A study has estimated that the Volkswagen scandal could cost 1,200 premature deaths in Europe Getty Images

In September 2015, the Volkswagen group admitted to having installed "defeat devices" in 11 million of its diesel cars sold around the world, between 2008 and 2015.

These devices effectively helped the manufacturer cheat the laboratory tests designed to check that its vehicles complied with environmental standards. They hid the fact that during on-road driving, the diesel cars emitted pollutants called oxides of nitrogen (NOx) at levels over four times higher than the applicable European regulatory emission limit of 180 mg NOx/km.

Although Volkswagen recalled the cars, scientists have assessed that the excess emissions already had a significant public health impact in the US and in Europe.

In a new study published in Environmental Research Letters, a team from MIT has established that 1.,200 people in Europe will potentially die early as a result of the emissions. They had previously said that the 482,000 vehicles sold in the US would lead to 60 premature deaths there.

Why do scientists say that it will cause premature 1,200 deaths in Europe?

The study looks at the impact of the 2.6 million affected cars sold in Germany and how the extra emissions they produced has affected the health of people in the country, but also across the whole of Europe.

The scientists used German Federal Motor Transport Authority's measurements of NO<sub>x emissions from Volkswagen cars and their spatial distribution. They also examined historic data relating to driving behaviours in Germany – estimating how many kilometres were driven every year and where people drove the most.

This allowed them to produce a map modelling excess emissions in Germany and to predict where they travelled given prevailing winds, temperature, and precipitation, and where they interacted with other compounds to form fine particulates and ozone.

From this model, the researchers were able to calculate the corresponding increase in population exposure to fine particulate matter and ozone in the European Union, Switzerland, and Norway.

Their results suggest that 1,200 premature death will occur in Europe due to the excess emissions that have already been released into the atmosphere between 2008 and 2015. The victims would lose as much as a decade of life. The scientists also estimated that would be €1.9bn in costs associated with life-years loss.

Out of the 1.200 deaths, 60% will happen outside of Germany, highlighting that pollution and fine particles know no borders.

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What are the health effects of car pollution? Getty

"Air pollution is very much transboundary," says co-author Steven Barrett. "[Pollution] doesn't care about political boundaries; it just goes straight past. Thus, a car in Germany can easily have significant impacts in neighbouring countries, especially in densely populated areas such as the European continent."

Can the worse health impacts of the scandal be avoided?

The scientists estimated that if the Volkswagen groups recalls and retrofits all affected vehicles to meet European standards by the end of 2017, 2,600 additional premature deaths may be avoided.

This would also mean avoiding 4.1 billion Euros in corresponding health costs, which would otherwise be expected in the absence of a recall.

Why would the cars cause more deaths in Europe than in the US?

The scientists say it is not surprising that their analyses reveal significant differences in mortality rates associated with the scandal in Europe and in the US.

First of all because much more cars were sold in Germany than in the US – 2.6 million vs. 482.000 diesel cars.

Also because differences in population density, driving behaviour, and atmospheric conditions – all important factors taken into account in the scientists' model – may explain the aggravated health impacts across Europe.

How has Volkswagen responded?

The Volkswagen group has contested the results from the study, saying that some of its basic assumptions are incorrect. In particular, the group disagrees with the idea put forward by the researchers that the maximum regulatory emission of 180 mg NOx/km can be applicable to all road trips.

"The basic assumption of the study that the cycle limit of 180 mg NOx/km applies to all road trips is not correct. Depending on the driving style, route and environmental conditions, all diesel vehicles can produce NOx emissions significantly higher than the limit. This applies to all manufacturers.In addition, the NOx emissions of our vehicles are not higher than those of our competitors' vehicles under real driving conditions", a spokesman for the company said in a statement.

The Volkswagen group also says that "it is difficult to understand why Volkswagen vehicles should be mentioned in connection with significant 'life-years lost'".

How can NOx emissions 'kill' people?

A chemical known as nitrogen is released during fuel combustion and combines with oxygen atoms to create nitric oxide (NO). NO then combines with oxygen to create nitrogen dioxide (NO2) which can be hazardous for the health at high concentrations. NO and NO2 are referred together as oxides of nitrogen (NOx).

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Fine particles can worsen people's asthma Reuters

The main negative effects of NOx on the health are respiratory. The oxides can cause inflammation of the airways when they are present at high levels in the atmosphere. Long term exposure can decrease lung function, increase the risk of respiratory conditions and increases the response to allergens. NOx also contributes to the formation of fine particles and ground level ozone, which increase health problems on the short and long terms.

On the short term, fine particles can cause nose, throat and lung irritation as well as coughing, sneezing, runny nose and shortness of breath. Studies have linked the pollutants with an increased risk of worsening asthma conditions. Exposure to fine particles can also affect lung function and increase the probability of cardiovascular disease.