New ozone-destroying gases on the rise

Doyle Rice | USA TODAY

In humanity's ongoing experiment with the Earth's atmosphere, scientists Monday warned of a growing threat from new man-made gases that are chewing away at the ozone layer.

Located high up in the atmosphere, the ozone layer blocks potentially harmful ultraviolet energy from reaching the Earth's surface. If unblocked, this energy can lead to increased rates of skin cancer and other ailments in humans and animals.

The gases in question are known as "very short-lived substances" (VSLS) such as dichloromethane, which is used in a variety of industrial processes.

"VSLS can have both natural and industrial sources," said Ryan Hossaini of the University of Leeds (U.K) and lead author of the study, which was published Monday in the the British journal Nature Geoscience.

"Industrial production of VSLS is not controlled by the United Nations' Montreal Protocol, because historically these chemicals have contributed little to ozone depletion," he said in a statement.

The Montreal Protocol is an international treaty signed by 196 countries in the late 1980s, one that limited the production of chlorofluorocarbons (CFCs) known to destroy the ozone layer.

"The increases observed for dichloromethane are striking and unexpected; concentrations had been decreasing slowly in the late 1990s, but since then have increased by about a factor of two at sites throughout the globe," said study co-author Stephen Montzka of the National Oceanic and Atmospheric Administration.

Though the long-term recovery of the ozone layer is still on schedule, increasing levels of dichloromethane will "lead to uncertainty in our future predictions of ozone and climate," said study co-author Martyn Chipperfield, also of Leeds.

The naturally occurring ozone high up in the atmosphere is the so-called "good ozone" and is in contrast to the "bad ozone" down here near the surface, which is pollution and can cause respiratory problems.

Scientists aren't exactly sure what's causing the growth of dichloromethane. "It could be partly due to the fact that dichloromethane is used in the manufacturing process of some HFCs, the ozone-friendly gases which were developed to replace CFCs," Hossaini said.

"This would mean, ironically, that production of ozone-friendly chemicals is actually releasing some ozone-destroying gases into the atmosphere." Hossaini said.

The study is titled "Efficiency of short-lived halogens at influencing climate through depletion of stratospheric ozone."