Nobel Laureate Sherwood Rowland lectured Monday night to a capacity crowd in the Sun Room of the Memorial Union about the causes of ozone depletion and the threat it poses.

Rowland, along with Mario Molina of Massachusetts Institute of Technology and Paul Crutzen of Max Planck Institute in Mainz, Germany, was awarded the 1995 Nobel Prize in Chemistry for his studies of the formation and decomposition of the Earth’s ozone layer.

His original work, done in the 1970s, set in motion the global concern for ozone-depleting emissions, namely chlorofluorocarbons (CFCs).

The global concern generated by Rowland’s work culminated in a 1987 treaty developed in Montreal to halt the use of CFCs.

“It all started with Dr. Rowland’s work,” Iowa State President Martin Jischke said in his introduction of Rowland.

Rowland explained that ozone exists both in the upper atmosphere and at ground level. He said the ozone in the upper atmosphere protects people from the sun’s ultraviolet radiation, but the ozone at the Earth’s surface causes harmful reactions with organisms, including humans, and with crops.

The two types of ozone are often described as “bad” ozone and “good” ozone, Rowland said.

Emissions of CFCs have a negative effect on the distribution of these two types of ozone, he said.

“We are removing the ozone where it benefits us and increasing it where it harms us,” he said.

Comparing new ozone data with information dating back 100 years ago indicates that ozone levels at the Earth’s surface have changed significantly and now vary with the season, which was not the case in the past, he said.

“The atmosphere has changed in the 100 years since those measurements were taken,” Rowland said.

One of Rowland’s first questions upon beginning his research was where the emissions let off by factories and other industries went upon release.

He discovered that the particles were converting to chlorine atoms and thereby destroying the natural formation and decomposition balance of the ozone layer.

“We started this out as an innocent chemistry project,” Rowland said.

His findings led to a global concern about the dissipation of the ozone layer.

Rowland’s lecture was sponsored by the ISU President’s Office and the International Institute of Theoretical and Applied Physics.