"This is the first time such an assessment has been undertaken – spanning scales from 1 km to 10,000 km," Steven Barrett of Massachusetts Institute of Technology told environmentalresearchweb. "Previously, the local air-pollution impacts of airports and the intercontinental pollution impacts of aircraft cruise emissions had been studied in isolation, which made it hard to know which really mattered more – cruise emissions or airport emissions."

Infographic on the health benefits of civil-aviation emissions

Aircraft emit particulate matter less than 2.5 μm in diameter (PM2.5) that can increase rates of lung cancer and cardiovascular and respiratory disease, and ozone, which is also linked to respiratory disease.

Barrett and colleagues looked at aircraft-plume-dynamics-related local dispersion (on a scale of about 1 km), near-airport dispersion (across roughly 10 km), and chemistry and transport on the regional (∼1,000 km) and global (∼10,000 km) scales. They assessed emissions during take-off and landing – when the plane was flying below 3000 feet – and during the whole flight.

The team estimated that take-off and landing emissions contributed, on average, a quarter of the 16,000 premature deaths due to PM2.5 and ozone from aviation. In North America, take-off and landing emissions contributed 43% of deaths, while in Europe the figure was 49% and in Asia it was 9%.

"These new results tell us that, overall, it is the cruise emissions that cause the greatest impact on air quality and human health," said Barrett. "Except in regions with high densities of airports like North America and Europe, where airport and cruise emissions are about as important as each other in terms of their health impacts."

The premature deaths cost around $21 billion per year, roughly the same order of magnitude as aviation's climate costs, and one order of magnitude larger than aviation-attributable accident and noise costs.

"It is important to keep in mind that today aviation contributes a very small fraction to air-pollution-related health risk," said Barret. "Perhaps on the order of 1%. However, other sectors are rapidly reducing their air-pollution-relevant emissions, while aviation is forecast to double or triple by mid-century, with greater challenges in finding new ways to reduce emissions."

So what's the best way to reduce these health-harming emissions? The researchers believe their results suggest that efforts to reduce cruise fuel burn will improve public health, which means there is a much greater opportunity for reducing health impacts than if only the 10% of fuel burn during landing and take-off were relevant.

Now, the team is assessing different ways to reduce the air pollution and climate impacts of aviation. "A current focus is biofuels," said Barrett. "These tend to burn more cleanly and do not have sulphur impurities – meaning that air-pollutant emissions are reduced. However NOx emissions are not thought to be affected by using biofuels – which means that's an area that will need a technological approach rather than a fuel-based approach."

Barrett and colleagues reported their results in Environmental Research Letters (ERL).

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