Excess emissions from Volkswagen diesels could cause 59 early US deaths

29 Oct 2015 iopp"> iopp

By Liz Kalaugher, environmentalresearchweb.

In September 2015, Volkswagen Group of America admitted that it had installed "defeat devices" in certain models of its diesel vehicles. Such devices, which are barred by the US Clean Air Act, assess whether the vehicle is under test and reduce emissions if so. As a result, the 482,000 vehicles in the US containing the devices have emitted more oxides of nitrogen (NOx) under normal driving conditions than they should. These pollutants can harm human health.

With that in mind, a team from MIT and Harvard University, both in the US, has estimated that the excess emissions of NOxfrom affected Volkswagen Group vehicles from 2008–2015 could cause 59 early deaths in the US, producing a social cost of around $450 m. The research is the first peer-reviewed study of the potential for premature mortality to result from the installation of the defeat devices.

"We all have risk factors in our lives, and [excess emissions] is another small risk factor," said Steven Barrett of MIT. "If you take into account the additional risk due to the excess Volkswagen emissions, then roughly 60 people have died or will die early, and on average, a decade or more early."

If all affected vehicles are amended to comply with US regulations by the end of 2016, roughly 130 early deaths will be avoided, according to the researchers, saving around $840 m in social costs.

Tests of on-road, rather than test-condition, emissions suggest that NOx emissions for certain Volkswagen 2.0 litre diesel-engine vehicles with model year 2009–2015 are 10–40 times higher than the US Environmental Protection Agency (EPA) standard.

Barrett and colleagues found that affected vehicles drove a total of 40.5 billion km between 2008 and 2015, corresponding to 36.7 million kg of excess NOx emissions. That is about 1% of the emissions from all light-duty vehicles.

"It seemed to be an important issue in which we could bring to bear impartial information to help quantify the human implications of the Volkswagen emissions issue," said Barrett. "The main motivation is to inform the public and inform the developing regulatory situation."

Nitrogen oxides (NO and NO2) can harm health by increasing concentrations of fine particulate matter (PM2.5) and ozone. In 2005, emissions from the road-transportation sector are estimated to have caused 52,800 early deaths due to PM2.5 and 5,250 due to ozone.

Fine particulate matter has been linked to early death due to cardiopulmonary disease and lung cancer, while ozone can bring premature mortality from chronic obstructive pulmonary disease (COPD) and exacerbation of asthma. Higher levels of these pollutants also increase illness, raising factors such as the number of days of bronchodilator use, hospital admissions and new cases of chronic bronchitis.

Of the 59 early deaths, 87% are attributable to PM2.5 exposure and 13% to ozone, the study indicates. The excess emissions are also likely to result in 31 cases of chronic bronchitis and 34 hospital admissions for reasons such as respiratory and cardiac problems, the researchers estimate, along with around 120,000 minor restricted activity days, roughly 210,000 lower respiratory symptom days, and around 33,000 additional days of bronchodilator use.

Over the same 2008–2015 timeframe, the vehicles would be likely to have been involved in 280 accident fatalities, according to the researchers. That indicates that the air-pollution death rate from the excess NOx emissions is around one-fifth of the accident fatality rate for an average US passenger car.

Without any recall of the vehicles, the total mortality costs could be around $1.4 bn in 2015 money, around $2,800 per vehicle, the team estimates. Recalling vehicles at a constant rate throughout 2016, and replacing all devices by the end of the year, should reduce the total cost of future mortality from $910 m to $61 m.

To come up with their figure of 59 early deaths, the researchers used vehicle sales data and the STEP (Stochastic Transport Emissions Policy) vehicle fleet model, which evaluates the distance travelled per year by assuming an average annual growth rate and accounting for ageing. The researchers ascribed the excess NOx emissions on a 50 km grid according to an EPA estimate of the distribution of NOx from light-duty vehicles. A GEOS-Chem adjoint-based rapid air-pollution exposure model assessed how much particulate matter and ozone these spatially resolved excess NOx emissions would create, taking into account the distribution of the US population. Finally, the team used concentration-response functions to estimate the effects of the particulate matter and ozone on human health.

In 2014, Volkswagen Group of America accounted for around 70% of new diesel passenger car sales in the US. The 482,000 vehicles with defeat devices include particular years of manufacture of the Jetta, Beetle, Audi A3, Golf and Passat. A Volkswagen press release issued on 13 October 2015 states that "diesel vehicles will only be equipped with exhaust emission systems that use the best environmental technology."

The issue began to come to light when the International Council on Clean Transportation commissioned West Virginia University, US, to study the in-use emissions of a 2012 Jetta and a 2013 Passat in 2014. The emissions were significantly higher than test values.

"Steve Barrett and colleagues have performed an outstanding first cut on both the NOx emissions totals from the VW issues, and used the Geos-Chem air-pollution exposure model to provide a rigorous evaluation of the scale of the impacts, which are potentially exceedingly serious," said Dan Kammen, editor-in-chief of Environmental Research Letters (ERL), where the results were published. "The Barrett et al analysis demonstrates the value of policy-inspired fundamental research where the air quality and health impacts of transgressions such as the VW issue can be calculated and made available for public discussion."

Barrett and colleagues reported their findings in Environmental Research Letters.