North American pollution is a killer abroad (Image: Lehtikuva OY / Rex Features)

More than 20,000 lives a year could be saved if major industrial regions cut their emissions of ozone-triggering gases by a fifth, a new study has found. And the whole world would benefit: many victims of ozone pollution live a long way from the machines that cause it.

Although ozone high in the atmosphere is vital for our survival, shielding us from harmful UV radiation, at ground level it is very harmful and has been linked to respiratory conditions, heart attacks and even cancer.

Ozone forms when sunlight interacts with gases such as methane, nitrogen oxides and carbon monoxide, emitted by ships, cars and power plants.


To investigate its effect on human health, Susan Anenberg of the University of North Carolina, Chapel Hill, and her colleagues used computer simulations to estimate how much ozone people in North America, the European Union, and south and east Asia would breathe if each region cut emissions of ozone triggers by a fifth.

The researchers then plugged this data into a public health model to estimate how many lives would be saved in each region thanks to such a drop in ozone levels.

Lethal traveller

They found that some 21,800 ozone-linked deaths a year could be avoided in the northern hemisphere alone.

But the biggest surprise was how many deaths blamed on ozone pollution in one region could be traced to emissions in another. Up to 76 per cent of the people whose lives could be saved by North American emissions cuts live outside the continent, the researchers found.

“Compared with the other regions, reducing emissions in North America could save the most lives abroad,” Anenberg says.

The study found that cutting emissions in North America saved more lives in the EU than it did at home. “Ozone is mainly being generated on the polluted east coast of the US and carried over to Europe by the prevailing winds”, says co-author Drew Shindell, of NASA’s Goddard Institute for Space Studies in New York.

Policy push

Anenberg hopes that the findings will spur US policy-makers to make more stringent cuts to the country’s ozone emissions.

“While the US commonly evaluates the domestic health benefits of proposed actions to reduce ozone pollution, this research shows that substantial benefits may result outside of national or continental boundaries,” she says.

The EU is the region where the most people die because of foreign ozone pollution, particularly North American emissions, the study found.

Indeed, if all four regions cut emissions by a fifth, over 50 per cent of the deaths avoided in the EU would be thanks to foreign cuts, the research suggests.

“Our results show that slightly more lives in Europe could be saved by reducing foreign emissions of ozone ‘precursors’ than by reducing European emissions,” says Anenberg.

Asia alarm

Some regions are mostly poisoning themselves, though. South Asia’s ozone pollution, for example, kills the most people, and 90 per cent of its victims live locally. Anenberg says that reducing ozone precursor emissions by 20 per cent in the region would save about 7600 lives a year there.

“Our results suggest that collective international agreements may be desirable to reduce emissions and improve human health throughout the northern hemisphere,” she says.

It would also buy time against the looming threat of global warming, says Shindell. “Given that many of the precursors of ozone – and ozone itself – are greenhouse gases, this finding adds even more to the rationale of tackling climate change.”

“All these results seem reasonable to me”, says Mark Schoeberl, an atmospheric scientist with NASA’s Earth Observing System based at Goddard Space Flight Center in Greenbelt, Maryland, who was not involved in the study. “They emphasise again that there is only one atmosphere and air pollution is a global problem, not just a local one.”

That opinion is echoed by environmental scientist Mark Potosnak of DePaul University, Chicago: “It’s a typical result when further exploring human impacts on the environment – the world is a bit smaller than we first thought.”

Journal reference: Environmental Science & Technology, DOI: 10.1021/es900518z