel engines are currently at the heart of economic growth and of all economic activity and, therefore, it is not feasible to replace and eliminate them at this stage;

• Transport is only one of the sectors using diesel engines. Industrial, agricultural, timber, commercial, institutional and household sector are some of the other economic sectors that use diesel engines;

• The commercial, institutional and household sectors are the most important source of PM_2.5 and PM₁₀;

• The transport sector is by far not the most significant source of PM emissions, nonetheless up till now it has been the most rigorous in introducing measures to address this issue;

• The transport sector is the most regulated sector where the most intensive initiatives and actions have been taken. Decisions and performance oriented emission regulations have been adopted that set limits and targets resulting in the dramatic decrease in PM and other emissions;

• Other economic sectors are lagging behind in their initiatives, strategies and actions to address their share of PM and pollutants emissions.

Substantial reductions in emissions will be needed if the limit value set in the Air Quality Directive of the European Union is to be reached, the paper noted. The 2012 revision of the Gothenburg Protocol to the UNECE LRTAP Convention set emission reduction targets for PM_2.5 based on 2005 emission totals, to be met by countries by or before 2020. By 2010, average annual reductions of PM_2.5 emissions in thirteen EEA‐32 countries were greater than that required to achieve their targets by 2020, and five countries had already achieved the reductions specified in the protocol. Therefore, the paper concluded, more strategically targeted actions should be taken.

Although transport is not the main source of particulate air pollution, according to the paper, the measures to improve the environmental performance of the transport sector should be continued and further fine‐tuning should be warranted. The paper recommends three tracks of actions.

An improved modal split. An improved modal split, particularly from individual to public transport in personal mobility and from roads to rail in long term freight transport while improving environmental performance at micro level.

Improved public transport and the promotion of walking and biking are desired measures to reduce the use of personal cars. Walking and biking requires appropriate infrastructure to be put in place, which can be at relatively low cost, but the benefits in terms of impact on health and quality of life are huge.

Public transport—“a massive solution” both for individual mobility, environmental performance and reducing congestion, is also attractive from an economic sustainable perspective since public transport provides more capacity at less marginal cost.

Land use and transportation funding policies heavily influence travel behavior and travel choices, the paper notes. Studies show that mixed‐use neighborhood with adequate pedestrian and bicycle facilities linked to public transport services is more likely to be a city with fewer car trips and a greater amount of trips by walking, cycling, and transit.

New technologies The paper suggests that a stricter timeframe for the replacement of old technology by new one and adoption of measures that promote such replacement is one possible pathway. Policies requiring the introduction of advanced vehicle technologies should also be coupled with measures introducing the necessary fuel quality improvements.

In some high exposure areas, policy measures may be needed that aim at replacing vehicles equipped with older engine technologies with new vehicles which comply with the new regulations or at retrofitting the existing engines with appropriate emission control devices and after‐treatment systems.

Review and evaluation of health risks for people working in transport related occupational groups. The amount of diesel exhaust people are exposed to varies greatly. Further, measuring the level of these exposures is not easy because diesel exhaust is chemically complex and many parts of it are found in many other sources. Truck drivers, tollbooth workers, miners, forklift drivers and other heavy machinery operators, railroad and dock workers, and garage workers and mechanics are among occupational groups with some of the highest exposures to diesel exhaust at work.

Commuting to and from work is a potential source of diesel exhaust exposure for many people. One particular area of concern is exposure of children to diesel exhaust and other pollutants while riding in school buses, as these buses themselves typically run on diesel fuel.

It is not easy to establish the possible health effects of diesel exhaust on people since it might be difficult to precisely define and measure the level of exposure due exclusively to diesel exhaust, the paper suggested. The main difficulty is that it might be necessary to factor in the other cancer risk factors that people who are exposed to diesel exhaust might have, such as smoking, nutrition, lifestyles, physical inactivity, etc. Therefore, more sophisticated screening methods would be needed for more evidence‐based results.

However, because particulate matters emitted in diesel engine exhaust are carcinogenic to humans, irrespective of the level of potential harm to health, and irrespective of the good progress in reducing these harmful effects, proactive measures have to be in place to further minimize the vulnerability of the transport workers who are most exposed to such pollutants in the transport sector, the paper said.

Among them truck or locomotive drivers or people in toll booths or collecting tolls on the curbs even without being in a booth could be considered at the highest potential risk. A review of their situation and of best practices in their protection would be a useful exercise to raise awareness and to facilitate exchange of information, particularly if such a review could result in a status report.

Nature study. Separately, a study published in Nature Communications found that in many Asian and European communities, elevated particulate matter levels can be a consequence of asymmetric pollution from two-stroke scooters—vehicles that constitute a small fraction of the fleet, but can dominate urban vehicular pollution through organic aerosol and aromatic emission factors up to thousands of times higher than from other vehicle classes. (Post.)

Resources

• Diesel Engines Exhausts: Myths and Realities Discussion Paper

• S.M. Platt et al. (2014) “Two-stroke scooters are a dominant source of air pollution in many cities,” Nature Communications 5, Article number: 3749 doi: 10.1038/ncomms4749