The looming threat of ozone

The urgency of patching up the hole in the ozone layer – our planet’s protector from the sun’s harmful UV rays – is one mission that all nations have been able to agree on and take swift action. International efforts seem to be paying off as a UN Environment Programme and World Meteorological Association report this month shows that the ozone gas (O3) in the layer is now increasing year by year.

However, while ozone in the stratosphere – six to 30 miles above the earth’s surface – acts as the planet’s shield from harmful ultraviolet light, ozone near the earth’s surface has serious consequences for human health and wellbeing, crop production and food security. And this ground-level ozone, which stems from man-made causes, is on the rise.

‘Ozone preserves life but at the same time at the surface it’s a pollutant which has a very negative impact on human health,’ said Dr Luca Pozzoli at the Eurasia Institute of Earth Sciences, Istanbul Technical University in Turkey, who leads the EU-funded MAQUIS project studying surface ozone. ‘It generates diseases like asthma and bronchopulmonary diseases, and it damages vegetation and can reduce crop production.’

Ground-level ozone, also called surface ozone, is a secondary effect of human activity including energy production and road traffic. These activities emit so-called ozone precursor gases, including oxides of nitrogen, carbon monoxide and volatile organic compounds. In the presence of sunlight, the precursor gases react to create ozone.

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‘Ozone preserves life but at the same time at the surface it’s a pollutant which has a very negative impact on human health.’

Surface ozone is a major greenhouse gas and has been described by the United Nations as the third most important contributor to the human enhancement of the global greenhouse effect, after carbon dioxide and methane. Other factors affecting surface ozone levels include meteorological influences like temperature and the transport of air masses blown from other continents.

High surface ozone levels can trigger respiratory illnesses like asthma, emphysema and bronchitis; it is also associated with more emergency room visits and hospital admissions, with children being particularly vulnerable. A 2013 report for the European Commission showed that between 2009 and 2011, 98 % of city dwellers were exposed to surface ozone levels above that of World Health Organization guidelines.

Dr Pozzoli and his team on the MAQUIS project are using mathematical models to examine what will happen to ground-level ozone in Europe by 2050, based on whether we take action to tackle the problem or not.

Modelling the future

Focusing on the Mediterranean region, MAQUIS looks at how climate change and air quality policy to reduce greenhouse gas emissions will affect ground-level ozone and particulate matter – two key pollutants affecting the quality of our air.

The best case scenario explores what will happen if the Intergovernmental Panel on Climate Change’s (IPCC) global climate policies and the EU’s air pollution measures under the National Emissions Ceiling Directive, are implemented.

‘There would be a reduction in the order of 40 to 60 % in air pollutant emissions,’ said Dr Pozzoli. ‘This would result in the reduction of summer ozone levels by 10 parts per billion.’

The largest reductions in surface ozone may be in southern Europe – Spain, Italy and the Balkan Peninsula.

However, the worst case scenario – what the researchers call ‘business as usual’ – looks at what will happen if we carry on as we are and no further climate or air pollution policies are enacted beyond what has been in place since 2005.

‘From this we have an increase in ozone everywhere – particularly in Eastern Europe and Russia,’ said Pozzoli. ‘For sure, it will impact human health and crop production. From the point of view of food safety it will be an issue.’

Climate change

Even in the best case scenario, there is a complication, as rising temperatures due to global warming cause an increase in surface ozone. ‘What I would expect with rising temperatures, is that a lot of the ozone reduction will be cancelled out by ozone production due to temperature increases,’ said Dr Pozzoli.

He said that countries in warmer areas will need to take additional measures, beyond what is agreed at an international level, to tackle the problem. ‘Regions like the Mediterranean area may be further penalised (in terms of surface ozone increase) by climate change and additional emission reduction measures may be necessary for those countries in order to counteract these particular climate disbenefits.’

Though the outlook for ozone in the air we breathe in Europe looks disheartening under MAQUIS’s models so far, Dr Pozzoli said that the research only ‘strengthens the importance of taking action’ on both greenhouse gases and other air pollutants.

Dr Sachin Ghude, an expert in atmospheric science from the Indian Institute of Tropical Meteorology in Pune, India, recently published a study showing that crop losses due to ground-level ozone in India in 2005 could have fed 94 million people.

If nothing is done – as in the worst case scenario presented by MAQUIS – Ghude said Europe could see similar impacts on crops: ‘It has already been shown in many studies that rising global temperature and ozone levels are causing millions of tons of food loss and if not controlled will be a threat to our food security. It will have a similar effect in Europe.’

He said that the initial results from MAQUIS highlight the ‘need to implement aggressive emission-control policies’.