Over the recent decades more proof has shown that air pollutants are related to adverse health effects, so it’s time to re-evaluate air quality guidelines and discuss detrimental health effects.
The European Union, through the Ambient Air Quality (AQQ) Directives, and the World Health Organization (WHO) have introduced exposure limits for NO2, PM10 and PM2.5. In addition, there is a massive body of legislation tackling air pollution at the source, this being to reduce emissions including the NEC Directive, the Euro standards and the industrial emissions Directive. An important difference is that the limit values set by the EU are legally binding, while the WHO values are recommendations. However, the latter ones are solely health-based, while EU limit values are the result of political compromise. Regardless, the health impacts of air pollutants are one that cannot be avoided, especially with the emerging evidence of pre and postnatal effects, such as diabetes and neurological conditions.
Health impacts from air pollutants
It is clear that air pollutants have large adverse impacts on human health. The main pollutants from road transport are listed below:
Particulate matter: ambient particulate matter is a form of air pollutant and is ranked as the 6th risk factor for total deaths globally, through cancer, lower and chronic respiratory diseases and cardiovascular diseases. Therefore, being the most harmful element of diesel exhaust to the human health. The severance of the harm caused is largely determined by how far a certain pollutant can penetrate into the human body after entering by the respiration system.
Soot particles (measured and also known as elemental carbon or black carbon) make up a small part of all the particulate matter in ambient air but are among the most dangerous elements emitted by road traffic.
NOx: evidence regarding the adverse health impacts of NOx have long not been attributed to the compounds itself (mainly NO2), but rather to particulate matter and ozone as these are formed by NOx. This air pollutant has a proven relation between short-term NO2 exposure and respiratory symptoms such as inflammation, aggravation of symptoms in asthma patients and aggravation of allergic reactions in the respiratory tract.
About 10,000 premature deaths of adults over 30 in 2013 in the EU28 and Switzerland that can be attributed to NOx emissions from diesel cars and light commercial vehicles. Half this could have been avoided if the NOx emissions of those vehicles would have been at the level of the laboratory tests.
Ozone: tropospheric (also known as ground-level) ozone (O3) is a secondary air pollutant. It is formed via multiple reactions between NOx, CO and volatile organic compounds (VOCs), in the presence of light (e.g. photo-chemically). Under specific weather conditions, a high concentration of ozone in the air can lead to smog which is especially a problem in warm urban areas. In some places the occurrence of smog is highly related to the season. Short-term exposure to ozone has proven to be causally related to respiratory effects such as inflammation, aggravation of asthmatic symptoms, increase in hospital admissions and respiratory related acute mortality.
Globally, ozone is ranked as the 33rd risk factor for total deaths, due to its severe causal relation to chronic respiratory diseases.
Non-methane volatile organic compounds (NMVOCs): these are formed upon incomplete combustion of fuels such as diesel, typically found in the gas phase of diesel exhaust. They are a great contributor to the formation of ozone and therefore are indirectly responsible for health effects caused by it. Moreover, some NMVOCs have been classified as carcinogens, amongst some of which occur in diesel exhaust.
Polycyclic aromatic hydrocarbons (PAHs): this air pollutant is an organic compound and is related to the carcinogenic nature of diesel exhaust. Additionally, new evidence is arising for its non-cancer health effects, such as cardiovascular diseases, neurological and prenatal effects.
The severe impact of air pollutants
In Europe, the WHO estimate the number of premature deaths attributed to air pollution is over 500,000. In contrast to other regions in the world, household air pollution does not play a large part in this number compared to outdoor air pollution. However, road transport contributes a significant amount to air pollution in the European region, which is confirmed by data from the European Environmental Agency
Air pollution is a phenomenon that knows no borders. An emitted air pollutant does not always stay within the country in which it was emitted in. As such, it makes sense to analyse and address this problem on a broader-than-country basis and furthermore bring the discussion to the ears of the public.