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Ozone protects us when it sits high in the atmosphere blocking UV rays, but is a health risk when we breathe the stuff in. So a report showing illegally high ozone levels on some US flights suggests that all aircraft should be fitted with ozone converters.

William Nazaroff of the University of California at Berkeley in the US and colleagues monitored ozone levels on 76 international and domestic flights. On four domestic flights, ozone levels exceeded federal limits of 100 parts per billion.

Breathing ozone can cause headaches and respiratory illness, and has even been linked to cancer.


Reports of high levels of ozone in flight cabins in the 1960s and 1970s prompted the US Federal Aviation Administration to impose a limit on the amount of ozone airline companies could legally allow in their cabins.

Since the 1980s, however, there have not been any studies carried out to monitor ozone levels in airplanes.

Storm stirring

Nazaroff’s team found that on average domestic flights had lower levels of ozone than international flights, because the international flight paths often pass through greater ozone concentrations at high latitudes.

The researchers also found that the flights with the highest levels of ozone coincided with large storms, which mix up atmospheric layers. Ozone is most concentrated in the stratosphere, around 15 kilometres (9.3 miles) above ground. Storms can bring some of that ozone down to the altitudes at which aeroplanes fly.

They also found that flights full of passengers are likely to have less ozone. Previous research shows that the gas reacts with skin oils, reducing ambient levels of the gas. It has been suggested that the by-products of these reactions may themselves pose health risks. Nazaroff points out that if flights were all equipped with ozone converters, it would eliminate this concern.

The research presents a case for fitting ozone converters on all aircraft. No domestic flights with converters had ozone levels above 10 parts per billion, and while international flights – which all carry converters – had higher levels, none got anywhere near federal limits.

Journal reference: Environmental Science and Technology (DOI: 10.1021/es702967k)

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