"We estimate that health costs due to global ozone pollution by 2050 will be $580 bn (in year 2000 US$), and that more than two million premature deaths will result from acute exposure," researcher Noelle Selin of Massachusetts Institute of Technology (MIT) told environmentalresearchweb. "These figures show that man-made atmospheric pollution can have large economic and human health costs. These costs are likely to grow in the future without further pollution control measures."

Emissions such as nitrogen oxides (NOx) and volatile organic compounds (VOCs) from vehicles and power plants are mainly responsible for ozone in the troposphere. These chemicals combine with oxygen to form ozone, especially on hot, sunny days. Ozone pollution can lead to acute respiratory problems, for example asthma and chest infections, particularly in children and the elderly.

Selin and colleagues from MIT and Michigan Technological University, US, used an atmospheric model – the GEOS–Chem global tropospheric chemistry model – to project future ozone levels. They combined this with an economic model, the MIT Emissions Prediction and Policy Analysis-Health Effects (EPPA-HE) model, that estimates the costs of being exposed to the pollutant.

The team used the EPPA–HE model to assess how ozone pollution contributes to human illness and death, quantifying the economic impacts of this damage in 16 regions around the world. They calculated how much ozone pollution will cost in real monetary terms with respect to working and leisure time lost – also known as "economic welfare". They did this by using year 2000 and projected 2050 levels of ozone from the GEOS–Chem model, and simulating how increasing levels of ozone directly influence economic welfare.

Increased temperatures, like those we will experience with climate change, can directly influence the chemistry of the reactions that form ozone, explains Selin. The projected increases in the amount of ozone precursors are very large – especially in developing countries that emit more pollution. More worrying still is that, in the scenario analysed by the MIT–Michigan team, the economic effects of these emission increases will be far higher than those expected from climate change alone. Indeed, they stand at nearly $600 bn, or 0.4% of the world's GDP, by 2050.

"Since ozone is not directly emitted, but formed in the atmosphere by reactions involving NOx and VOCs, controls on these precursors reduce the formation of ozone and thus human exposure to this pollutant," says Selin. Although certain regulations – in the US and Europe, for example – already set limits on ozone concentrations, the new study suggests that health costs may be too high, even at the currently controlled levels.

The team is now assessing the economic impacts of polluting particles in the atmosphere, and exploring how future climate polices can help to reduce overall air pollution.

The work was reported in Environmental Research Letters.